Sensitive Amphibians and Riparian Reptiles
Amphibian species live in the water or must visit there to reproduce and some reptile species, like the western pond turtle are also largely aquatic. The presence or absence of these species and their population health are indicative of aquatic habitat quality and they are an important part of our natural California heritage. Examples of sensitive amphibian and semi-aquatic reptile species below are not meant to be comprehensive, but rather illustrate use of amphibians in understanding healthy northern California aquatic habitats and riparian conditions.
In the redwood or Douglas fir forests of northwestern California, sensitive amphibian species like the tailed frog (Ascaphus truei) and southern torrent salamander (Rhyacotriton variegatus) may be better indicators of stream health than salmon and steelhead. They have very exacting habitat requirements and do not travel extensively during the course of their lives. Their viability has been linked to the presence of cold water and clean coarse streambed substrates (Welsh and Ollivier, 1998). If these creatures are diminished or disappear, it is often as a result of habitat change in their immediate, local environment. By comparison, salmon and steelhead travel thousands of miles during their life and may be impacted by adverse habitat conditions in main river environments, estuaries or in the ocean. In low flow years, anadromous fish may not reach some upper watershed areas. In addition, commercial and sport fisheries may sometimes factor into population declines of salmon and steelhead, not so with these two amphibians .
The southern torrent salamander inhabits headwater streams where it often spawns in springs and seeps in headwall areas. The adult southern torrent salamander and the adult tailed frog both breathe through their skin and, therefore, require cool, highly humid riparian zones for survival. Adult tailed frogs may live up to sixteen years, hiding under rocks in streams during summer and venturing into the forest during cooler periods in winter. The male tailed frog gives the name to the species, being the only frog species with an external copulatory organ. Tadpoles can take from one to five years in the stream to mature, and have a unique suction cup-like mouth which they use to maintain position in swift, headwater streams and to scrape periphyton off the rocks for food. The southern torrent salamander begins to show signs of thermal stress at 17.2 degrees C (Welsh and Lind, 1996) and tailed frog eggs are destroyed at 18.5 degrees C (Brown, 1975), so streams that support these species must maintain a cold-water thermal regime similar to that required by coho salmon (Welsh et al., 2001).
Both the southern torrent salamander and the tailed frog can be adversely impacted by logging (Bury and Corn, 1988; Welsh et al., 2000). Studies in Prairie Creek Redwoods State Park showed that increases in fine sediment negatively impacted both species (Welsh and Ollivier, 1998). Extensive studies in the Mattole River watershed indicate that both these species are now at extremely low levels in the basin and restricted to the remaining old growth forest habitat (H. Welsh, unpublished data). Stream conditions after logging are often profoundly changed as temperatures increase, making egg survival problematic. Even partial removal of stream canopy can increase water temperatures and decrease relative humidity along the stream corridor which can make these areas unsuitable for southern torrent salamanders (Welsh and Lind, 1996) and tailed frogs (Bury and Corn, 1988). The southern torrent salamander may be more tolerant of stream canopy removal in the redwood forests in the zone of marine influence (summer fog), based on its present distribution in altered landscapes (Diller and Wallace, 1994 as cited in Welsh et al., 2000). See summary charts by Dr. Hartwell Welsh of tailed frog and southern torrent salamander habitat relationships and pictures of habitats surveyed in the Mattole River basin.
The red-legged frog (Rana aurora) is not as good an aquatic indicator species as are the tailed frog and southern torrent salamander, because they may spend part of their lives ranging into upland areas. According to Welsh et al. (1992) the red-legged frog in California: "Occurs predominantly west of the Sierra crest; found in all manner of still to slow moving water: lakes, ditches, ponds, and slow streams. Normally found in or next to dense vegetation and are most active at night. Ranges from British Columbia to Baja California. Sea level to 4,500 feet in California". Their preference for slow moving water would make them more likely to frequent lower gradient, larger streams as opposed to steep and swift upland tributaries. According to the U.S. Fish and Wildlife Service: "The decline of the California red-legged frog is attributed to the spread of exotic predators such as bullfrogs, and the widespread changes that have fragmented habitat, isolated populations, and degraded streams". The bull frog (Rana catesbeiana) is widely introduced and directly predates on smaller frogs.
