Twelve amphibian and 22 reptile species inhabit Yosemite National Park. They are often considered together because both are poikilotherms, animals that lack the ability to generate their own body heat, relying instead on their environment to regulate body temperature. Amphibians spend the early part their life cycle in water as larva before metamorphosing into adults that live on land. Toads are a good example. As tadpoles, they are restricted to aquatic environments, but spend almost all of their time on land as adults. In contrast, reptiles are generally terrestrial throughout their life cycle. Amphibians are also characterized by moist, highly vascularized skin while reptiles are typically covered by scales.
At nearly 750,000 acres (303,525 ha), and elevations that range from 2,000 feet (610 m) to over 13,000 feet (3,962 m), Yosemite National Park provides habitats for many bird species. Over 150 species regularly occur in the park, with around 80 additional species that have been seen in Yosemite only a few times (see species list ). Of the regularly- occurring species, approximately 80% are known or suspected to breed in the park. Most of these bird species migrate to lower elevations or latitudes in the late summer and fall. For example, of the 84 species known to nest in Yosemite Valley, 54% are rare or absent in winter. Fewer yet remain at higher elevations.
Most fish in Yosemite National Park have been introduced. Prior to trout stocking for sport fishing, native fish were limited in both range and number of species (see species list ). The series of glaciations that covered much of the area that is now the park eliminated all fish from the high country. After the glaciers retreated, the waterfalls and steep gradients that were created on the rivers and streams by glaciation prevented repopulation of fish by upstream migration. Only the lower reaches of the Tuolumne and Merced Rivers were populated by fish when Euro-Americans first arrived in Yosemite in the mid-1800s.
Yosemite is home to 90 species of mammals in seven orders, including marsupials, insectivores, bats, lagomorphs, rodents, carnivores and hooved animals. The Virginia opossum is the lone marsupial. Seven species of shrews and one mole comprise insectivores. Lagomorphs include one rabbit, the pika, and three hares. Bats and carnivores number 17 and 19 species, respectively. Rodents form the largest group with 39 species. The two hooved mammals inhabiting the park are the California mule deer and the Sierra Nevada bighorn sheep. One species, the Mount Lyell shrew is endemic to the Yosemite region while two others, the Virginia opossum and beaver are non-native introductions.
Yosemite has more than 300 species of vertebrate animals, and 85 of these are native mammals. Black bears are abundant in the park, and are often involved in conflicts with humans that result in property damage and, occasionally, injuries to humans. Visitor education and bear management efforts have reduced the bear-human incidents and property damage by 90% in the past few years. Ungulates include large numbers of mule deer. Bighorn sheep formerly populated the Sierra crest, but have been reduced to several remnant populations. There are 17 species of bats, 9 of which are either Federal or California Species of Special Concern. Over 150 species of birds regularly occur in the parks. Great gray owls are of special interest in Yosemite because here they reach the furthest southern extent of their global range, and they are isolated by hundreds of miles from the next closest population in far northern California.
Yosemite has an elevation range from 2,000 to 13,123 feet and contains five major vegetation zones: chaparral/oak woodland, lower montane, upper montane, subalpine and alpine. Of California 's 7,000 plant species, about 50% occur in the Sierra Nevada and more than 20% within Yosemite . There is suitable habitat or documented records for more than 160 rare plants in the park, with rare local geologic formations and unique soils characterizing the restricted ranges many of these plants occupy.
With habitats ranging from thick foothill chaparral to expanses of alpine rock, Yosemite National Park supports over 250 species of vertebrates, which include fish, amphibians, reptiles, birds, and mammals. This high diversity of species is also the result of habitats in Yosemite that are largely intact, compared to areas outside the park where various human activities have resulted in habitat degradation or destruction.
Along much of Yosemite's western boundary, habitats are dominated by mixed coniferous forests of ponderosa pine, sugar pine, incense cedar, white fir, and Douglas fir, and a few stands of giant sequoia, interspersed by areas of black oak and canyon live oak. A relatively high diversity of wildlife species are supported by these habitats, due to relatively mild, lower-elevation climate, and the mixture of habitat types and plant species. Wildlife species typically found in these habitats include black bear, bobcat, gray fox, mountain kingsnake, Gilbert's skink, white-headed woodpecker, brown creeper, spotted owl, and a wide variety of bat species. In the case of bats, large snags are important as roost sites.
