Avoiding Wildlife Problems

Coyotes (Canis latrans) are found throughout most of California. The California Department of Fish and Wildlife estimates a population range of 250,000 to 750,000 individuals. Coyotes are very adaptable and inhabit most areas of the state with the exception of the centers of major metropolitan areas. They are medium sized animals belonging to the dog family. Most adults weigh between 22 to 25 pounds on the average, with males being the larger sex. With large erect ears, slender muzzle, and bushy tail they resemble a small collie dog. In the hotter drier regions of California, coyotes are tan-brown in color with streaks of gray. In the more mountainous or humid areas, the color is darker with less brown. In the winter the coats become quite dense, especially in the colder areas. The voice of the coyote is quitedistinctive, consisting of various howls, high-pitched yaps, and occasional dog like barks. Coyotes are proficient predators, possessing the speed, strength, and endurance necessary to tackle prey as large as adult deer.

Biology

In California, coyotes breed mainly during January, February, and March. The gestation period is about 60-63 days. Young are born March through May, with litter sizes averaging 5-6 pups. Coyotes produce one litter per year. The young are weaned at 5 to 6 weeks and leave the parents at 6 to 9 months. Most adults breed first in their second year. Nonbreeding, yearling, coyotes often stay with the adult parents and help care for the pups. Coyote dens are found in steep banks, rock crevices, sinkholes, and underbrush. Coyote dens are often holes that have been used by badger, skunks, foxes, or other animals, with entrances enlarged to about one foot in diameter. Dens vary from 4 to 5 feet deep to 50 feet deep.

The diet of the coyote consists mainly of mice, rats, ground squirrels, gophers, rabbits, and carrion. They also eat insects, reptiles, amphibians, fruits, birds and their eggs, and deer fawns. In some rural areas of California they prey heavily on sheep, cattle, and poultry. In urban and suburban areas, garbage, domestic cats and dogs, other pets, hobby animals, and pet food can be important food items.

Coyotes are most active at night and during the early morning and late evening hours. In areas where they are not disturbed by human activities, and during the cooler times of the year, they may be active throughout the day. Urban coyotes are becoming very tolerant of human activities. Young coyotes tend to be more active during daylight hours than adults. Home range size varies depending on food availability.

Damage

Coyotes can cause substantial damage. In rural areas they oftentimes kill sheep, calves, and poultry. In some parts of the state they cause damage to drip irrigation systems by biting holes in the pipe. In other areas they cause considerable damage to watermelons, citrus fruits, and avocados. Aircraft safety is often jeopardized when coyotes take up residence on or near runways. Coyotes have also been known to prey on various endangered/threatened species, including the San Joaquin kit fox and the California least tern. In urban and suburban areas, coyotes commonly take domestic house cats, small dogs, poultry, and other domestic animals. Coyotes have been known to attack humans, and in one case, a three-year-old girl was killed by a coyote in southern California.

Disease

Distemper and canine hepatitis are among the most common diseases of coyotes. Rabies and tularemia also occur and may be transmitted to humans and other animals. Coyotes often carry parasites including mites, ticks, fleas, worms, and flukes. Mites which cause sarcoptic mange are an important ectoparasite of coyotes. Heartworm is one of the most important endoparasites in California's coyote population. This parasite can be transmitted to domestic dogs by mosquitoes.

Problem Prevention

Coyotes are attracted to urban/suburban areas by the easy accessibility of food, water, and shelter. Reducing or eliminating the availability of these elements will often encourage coyotes to leave. Garbage can lids should be secured at all times or garbage stored indoors. Pets should be fed during daylight hours and all pet food removed before darkness. Water bowls should be emptied and not left out after dark. Ripe fruits and vegetables should be covered at night or the garden/fruit trees enclosed by a coyote proof fence to prevent access by hungry coyotes. All windfall fruit/vegetables should be picked up daily. In areas where predation on pets has been documented, cats and small dogs should not be left out after dark unless enclosed in a coyote proof enclosure. Food should never intentionally be left out for wild mammals. In suburban areas where livestock such as lambs, piglets, calves, or poultry are raised and coyote predation has been documented, precautions should be taken to prevent further losses. Animals can be brought into barns, sheds, or coyote proof enclosures at night, or in certain instances the confinement areas can be lit at night.

To exclude coyotes, fences should be constructed which are at least 5 1/2 feet tall. These can be made of solid wood, cement blocks, brick, or wire. If net wire fencing is used, the bottom portion should be at least 3 l/2 feet tall with squares smaller than 6 inches. If high tensile fence is used, it should be electrifed with a fence charger to prevent coyotes from going through. All fences should have some sort of galvanized wire apron buried at least 4 to 6 inches in the ground which extends out from the fence at least 15 to 20 inches. The apron should be securely attached to the bottom of the fence. Coyotes are very adept diggers and prefer to dig under fences rather than jump them.

Brush and vegetation should be cleared from backyards and adjacent areas to eliminate habitat for prey which could attract coyotes. Landscaping should be pruned on a regular basis. These actions also remove hiding cover used by coyotes to stalk domestic pets. If cats cannot be contained indoors, and predation is viewed as a problem, posts can be installed in open space areas which provide an escape for the cats. These posts should be at least 7 feet tall, made of material that the cat can climb, and have enough space on top for the cat to sit.

During the time of the year when adult coyotes are caring for young (May-September), they can be very aggressive when their young are threatened. Domestic dogs are especially vulnerable to attack during this thne. Even dogs on leases have been attacked when they got too close to a family of coyotes. In urban settings where a den site has been identified, caution should be taken to keep dogs out of the area. These areas should be posted with signs and people concerned about attacks on their dogs should avoid the area. Increased predation on domestic pets can be expected around den sites, and extra precautions should be taken by residents to protect valued domestic cats or small dogs. In some cases a family group of coyotes can be harassed enough to encourage them to move.

Whenever possible, coyotes should be harassed or scared to condition them to avoid humans.

Direct Control

Where coyotes continue to be a problem after non-lethal methods have proven unsuccessful or when human health and safety is jeopardized, it is sometimes necessary to kill one or more animals. Coyotes can be shot where legal and appropriate or captured using a variety of restraining devices. Generally speaking, cage traps are not effective in capturing adult coyotes.

Laws and Regulations

Coyotes are not threatened or endangered in California. They are classified as nongame mammals by the Department of Fish and Wildlife and as such can be taken at any time using approved methods. California Department of Fish and Wildlife regulations prohibit the relocation of coyotes without written permission from the Department. For further information on the legal status of coyotes and other wildlife contact your local California Department of Fish and Wildlife Regional Office at (916) 358-2900.

Raccoons (Procyon lotor) are common throughout California. They are medium sized animals 12 to 35+ lbs. and 20 - 40 inches long, including a bushy tail with 4 to 7 black rings. The fur has a salt and pepper appearance with the black mask marking on a whitish face characteristic of the species. The tracks of the raccoon are very distinctive. The hind foot is long, narrow, and rests flat on the ground like those of a bear. The front paw is hand-like, with toes that are long and well separated. This permits the use of the front paw with almost the facility of a monkey's hands.

Biology

Raccoons breed mainly in February and March, but matings may occur from December through June. The gestation period is about 63 days. Most litters are born in April or May, but some late breeding females may not give birth until June, July, or August. Raccoons produce one litter per year. The average litter size is 3 to 5 young. The offspring are weaned between 2 and 4 months of age and usually stay with the female until the following spring. Yearling females do not always breed but adult females normally breed every year, especially if food is plentiful.

The diet of the raccoon is extremely diverse. They will eat fruit, berries, grain, eggs poultry, vegetables, nuts, mollusks, fish, insects, rodents, carrion, pet food and garbage. Individual animals may learn to use specialized foods such as poultry, fruit crops, small livestock, or garbage by watching other raccoons. Contrary to popular myth, raccoons do not always wash their food before eating, although they frequently play with their food in water.