The foothill yellow-legged frog (Rana boylii) does not currently have protected status in California, although a petition to list its cousin, the mountain yellow-legged frog (Rana muscosa), is underway because of the decline of this species in the Sierra Nevada. Ashton et al. (1997b) notes that the foothill yellow-legged frog may also be in trouble from the Salinas River south as a result of anthropogenic changes to habitat. According to Welsh et al. (1991) the foothill yellow-legged frog in California: "occur west of the Cascade crest, Sierra foothills, and coast range from Oregon to Baja California. Sea level to approximately 7,000 feet (rare over 4,800 feet)." Yellow-legged frogs may persist in streams that are aggraded because they take advantage of warm side channels where tadpoles thrive. Altered flow regimes in regulated rivers, such as the Trinity River below Lewiston Dam, may disrupt breeding (Lind et al., 1996).
The Pacific giant salamander (Dicamptodon tenebrosus) may remain in freshwater and retain gills (picture at left) or may also shed its gills as an adult and walk overland (Welsh, 1993). This dispersal mechanism is highly adaptive because Pacific giants may move when aquatic habitats are disrupted. Welsh (1993) found Pacific giants to be less capable of resisting ecosystem disturbance in interior basins, as opposed to coastal areas where summer fog may aid survival after habitat alteration. The species may use virtually all types of habitat in small and intermediate streams, with different size and age classes using different stream habitats (Ollivier et al., 1993). Pacific giant salamanders were found to be the only vertebrate fauna in upper Moat Creek (Higgins, 1994), a small coastal tributary south of Point Arena. In some coastal case studies where widespread simultaneous disruption of the landscape and aquatic ecosystems occur, Pacific giants may become scarce, such as in the Gualala River basin (Higgins, 1997). Western aquatic garter snakes (Thamnophis couchii) may predate heavily on juvenile Pacific giant larvae (Lind and Welsh, 1990).
The western pond turtle (Clemmys marmota) is widespread in northwestern California, often seen sliding silently off large wood into the water. The life span of this species is 50-70 years and they often have high site fidelity with one specimen captured at the same location 50 years later (Ashton et al., 1997a). "Aquatic habitats with access to areas of deep slow water with underwater refugia and emergent basking sites are favored by adult and juvenile turtles. Hatchlings are relatively poor swimmers and tend to seek areas with slow, shallow, warmer water, often with emergent vegetation" (Ashton et al., 1997a). While aquatic habitat is important for this species, Reese and Welsh (1997) note that: "the terrestrial habitat is as important as the aquatic habitat to the viability of western pond turtle populations" because adults may range up to 1500 feet upslope to nest or forage. It was also noted by Ashton et al.(1997a) that "Grazing, conversion of wetlands to farmland, water diversions, irrigation, channelization, dams, mining, logging, urbanization, and population fragmentation all can have significant negative impacts to turtle populations." Changes in flow regimes, temperatures and channel conditions of the Trinity River below Lewiston Dam has reduced successful recruitment of juvenile western pond turtles and slowed adult growth rates (Reese and Welsh, 1998).
Ashton, D.T., A.J. Lind and K.E. Schlick. 1997a. Western Pond Turtle (Clemmys marmorata) Natural History. US Forest Service. Pacific Southwest Research Station. Arcata, CA. 22 pp. Unpublished report.
Ashton, D.T., A.J. Lind and K.E. Schlick. 1997b. Foothill Yellow-legged Frog (Rana boylii) Natural History. US Forest Service. Pacific Southwest Research Station. Arcata, CA. 22 pp. Unpublished report.
Brown, H. A., 1975. Temperature and development of the tailed frog, Ascaphus truei. Comp. Biochem. Physiol. 50 A: 397-405.
Bury, R.B. and P.S. Corn. 1988. Responses of aquatic and streamside riparian amphibian species to timber harvest: a review. In: K. Raedeke (ed.) Streamside Management: Riparian Wildlife and Forestry Interactions. pp. 165-181. Institute of Forestry Resources. Cont. 59. University of Washington, Seattle, WA.
Diller, L. V., and R. L. Wallace. 1994. Distribution and habitat of Rhyacotriton variegatus on managed, young growth forests in north coastal California. Journal of Herpetology. 30: 184-191.
Diller, L. V., and R. L. Wallace. 1999. Distribution and habitat of Ascaphus truei in streams on managed, young growth forests in north costal California. Journal of Herpetology. 33: 71-79.
