Jeff Koenings, Ph.D.
Director

Jerry Gutzwiler
Chairman
Washington Fish &
Wildlife Commission
 

Project offers endangered turtles a head start to recovery
Posted July 2002

Summary
The western pond turtle, an endangered species in Washington, may be making a comeback thanks to a cooperative recovery project involving the Washington Department of Fish and Wildlife, Seattle's Woodland Park Zoo, the Oregon Zoo, Seattle turtle experts Frank and Kate Slavens and a team of volunteers. Each year for the past decade the recovery workers have taken to the field to collect newly hatched turtles from their nests and offer them a safe head start in zoo facilities until they grow large enough to survive predators such as non-native bullfrogs and large-mouth bass.

The headstarted turtles are returned to the wild where they appear to be surviving and successfully reproducing. Due to the head starting project and other recovery efforts the native pond turtle population has grown from a low of 150 to an estimated 600 and appears to be continuing to rise.

Project offers endangered turtles a head start to recovery

Once common in lakes and ponds of Southern Puget Sound and the Columbia River Gorge, the western pond turtle (Clemmys marmorata) is struggling for survival.

One of only two native turtles in the state, this is a species older than the dinosaurs. A mere decade ago it hovered on the brink of extinction. Fewer than 200 animals remained in the wild when the state increased the species' protection listing from threatened to endangered in 1993.

Today, however, the turtle's numbers are more than twice that and rising, thanks to a cooperative project involving the Washington Department of Fish and Wildlife (WDFW), Seattle's Woodland Park Zoo, the Oregon Zoo in Portland, a Seattle couple, Frank and Kate Slavens and numerous volunteers.

The four components of the joint recovery project -- captive breeding, headstarting, predator control and habitat protection -- are the cornerstones of a state western pond turtle recovery plan, written in 1999 by WDFW wildlife biologists. The plan is accessible on-line at http://wdfw.wa.gov/wlm/diversty/soc/recovery/pondturt/wptxsum.htm on the Internet.

Recovery plan goals are to establish three self-sustaining populations of western pond turtles in the Puget Sound area and four in the Columbia Gorge.

A captive breeding program has been underway to build a population of turtles for release into suitable Puget Sound habitat. A headstart program is being used to enhance the survival of hatchling turtles from both wild nests and the captive breeding. Predator control and habitat protection and enhancement efforts are under way where western pond turtle populations are found. The Department of Fish and Wildlife has acquired critical habitat in Klickitat County which supports one of the two surviving western pond turtle populations in the state.

Cooperative project offers safe start

Frank Slavens, Woodland Park Zoo's former reptile curator, and Kate Slavens, a seasonal WDFW biologist, are teaming with WDFW scientists, Seattle and Portland zoo experts, and volunteers, to increase the western pond turtle's shot at survival by producing captive bred young turtles and giving both captive-bred and young turtles from wild nests a head start on life in the relative safety of the zoo.

Headstarting helps the pond turtle survive its worst predators -- non-native species such as bullfrogs and largemouth -- bass that take a heavy toll on newly-hatched young.

The goal of the headstarting program is to rear the juvenile hatchlings in a protected setting until they are " bigger than a bullfrog's mouth," says Harriet Allen, WDFW's endangered and threatened species manager.

Captive breeding is being used for the Puget Sound region, which had turtles genetically distinct from the Columbia Gorge turtles. No populations remained in Puget Sound, only scattered remnant individuals. The captive breeding project was launched at Woodland Park Zoo in 1991 with three groups of breeding turtles. One group was collected from Puget Sound lowlands, one from the Columbia Gorge and the third from Oregon. The south Sound turtles were animals found by citizens in some unlikely spots -- a male turtle discovered in an industrial area along Tacoma's Commencement Bay, a female found by a worker clearing Wapato Creek near Fife, and another female turtle picked up along a roadside near Port Orchard.

