Tortuga Gazette 22(10):3-5, October 1986

Pacific Pond Turtle, Clemmys marmorata*

by R. Bruce Bury

Drawing by Robert Savannah, USFWS

The Pacific pond turtle (Clemmys marmorata) is the only native freshwater turtle in northern Baja California, California, southern Oregon and Nevada (isolated patches near Reno). This species also occurs in western Oregon and Washington and southern British Columbia,* where its range overlaps that of the painted turtle (Chrysemys picta).

Actually, Pacific pond turtles are only rarely pond dwellers. In the western United States there were relatively few ponds or lakes prior to the construction of reservoirs and farm ponds. Clemmys marmorata occurs in a variety of habitats, but my experience has shown that this turtle is most at home in streams, large rivers, slow-moving sloughs, and quiet waters. Many of its habitats are rocky, or strewn with gravel and boulders. Clemmys marmorata is remarkably well adapted to survive the aridity and annual drought of the Mediterranean climate typical of the region from southern Oregon to northern Baja California. In this portion of their range, C. marmorata populations reach high densities. Wily individuals survive times of low water levels by moving to remaining pools or pockets of moisture. For example, I found 12 adult turtles in one small pool (3 feet by 10 feet and one foot deep) along Nicasio Creek, Marin Co., California. These turtles are capable of moving long distances (at least one mile overland) and of locating remaining water sources when streams and rivers dry up in late summer. They apparently can survive droughts by digging into the mud on the bottom of water courses.

As part of my graduate studies, I spent four summers studying and enjoying C. marmorata in a stream in northern California. The turtle is secretive and wary, but through intensive search and collecting (mostly by diving) I captured and marked 578 turtles in a 2.2 mile stretch of stream. I estimated the population density at 85 turtles per acre of water (215 per hectare!). I recaptured many individuals for a total catch of 1,500 turtles over the four summers. On one occasion I caught about 50 turtles in one deep pool along the stream.

Thus C. marmorata may reach high local densities in flowing waters. Other abundant populations frequent some western waters. However, due to their elusive habits they are not easy to find anywhere in the range. The largest populations are scattered from southern Oregon to central California. Elsewhere (with a few exceptions), the species appears to be scarce. They are extremely rare in the states of Washington and Nevada.

In most states the turtle is protected by law; this is necessary to limit collection for the pet trade. In the early 1960's, one wholesale dealer obtained about 500 C. marmorata from one southern California lake; these were shipped to Europe. today one would be hard-pressed to find any C. marmorata population this large in southern California, where intensive collection for pets and habitat destruction have greatly reduced the number of turtles.

Although the species is hardy and easy to maintain in captivity, I do not keep one as a pet. I strongly believe that this turtle belongs in its natural habitat where it is an important omnivore and scavenger in quiet and flowing waters. If you wish to enjoy the Pacific pond turtle, grab a pair of binoculars and sneak up to a pond or stream early in the day. You may see C. marmorata swimming, feeding or interacting socially. Sighting this wary turtle emerging onto a rock or log to bask in the sun will be a special event in your life. And, continued watching will reveal Pacific pond turtles in aggressive behavior as the basking site becomes crowded. Turtles push and ram each other, threaten one another with open-mouthed gestures, and occasionally bite other turtles. They are feisty turtles and their antics provide excellent outdoor entertainment. Turtle watching is more intriguing than it first seems and can be as addictive as bird watching.

Suggested Reading

Bury, R. B. 1970. Clemmys marmorata. Catalogue of Am. Amphib. Rept. 100.1-100.3
Bury, R. B. and J. H. Wolfheim. 1973. Aggression in free-living pond turtles (Clemmys marmorata). Bioscience 23:659-662.
Carr, A. 1952. Handbook of turtles. Comstock Publ. Assoc., Ithaca, N.Y. 542 pp.
Ernst, C. H. and R. W. Barbour. 1972. Turtles of the United states. Univ. Kentucky Press, Lexington, 347 pp.
Evenden, F. G., Jr. 1948. Distribution of the turtles of western Oregon. Herpetologica 4:201-204.
Pritchard, P. C. H. 1979. Encyclopedia of turtles. T.F.H. Publications Inc., Neptune, N.J. 895 pp.
Storer, T. I. 1930. Notes on the range and life-history of the Pacific freshwater turtle, Clemmys marmorata. Univ. California Publ. Zool. 32:429-441.

*Webmaster's (MJC) Notes: Most authors now assign the Western or Pacific pond turtle to the genus Actinemys or Emys.  Actinemys marmorata is now extirpated from British Columbia, and is almost extinct in Washington State. The original article was accompanied by 3 photographs showing intraspecific aggression in wild A. marmorata.