Raccoons are nocturnal or night-time active animals. Urban raccoon populations are frequently underestimated because people seldom see them traveling during the day. They are also territorial, particularly the males. Adult males may occupy areas of 3 to 20 sq. mi.; females have a much smaller territory of 1 to 6 sq. mi. Raccoons den up in hollow trees, drain pipes, homes and buildings, under decks and storage buildings, brush piles and abandoned burrows.

Damage

Raccoons can cause substantial damage. In urban areas, raccoons damage buildings (particularly attics and roofs), gardens, fruit trees, lawns, garbage cans and trash containers. They are also attracted to pet food left outdoors and will attack pets. Occasionally, one or more raccoons will establish a communal toilet area resulting in time to the deposition of a large number of scats. In rural areas, raccoons may feed on farm crops or raid poultry houses. A raccoon typically attacks birds by biting the head or upper neck area. The heads of adult birds are usually bitten off and left some distance from the body. The crop and breast may be torn and chewed and the entrails eaten. Raccoons have been known to mutilate poultry in cages by pulling heads or legs off. Several kills may be made during a single night raid with part of one or more carcasses fed upon. Dead fowl may be at the kill site or dragged several yards away. Raccoons are also serious predators of wild bird populations. Reports indicate that raccoons have been responsible for eliminating local populations of some nesting waterfowl.

Diseases

Since free roaming wildlife does not receive veterinary care, all wildlife species can carry diseases and parasites. Raccoons are known carriers of rabies, canine distemper, encephalitis, histoplasmosis, trypanosomiasis, coccidiosis, toxoplasmosis, tularemia, tuberculosis, listeriosis, leptospirosis, roundworms and mange. They are also infested with fleas, ticks, lice and mites which are known transmitters of disease. Children and pets are particularly at risk.

Problem Prevention

Raccoons are attracted to urban areas by the easy accessibility of food, water and shelter. Reducing or eliminating the availability of all of these factors will encourage raccoons to leave. Tight fitting lids should be kept on garbage cans; pets should be fed during daylight hours and any leftovers removed immediately; water bowls should be emptied or taken inside at night; gardens should be frequently harvested and windfall fruit picked up. Food should never be intentionally left out for wild mammals.

Raccoons can be excluded from buildings by covering foundation vents with slotted metal vent covers and by using 1/4 inch grid screening to cover attic vents and chimneys. They have been known to enter homes through pet doors; be sure these are locked at night. Raccoons sometimes take up residence under a low deck. They may be excluded by using 1/4 inch grid screening or solid metal flashing. Trench around the perimeter of the deck a minimum of 12 inches deep, insert screening in trench and backfill. Attach top of screening to facade of deck with nails or fence post staples. Before completing final seal on the last entry point, it is wise to make sure no animals are trapped inside. On the night before completing repairs sprinkle flour in the entrance hole and check for tracks the following morning. If no tracks are evident for 3 consecutive nights, no animals are likely to be present. You may wish to make a temporary one way exit using 1/4 inch grid screening. Form the screening into a cone or funnel shape that will permit animals to leave but not to re-enter. The large end should be sized to encircle the entry hole and be attached over the hole to the facade of the deck or building with nails or fence post staples. The small end should face away from the house and be 4 - 6 inches in diameter.

Raccoons may be kept away from roof areas by trimming tree branches 10 feet from roof and by keeping climbing plants trimmed away from root and eave areas.

Exclusion of raccoons from coops and poultry yards is usually the most practical and effective method to prevent losses. At night, poultry should be kept in raccoon-proof sheds or houses. Ideally, poultry should be confined day and night in a sturdy house combined with a predator-proof outdoor run area. This also provides protection from many other types of predators. Often, with a few simple tools and a little material, even somewhat dilapidated coops can be rejuvenated into raccoon-proof condition. Keep in mind that raccoons are good climbers. Moreover, they are strong animals capable of seizing and pushing or pulling objects with considerable force. Usually raccoons are not inclined to break through walls or fences that are intact and in reasonably good condition. Entry is usually made through open, weak, or loose places. Following is a list of measures you can use to protect poultry from raccoons.

1. Cover tops of outdoor runs with wire mesh and/or suitable paneling material and fasten securely. If this is not practical, shut poultry indoors at night.
2. Patch or repair all holes or weak places in existing wire or wood (house or run).
3. Check all edges of overlapping or stapled chicken wire for tightness and tie or staple securely.
4. Check ground edges of coop for tightness. Raccoons may dig under fencing or enlarge existing spaces.
5. Coop doors should be close fitting and sturdy. Beware of plywood doors which may have substantial warp at corners.
6. Simple door fasteners, such as plain hooks, should be replaced with more sophisticated devices such as safety hooks or locking hasps. Raccoons can manipulate and open elementary door latches.
7. To prevent raccoons from reaching in and grabbing poultry, night roosting or standing areas should be at least 12 inches away from cracks or wire mesh of more than 3/4 inch sq. spacing. Smaller size wire can be installed near roosting areas.
8. Birds housed in wire or plastic cages should be kept within the confines of raccoon-proof buildings at night. An alternative solution is to hang or suspend cages from ceilings at least 4 feet above the floor and 5 feet away from walls.
9. The use of a watch dog may prove advantageous in preventing damage in some situations. However, this is not recommended due to the fact that raccoons can be extremely vicious.
10. Raccoons causing lawn and turf damage may be encouraged to leave by controlling the grub worms or other subsoil insects that raccoons eat.

Direct Control

Where raccoons become so numerous that they are a serious pest, they must be excluded or removed. In rural areas, nuisance and damaging raccoons may be trapped or shot. Since raccoons are classified as furbearers, a trapping license or depredation permit may be required before taking any animals. In urban areas, trapping with baited cage traps is the most satisfactory way to remove raccoons. Since raccoons and skunks occupy similar habitats, it is advisable to cover the top, bottom, and sides of an open grid cage trap with heavy cardboard or 1/4 inch plywood. Place the trap in raccoon trails or in areas of known activity. Almost any food is acceptable as bait to trap raccoons. Using fruit, berries, vegetables, raw egg, or peanut butter instead of meat will reduce the likelihood of trapping neighborhood cats. The addition of a wadded up piece of aluminum foil in the trap may help to stimulate curiosity.

There are no Federally registered chemicals to control raccoons. Approved chemical repellents have not been found to be effective.

Laws and Regulations

Raccoons are not threatened or endangered. They are classified as furbearers in California. Fur harvest regulations are set by the California Department of Fish & Wildlife. A trappers license or depredation permit may be required before taking any raccoons. It is a violation of California state law for any wildlife to be kept as pets. Only authorized wildlife rehabilitators may keep injured or orphaned wildlife, and then only for limited periods of time. California Department of Fish & Wildlife Regulations prohibit the relocation of raccoons and other wildlife without written permission of the Department. For further information on the legal status of raccoons and other wildlife, contact your California Department of Fish & Wildlife Regional Office.

Many people consider skunks odorous, obnoxious pests that should be avoided at all costs. However, these animals have some beneficial habits; they kill insects and rodents. The striped skunk (Mephitis mephitis) is the most common species in California, although the smaller spotted skunk (Spilogale putorius) can be a local problem around dwellings. The striped skunk is a house-cat sized animal (4 -10 Ibs.) that has long black fur with two variable broad white stripes down the back. The head is triangular; the tail large and bushy. The strong musk characteristic of skunks is expelled from two scent glands near the anus.