Going higher in elevation, the coniferous forests become purer stands of red fir, western white pine, jeffrey pine, and lodgepole pine. Fewer wildlife species tend to be found in these habitats, due to their higher elevation, and lower complexity. Species likely to be found include golden- mantled ground squirrel, chickaree, marten, Steller's jay, hermit thrush, and northern goshawk. Reptiles are not common, but include rubber boa, western fence lizard, and alligator lizard.
As the landscape rises, trees become smaller and more sparse, with stands broken by areas of exposed granite. These include lodgepole pine, whitebark pine, and mountain hemlock that, at highest elevations, give way to vast expanses of granite as treeline is reached. The climate in these habitats is harsh and the growing season is short, but species such as pika, yellow-bellied marmot, white-tailed hare, Clark's nutcracker, and rosy finch are adapted to these conditions. Also, the treeless alpine habitats are the areas favored by Sierra Nevada bighorn sheep. This species, however, is now found in the Yosemite area only around Tioga Pass, where a small, reintroduced population exists.
At a variety of elevations, meadows provide important, productive habitat for wildlife. Animals come to feed on the green grasses and use the flowing and standing water found in many meadows. Predators, in turn, are attracted to these areas. The interface between meadow and forest is also favored by many animal species because of the proximity of open areas for foraging, and cover for protection. Species that are highly dependent upon meadow habitat include great gray owl, willow flycatcher, Yosemite toad, and mountain beaver.
Despite the richness of high-quality habitats in Yosemite, three species have become extinct in the park within historical time, and another 37 species currently have special status under either California or federal endangered species legislation. The most serious current threats toYosemite's wildlife and the ecosystems they occupy include loss of a natural fire regime, exotic species, air pollution, habitat fragmentation, and climate change. On a more local basis, factors such as road kills and the availability of human food have affected some wildlife species.
Black bears are omnivores and will eat almost anything. They spend most of their days foraging for grasses, seeds, berries, acorns, and insects and occasionally feed on carrion. Bears tear open rotten logs or old stumps in search of insect larvae. Meadows also furnish a wide variety of food, such as grass, clover, lily, wild onion, and brodiaea bulbs. Research in Yosemite shows that plants, including acorns, comprise 75% of the diet of Yosemite bears. Bears are also fond of fruit, particularly manzanita, service berry, elderberry, and wild cherry. Chipmunks, ground squirrels, marmot, pocket gophers, and mice are also a part of their diet. In the fall, bears are often seen beneath oak trees searching for acorns. Unfortunately, many Yosemite bears have also perfected the skill of obtaining food from humans.
Never approach a bear regardless of its size. If you encounter a bear, act immediately: throw small stones or sticks toward the bear from a safe distance. Yell, clap hands, and/or bang pots together. If there is more than one person, stand together to present a more intimidating figure, but do not surround the bear. Use caution if you see cubs, as a mother may act aggressively to defend them.
When done immediately, these actions have been successful in scaring bears away. Never try and retrieve anything once a bear has it. Report all incidents to a park ranger.
American black bears ( Ursus americanus) are an integral part of the Sierra Nevada ecosystem and are only one of the many animal species protected in Yosemite National Park. Black bears forage on a wide variety of natural foods, including grasses, insects, berries, and acorns. The bears, however, are intelligent and adaptable, and will readily accept human foods when they are available. Bears that are exposed to human food often change their behavior and begin seeking it in campgrounds, parking lots, and from backpackers. This results in property damage and dangerous confrontations between humans and bears. The ecological role of such bears is also changed - their use of natural foods diminishes, they become more nocturnal, and the elevation range of habitat use changes. When a bear's search for human food makes them aggressive toward humans, it poses an unacceptably high threat and must be killed. As a result, black bears have been the subject of intense management efforts in Yosemite for many years, to protect both people and the bears.
