Mammals of Torrey Pines State Natural Reserve

(This information on mammals has been selected from the booklet, Vertebrates of Torrey Pines Reserve, by D. Hunsaker.)

The two basic types of land mammals are the predators and the prey species, and neither of these two likes to be around humans. As a result, although there are numerous land mammals around, we seldom see them and often have to be content with second-hand evidence of their activities. Tracks, droppings, den sites and other clues can often inform us as to their activities. The most commonly seen mammals will be the California Ground Squirrel and the Cottontail Rabbits. Both these species are relatively tolerant of humans, are moving about during the daytime, and can be observed with little difficulty. The larger black-tail jackrabbit can be seen in the more open areas near the lagoon and in the flat lands. Most of the other animals are nocturnal and will be seen in the early morning or late afternoon as they begin or end their nocturnal movements. Skunks, raccoons, opossums, weasels, pocket gophers, gray fox, coyotes, and mule deer will all be seen occasionally by a good observer.

Mule Deer (Odocoileus hemionus) There is only one species of deer in Southern California, the Mule or Black Tail Deer. Although tame in many national and state park areas, the ones that live in the Reserve are very secretive. They can occasionally be observed feeding in the flat lowlands in the early mornings and then retreat to brushy cover during the day. They feed commonly at night and are sometimes killed by cars on the highway, The Reserve is a true haven for this species, which is becoming increasingly rare as the urban development spreads.

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Carnivorses

Bobcat (Felis rufus) Bobcats are not common in the Reserve but certainly there are a few resident cats. The tracks are distinctive because the cat's claws are retracted and they do not leave claw marks in the dirt or mud. They are smaller than most people think, usually less than 15 pounds and about 30 inches long. The majority of the food they eat includes rabbits, wood rats, pocket gophers, and meadow mice, although a few birds are eaten.

Photo by Todd Nordness

They are not as destructive to bird life as most people think. They prefer dense cover for their hunting and denning area. The dens are frequently associated with rocky outcrops where three kittens are born in February, April, or May. A sharp eye is needed to distinguish these cats sunning themselves in the morning while partially concealed on a rock or log.

Coyote (Canis latrans) The coyotes have learned to adapt to human civilization and as a result are very common within the city limits of San Diego. They will eat almost anything and it is not unusual to find pieces of plastic, candy wrappers, and paper in their droppings. Primarily they feed on mice but commonly eat seeds when they are available. It is almost impossible to distinguish the tracks of a coyote from the common dog, but any large sized scat (fecal material) that contains a significant amount of hair, fur, and seeds can be considered to be a coyote. They raise their families of six or seven pups in the early spring, concealed in dens dug into the side of a bank or in tree roots. They can be seen occasionally trotting across the road or out across open spaces where they can be identified by the habit of dragging the tail down rather than elevated as the domestic dog does. return to top

Gray Fox (Urocyon cinereoargenteus) This very common animal is seldom seen, but the small tracks, about one inch across with well defined claw marks, suggest that it is active throughout the Reserve. The fox preys primarily on gophers, mice, and wood rats and is especially fond of manzanita and toyon berries when they are in season.

Raccoon (Procyon lotor) The raccoons, like the bears, have a plantigrade foot, which means they walk on the sole of their foot and the palm of their hand, instead of only on their digits, like many other animals. The raccoon is easily identified by the black mask and ringed tail and is most commonly associated with the lowlands where it feeds on crayfish, crustaceans, seeds, etc. The tracks are very distinctive with a large hind foot track with very distinct toe marks and a smaller front foot track. On damp and rainy nights in the fall, they can often be heard vocalizing with a rather plaintive and drawn out "whooo" call.

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Rabbits and Hares

Audubon Cottontail (Sylvilagus auduboni) This is one of the most common mammals that will be seen at Torrey Pines. It prefers to live in rather open brush and can be seen darting from bush to bush when it is surprised by another animal or person. Its small, fur-lined nest built on open ground can sometimes be seen by a careful observer. Very usually there are one to five baby rabbits born in the litter, all born with their eyes closed and no fur. The cottontail rabbit has dark hair and fur on the tips of the relatively short ears and a conspicuous white tail.

Brush Rabbit (Sylvilagus bachmani) This smaller version of the cottontail may be easily confused with it. The main difference is the smaller tail and the ears are solid brown without the darker tips. It breeds primarily in the spring time and has from three to six babies per litter. It prefers much denser brush than the cottontail.

Blacktailed Jackrabbit (Lepus califomicus) This large rabbit, which is really a hare, can be seen in the open areas of the lowlands. It seeks shelter in the brush when disturbed, but usually relies on its long legs and rapid speed to avoid predators. They breed year round and will produce as many as seven young hares per litter. The young are born fully haired, with the eyes open, and therefore referred to as precocial.