Biology

Skunks are nocturnal, preferring to hunt at night for insects, small rodents, carrion, poultry, eggs, nestling birds, fruit, pet food, and garbage. Because they are active at night, many people never see the animals as they travel through their neighborhood, even in areas with a large skunk population. Skunks will use any sheltered place as a den, including wood piles, animal burrows, culverts, under houses, decks, and sheds. Breeding may begin as early as January, but usually occurs during February and March. Males are viciously competitive for females, and bred females will attack males attempting to breed with them. One or both animals frequently spray during this intra-specific aggression. Litters are born 9 weeks after conception, with an average of 4 - 8 young. The young skunks stay with the female for several months, but usually begin to disperse by mid to late summer.

Damage

Skunks become a problem when their activities conflict with human interests. When skunks take shelter under homes, decks, or in garages, their presence is not usually tolerated by occupants of the building. All skunks have the ability to discharge a nauseating musk from their anal glands. They are capable of spraying their musk several times with accuracy to about 10 feet. Confrontation with pets often results in the pet being sprayed or bitten.

Skunks can also cause severe damage to gardens and lawns by their digging activities. While searching for grubs and other subsoil insects, skunks frequently uproot turf and other plants. This damage consists of small pits ranging from 3 to 5 inches across, or sometimes large sections of sod are rolled back.

Skunks are predators and can decimate ground-nesting wild bird populations and local populations of endangered species of small mammals. In addition, skunks can cause significant economic losses to egg/poultry raisers.

Disease

Skunks are the primary carrier of rabies in California. Approximately 65 percent of the skunks checked for rabies tested positive for the disease during the past 5 years. Rabies is a viral disease that is fatal in mammals, including man and domestic animals (dogs, cats, livestock). It is transmitted by the bite of an infected animal. Rabies is preventable in man and domestic animals through routine vaccination but is not curable after onset of symptoms. Vaccines developed for domestic animals have not proven to be reliable in preventing rabies in wildlife. California wildlife species have shown an overall increase of 7% in confirmed cases of rabies from 1978 through 1988. In addition to rabies, skunks can curry leptospirosis, listeriosis, canine distemper, canine hepatitis, Q-fever, tularemia, and trypanosoma. They are also heavily infested with ticks, fleas, and mites which are known carriers and transmitters of disease.

Problem Prevention

Skunks are often attracted to residential areas by the availability of food, water, and shelter. They can be encouraged to leave by reducing or eliminating these attractants.

Remove unused pet food and water bowls at night, and keep tight fitting lids on garbage cans. Store pet food in animal proof containers. Gardens should be harvested frequently and windfall fruit picked up. Food should never be intentionally left out for wild mammals.

Seal up entry holes in and under buildings and decks. Keep pet access doors locked. Slotted metal vent covers are preferable to screen wire in keeping skunks from entering houses through foundation vents. Low backyard decks have proven to be extremely attractive shelters for skunks. They may be excluded by using 1/4 inch grid screening or solid metal flashing. Trench around the perimeter of the deck a minimum of 12 inches deep, insert screening in trench and backfill. Attach top of screening to facade of deck with nails or fence post staples. This technique may also be used along fence lines to prevent skunks from entering yards and gardens. Before completing final seal on the last entry point on a building or deck, it is wise to make sure no animals are trapped inside.

On the night before completing repairs sprinkle flour in the entrance hole, and check for tracks the following morning. If no tracks are evident for 3 consecutive nights, no animals are likely present. You may wish to make a temporary one-way exit using 1/4 inch grid screening. Form the screening into a cone or funnel shape. The large end should be sized to encircle the entry hole and be attached over the hole to the facade of the deck or building with nails or fence post staples. The small end should face away from the building and be 4 to 6 inches in diameter so that skunks can squeeze out of the hole but not re-enter.

Skunks causing lawn and turf damage may be encouraged to leave by controlling grub worms and other subsoil insects. Chemicals to control these insects may be obtained at hardware or garden supply stores.

Poultry and egg losses may be eliminated by proper fencing and by keeping well maintained, secure coops. Exclusion of skunks from coops and poultry yards is usually the most practical and effective method to prevent losses. At night, poultry should be kept in skunk-proof sheds or houses. Ideally, poultry should be confined both day and night in a sturdy house combined with a predator-proof outdoor run area. This also provides protection from many other types of predators. Usually skunks are not inclined to break through material such as chicken wire which is intact and in reasonably good condition. Entry is usually made through open, weak or loose places in fences or buildings. Skunks are excellent diggers and may try to gain entry by digging under fences. Following is a check list of measures you can use to protect poultry from skunks:

1. Cover outdoor runs with wire mesh and/or suitable paneling material and fasten securely. If this is not practical, shut poultry indoors at night.
2. Patch or repair all holes or weak places in existing wire or wood coops or runs.
3. Check all edges of overlapping or stapled chicken wire for tightness, and tie or staple securely.
4. Check ground edges of coop for tightness. You may need to bury fencing to a minimum depth of 12 inches.
5. Coop doors should be close fitting and sturdy. Beware of plywood doors which may have substantial warp at corners.
6. To prevent skunks from reaching in and grabbing poultry, night roosting or standing areas should be at least 12 inches away from cracks or wire mesh that is more than 3/4 inch square in spacing. Smaller size wire can be installed near roosting areas.
7. Other birds housed in wire or plastic cages should be kept within skunk-proof buildings at night. An alternative solution is to hang or suspend cages from ceilings at least 4 feet above the floor and 5 feet away from walls or fences.

Direct Control

Shooting and live trapping can be used to remove skunks from rural areas. In urban settings, live trapping with baited 10x12x32 inch cage traps is the most desirable method. When trapping for skunks with an open grid cage trap, it is a good idea to cover the top, bottom, and sides of the trap with heavy cardboard or 1/4 inch plywood. This reduces the chance that the person picking up the trap will be sprayed. The trap should be placed in the area of greatest skunk activity or near a suspected entry point. Do not place traps under a building or deck. This does not increase trap success, but it does greatly increase the chance of getting sprayed. Preferred baits for trapping skunks include raw whole egg, peanut butter, sardines, raw chicken parts, or pet food.

There are no Federally registered pesticides for control of skunks in or around buildings.

Odor

Individual reaction to skunk musk ranges from mild irritation to severe headache, nausea, vomiting, and burning of eyes and nostrils. No diseases are known to be transmitted through the musk. Skunk musk on clothing, outdoor furniture and other objects may be neutralized by a strong detergent washing followed by the liberal use of vinegar or household ammonia and a final rinse. Airing these articles on hot, sunny days will also help. To deodorize in or under buildings: maximize ventilation and place cotton balls saturated with a few drops of a strong commercial deodorizer, or Neutroleum alpha, or oil of wintergreen to give favorable results.

To remove musk sprayed on pets, first rinse the eyes gently with clear water, bathe with a "No Tears" shampoo taking special care around the eyes, then rinse with clear water. You may wish to rinse the pet with tomato juice or a dilute solution of vinegar and water. If you take this extra step, you must then shampoo and rinse the pet again. This treatment may need to be repeated. You may use any over-the-counter eye drops as a final soothing eye treatment. If your pet was bitten by the skunk, take it immediately to your veterinarian.

Laws and Regulations

California state law does not classify skunks as endangered or threatened, nor as furbearers or game animals. There is no season or bag limit on skunks. It is against California state law for any wildlife to be kept as pets. Only authorized wildlife rehabilitators may keep injured or orphaned wildlife, and then only for limited periods of time. California Fish and Wildlife regulations prohibit the relocation of skunks and other wildlife without written permission of the Department. For further information on the legal status of skunks and other wildlife, contact your California Fish and Wildlife Regional Office.