A majority of animal matter in a black bear's diet is insects, such as ants, termites, and grubs ripped from rotting logs.
Black bears ( Ursus americanus ) in Yosemite have long been of intense interest to both park visitors and park managers. For visitors, the sight of a bear can evoke a mixture of excitement, awe, and fear; all of which can mark the highlight of a vacation. For park managers, black bears offer the challenge of preserving an ecologically-important species that, by its nature, can easily be corrupted by human influences in Yosemite.
When Euro-Americans arrived in California, grizzly bears ( Ursus arctos ) inhabited most of the state, including the area that is now Yosemite National Park. The grizzlies, however, were seen by the settlers as a dire threat to life and property and were killed in large numbers. By the early 1900s, few grizzlies and little of their prime habitat in the Central Valley remained. The last known grizzly bear in California was killed in the Sierra foothills south of Yosemite in the early 1920's. Many years ago, the National Park Service maintained bear feeding pits to entertain visitors and draw bears out of developed areas. This practice, however, led to many human injuries and many killed bears, and ended in the 1950s. NPS photo.
In contrast, black bears have fared much better. Much of their preferred habitat in the foothills and mountains remains suitable, and their more timid behavior has limited persecution by humans. Black bears have proven to be adaptable to many human-caused changes to their habitat in the Sierra Nevada and eagerly take advantage of food sources these changes sometimes provide - such as garbage cans and dumps, orchards, and domestic beehives. These food sources, however, often bring the bears into conflict with humans, for which the bears can pay with their lives. Nonetheless, there are an estimated 20,000 to 24,000 black bears in California, despite a fall hunting season that annually removes up to 1,500 bears from the population. No scientific census of bears has occurred in Yosemite, but it is estimated that there are roughly 300 to 500 black bears in the park.
Despite their name, most black bears in Yosemite are not black in color. Most are some shade of brown, ranging from almost blond, to reddish brown, to a dark chocolate color. Truly black black bears are relatively rare here. In other areas of the country, such as the eastern United States, and the Pacific Northwest, black bears with black fur are the most common. A large Yosemite black bear "sizes up" the photographer.
One common question is how big are Yosemite's bears? This is a difficult question to answer because bears, like people, can vary greatly in size. Also, an individual bear's weight can change greatly throughout the year. Before entering winter hibernation, a bear's weight can be double what it was when it emerged from its den the previous spring, if food sources are rich enough. In general, however, the weight of an average, adult male Yosemite black bear in summer is 300 to 350 pounds (136 to 159 kg). Females are smaller, with typical weights ranging from 200 to 250 pounds (91 to 113 kg). Much bigger bears, however, do occur. The largest black bear ever captured in Yosemite weighed 690 pounds (375 kg)!
Bears are classified as carnivores, in the same taxonomic order as dogs and cats, but a majority of a black bear's diet is made up of vegetable matter. In the spring, after emerging from winter dens, the bears feed largely on meadow grasses, which are relatively low in nutrition, but sustain the bears until more nutritious foods become available. As berries of various plant species ripen in the summer, the bears shift to these higher-calorie foods. Animal matter that is eaten consists primarily of ants, termites, and insect larvae ripped out of logs or dug from the ground. Black bears also sometimes kill young deer or scavenge the kills of other predators, such as mountain lions and coyotes. In the fall, black bears gorge on acorns, which are especially important to the bears as they fatten before going into winter dens for hibernation. The capture and handling of bears requires a complex array of equipment.
Winter dens are typically established in hollow trees or logs, under the root mass of a tree, or in caves formed by the jumble of large rocks on a talus slope. Here, the bears enter a state of reduced body temperature, pulse rate, and respiration that enables them to conserve energy. They neither defecate nor urinate while hibernating, and even have unique metabolic pathways that enable them to extract energy from body wastes. Their sleep, however, is not a deep one, and bears may leave the den periodically. Cubs are born in the winter den, weighing less than 1/2 pound (0.23 kg) at birth, and typically number from one to three cubs in a litter. The fast-growing cubs will remain with its mother through another winter, before leaving her in the spring at about 16 to 17 months of age. By spring, a hibernating bear can lose as much as half of its body weight. This is especially true of females nursing cubs. Human-Bear Management Program Black bears in Yosemite have caused hundreds of thousands of dollars in property damage as they seek food improperly stored in vehicles.