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Rodents

California Ground Squirrel (Otospermophilus beecheyi) This is the most common mammal in the Reserve and can be seen feeding near the mouth of its burrows. It is diurnal and leaves well-marked trails where it lives. It can be seen both in the upland and lowland areas, but prefers dry rocky soil to live in. It is considered a pest by many, but its ringing call is very distinctive and they are very pleasant animals to watch as they industriously raise their families and sun themselves on the rocks.

Valley Pocket Gopher (Thomomys bottae) Gophers are very common but will seldom be seen above the ground. They do spend a lot more time above ground than most people think and can occasionally be seen cautiously moving from one area to another with their tiny eyes and small ears testing each movement and sound of the environment. Most of the time they stay underground eating roots and occasionally you can see a blade quiver and suddenly disappear directly into the ground before your eyes. The burrows are quite extensive and can be interconnected for a distance of 50 feet. They dig to the surface of the ground in the excavations and then refill the hole with the soil, Although they are the scourge of many gardeners, they are part of the ecosystem return to top

Pocket Mice (Perognathus) There are two species of Pocket Mice, the California Pocket Mouse (P. californicus) and the San Diego Pocket Mouse (P. fallax), both of which are found in the Reserve. The California Pocket Mouse lives in more brushy areas than the San Diego Pocket Mouse which is more adapted to a drier environment. Both are named because of the fur-lined pouches which they fill with seeds and take back to the burrows to be stored and eaten later. They are mouse-sized animals with long tails and a tuft of hair on the end.

Pacific Kangaroo Rat (Dipodomys agilis) The kangaroo rats are remarkable animals which can live without any surface water. They manufacture their own or extract it from the food that they eat. They live underground and close the entrance to their burrows in the daytime so they can maintain adequate moisture and heat control in their burrow system. The total length, including the long tail, is about 12 inches and when seen at night, they are hopping around with their elongated hind legs and long tail with a large tuft of hair on the end dragging on the ground. When excited they can leap straight into the air and land two or three feet from where they started. They are very gentle creatures and spend their active hours filling their cheek pouches with seeds and trying to avoid predators.

Western Harvest Mouse (Reithrodontomys megalotis) These nocturnal mice can be found in the lowland areas and are one of the few rodents that are active on moonlit nights. They are well adapted to living in the coastal marsh area since they can drink sea water and excrete the salt. Pregnant females can be seen every month of the year and raise a family in small round nests built of grass leaves that are above the ground. They line the inside of the nest with fur and raise from four to six young.

Deer Mice (Peromyscus ) There are three species of deer mice that live in the area: the California Mouse (P. califomicus) which is a rather large mouse about 10 inches in length with very large prominent ears; the Deer Mouse (P. maninclatus), which is a smaller mouse, about 7 inches long and can be distinguished from the others because its tail is shorter than the body length. The Cactus Mouse (P. eremicus) is about 8 inches long and inhabits the drier parts of the Reserve. The population of these mice is usually very dense, and they serve as a very basic food supply for many of the carnivores which live in the area. All are nocturnal and feed on larvae and pupae of insects as well as seeds and plant material. Some species breed in the fall, others breed all year round, but all produce litters numbering from 3 to 6 young with a gestation period of 22 to 25 days. return to top

Grasshopper Mouse (Onychomys torridus) These are rather small mice which can be distinguished from the deer mice by the fact that the tail is less than 70 percent of the body length. They live in grassy areas and are fond of feeding on insects and other arthropods that live in the grass. They are one of the most vocal of the rodents and can sometimes be heard squeaking in the grass, giving their alarm call or possibly fighting each other. They breed all year round and raise a family at the end of a short underground burrow. They are a very beneficial mouse within a very important part of the ecosystem because they feed on the arthropods which, if uncontrolled, could do a considerable amount of damage to the plant life.

California Meadow Mouse (Micrstus californicus) This common mouse lives in a well-defined series of burrows and is one of the few rodents that are active during the daytime. They prefer to live in meadows and grassy environments. They have very small ears and short tails and give the general appearance of being somewhat near-sighted when they are looking at you from the safety of their burrow.

House Mouse (Mus musculus) The ubiquitous house mouse will be found wherever people are. It can be identified by its solid gray-brown color, and the hairs on the tail are so scarce that the tail has a scaly appearance. It will be found near the office and any other human habitation.

Common Rat (Rattus rattus) This is another animal that lives wherever people are. It too has a scaly tail with few hairs. It will be seen wherever people are because it has lived with them for generations. return to top

Wood Rat (Neotoma) There are two species of wood rats that live in the Reserve: the Dusky-footed Wood Rat (N. fuscipes) and the Desert Wood Rat (N. lepida). Both these species build a rather complex nest, the dusky-footed wood rat with small sticks and the desert wood rat using pieces of cholla or beaver-tail cactus. The nests of the former can reach an amazing size of 3 to 4 feet high by 5 or 6 feet long. The desert wood rat is slightly smaller than the dusky-footed wood rat and has a tail about three-quarters the length of the head and body. The dusky-footed wood rat has a tail the same length as the head and body. They are primarily herbivores and breed in the springtime. The young stay attached to the teats of the mother while she is in the nest and if disturbed she will leave the nest and scurry away with the young family attached to her.