Biology

The black bear (Ursus Americanus) is the smallest and most widely distributed of the North American bears. Adults typically weigh 100 to 400 pounds and measure from 4 to 6 feet from tip of nose to tail. Some adult males may attain weights of over 500 pounds.

Food Habits

Black Bears are omnivorous and feed on a wide range of both plants and animals. Their diet can include grasses, wood fiber, berries, nuts, acorns, tubers, insects, animals, carrion and garbage.

Food shortages occur in bear ranges when summer and fall mast crops (berries and nuts) are no longer available. During such periods, bears become bolder and travel more widely in their search for food. Human encounters with bears may be more frequent during such time periods, as are complaints of crop damage and livestock losses.

Damage

Damage caused by black bears is quite diverse, ranging from trampling sweet corn fields and tearing up turf to destroying beehives and killing livestock. Black bears are noted for nuisance problems such as scavenging in garbage cans, breaking in and demolishing the interiors of houses and garages. Bears will also raid campsites, food caches and sometimes maul people. Bears also become a nuisance when they forage in garbage dumps and landfills.

Problem Prevention

Most urban bear problems can be solved by removing the available food source. This can be done in a number of ways.

Never feed bears! Often people leave food out for bears so they can take pictures of them or show them to visiting friends. Doing this only conditions the bear to associate people and residences with a food source.

Pets should be fed during daylight hours and all pet food removed before darkness. All ripe and windfall fruit/vegetables should be picked daily. Food should never intentionally be left out for wild animals. In suburban areas where livestock such as lambs, piglets, calves, or poultry are raised and predation has been documented, precautions should be taken to prevent further losses. Animals can be brought into barns, sheds or enclosures at night to minimize losses.

The smell of garbage can attract bears from a long distance. Food scraps and other odor producing garbage should be sealed in plastic bags before being disposed of. Hauling garbage to the dump more often and using bear proof containers will reduce problems. Some homeowners or associations have built bear proof sheds to store the garbage in until it can be hauled away.

Small areas can be enclosed with an electric fence. The electric fence ribbon seems to work better for bears than the smooth wire. A ground apron will make it more effective.

When camping in bear habitat, food should be kept in a bear proof metal box or hung from trees a short distance from camp where it is not accessible to bears.

For further information regarding deterring bears from campsites, refer to the land managing agency, California Department of Fish and Wildlife, or the camp director.

Frightening Devices

The use of frightening devices such as exploder cannons, barking dogs, fireworks, radios, and human effigies with recorders may provide temporary success in reducing problems, but over time, bears can become very tolerant of these methods. These methods should be used at the first signs of bear problems.

Before using audio repellents, consideration should be given as to the proximity of neighbors and the impacts of the audio repellents on those neighbors.

Laws and Regulations

The black bear is classified as a generally protected mammal in California. Any bear that is encountered in the act of inflicting injury to, molesting or killing livestock or domestic animals can be taken immediately by the owner of the livestock or domestic animal, or the owner's employee, providing the taking is reported to the California Department of Fish and Wildlife the following work day after the incident. Only individual animals causing damage to property, livestock or human health and safety can be taken. The Department of Fish and Wildlife may remove or take any bear or authorize an appropriate local agency with public safety responsibility to remove or take any bear that is perceived to be an imminent threat to public health or safety.

An individual is not guilty of a violation if it is demonstrated that, in taking or injuring a bear, the individual was acting in self-defense or in defense of others.

Any owner or tenant or agent suffering from damage/destruction to property by bears can apply to the California Department of Fish and Wildlife for a revocable permit to take the offending bear. Call the State Conflict Message Line at: (916) 358-2917.

The opossum (Didelphis virginiana) is a house cat sized mammal (4 -14 Ibs.) with moderately long fur that ranges in color from white to dark gray. The fur is frequently darker on the legs and lighter on the back. Its face is long and pointed with dark, rounded, paper-thin, hairless ears. Opossums have 50 teeth, more than any other North American mammal. The tail is hairless, scaly and prehensile. They have five toes on each foot and the inside toe on the hind foot is opposable. Opossums have expanded their range to include all of California.

Biology

Opossums are the only marsupials (pouched mammals) in North America. They breed from January through November and produce two litters per year. The undeveloped young are born 13 days after mating. They crawl to the female pouch (marsupium) and attach themselves to one of the 7-13 teats. Development continues in the pouch for 7 - 8 weeks. Young opossums will stay with the female until they are weaned at about 4 months of age. Except for females with young, opossums are solitary animals.

Opossums are omnivores and eat a wide variety of foods including fruits, vegetables, nuts, meat, eggs, insects, carrion, pet food, and garbage. They are found in many different habitats from woodlands to highly developed residential areas. In urban areas, they have been found living in attics, garages, chimneys, woodpiles, under houses or decks, or in any place that offers protection. Although they are very common in urban areas, opossums are not often seen due to their nocturnal habits.

Damage

Opossums become a nuisance when they move into urban areas. When they live in or near inhabited buildings, the animal's smelly nesting habits and discharge of anal fluids cause offensive odors. Opossums can damage buildings by pushing in screened vents or window screens, scattering insulation, and chewing electrical wiring. They frequently get into garbage and may injure pets or expose them to disease in disputes over pet food. Opossums prey on wild birds and are capable of eliminating local populations of some species.

Disease

Opossums are carriers of many diseases: tuberculosis, relapsing fever, herpes virus, tularemia, salmonella, spotted fever, toxoplasmosis, coccidiosis, trichomoniasis, Chagas Disease, yellow fever, and rabies (rarely). They are important reservoirs for leptospirosis (hemorrhagic jaundice) in wildlife and humans. Leptospirosis is transmitted through the urine and feces of infected animals. Humans frequently pick up the disease by eating unwashed produce or windfall fruit, or by putting unwashed hands to their mouth (gum, cigarettes, etc.). Opossums are also heavily infested with fleas, ticks, mites and lice which are known carriers and transmitters of disease.

Problem Prevention

Opossums are attracted to urban areas by the easy accessibility of food, water, and shelter. Reducing or eliminating the availability of all of these factors will keep opossums from moving in or encourage them to leave. Tight fitting lids should be kept on garbage cans; pets should be fed during daylight hours and any leftovers removed immediately, water bowls should be emptied or taken in at night; gardens should be frequently harvested and windfall fruit picked up. Food should never be intentionally left out for wild mammals.

Opossums can be excluded from buildings by covering foundation vents with slotted metal vent covers and by using 1/4 inch grid screening to cover attic vents and chimneys. Opossums have been known to enter homes through pet doors. Keep pet doors locked at night. Opossums sometimes take up residence under low decks. They may be excluded by using 1/4 inch grid screening or solid metal flashing. Trench around the perimeter of the deck a minimum of 12 inches deep, insert screening in trench and backfill. Attach top of screening to facade of deck with nails or fence post staples. Before completing final seal on the last entry point, it is wise to make sure no animals are trapped inside. On the night before completing repairs, sprinkle flour in the entrance hole and check for tracks the following morning. If no tracks are evident for 3 consecutive nights, no animals are likely to be present. You may wish to make a temporary one-way exit using 1/4 inch screening. Form the screening into a cone or funnel shape. The large end should be sized to encircle the entry hole and be attached to the facade of the deck or building with nails or fence post staples. The small end should face away from the house and be 4 inches in diameter.

Opossums can be kept away from roof areas by trimming tree branches 10 feet from roof and by keeping climbing plants trimmed away from eave areas.

Direct Control

Opossums may be trapped with a 10x12x32 inch cage trap or they may be shot in rural areas. In urban areas, live trapping with baited cage traps is the best method of control. Since opossums and skunks occupy the same habitat types, open grid cage traps should be covered (top, bottom and sides) with heavy cardboard or 1/4 inch plywood. Almost any type of food can be used as bait to trap opossums. Using fruit, berries, raw egg, or peanut butter rather than meat will reduce the chance of catching neighborhood cats. Place trap in areas of greatest activity or near entry holes.

