Amphibians of the Angelo Coast Range Preserve, Mendocino County, California
The Angelo Coast Range Preserve is located about 32 km west of Laytonville, on the South Fork of the Eel River. Originally protected by Heath and Marjorie Angelo, the preserve was later purchased by The Nature Conservancy. At the time it was referred to as the Northern California Coast Range Preserve. Eventually it was transferred to the University of California (UC). Today it is part of the UC Natural Reserve System.
The preserve totals 3,166 hectares (7,915 acres) in size, including 1,766 hectares (4,415 acres) of UC land, and 1,400 hectares (3,500 acres) controlled by the Bureau of Land Management. Elevations range from 378 to 1,290 meters (1,240 to 4,231 feet) above mean sea level. Except for level terraces along the Eel River, the site is characterized by steep terrain.
The Angelo Coast Range Preserve protects one of the largest remaining stands of old-growth Douglas fir in California. Other natural communities widespread on the site include chaparral on south facing slopes, and annual grassland openings on the Eel River terraces. Smaller areas of Oregon oak woodland, knobcone pine woodland, and various other communities are present. A few redwoods occur near the river. The entire watersheds of Elder Creek and several smaller streams are protected within the preserve.
The preserve is characterized by hot, dry summers and mild, rainy winters. Below freezing temperatures are relatively uncommon and snow is rare. Average annual precipitation is 216 cm (85 inches), almost all of it between October and April.
This report summarizes my site inventory efforts conducted in the winters of 1985 and 1986; in the fall of 1992; and in the spring of 1995. Additional amphibian inventory information is available from Mackey (1981) and Welsh and Lind (1988, 1991). Mackey's information is for the entire preserve. That of Welsh and Lind is lumped with numerous other sites in California and Oregon, and no site specific information has been published by them.
Visual encounter surveys were conducted on January 23, 1985; February 14-21, 1986; October 16-17, 1992; and March 12-13, 1995. The greatest effort was concentrated within Douglas fir forest, especially along Skunk Creek and lower Elder Creek, and in the grassland openings. Cover objects were turned and replaced. Most work was done during the day, although some limited nocturnal searches were also conducted. The 1986 sample was conducted during sustained heavy rainfall and flood conditions.
Animals were counted and released. Location and habitat type were noted. Representative examples were photographed for documentation.
The following accounts rely primarily on my own field data, but also include material from preserve managers where appropriate.
A total of 149 individual ampibians were observed. I was able to document the presence of nine amphibian species (seven salamanders and two frogs) at the Angelo Coast Range Preserve. One additional salamander and three additional types of frogs have been reported. Abundance and habitat information is included below in each species account.
One species, the California Slender Salamander, made up 45.6 percent of all observations. It and two additional species, the Rough-skinned Newt and the Ensatina, account for 76.5 percent of observations.
Northwestern Salamander - Ambystoma gracile. Although not noted during my site visits or reported by Mackey (1981), former preserve manager Cameron Barrows reported a single 1984 observation of this species near lower Sugar Creek. Very little suitable breeding habitat is present in or near the preserve. Northwestern Salamanders are reportedly more common near the coast at Rockport. They are also known from Usal, at the southern end of Sinkyone Wilderness State Park (Lynne Houck, pers. comm.).
Pacific Giant Salamander - Dicamptodon tenebrosus. Larvae are common and easily found in most perennial streams on the preserve; in Fox Creek they are the most abundant vertebrate (Parker 1994). Adults are less often encountered. In 1986, I observed a large adult behind a small waterfall in the mid-reaches of Skunk Creek. Large neotenic adults, often over 200mm total length, occur in the larger streams (Parker 1994).
Southern Torrent Salamander - Rhyacotriton variegatus. Four adults were observed on three different site visits. two were along Skunk Creek, and two on Sugar Creek. All were within the splash zone of small cascades. The species has also been reported from headwater streams in the Elder Creek drainage (C. Barrows, pers. comm.). This locality is near the southern/inland limits of the range for the species.
Rough-skinned Newt - Taricha granulosa. Newts are moderately common on the preserve, and were observed on three of four visits. Several were in the open and active on overcast days, while others were found under cover objects. Most were within Douglas fir forest.
Black Salamander - Aneides flavipunctatus. This species was observed only during the spring visit. Specimens were noted near forested stream margins, and under a log on the partially open edge of Wilderness Road.
Wandering Salamander - Aneides vagrans. Both specimens were found under loose bark of Douglas fir snags in a small forest clearing on lower Elder Creek, near the USGS gaging station.
California Slender Salamander - Batrachoseps attenuatus. This is the most frequently observed amphibian on the preserve. A total of 68 individuals were seen, and it was the only species noted on every site visit. Observations were made in Douglas fir forest, Oregon oak woodland, and in grassland openings.
Ensatina - Ensatina eschscholtzii. This is another common species, seen on three of four visits. Observations were made both in wooded and grassland areas.
Tailed Frog - Ascaphus truei. This species was not observed by me. It is reportedly relatively common in the upper part of the Elder Creek drainage, with most observations made at night during the summer months (C. Barrows, pers. comm.). This locality is near the southern/inland limits of the range of the species (Welsh, 1985).
Western toad - Bufo boreas. Most reports have been from the spring months, usually in grassland openings or around buildings. It was not noted during this study, but was found by Mackey (1981).
Pacific Tree Frog - Pseudacris regilla. A few individuals were found under rocks on an open hillside near Wilderness Lodge.
Foothill Yellow-legged Frog - Rana boylii. Observed only during the fall visit. Numerous juveniles and a few adults were seen among rocks at the shallow margins of the Eel River. Two juveniles were found under rocks in lower Elder Creek.
Bullfrog - Rana catesbeiana. This non-native eastern species was not known from the preserve during the early part of my study, but reportedly moved up the Eel River sometime prior to 1995 (P. Steel, pers. comm.).
Table 1. Amphibian observations by year, 1985-1995
Table 2. Observations by Mackey (1981) and by Mierzwa (this report)
| ||Mackey (1980-81)||Mierzwa (1985-95)|
Preserve managers Cameron and Kate Barrows (1985) and Peter Steel (1986 to present) provided hospitality and valuable information. Ellin Beltz participated in 1995 field work.
Mackey, James P. 1981. An inventory of the amphibians and reptiles of the Northern California Coast Range Preserve (Mendocino County). Unpublished Report, San Francisco State University. 29p.
Parker, Michael S. 1994. Feeding ecology of stream-dwelling Pacific Giant Salamander larvae (Dicamptodon tenebrosus). Copeia 1994:705-718.
Welsh, Hartwell H., Jr. 1985. Geographic distribution: - Ascaphus truei. Herpetological Review 16:59.
Welsh, Hartwell H., Jr., and Amy J. Lind. 1988. Old growth forests and the distribution of the terrestrial herpetofauna. Pp. 439-455 - in: Robert C. Szaro, Keith A. Severson, and David R. Patton (eds.), Management of amphibians, reptiles and small mammals in North America. Proceedings of the Symposium. Flagstaff, AZ, July 19-21, 1988. USDA Forest Service Gen. Tech. Rept. RM-166.
Welsh, Hartwell H., Jr., and Amy J. Lind. 1991. The structure of the herpetofaunal assemblage in the Douglas-fir/hardwood forests of northwestern California and southwestern Oregon. Pp. 394-413 - in: L. F. Ruggiero, K. B. Aubry, A. B. Carey, and M. F. Huff (tech. coords.), Wildlife and vegetation of unmanaged Douglas-fir forests. USDA Forest Service Gen. Tech. Rept. PNW-GTR-285. 533p. Portland, OR.