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Stebbins Cold Canyon Reserve

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Cold Canyon is home to a fair diversity of the "lower vertebrates" - especially amphibians and reptiles - but the secretive nature of these creatures makes it difficult for naturalists and hikers to appreciate them. There are two other reasons it might be difficult to observe the reserve's resident amphibians and reptiles. First, as previously described, certain species may be active only during particular times of the day or during certain seasons. Second, some amphibians and reptiles live in restricted habitats of Cold Canyon and are therefore difficult to locate. For example, coachwhip and whiptail lizards prefer the dense growth of chaparral and thus do not come into contact with most humans. Other reptiles are primarily fossorial (underground dwellers) and so rarely see the light of day. As a result of these factors, some species are suspected to occur in Cold Canyon but have not been confirmed with a positive identification.
Below are descriptions of the most common fish, amphibians, and reptiles found in Cold Canyon. For a complete list of known and suspected species, look at the complete checklist.

Fish

Rainbow trout (Oncorhynchus mykiss). This native species is the only fish species that might on occasion be found in the creek. During rainy years, Cold Creek swells in its banks and some rainbow trout are capable of moving up from Putah Creek. When the creek dries in the summer, permanent pools in Wildhorse Canyon can provide a home for these trout. In such situations, these fish may survive to reproduce-starting a new generation in Cold Creek. However, this is a rare occurrence. In most years, the pools dry up and trout are excluded from the area, so rainbow trout cannot truly be considered permanent residents of Cold Canyon.

Amphibians

California newt (Taricha torosa). The California newt is a medium-sized salamander (5 to 7 in., or 12.7 to 17.8 cm, from head to tail), with textured skin that is tan colored on its back and orange on its belly. Newts have a complex and intriguing life cycle. In the pools of the creek, they hatch from eggs as tadpole-like juveniles. As the pools dry up, they metamorphose into their adult form and head for moist logs and holes in the ground. After the fall rains replenish the water in the stream, the adult newts return to the pools and actually metamorphose back into a larval form, which is larger but otherwise similar to the juvenile form, and reproduce. The best places to spot California newts are near the stream and on moist portions of the trail. In winter you can find the newts heading for the water, and in the spring you can find them heading back into the hills. At all times, newts move slowly and seem oblivious to other animals. Their nonchalance is likely due to their toxic skin-each gland contains noxious poison. They advertise this weapon with their bright orange belly, a warning recognized by most predators.

California slender salamander (Batrachoseps attenuatus). While these tiny (1 to 3 inches, or 2.5 to 7.6 centimeters, long), brown, wormlike salamanders are most active during the winter and early spring, they can be found in moist places under rocks and logs as late as June. Unlike newts, slender salamanders do not spend any of their life cycle in the water. In the winter, they lay their eggs underground. These hatch in the early spring, and the young are born looking like smaller versions of their parents.

Western toad (Bufo boreas). Western toads are 2 to 5 inches (5.1 to 12.7 centimeters) long, brown, and covered with warty bumps. These bumps hold toxins that make them unpalatable to potential predators. Toads spend their adult lives hiding in leaf litter and burrows and are usually active only at night. During the wet season starting in January, they come out of hiding to breed in Cold Canyon's pools. Males station themselves around the pools and attract females with weak, chirpy calls. Females lay fertilized eggs in the creek, and tadpoles hatch within several weeks. The tadpoles develop rapidly, metamorphose into tiny toadlets, and are out of the creek pools and hiding in the wooded slopes of the canyon by May.

Pacific treefrog (Hyla regilla). These 1- to 2-in. (2.5- to 5.1-cm) frogs are the most common frogs in California. They come in many colors, from green to tan to brown, and individuals can actually change color fairly rapidly. Fortunately, a dark eyestripe that does not change color distinguishes these frogs from all others in Cold Canyon. Contrary to their name, Pacific treefrogs generally stay near the ground, although their padded toes enable them to climb if they need to. Like western toads, Pacific treefrogs breed in the pools of Cold Creek from January to May, and, during this time, males attract females by calling. Their repeated krek-ek calls, which seem much too loud for such a small creature, are the most common type of frog call that Californians hear. Eggs are laid in streams and hatch into tiny black tadpoles, which rapidly metamorphose into the adult form.

Foothill yellow-legged frog (Rana boylei). These medium-sized (1- to 3-in., or 2.5- to 7.6-cm) frogs can be identified by their mottled back and yellow underside and their tendency to dive into pools and hide in the muck at the bottom when disturbed. Yellow-legged frogs breed from March to May and will stay in the vicinity of the creek the entire year. As a result, they are the first to return after the fall rains begin, and male yellow-legged frogs initiate the breeding season with their grating, guttural calls. Of all the amphibians in Cold Canyon, the foothill yellow-legged frog is perhaps the most endangered. Although they are locally abundant, yellow-legged frogs have suffered huge declines across the state, largely due to habitat destruction and introductions of non-native predatory fish.