There are no Federally registered pesticides for the control of opossums.

Laws and Regulations

Opossums are not native to California. They are not threatened or endangered, nor are they classified as game animals or furbearers. It is a violation of California state law for any wildlife to be kept as pets. Only authorized wildlife rehabilitators may keep injured or orphaned wildlife, and then only for limited periods of time. California Fish and Wildlife Regulations prohibit the relocation of opossums and other wildlife without written permission of the Department. For further information on the legal status of opossums and other wildlife, contact your California Department of Fish and Wildlife Regional Office.

Mountain lions (Felis concolor) are the largest native North American cat except for the slightly larger jaguar. Mountain lions are known by a number of different names - cougar, panther, painter, catamount, and puma. They are primarily nocturnal, shy, elusive, and solitary (except during the breeding season and when young are traveling with the female). They are very fast animals over a short distance, but because of relatively small lung capacity, cannot run great distances. They are agile tree climbers. Males are generally larger tan females averaging 130 to 150 pounds in weight and ranging in length from 72 to 90 inches. Females average 65 to 90 pounds. Pads on the forefeet are larger than those on the hind feet. Heel pads on both the fore and hind feet have a distinctive three-lobe appearance. Claw marks seldom show in the tracks of this species.

Biology

Mountain lions are mainly nocturnal, preferring to hunt at night. Deer are their favorite prey. They have also been known to prey on beaver, porcupines, rabbits, skunks, domestic livestock, pets, and other small mammals, birds, and even fish. Larger animals are usually killed by a bite to the back of the neck. Lions usually remove the viscera and eat the heart, liver, and lungs first. Uneaten portions of prey items are often cached (covered with vegetation, dirt, snow, or other debris). These food sources are generally fed upon until consumed or they spoil. Lions generally move the carcass and re-cover it after each feeding. Dens can be found in any concealed, sheltered spot. Male lions roam widely, females less widely, especially when the cubs are small.

Adult male home ranges often encompass more than 100 square miles. Adult males use their hind feet to scrape duff into a small pile to declare their territory. These "scrapes" or "scratches" are often 6 to 18 inches long and 6 to 12 inches wide. Females generally occupy ranges from 20 to 60 square miles. Females breed first at two or three of age, then every 18 to 20 months thereafter. Young may be born at any time of the year. Gestation period is 88 to 97 days. Litters range from one to six, generally two or three. Juvenile markings (spots) disappear by fifteen months.

Damage

Mountain lions are significant predators of sheep, goats, cattle, horses, house cats, dogs, and poultry in some areas of California. Damage is often random and unpredictable, but when it occurs, large numbers of livestock can be killed in short periods of time, a behavior known as surplus killing. The number of depredation permits issued by the Department of Fish and Wildlife has increased substantially in recent years.

Several attacks on humans have been documented in California, with two (1994) fatal attacks.

What If You Live in Lion Country?

Now that people and mountain lions occupy so much of the same geographical areas in California, encounters are expected to increase. If you live in mountain lion habitat, here's what you can do to reduce your chances of encountering a mountain lion near your home:

• Don't Feed Wildlife: By feeding deer, raccoons or other wildlife in your yard, you will inadvertently attract mountain lions, which prey upon them.
• "Deer-Proof" Your Landscape: Avoid using plants that deer prefer eat; if your landscaping attracts deer, mountain lions may be close by. The California Department of Fish and Wildlife has a brochure entitled "Gardening To Discourage Deer Damage" available at most Department offices.
• Landscape For Safety: Remove dense and/or low-lying vegetation that would provide good hiding places for mountain lions, especially around children's play areas; make it difficult for mountain lions to approach your yard unseen.
• Install Outdoor Lighting: Keep the perimeter of your house well lit at night- especially along walkways - to keep lions visible.
• Keep Pets Secure: Roaming pets are easy prey for hungry mountain lions. Either bring pets inside or keep them in a kennel with a secure top. Don't feed pets outside; this can attract other mountain lion prey.
• Keep Livestock Secure: Where practical, place livestock in enclosed sheds and barns at night, and be sure to secure all outbuildings.
• Keep Children Safe: Keep a close watch on children whenever they play outdoors. Make sure children are inside between dusk and dawn. Teach your children what to do if they encounter a lion.

What Should You Do If You Encounter a Mountain Lion?

There's been very little research on how to avoid mountain lion attacks. But mountain lion attacks that have occurred are being analyzed in the hope that some crucial questions can be answered: Did the victim do something to inadvertently provoke an attack? What should a person who is approached by a mountain lion do - or not do? The following suggestions are based on studies and analysis of attacks by mountain lions, tigers and leopards:

• Do Not Hike Alone: Go in groups, with adults supervising children.
• Keep Children Close To You: Observations of captured wild mountain lions reveal that the animals seem especially drawn to children. Keep children within your sight at all times.
• Do Not Approach a Lion: Most mountain lions will try to avoid a confrontation. Give them a way to escape.
• Do Not Run From a Lion: Running may stimulate a mountain lion's instinct to chase. Instead, stand and face the animal. Make eye contact. If you have small children with you, pick them up if possible so they don't panic and run. Although it may be awkward, pick them up without bending over or turning away from the mountain lion.
• Do Not Crouch Down or Bend Over: In Nepal, a researcher studying tigers and leopards watched the big cats kill cattle and domestic water buffalo while ignoring humans standing nearby. He surmised that a human standing up is just not the right shape for a cat's prey. On the other hand, a person squatting or bending over looks a lot like a four-legged prey animal. If you're in mountain lion country, avoid squatting, crouching or bending over, even when picking up children.
• Do All You Can to Appear Larger: Raise your arms. Open your jacket if you are wearing one. Again, pick up small children. Throw stones, branches, or whatever you can reach without crouching or turning your back. Wave your arms slowly and speak firmly in a loud voice. The idea is to convince the mountain lion that you are not prey and that you may be a danger to it.
• Fight Back If Attacked: A hiker in Southern California used a rock to fend off a mountain lion that was attacking his son. Others have fought back successfully with sticks, caps, jackets, garden tools and their bare hands. Since a mountain lion usually tries to bite the head or neck, try to remain standing and face the attacking animal.

Direct Control

Shooting or capture with trailing dogs or live traps are effective, and the only legal ways, to take depredating mountain lions under a permit issued by the Department of Fish and Wildlife. There are no federally listed chemical repellents or toxicants registered for mountain lion control.

Laws And Regulations

The mountain lion is classified as a specially protected mammal in California. Only individual animals causing damage to property, livestock or human health and safety can be taken. Any mountain lion that is encountered in the act of inflicting injury to, molesting or killing livestock or domestic animals can be taken immediately providing the taking is reported to the California Department of Fish and Wildlife within 72 hours. The Department of Fish and Wildlife may remove or take any mountain lion or authorize an appropriate local agency with public safety responsibility to remove or take any mountain lion that is perceived to be an imminent threat to public health or safety.

An individual is not guilty of a violation if it is demonstrated that, in taking or injuring a mountain lion, the individual was acting in self-defense or in defense of others.

Any owner or tenant or agent suffering from damage/destruction to property by mountain lions can apply to the California Department of Fish and Wildlife for a revocable permit to take the offending mountain/lions.

For further information on the legal status of mountain lions or assistance with a mountain lion depredation problem, contact your local California Department of Fish and Wildlife office.

For additional information or assistance with the capture of a depredating mountain lion, contact the USDA-APHIS-ADC State Office (916) 979-2675, or California Department of Fish and Wildlife (916) 358-2917.

