Mammal Species at Risk

Salt marsh wandering shrew Sorex vagrans halicoetes (CSC)

The Salt marsh wandering shrew is a subspecies of the more common vagrant shrew, differentiated by its larger size and darker color. Although they have relatively large litters, with 2-9 young, less than half survive to adulthood. Salt marsh wandering shrews are mostly found in moist soils near the San Francisco Bay. They may also be found on the coastlines of Contra Costa, Alameda, Santa Clara and San Mateo counties. They prefer high grounds where Salicornia is more prominent, as the plant protects them from predators and gives them shelter. Currently their habitat is 6 to 8 feet above sea level but sea level rise is threatening their survival. They have been listed as a California Species of Special Concern due to human development of salt-marshes specifically in San Francisco Bay.

Monterey vagrant shrew Sorex vagrans paludivagus

The Monterey vagrant shrew is a subspecies of the vagrant shrew, which is found throughout the Pacific Northwest. The Monterey vagrant shrew is most common in the Sierra Nevada and along the coastlines of Monterey Bay. In the bioregion, they are mostly found in salt marshes all along the South San Francisco Bay and coastline. Their range includes San Mateo and Santa Clara Counties. The Monterey vagrant shrew’s habitat is currently threatened by human development, including fragmentation, land conversion, and burning. Its habitat and population is projected to be negatively impacted by sea level rise and pollution.

Pallid bat Antrozous pallidus (CSC)

The pallid bat is a yellowish-brown bat with white or cream fur on its belly. This species is notable for its incredibly large ears, which are equivalent to half the length of their head and body. Pallid bats prey on large ground arthropods, such as Jerusalem crickets and scorpions, catching their food primarily by passive listening for the sounds of arthropods on the ground. They are found throughout the western United States, as far north as British Columbia and as far south as Central Mexico. These social bats roost in colonies of 20 to 100 individuals in caves, crevices, buildings, and old mines. In Central California, their main roosting habitats include old oak trees as well as buildings and bridges. They are not very common in the bioregion but they have been found roosting in the Red Barn in La Honda. They are most affected by human disturbance to their roosting areas, such as destruction or restoration of old buildings. In addition, they are threatened by human development from habitat loss and pesticide use.

Townsend's western big-eared bat Corynorhinus townsendii (CSC)

Townsend's western big-eared bat is a medium sized bat with long ears. When extended, their ears are half the length of their body. They prey on moths, beetles, and other flying insects; foraging along the edge of vegetation. They are found throughout the western United States, as far north as British Columbia, and as far south as Central Mexico. They prefer to roost in large cave-like features, rather than the cracks and crevices preferred by other bats. This species is incredibly sensitive to human interference, and will abandon a roost site if it has been altered. In the bioregion, they depend on abandoned buildings and natural caves, putting their colonies at risk when these structures are renovated or destroyed. Historically in the bioregion, they roosted in hollows of old growth redwood trees and can still be found in redwood hollows. However, second growth forests lack sufficiently large hollows and this cave-like roosting feature is less available. There is evidence of Townsend's western big-eared bat living on UCSC campus as well as evidence of a colony living in the old creamery in the Año Nuevo state reserve.

Western red bat Lasiurus blossevillii (CSC)

The western red bat is a solitary species that roosts in the foliage of trees and shrubs, usually adjacent to streams and open fields. This bat is distinguished from other Myotis species, as they do not form large colonies and prefer trees to caves and buildings. The range of this species extends through Canada, the western United States, Mexico and Central America. Within the bioregion, this species may be found throughout the San Francisco Bay Area and surrounding foothills. However, there is also documentation of western red bats roosting on the University of California, Santa Cruz Campus. The western red bat is a migratory species, moving to the southern part of their range to hibernate through winter and gathering at nursery roosts in the summer. There is currently no proposal for listing this bat as threatened or endangered in the United States but bat specialists are concerned that the loss of suitable habitat is affecting population numbers. The main factors putting the western red bat at risk are the loss of habitat due to agricultural land development and creation of water storage reservoirs. However, intensive use of pesticides in fruit orchards may also pose a threat to roosting bats and significantly reduce the amount of insect prey available. Controlled burns and wildfires also pose a threat to this species, due to their roosting habits. This migratory species may also be affected by collisions with wind turbines, resulting in a high rate of mortality.