Higgins, P.T. 1994. Assessment of Moat Creek fisheries and prospects for restoration. Prepared for Moat Creek Management Agency. Arcata, CA. 19 pp. [6.8Mb] **
Higgins, P.T. 1997. Gualala River Watershed Literature Search and Assimilation. Funded by the Coastal Conservancy under contract to Redwood Coast Land Conservancy. Gualala, CA. 59 pp.
Lind, A.J., and H.H. Welsh, Jr. 1990. Predation by Thamnophis couchii on Dicamptodon ensatus. (32k) Journal of Herpetology 24:104-106. http://www.rsl.psw.fs.fed.us/projects/wild/lind/lind1.PDF
Lind, A.J., H.H. Welsh, and R.A. Wilson. 1996. The Effects of a Dam on Breeding Habitat and Egg Survival of the Foothill Yellow-legged Frog (Rana boylii) in Northwestern California. In: Herpetological Review. 27(2):62-67. http://www.rsl.psw.fs.fed.us/projects/wild/lind/lind6.pdf
Reese, D.A. and H.H. Welsh. 1997. Use of Terrestrial Habitat by Western Pond Turtles, Clemmys marmorata: Implications for Management. Proceedings: Conservation, Restoration, and Management of Tortoises and Turtles. An International Conference, pp. 352-357 held in 1997 by the New York Turtle and Tortoise Society. http://www.rsl.psw.fs.fed.us/projects/wild/reese/reese3.pdf
Reese, D.A., and H.H. Welsh, Jr. 1998. Comparative demography of Clemmys marmorata populations in the Trinity River of California in the context of dam-induced alterations.(258K) Journal of Herpetology 32(4):505-515. http://www.rsl.psw.fs.fed.us/projects/wild/reese/reese1x.PDF
Welsh, H. 1990. Relictual amphibians and old-growth forests. Conservation Biology 4. pp. 309-319. http://www.rsl.psw.fs.fed.us/projects/wild/welsh/welsh9.pdf
Welsh, H.H. 1993. Hierarchical Analysis of the Niche Relationships of the Pacific Giant Salamander. Chapter 6 in Doctoral Thesis for University of California, Berkeley. 202 p. http://www.rsl.psw.fs.fed.us/projects/wild/welsh/phd/chap_6.pdf
Welsh, H.H., A.J. Lind, & D.L.Waters. 1991. Monitoring Frogs and Toads on Region 5 National Forests. As FHR Currents # 4. US Forest Service, Region 5. Eureka, CA. 12 pp.
Welsh, H.H. and A.J. Lind. 1996. Habitat Correlates of the Southern Torrent Salamander, Rhyacotriton variegatus (Caudata: Rhyacotritonidae) in Northwestern California. Journal of Herpetology. Vol. 30, No.3 pp 385-396.http://www.rsl.psw.fs.fed.us/projects/wild/welsh/welsh2.PDF
Welsh, H.H. and Hodgson, G. 1997. A hierarchical strategy for sampling herpetofaunal assemblages along small streams in the western U.S., with an example from northern California. 1997 Transactions of the Western Section of the Wildlife Society. 33. pp 56-66. http://www.rsl.psw.fs.fed.us/projects/wild/welsh/welsh6.pdf
Welsh, H.H. and L.M. Ollivier. 1998. Stream amphibians as indicators of ecosystem stress: a case study from California's redwoods. Ecological Applications 8(4):1118-1132. http://www.rsl.psw.fs.fed.us/projects/wild/welsh/welsh1.pdf
Welsh, H.H., G.R. Hodgson, M.F. Roche, B.C. Harvey. 2001. Distribution of juvenile coho salmon (Oncorhynchus kisutch) in relation to water temperatures in tributaries of a northern California watershed: Determining management thresholds for an impaired cold-water adapted fauna. Submitted to North American Journal of Fisheries Management. http://www.rsl.psw.fs.fed.us/projects/wild/welsh/welsh5.pdf
Welsh, H.H., Jr., T.D. Roelofs, and C.A. Frissell. 2000. Aquatic ecosystems of the redwood region. (316k) Pages 165-199 in R.F. Noss, ed., The Redwood Forest: History, Ecology, and Conservation of the Coast Redwoods. Island Press, Covelo, California. http://www.fs.fed.us/psw/publications/welsh/welsh12.pdf