Mountain Lion Information Links

• Keep Me Wild

All information was resourced from the United States Department of Agriculture. For more information, visit USDA Animal & Plant Health Inspection Service - Wildlife Services.

Walter E. Howard
Professor Emeritus of Wildlife Biology and Vertebrate Ecology
Department of Wildlife, Fisheries and Conservation Biology
University of California
Davis, California 95616

Introduction

Rattlesnakes are distinctly American serpents. They all have a jointed rattle at the tip of the tail, except for one rare species on an island off the Mexican coast. This chapter concerns the genus Crotalus, of the pit viper family Crotalidae, suborder Serpentes. Since snakes evolved from lizards, both groups make up the order Squamata.

Fig. 1. Prairie rattlesnake, Crotalus viridis viridis

This article describes the characteristics of the common species of rattlesnakes that belong to the genus Crotalus. These include the eastern diamondback, (C. adamanteus); the western diamond (back) rattlesnake, (C.atrox); the red diamond rattlesnake, (C.ruber); the Mohave rattlesnake, (C.scutulatus); the sidewinder, (C. ceraster); timber rattlesnake, (C. horridus); three subspecies of the western rattlesnake, (C. viridis): the prairie rattlesnake (C. v. viridis); the Great Basin rattlesnake (C. v. lutosus); and the Pacific rattlesnake (C. v. oreganus).

There are 15 species of rattlesnakes in the United States and 25 in Mexico. Other front-fanged poisonous snakes of the Crotalidae family, which are not included in this discussion, are the massasauga and pigmy rattlesnakes, both of the genus Sistrurus. Also not included are two snakes that do not have rattles, hence are not called rattlesnakes: the water moccasin or cottonmouth, and the copperhead, both of the genus Agkistrodon. Two other genera of poisonous snakes in North America are coral snakes (Micrurus and Micruroides) of the family Elapidae.

Damage Prevention and Control Methods

Note: Information pertains to other poisonous snakes

• Exclusion— Construct a snake-proof fence around areas of human activity.
• Seal entrances to buildings and structures.
• Habitat Modification— Eliminate shelter for snakes.
• Control rodents— they attract snakes.
• Repellents— None are available.
• Toxicants— None are available.
• Fumigants— Generally not effective in dens.
• Trapping— Effective in some situations when properly placed. Glue boards are useful in removing rattlesnakes from buildings.
• Shooting— Effective where safe.
• Other Methods— Organized snake hunts may be successful in spring or early summer.
• Snake Bite— Wear protective clothing and be careful when climbing and walking. If a bite occurs, keep the victim calm, warm, and reassured. Seek medical attention immediately.

Identification

Rattlesnakes are usually identified by their warning rattle - a hiss or buzz - made by the rattles at the tip of their tails. A rattlesnake is born with a button, or rattler, and acquires a new rattle section each time it molts. Rattlesnakes also are distinguished by having rather flattened, triangular heads. The heads of all Crotalus rattlesnakes are about twice as wide as their necks. Only pit vipers possess this head configuration; coral snakes do not.

Rattlesnakes belong to the pit viper family Crotalidae, so named because all possess visible loreal pits, or lateral heat sensory organs, between eye and nostril on each side of the head.

Fig. 2. Rattlesnake head showing "cat-eye" elliptical pupil and location of large loreal pit, characteristic of pit vipers.

These heat sensory pits are not present in true vipers, which do not occur in the Western Hemisphere. The facial pits enable rattlesnakes to seek out and strike, even in darkness, warm objects such as small animal prey, as well as larger animals that could be a threat. The vertically elliptical eye pupils, or "cat eyes," are also a characteristic of rattlesnakes. Identifying a dead rattler whose rattles are missing can be done by looking at the snake's scales on the underside in the short region between the vent and the tip of the tail. If the scales are divided down the center, the snake is harmless. The scales on rattlesnakes are not divided. Rattlesnakes come in a great variety of colors, depending on the species and stage of molt. Most rattlers are various shades of brown, tan, yellow, gray, black, chalky white, dull red, and olive green. Many have diamond, chevron, or blotched markings on their backs and sides.

Range and Habitat

Rattlesnakes occur only in North and South America and range from sea level to perhaps 11,000 feet (over 3,000 m) in California and 14,000 feet (4,000 m) in Mexico, although they are not abundant at the higher elevations. They are found throughout the Great Plains region and most of the United States, from deserts to dense forests and from sea level to fairly high mountains. They need good cover so they can retreat from the sun. Rattlers are common in rough terrain and wherever rodents are abundant.

Food Habits

Young or small species of rodents comprise the bulk of the food supply for most rattlesnakes. Larger rattlers may capture and consume squirrels, prairie dogs, wood rats, cottontails, and young jackrabbits. Occasionally, even small carnivores like weasels and skunks are taken. Ground-nesting birds and bird eggs can also make up an appreciable amount of the diet of some rattlers. Lizards are frequently taken by rattlers, especially in the Southwest. The smaller species of rattlesnakes and young rattlesnakes regularly feed on lizards and amphibians.

Rattlesnakes consume about 40% of their own body weight each year. Many prey are killed but not eaten by rattlesnakes because they are too large or cannot be tracked after being struck. One male rattler captured in the field had consumed 123% of its weight, but young rattlers frequently die due to lack of food. Domestically raised rattlesnakes will survive when fed only once a year, but in the field, snakes usually feed more than once, depending on the size of prey consumed. A snake may kill several prey, one after another, and of different species. When rodents and rabbits are struck, the prey is immediately released. The snake then uses its tongue to track the prey to where it has died.

Digestion is quite slow and usually no bones remain in the feces, called "scats." Hair, feathers, and sometimes teeth, however, can usually be identified in scats. Rattlesnakes use very little energy except when active, and they probably are active for less than 10% of their lives. They are not very active unless food is scarce. They store much fat in their bodies, which can last them for long periods.

General Biology, Reproduction and Behavior

When a rattlesnake strikes its prey or enemy, the paired fangs unfold from the roof of its mouth. Prior to the completion of the forward strike motion, the fangs become fully erect at the outer tip of the upper jaw. The erectile fangs are hollow and work like hypodermic needles to inject a modified saliva, the venom, into the prey. Rattlesnakes can regulate the amount of venom they inject when they strike.

Mature fangs generally are shed several times a season. They may become embedded in the prey and may even be swallowed with the prey. When one mature fang in a pair is lost, it will soon be replaced by another functional mature fang. A series of developing fangs are located directly behind one another in the same sheath at the roof and outer tip of the mouth (Fig. 3).

If a newly replaced fang is artificially removed, it may require weeks or longer before another replacement will be fully effective. One fang can function, however, while the other in the pair is being replaced. Fangs that get stuck in a person's boot are not very dangerous; they cannot contain much venom since they serve only as a hollow needle. The external opening of the hollow fang is a groove on the outside of the fang, set slightly back from the tip to prevent it from becoming plugged by tissue from the prey (Fig. 3).

Fig. 3. Head of a rattlesnake in striking position. Supplementary fangs are covered by a sheath of tissue. Each fang is located in a double socket. Replacement fangs appear in what are currently empty sockets.

Rattlesnakes cannot spit venom, but the impact of a strike against an object can squeeze the venom gland, located in the roof of the mouth, and venom may be squirted. This can happen when a rattler strikes the end of a stick pointed at it, or the wire mesh of a snake trap. The venom is released involuntarily if sufficient pressure is exerted, as occurs when venom is artificially "milked" from live snakes. Such venom is dangerous only if it gets into an open wound. Always wear protective clothing when handling rattlesnakes. Female rattlesnakes are ovoviviparous. That is, they produce eggs that are retained, grow, and hatch internally. The young of most species of rattlesnakes are 6 to 8 inches (15 to 20 cm) when born. They are born with a single rattle or button, fangs, and venom. They can strike within minutes, but being so small, they are not very dangerous. Average broods consist of 5 to 12 young, but sometimes twice as many may be produced.