Fringed myotis Myotis thysanodes

The fringed myotis is a member of the long-eared myotis group, named for the short, wire-like hairs on the membrane between their hind legs. They are light brown or olive in color, with white undersides. The fringed myotis preys on flying insects such as beetles and moths, using the wire-like hairs on their hind legs to help them catch prey in flight. They are found throughout the western United States, as far north as British Columbia, and as far south as Central Mexico. Their preferred habitat is desert shrubland, grassland, woodland, and coniferous forests where they like to roost in trees. They inhabit the entirety of the bioregion, but are threatened by human disturbance to their roosts. Like many other sensitive bat species, they will abandon their roosts if they have been disturbed. They also face habitat loss and destruction.

Long-legged myotis Myotis volans

The long-legged myotis is a bat so named because their legs are long relative to their feet. They can be found in forests in western North America and central Mexico. They establish their roosts in trees, rock crevices and stream banks. Their ears are relatively short in the myotis family and some vary in fur color; either a reddish brown to nearly all black. They mostly feed off termites, spiders, flies and beetles. Currently bats in temperate North America are being threatened by a fungal disease named “white-nose syndrome”. This disease is deadly, and can spread rapidly in cold humid temperatures during the hibernation season.

Ringtail Bassariscus astutus (FPS)

The ringtail is a nocturnal, cat-sized mammal of the raccoon family that can be found throughout the southwest United States. It has a raccoon-like tail that is nearly as long as its whole body, with white and black stripes. Ringtails are omnivorous, and known to eat a variety of foods from reptiles, birds, and rodents to fruits and insects. They are typically found in chaparral, oak forests, redwood forests, and riparian areas; preferring rocky areas with water available. They raise their offspring in dens, which they switch every two to three days to avoid predators. These dens are made in tree hollows, under rocks, abandoned dens from other animals, or mine shafts. The once common ringtail was trapped excessively for its fur in the past, leading to a drastic decline in the population. In 1968, it was granted fully protected status, allowing populations to slowly recover. Although the species has recovered throughout the southwest, there is little known about the state of ringtail populations in the bioregion. It is currently listed as a Federally Protected Species (FPS), and is also protected under the California Game and Fish code.

Santa Cruz kangaroo rat Dipodomys venustus venustus

The narrow-faced kangaroo rat, also known as the Santa Cruz kangaroo rat is a subspecies endemic to the Santa Cruz Mountains. They have similar characteristics to mice but their darker skin, larger ears and wide feet set them apart. They have long tails and use their long legs to hop around, hence their name. They are about the same size as a mouse but the males are slightly larger than the females. Several species of kangaroo rats can be found in the coastal ranges of central California from San Francisco south nearly to Santa Barbara. Kangaroo rats are burrowing rodents and live in underground dens made in sandy soils associated with grasslands or chaparral habitats. In the bioregion they occur in Ben Lomond Sandhills and on the east side of the Santa Cruz mountains. They mostly feed on seeds, gains and nuts. Habitat fragmentation, introduced predators (such as house cats) and habitat destruction are major threats. Habitat restoration through prescribed burning can help expand the kangaroo rat’s range.

Beaver Castor canadensis

The beaver is native to the bioregion but has been re-introduced after a drastic decline in populations to the watersheds of coastal California and the San Francisco Bay. They can now be found in Pescadero Creek, Los Gatos Creek, and the Guadalupe River. Beavers inhabit permanent water-bodies including lakes, streams, ponds, and rivers. Beavers are considered a keystone species because of their strong influence on their aquatic habitat – having the ability to build dams to meet their needs. This makes them adaptable to diverse landscapes and helps to create habitats for other wetland-loving species. Factors putting this species at risk include threats to their habitat such as destruction and degradation. The growth of human populations and the increasing demands for water resources lead to water storage, diversion, and channelization projects that affect bodies of water inhabited by beavers. Intense grazing from livestock in riparian zones also contributes to the degradation of beaver habitat.

San Francisco Dusky-footed Woodrat  Neotoma fuscipes annectens  (CSC)

The San Francisco dusky-footed woodrat is currently not at risk of extirpation in the Bioregion but is considered to be a keystone species in several biotic communities. It is one of 11 subspecies that live in California and the arid west. They are medium-sized rodents, about the size of an adult rat, with a body around 7 inches long, nose to rump, and a furred tail. They live in a variety of brushy and forested habitats. Woodrats are relatively common and widespread in our bioregion, but their complex social structure makes them particularly vulnerable to disturbance. A different subspecies found elsewhere, the riparian woodrat (N. f. riparia), has been listed as Endangered on the federal list because of habitat loss and disturbance.