Offspring from the genetically-distinct south Sound turtles were released to establish a population in several small ponds at a WDFW wildlife area near Steilacoom, beginning in 1996. Only a few Columbia Gorge turtles were bred in captivity for a short time as husbandry techniques were being developed, since two wild populations still existed in the Gorge. The captive-bred offspring were returned to their native settings in Klickitat and Skamania counties, while turtles collected from Oregon wildlife rehabilitators were used to help refine captive breeding techniques.

Native turtle needs wetland and meadow habitat

Not to be confused with the red-eared slider, the common snapping turtle or the Reeve's turtle, all exotic species that have been released by humans into the region's lakes and ponds, the western pond turtle is a Washington native. Historically the species was once well-distributed in southern Puget Sound lowland lakes and ponds and in the Columbia River Gorge.

The pond turtle's range extends down the west coast into California. In Oregon, where the species is listed as sensitive, there are an estimated 2,000 turtles remaining.

Click map to enlarge

The western pond turtle lives up to 50 years, but reproduces relatively slowly. Females take an average of eight to 10 years to reach sexual maturity and when mature, lay only six to 10 eggs a year. As a result, pond turtle populations can decline rapidly with the loss of only a few adults.

Because they spend much of their lives in water but nest on land, the turtles require an environment with both meadows and ponds that is relatively free of human disturbance. But as that habitat was lost -- more than 92 percent of south Puget Sound's wetlands and native prairie land have been lost and Columbia River Gorge turtle habitat has been altered and isolated by development -- the pond turtle also went into a sharp decline.

Adding to the habitat squeeze, predators took a heavy toll on the turtles. Although the pond turtle has a number of natural predators­ including herons, otters, raccoons and skunks­ it was non-native, released species such as bullfrogs and largemouth bass that proved most devastating. Bullfrogs are a particular threat because they occupy the same shallow pond margins favored by young turtles.

When a third challenge, disease, threatened to wipe out the few remaining pond turtles in a 1990 pneumonia-like outbreak, the captive breeding and headstarting program was launched in a effort to save the species.

Turtle populations restored with captive breeding and headstarting

Both captive-bred offspring and young from wild Columbia Gorge nests are headstarted to get them to a safe size to be released to the wild. Off-spring from the genetically-distinct south Sound turtles are being used to establish a new population at a WDFW wildlife area near Steilacoom. Only a few Columbia Gorge turtles were bred in captivity for a short time as husbandry techniques were being developed since two wild populations still existed in the Gorge. Headstarted juvenile wild turtles are being used to boost the two existing Columbia Gorge populations and to establish new populations in the Gorge.

The first 17 turtles headstarted from wild nests in the Gorge were returned to the existing Klickitat County population in 1991. Beginning in 1996, the first 15 headstarted, captive-bred Puget Sound turtles were released at the south Sound wildlife area.

Since then 600 turtles have been headstarted and released. Some 554 juvenile turtles have been returned to the Columbia Gorge and a total of 46 have been re-introduced in the south Sound wildlife area. In 2000, efforts were initiated to establish the first new population in the Gorge. Forty juvenile turtles were released at a U. S. Fish and Wildlife Service National Wildlife Refuge, and for the first time, 16 of the juveniles were outfitted with tiny, half-ounce radio transmitters glued to the tops of their shells to enable project coordinators to keep track of their habitat use and overall survival. The transmitters are each about the size of two garden peas with a five-inch long trailing antenna.

Besides giving the juvenile turtles a headstart in growth, recovery workers have tried to boost their odds by removing non-native predators such as bullfrogs and warmwater fish from the turtles' environment. In spring months, volunteers combed the shorelines of turtle ponds, searching for bullfrog egg masses and removing them with dip nets.