The breeding season lasts about 2 months in the spring when the snakes emerge from hibernation. Sperm is thought to survive in the female as long as a year. During summer, pregnant females usually do not feed, so few are ever captured that contain eggs about to hatch. The young are born in the fall. Most rattlesnakes are mature in 3 years, but may require more time in northerly areas. Rattlesnakes may not produce young every year.

The sex of a rattlesnake is not easy to determine. Even though the tail of the rattlesnake (the distance between the vent and the raffles) is quite short, it is much longer in males than in females of the same size. The paired hemipenises of male snakes are not visible except during mating, when one of these paired hollow organs is turned inside out and extruded from the cloaca. If both are extruded artificially, they appear like two forked, stumpy legs.

Snakes never close their eyes, since they have no eyelids. They are deaf, but can detect vibrations. They have a good sense of smell and vision, and their forked tongues transport microscopic particles from the environment to sensory cells in pits at the roof of the mouth. A rattlesnake uses these pits to track prey it has struck and to gather information about its environment.

Snakes have a large number of ribs and vertebrae with ball-and-socket joints. Each rib is joined to one of the scales on the snake's underside. The snake accomplishes its smooth flowing glide by hooking the ground with its scales, which are then given a backward push from the ribs. Rattlesnakes often look much larger when seen live than after they have been killed. This happens because their right lung extends almost the full length of the tubular body, and when the snakes inhale they can appear much fatter and more threatening. The expulsion of the air can produce a hiss.

Rattlesnakes, like other snakes, periodically shed their skin. When the new skin underneath is formed, the snake rubs its snout against a stone, twig, or rough surface until a hole is worn through. After it works its head free, the snake contracts its muscles rhythmically, pushing, pulling, and rubbing, until it can crawl out of the old skin, which peels off like an inverted stocking. Each molt produces a new rattle. Some rattles usually break off from older snakes. Even if no rattles have been lost, they do not indicate exact age because several rattles may be produced in one season.

Even though the optimum temperature for rattlesnakes is around 77 to 89 degrees F (25 to 32 degrees C), the greatest period of activity is spring, when they come out of hibernation and are seeking food. If lizards are active, be alert for rattlesnakes. The activity period for rattlers can vary from about 10 months or so in warm southern regions to perhaps less than 5 months in the north and at high elevations. Depending upon availability of good, dry denning sites below the frost line, rattlesnakes may hibernate alone or in small numbers. However, sometimes they den in large groups of several hundred in abandoned prairie dog burrows or rock caverns, where they lie torpid in groups or "balls." All dens must be deep enough so the temperature is not affected by occasional warm days. If not, the snakes might emerge too early in spring only to become sluggish and vulnerable should the weather again turn cold. Since snakes are coldblooded animals and their body temperature is altered by air temperature, refrigeration makes them sluggish and easy to handle for displaying.

Rattlesnakes usually see humans before humans see them, or they detect soil vibrations made by walking. They coil for protection, but they can strike only from a third to a half of their body length. Rattlers rely on surprise to strike prey. Once a prey has been struck, but not killed, it is unlikely that it will be struck again. Experienced rodents and dogs can evade rattlesnake strikes.

Rattlesnakes may appear quite aggressive if exposed to warm sunshine. Since they have no effective cooling mechanism, they may die from heat stroke if kept in the sun on a hot day much longer than 15 or 20 minutes.

If a rattlesnake has just been killed by cutting off its head, it can still bare its fangs and bite. The heat sensory pits will still be functioning, and the warmth of a hand will activate the striking reflex. The head cannot strike, but it can bite and inflict venom. The reflex no longer exists after a few minutes, or as long as an hour or more if it is cool, as rigor mortis sets in.

Damage and Damage Identification

The greatest danger to humans from rattlesnakes is that small children may be struck while rolling and tumbling in the grass. Only about 1,000 people are bitten and less than a dozen people die from rattlesnake venom each year in the United States. Nevertheless, it is a most unpleasant experience to be struck. The venom, a toxic enzyme synthesized in the snake's venom glands, causes tissue damage, as it tends to quickly tenderize its prey. When known to be abundant, rattlesnakes detract from the enjoyment of outdoor activities. The human fear of rattlesnakes is much greater than the hazard, however, and many harmless snakes inadvertently get killed as a result. Death from a rattlesnake bite is rare and the chance of being bitten in the field is extremely small.

Experienced livestock operators and farmers usually can identify rattlesnake bites on people or on livestock without much difficulty, even if they did not witness the strike. A rattlesnake bite results in almost immediate swelling, darkening of tissue to a dark blue-black color, a tingling sensation, and nausea. Bites will also reveal two fang marks in addition to other teeth marks (all snakes have teeth; only pit vipers have fangs too). Rattlesnakes often bite livestock on the nose or head as the animals attempt to investigate them. Sheep, in particular, may crowd together in shaded areas near water during midday. As a consequence, they also frequently are bitten on the legs or lower body when pushed close to snakes. Fang marks and tissue discoloration that follows in the major blood vessels from the bite area are usually apparent on livestock that are bitten (see Wade and Bowns 1982, pages 32 and 34 in the Damage Identification section of this book).

Legal Status

Most species of rattlesnakes are not considered threatened or endangered. Since they are potentially dangerous, there has not been much support for protecting them except in national parks and preserves. However, since there are state and local restrictions, contact local wildlife agencies for more information.

Damage Prevention and Control Methods

An occasional single poisonous snake can be destroyed if one has enough determination. In areas where the habitat is favorable for rattlesnakes, copperheads, or water moccasins, a significant reduction in their population density may be difficult. In snake country, most people learn to "keep their eyes open" and be cautious.

Exclusion

When feasible, the most effective way for a homeowner to protect a child's play area from rattlesnakes is to construct a rattlesnake-proof fence around it. The fencing must be tight. If wire mesh is used, it should be 1/4-inch (0.6-cm) mesh and about 3 feet (1 m) high. Bury the bottom 3 or 4 inches (8 or 10 cm) or bend outward 3 or more inches of the base of the wire to discourage other animals from digging under the fence. Put the stakes on the inside and install a gate that is tight-fitting at the sides and bottom, equipped with a self-closing spring. The benefit of the fence will be lost if wood, junk, or thick vegetation accumulates against the outside of the fence. Vegetation that has ground-level foliage also provides attractive hiding places for rattlesnakes, so it should be removed or properly pruned. Tight-fitting doors will prevent snakes from entering outbuildings. The foundations of all buildings should be sealed or tightly screened with 1/4-inch (0.6-cm) wire mesh to keep out snakes.

Habitat Modification

It is always desirable to use non-lethal biological means of control when feasible. Although good quantified data are not available to evaluate the effectiveness of removing the prey of snakes, effective, sustained rodent control will reduce the attractiveness of a rural residence or other facility to rattlesnakes. Snakes will not remain in habitat made less favorable for them. Hiding places under buildings, piles of debris, or dense vegetation should be removed. Hay barns and feed storage areas that encourage rodents will attract rattlers.

Frightening

No methods are known that will frighten rattlesnakes. Sounds certainly will not work because snakes are deaf.

Repellents

Many potential snake repellents have been researched, only to be found ineffective. All species of snakes are likely to cross a strip of repellent substance if they want to get to the other side.