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Mustelids

Long-tailed Weasel (Mustela frenata) This curious long-bodied animal can occasionally be seen moving rapidly through the brush in search of small rodents and birds. Its yellowish-brown body and daytime activity periods make it reasonably easy to observe. It is generally unafraid of people and will sometimes sit on its rump with its body erect and look directly at you as if to challenge your right to be in its territory. They breed in the latter part of the summer and after a gestation period of 279 days the six to nine offspring are born in the spring. They have very well-developed scent glands and have a very strong odor.

Skunks (Mephitis spilogale) The striped skunk (Mephitis mephitis) and the smaller spotted skunk (Spilogale putorious) can occasionally be observed during the daytime but are primarily nocturnal animals which move through both the upland and lagoon areas of the Reserve. The spotted skunks are much more active and graceful than the striped skunks and have a very curious method of protecting themselves. In addition to erecting its tail, it will stamp its forefeet on the ground and, if pushed even further, it will do a handstand on its front feet, all the time with its beady eyes watching you intently and with its scent gland on the ready. This has an excellent advantage in that, if a dog or coyote approaches the animal and bites it, the part of the animal that is presented next to the predator is the tail, which has dense hairs and would not cause any particular problems if it was bitten. In addition to this, the predator gets a full face spray of the scent which would deter it. The striped skunk usually will make short rushes towards an adversary, growling and stamping the ground with its forefeet, and if molestation continues, it will spray the oily secretions of the scent gland directly into the face of the intruder. Both species are insectivorous and also feed on rodents, small bird eggs, and will occasionally raid a trash can.

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Marsupials

Virginia Opossum (Didelphis virginiana) The opossum is an introduced species which has done very well in San Diego County and is now considered to be a permanent resident. It was first introduced in 1890 by a 'possum lover in Los Angeles and has subsequently spread from Canada to Baja California. Breeding takes place in January and February, and the young are born 13 days after copulation. The babies are born and crawl across the mother's stomach into a pouch where they spend the next two months firmly attached to the nipples. By the time they are 100 days old, they are ready to fend for themselves and leave the mother to begin a rather solitary existence. They eat almost everything and appear to do very well in close proximity to human habitations and can be expected to be found in all parts of the Reserve.

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Insectivora

Ornate Shrew (Sorex ornatus) This shrew is distributed along the southwestern portion of the state and lives in the grassy areas in the lower part of the Reserve. They are about the size of a house mouse or a little smaller with very small eyes and very quick nervous movements. They are carnivorous and are continuously on the search for insects and small mice on which they feed.

Gray Shrew (Notiosorex crawfordi) This small and very rare shrew can be expected to occur in the drier areas of the Reserve. It is primarily adapted for living in arid areas rather than damp areas like the ornate shrew.

Broad-handed Mole (Scapanus latimanus) This species will seldom be seen above ground but the burrows through the soft ground of the lowlands will be seen from time to time. They burrow immediately under the ground and as a result leave a raised path of soil which marks their underground tunneling. They are almost blind, and the front feet are very broad and flattened to enable the animal to literally swim under the ground as it digs. They feed on earthworms primarily, but also eat the roots and seeds of many of the plants that are found in the habitat.

Bats

The bats of Torrey Pines State Natural Reserve are rather rare because the wings are highly vascularized, and the low temperatures of the air lower the body temperature. The wing membranes are leathery and are spread between the third, fourth, and fifth digits, the forearm, the upper arm, and the hind leg. The thumb remains as a very small claw-like appendage on the front of the wing, and the hind foot still has distinct toes and claws on it. The Myotis Bats are the most common in the area. There are three or four species which are very difficult to identify, even when you have them in your hands. Larger bats that are seen will be either the Hoary Bat (Lasiurus cinerus) or the Red Bat (Lasiurus borealis). All the bats are insectivorous and nocturnal. Bats can serve as carriers for rabies and because of this, injured or sick bats should never be handled. This is a more complete list of bat species observed in the Reserve or nearby:

California Myotis (Myotis californicus)
Yuma Myotis (Myotis yumanensis)
Big Brown Bat (Eptesicus fuscus)
Hoary bat (Lasiurus cinereus)
Western Red Bat (Lasiurus blossevillii)
Mexican Free-tailed bat (Tadarida brasiliensis)
Pocketed Free-tailed bat (Nyctinomops femorosaccus)
Western Mastiff Bat (Eumops perotis)

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Aerial photos of Torrey Pines State Beach