Woodrats build mounded stick lodges that may range in size from 3 to 8 feet across at the base and as much as 6 feet tall, and they tend to live in colonies of 3 to 15 or more lodges. The lodges or houses can be quite complex inside, with multiple chambers for general living, nesting, latrine use, food storage, and other activities. The availability of suitably-sized sticks may limit the number of woodrat houses.

Each house is occupied by a single adult; adult females share the nest with their litters for a few months until the young disperse to nearby nests. Adult female woodrats live in the same nest until they die, when the nest is taken over by one of the female offspring. In this manner nests may be occupied and maintained by the same family for decades. Individual lodges may persist for 20 to 30 years. Reptiles, amphibians, small mammals, and invertebrates are frequent commensals with the woodrats, sharing the lodges for shelter. Woodrat nests provide protection from temperature and moisture extremes and allow animals that might not otherwise tolerate local conditions to live there, increasing the biotic diversity.

Salt-marsh harvest mouse Reithrodontomys raviventris (SE, FE, FPS)

The salt-marsh harvest mouse is currently listed at risk at both the federal and state level. They are split into two subspecies, northern and southern. The northern subspecies can be found to the north of the bioregion (Napa, Petaluma, and Suisun marshes); the Southern subspecies is found in south San Francisco Bay (San Francisco, San Mateo, Fremont, and Alviso marshes). These species are supported by dense, high salinity tolerant vegetation, specifically pickleweed (Salicornia). Pickleweed serves as food and, along with adjacent cordgrass (Spartina), serves a safe escape during high tides. The tidal salt marshes home to this species have been heavily fragmented due to levees, construction and human activity. This low-lying habitat is also at high risk to rising sea levels, and much habitat was previously lost by land subsidence and levees constructed in response to flooding risk.

American badger Taxidea taxus (CSC)

The American badger has been listed as a California Species of Special Concern. It is currently at risk within the bioregion and throughout their entire range in California. Its range has contracted in recent years but little is known about population size. They are potentially rare within the Santa Cruz bioregion. They prefer habitats with sufficient prey food sources, friable soils, and relatively open land. They feed mainly on burrowing rodents and some insects. The American badger once had the largest range of all badger species, being native to the North American grasslands stretching from Canada down through Mexico. Within the bioregion they can be found in the grasslands, ranging from coastal terraces, such as near UCSC to the summit. Habitat fragmentation has been the primary cause of the population decline of American badgers in California due to agricultural land and urban developments and to highways with fences or K-rails. Mortality on highways is high. Rodent poisons used on agricultural land also poses a threat through direct and secondary poisoning, and also by elimination of food that the badgers depend on.

Mountain lion Puma concolor (CSC)

Mountain lions, also known as cougars or pumas, are the fourth-largest cat species in the world. Their range is quite large extending from Canada to South America. The lengths of mountain lions from nose to tail are usually 7 feet long for males and 6 feet for females. Males weigh around 130-150 pounds while the females weigh between 65-90 pounds. Their fur is usually unspotted with light brown color. They live in a wide range of habitats from deserts to mountains, and lowlands to canyons. Their preferred habitats in the bioregion are forested areas. Mountain lions are solitary creatures and are rarely sighted by humans. They rarely attack people and mostly keep their distance. Deforestation, habitat fragmentation and highways (with associated road kill) pose a problem for the species. Though their numbers overall are stable, in some regions they are close to endangered or extinction. Due to large home ranges, and low population density, sustaining mountain lions in the bioregion may depend upon maintaining movement corridors with the Diablo range to the east and the Gabilan range to the south. Immigration may be necessary to maintain genetic diversity and population density.

Acknowledgements: The Bioregional Council would like to express its gratitude to UCSC Environmental Studies interns Carmela Ceniceroz, Fiona Donovan, and Maya Lara for contributing these descriptions of sensitive mammals. We would also like to extend our thanks to instructor Justin Luong and the Norris Center for Natural History at the University of California at Santa Cruz.