Dr. T's Snake-A-Way (registered trademark), a mixture of sulphur-naphthalene, has been registered by EPA; however, its registration in California was denied as of July 1991, because required data was not submitted. A Y-shaped laboratory enclosure that provided rattlers with a choice of crawling into a tunnel with odor or one free of odor showed they usually chose the passage free of odor. No field test data is available. To be of practical use, the odor of a snake repellent must not be too objectionable to people.

Toxicants

No effective toxicant is registered for the control of rattlesnakes. When rodents were poisoned with various rodenticides and then fed to rattlesnakes, the snakes were not affected. Apparently, digestion is too slow for the toxicants to have an effect on snakes.

Fumigants

It may be possible to kill rattlesnakes in burrows and rock dens with toxic gas, although this is not a very practical method. Calcium cyanide is a chemical frequently recommended, but no lethal gas has had good success because snakes have such a slow rate of metabolism, especially when in hibernation. In addition, susceptible nontarget species in the burrows or dens may become victims.

Trapping

Various combinations of fencing and traps at known rattlesnake dens can be very successful if one is trying to collect rattlesnakes, because in some localities several hundred rattlesnakes may occupy the same den. If all but one opening can be blocked, it is then quite simple to pipe or otherwise channel the emerging rattlesnakes into a large oil drum or other receptacle. If it is not possible to find all den openings, inward-sloping drift fences of Image of Snake Trap1/4-inch (0.6-cm) hardware cloth mesh, 1 or 2 feet (0.5 m) high, with fish-type funnel traps (Fig. 4) will suffice.

Fig. 4. A fish-type funnel trap of 1/4-inch hardware cloth attached to an inward-sloping drift fence of the same wire mesh can be useful in trapping snakes as they emerge from a multi-opening den. Escape will be reduced if a wooden nest box is attached to the funnel trap.

The inward sloping funnel makes it difficult for the snakes to escape. If a wooden nestbox is attached to one side of these traps, the snakes will usually hide in the box and not spend as much time trying to escape. Drift-fence funnel traps also catch many other animals. Therefore, this control method requires daily inspection and usually is not very practical except at dens.

Glue boards are useful for trapping rattlesnakes that are in or under buildings (Knight 1986). To trap rattlesnakes, use a plywood board approximately 24 x 16 inches (61 x 41 cm). Securely tack a 6 x 12-inch (15 x 30-cm) rodent glue trap (or use bulk glue to make a similar-sized glue patch) to the plywood (Fig. 5). Place the board against a wall, as this is where snakes are likely to travel. The rattlesnake will become stuck while attempting to cross the board. Do not place the board near any object (pipes, beams) that the snake can use for leverage in attempting to free itself.

Fig. 5. A glue trap to catch rattlesnakes can be made by attaching three to six rodent glue traps to a wooden board.

The glue trap can be removed easily using a long stick or pole with a hook or by an attached rope if a hole is drilled through the plywood board. Animals trapped in the glue can be removed with the aid of vegetable oil, which counteracts the adhesive.

Do not use glue boards outdoors or in any location where they are likely to catch pets or desirable non-target wildlife. The glue can be quite messy and is difficult to remove from animals.

Shooting

A shotgun has often been used to eliminate individual rattlesnakes around a rural homestead. Similarly, a pistol loaded with birdshot is very effective at close range. Shooting is not considered effective for reducing large populations.

Other Methods

Dynamite blasting of known dens is dangerous and has questionable advantages. There is no way to know what kinds and how many snakes have been killed, and the blast may create an even better den for future rattlesnakes.

Rattlesnakes have natural predators, but the predators are not likely to help much in controlling rattlesnake populations. Some dogs, especially if they have experienced a snake bite, become excellent guards for children. They will bark when a snake is discovered, and many can kill rattlesnakes as well. Domestic geese and turkeys may also help, by acting as an alarm and by frightening snakes. Hogs do not provide practical protection around a homestead.

Snake Bite

The best protection for humans when traveling in snake country is common sense in choosing protective foot and leg wear. When climbing, one should beware of putting a hand up over rocks. Rattlesnakes might be waiting there for a rodent, and the warmth in a hand may cause the snake to strike reflexively. Care should be taken at night, when snakes are more active, and the chance of stepping on a snake is greater. Fortunately, rattlesnakes try to avoid people.

The best first aid for a poisonous snake bite is to seek immediate medical care and to keep the victim calm, warm, and reassured. Do not drink alcohol or use ice, cold packs, or freon spray to treat the snake bite or cut the wound, as was once recommended.

If a victim of snake bite is several hours from a car and medical aid, apply a light constricting cloth or other band on the bitten limb, 2 to 4 inches (5 to 10 cm) from the bite and between bite and heart. Make sure it is not as tight as a tourniquet. It should be easy to insert a finger under the band. Loosen it if swelling occurs. Apply suction at the wound for at least 3/4 of an hour by mouth (if no mouth sores), or with a snakebite kit, but again, only if medical assistance is several hours away.

The causes of human death from rattlesnake venom are varied, but usually occur from extended hypotension and cardiopulmonary arrest. Usually within a few minutes after being struck the victim will experience pain and swelling at the wound site.

Economics of Damage and Control

The greatest economic loss to humans from rattlesnakes comes from the number of domestic livestock and pets that are killed. Horses and cattle are most frequently struck in the head while grazing. Some have claimed that rattlesnakes benefit ranchers by the number of rodents they eat, but current predator-prey theory discounts this. It is very doubtful that snakes have much effect on the density of rodents.

The commercial value of rattlesnakes consists of the venom, rattles, skins and, to a limited degree, the meat.

Acknowledgements

• Figures 1 through 3 by Emily Oseas Routman.
• Figures 4 and 5 by Jill Sack Johnson.

For Additional Information

• Dunkle, T. 1981. A perfect serpent. Science 81 2:30-35.
• Duvall, D., M.B. King, and K.J. Gutzwiller. 1985. Behavioral ecology and ethology of the prairie rattlesnake. Natl. Geogr. Res. 1:80-111.
• Dolbeer, R. A., N.R. Holler, and D.W. Hawthorne. 1994. Identification and control of wildlife damage. Pages 474-506 in T. A. Bookhout ed. Research and management techniques for wildlife and habitats. The Wildl. Soc. Bethesda, Maryland.
• Kilmon, J., and H. Shelton. 1981. Rattlesnakes in America. Shelton Press, Sweetwater, Texas. 234 pp.
• Klauber, L.M. 1972. Rattlesnakes: their habits, life histories, and influence on mankind, 2 vols. Univ. California Press, Berkeley. 1533 pp.
• Klauber, L.M. 1982. Rattlesnakes: their habitats, life histories, and influence on mankind. Abridged by K. H. McClung. Univ. California Press, Berkeley. 350 pp.
• Knight, J. E. 1986. A humane method for removing snakes from dwellings. Wildl. Soc. Bull. 14:301-303.
• Marsh, R.E., and W.E. Howard. 1982. Vertebrate pests. Pages 791-861 in A. Maillis, ed. Handbook of pest control, 6th ed. Franzak and Foster Co., Cleveland, Ohio. 1001 pp.
• Pinney, R. 1981. The snake book. Doubleday & Co., New York. 248 pp.
• San Julian, G.J., and D.K. Woodward. 1986. What you wanted to know about all you ever heard concerning snake repellents. Proc. Eastern Wildl. Damage Control Conf. 2:243-248.
• Seigle, R A., J.T. Collins, and S.S. Novak. 1987. Snakes: ecology and evolutionary biology. Macmillan Publ. Co., New York. 529 pp.
• Story, K. 1987. Snakes: separating fact from fantasy. Pest Control Technol. 15(11):54,55,58,60.
• Wade, D.A., and J.E. Bowns. 1982. Procedures for evaluating predation on livestock and wildlife. Bull. No. B-1429, Texas A & M Univ., College Station. 42 pp.