Headstarting takes months

Headstarting wild turtles takes place over the course of months: In April recovery workers go into the field to trap adult, female turtles and outfit them with radio transmitters. From May 15 to mid-July, the workers return, following radio signals to locate the turtles and their nests. The underground nests are dug by the female turtles as a flask-shaped cavity with a narrower entry. After digging, the turtle deposits her eggs and then covers the nest by scooping and tamping down dirt with her hind legs. Eggs are generally laid in a clutch of six to 10. Wire cages are staked over the top of nests to prevent predators from digging up and eating the eggs.

Success of the hatch depends on weather conditions; a long, wet spell in June can drown the nest. About 94 days after the eggs are laid, the young turtles hatch out. At that point recovery workers return to the field to retrieve the juveniles and take them to the zoos to grow in safety.

Between 80 and 120 hatchlings are headstarted at a time in the zoos, generally remaining for about 10 months.

The size of a quarter when they are first collected from the nest, the young turtles are two to three inches wide by the time they are returned to the wild the following summer. Releases take place in warm months when the turtles' chief foods -- dragonfly larvae, tadpoles, leeches, snails and aquatic beetles -- are the most abundant.

Marking and transmitters help workers track success

The success of the headstarting effort is tracked through mark-recapture methods. Before release, each young turtle is marked with tiny notches on the edge of its shell and a passive integrated transponder (PIT) is tag inserted under the skin of its hind leg.

By placing the shell markings according to a numbering system devised by recovery workers, each released turtle can be individually recognized. Many of the marked turtles are briefly recaptured and counted each April when workers are in the field to locate adult females.

The biggest challenge facing recovery workers is locating suitable habitat where new populations can be established to achieve recovery goals -- areas that contain both sunny, open grassland for future nest sites and swampy areas that can produce the tadpoles, snails, leeches and insect larvae that are the turtles' favored foods. Release sites are chosen to offer the turtles protection from human intrusion, dogs and traffic.

With the two existing pond turtle populations in the Columbia Gorge, and a third being established, one more is needed to achieve recovery plan goals for the Gorge. Biologists hope the turtles can produce enough young to overcome predation effects. Two or three additional sites need to be populated with turtles for recovery goals to be achieved for the Puget Sound area.

An encouraging sign of the success of the headstarting and captive breeding project is the nesting activity by female turtles that were themselves headstarted and released back into the wild. It takes eight to10 years for a wild turtle to reach sexual maturity and begin nesting. In 2000 the first headstart female nested in Klickitat County and in 2001 three headstart females nested; two in the gorge and one at the Puget Sound wildlife area. This was the first known nesting of a wild western pond turtle in Puget Sound in many decades.

Survival rates of headstarted turtles have been excellent. At the ponds near Steilacoom, where a complete census is possible, survival has averaged 88 percent per year; and radio-monitored juveniles in the Columbia Gorge have averaged over 90 percent survival. With time and adequate habitat the captive breeding and head-starting programs appear likely to keep another Washington native from extinction.

Pond turtle vital statistics: Weight at maturity: Up to two pounds Length at maturity: Up to eight inches Shell color: Carapace (upper shell) drab brown to black; plastron (lower shell) black and yellow Favorite foods: Tadpoles, snails, leeches, aquatic beetles, dragonfly larvae Habitat: Basking on logs in areas of slow- moving water; females lay their eggs in underground nests on land Estimated Washington population in 1992: 150 Estimated Washington population in 2002: over 600

Related Western Pond Turtle Web Links

WDFW Western pond turtle recovery plan:
http://wdfw.wa.gov/wlm/diversty/soc/recovery/pondturt/wptxsum.htm

From the Ponds: The Electronic Newsletter of the Western Pond Turtle Project in Washington
http://wdfw.wa.gov/wlm/regions/reg5/frompond.htm

Washington Herp Atlas:
http://www.dnr.wa.gov/htdocs/fr/nhp/refdesk/herp/index.htm

Frank and Kate Slavens' Western pond turtle homepage:
http://fslavens.home.mindspring.com/ptmain.html

Woodland Park Zoo
http://www.zoo.org/