The history of interactions between humans and black bears in Yosemite is a long one, marked by some periods that we now look upon as shameful. Early in the park's history, little was done to keep bears from becoming conditioned to human food. Garbage was readily available in developed areas, and little was done to discourage visitors from feeding bears. Indeed, the National Park Service maintained several bear pits in the park where bears were fed garbage in an attempt to keep them out of park campgrounds and lodging areas, and to provide visitor entertainment. Human injuries were common, and many bears were killed in the name of public safety.
Thankfully, times have changed, and the emphasis is now on managing the behavior of humans rather than the behavior of bears. All outdoor garbage cans and dumpsters are bear-resistant. All campsites, parking lots, and major trailheads are equipped with bear-proof food storage lockers that allow visitors to remove food from their cars and store it safely away from bears. In recent years, increased staffing has allowed more patrols to detect and correct food storage problems and to provide visitor education. Also, all park employees - of the National Park Service, the concessioner, and other park partners - have accepted larger roles in protecting the bears, whether it is diligence in emptying trashcans or dispensing information to visitors. As a result, human-bear incidents and property damage have declined by nearly 90% over the last three years. To continue this success and protect Yosemite's bears, strict compliance with the park's food storage regulations is necessary. Use of bear-resistant food canisters is required in some areas of Yosemite's wilderness, but all backpackers are strongly encouraged to use canisters to protect themselves and the bears.
The bear management program still involves some actions that deal directly with the bears. Bears are hazed out of developed areas, while others are captured, tagged, and released . Some of these bears are relocated to other areas within the park, although most of them just return. Despite all the improvements in facilities and education, some bears become dangerously aggressive and must be killed, usually two to three per year. These sad events indicate that further progress must be made in making human food unavailable to bears in Yosemite. To learn more about how to avoid dangerous encounters with bears, see our bear safety page .
The Hornocker Wildlife Institute, a program of the Wildlife Conservation Society , recently examined and evaluated factors influencing human-bear interactions in order to accurately identify methods to improve bear management, reduce the number of human-bear incidents, and provide for the continued, long-term existence of bears in Yosemite National Park.
Specific recommendations included maintaining personal contacts by park staff to remind visitors of food storage regulations, increasing the level of human interest in the messaging used to educate visitors about bears and bear-related regulations, stronger law enforcement efforts, more effective waste management, more aggressive aversive conditioning techniques on bears visiting developed areas, and research into the transmission of the damage behavior throughout the bear population. Additional information regarding the 2000-2003 research effort and copies of the final report and scientific publications can be found here .
Mountain lion sightings and encounters have increased throughout Yosemite over the past several years. The lions are an important part of the park ecosystem, helping to keep deer and other prey populations in check. Although lion attacks are rare, they are possible, as is injury from any wild animal. We offer the following recommendations to increase your safety:
Do not leave pets or pet food outside and unattended, especially at dawn and dusk. Pets can attract mountain lions into developed areas. Avoid walking alone. Watch children closely and never let them run ahead or lag behind on the trail. Talk to children about lions and teach them what to do if they meet one.
Store food according to park regulations.
Never approach a mountain lion especially one that is feeding or with kittens. Most mountain lions will try to avoid confrontation. Always give them a way to escape. Don't run. Stay calm. Hold your ground or back away slowly. Face the lion and stand upright. Do all you can to appear larger. Grab a stick. Raise your arms. If you have small children with you, pick them up. If the lion behaves aggressively, wave your arms, shout and throw objects at it. The goal is to convince it that you are not prey and may be dangerous yourself. If attacked, fight back!
Generally, mountain lions are calm, quiet, and elusive. The chance of being attacked by a mountain lion is quite low compared to many other natural hazards. There is, for example, a far greater risk of being struck by lightning than being attacked by a mountain lion.