Reptiles

Western fence lizard (Sceloporus occidentalis). These "blue-bellies" are the most common reptiles in Cold Canyon and probably all of California. They are 4 to 6 inches long from head to tail, with brown and black blotches or lines on their spiny-scaled back. They can be seen along much of the trail and colonize the creek bed when it dries up. Most lizards, especially the males, sport blue patches on their throats and the sides of their bellies. They use these to communicate by "push-up" displays, during which they lift the front of their bodies repeatedly with their front legs. Western fence lizards provide a surprising service for humans and potentially other mammals in the canyon. Deer ticks, which carry Lyme disease, bite lizards as well as humans, but unlike humans or any other vertebrate, western fence lizards produce a substance that kills Lyme disease. When a tick attaches to a lizard, the substance in the lizard's blood enters the tick and kills the Lyme disease bacteria inside the tick. As a result, areas that have lots of western fence lizards have a low prevalence of ticks infected with Lyme disease. Therefore, a large population of lizards reduces the possibility of Lyme disease infection in humans.

Western skink (Eumeces skiltonianus). Western skinks are small (3- to 7-in., or 7.6- to 17.8-cm), smooth-scaled lizards that undergo a change of color as they grow into adults. Young skinks are brightly striped and have showy, almost neon blue tails, while adults are generally brownish with an orange head and tail. Herpetologists speculate that the blue tails of young skinks help them escape predators. If the predator is quick enough to catch a young skink, it is attracted to the coloration of the tail. When grabbed, the tail readily breaks off and thrashes about with a life of its own, distracting the predator, while the skink quickly runs for cover.

California whiptail (Cnemidophorus tigris). Whiptails are the sprinters of the reptile world. These medium-sized lizards (4 to 8 in., or 10.2 to 20.3 cm), characterized by stripes and bars coloring their small scales, can run up to 30 miles an hour if pressed. Usually they are seen moving nervously underneath shrubs. Approach them, and they will rapidly skitter into the chaparral. Like skinks, whiptails are born with blue tails, which they lose as adults.

Southern alligator lizard (Gerrhonotus multicarinatus). These are the largest lizards in Cold Canyon, ranging from 6 to 12 inches (15.2 to 30.4 centimeters) in length from head to tail-tip. Alligator lizards have smooth tan scales with darker bars, and they never seem to blink their beady eyes. They are often found in grasslands chasing insects, small lizards, and young mice, but will also climb trees and eat bird eggs.

Western yellow-bellied racer (Coluber constrictor). These olive or brown smooth-scaled snakes can get up to 7 feet (2.1 meters) long. They are well named, for they move at surprising speeds when chased. Racers are often found in grasslands and savannas. They prey on many small vertebrates, especially lizards.

Gopher snake (Pituophis melanoleucus). These 3- to 8-foot-long snakes (0.9 to 2.4 meters) have cream-colored, keeled scales with brownish blotches or stripes. They often look like rattlesnakes, and in fact they are known to imitate them. A defensive gopher snake will often rear up, hiss, and shake its tail in the leaf litter to simulate a rattle. While they have a nasty temper, gopher snakes are not poisonous and kill their primarily mammalian prey by constriction.

Western aquatic garter snake (Thamnophis couchi). These thin, striped snakes may get up to 6 feet (1.8 meters) long, but most are about 3 feet (0.9 meters) in length. Aquatic garter snakes are dark green with a yellow stripe running down each side of their body. They are often found in Cold Creek's pools or basking on nearby rocks. Garter snakes do not lay eggs, but instead allow the eggs to develop in their body and bear the young live.

Western rattlesnake (Crotalus viridis). This is the only venomous snake living in Cold Canyon and Northern California. It grows up to 6 feet (1.8 meters) in length and is covered in gray or brown keeled scales. This snake uses its conspicuous rattle at the end of its tail to create a buzz-like warning noise when it is startled. It is active from April to October, but is most frequently encountered from May to July. Rattlesnakes are common in the reserve, but are most often seen on the dry hillsides rather than in the canyon bottoms. Although potentially deadly, this rattlesnake is not aggressive and usually retreats unless cornered or provoked. Young rattlers tend to be more dangerous than adults, because young do not retract their fangs when they strike, and therefore are much more likely to inject large quantities of venom into the bite. Rattlesnakes eat all types of small mammals, but they are best adapted to capture small mammals and birds. Small pits located on their faces enable the snakes to detect temperature differences. Therefore, they are readily attracted to warm-blooded animals. Not surprisingly, they often hunt at dusk, when they can most easily detect these temperature differentials.

Credits: All pictures except the Pacific treefrog image were obtained from Calphotos (http://galaxy.cs.berkeley.edu/photos/fauna/). The Pacific treefrog image was obtained from Mike Benard.

Last Updated 03/09/06