It is January 2024, and a young northwestern pond turtle (Actinemys marmorata) swims through a stand of plastic aquarium plants and scrabbles against the sides of its tub at Seattle's Woodland Park Zoo. The animal, with a dark shell that’s round as a silver dollar and not much bigger, is one of 41 turtles hatched the year before and part of the 2023-24 class of the zoo’s “headstarting” program.

As the program’s name suggests, this graduating class will have a leg up. While their wild counterparts have been resting in quiet dormancy — perhaps buried in a pond a few dozen miles from here — these turtles have been in training.

Inside the lab at the zoo, the temperature has been a balmy 70-something degrees, and the turtle cohort has stayed warm and active and well-fed all winter. The result, scientists say, will be stronger, bigger animals that are more prepared for the many challenges of being endangered species.

Come summer, when they are released back into their natal pond, the one-year-olds will be the size of three-year-old wild-reared turtles, or most crucially, as zoo curator Erin Sullivan puts it, “bigger than a bullfrog’s mouth.”

Bullfrogs (Lithobates catesbeianus), native to the eastern United States, are considered an invasive species in Washington and are a ravenous predator of young turtles. But they are only one of a gauntlet of threats facing the northwestern pond turtle, a list that also includes habitat loss, fragmentation, and degradation; climate change; and an emerging shell-rot disease.

Today, only about 1,000 northwestern pond turtles remain in Washington. The species was listed as endangered at the state level in 1993, and proposed for listing as threatened under the federal Endangered Species Act last September. Their plight reflects the need for restoration of natural habitats – but also the active care that many of the state’s small, sensitive imperiled species are likely to continue to need even with improved habitat conditions, researchers say.

Turtle trouble

The northwestern pond turtle is one of just two species of freshwater turtles native to Washington State. The Puget Sound region is near the northern limit of its historic range, which extends south through Oregon to the San Francisco Bay Area and Central Valley of California. The turtles, which grow to about 7 inches in length and can live for more than 50 years, were likely once common in some parts of the central and southern Puget Sound lowlands and in the Columbia River Gorge.

The species began running into trouble in the late 1800s, when more than half a million were harvested for food. Facing high mortality from a host of native predators when they are young and taking 8 to 12 years to reach breeding age, the turtles had a hard time bouncing back. Meanwhile, the turtles’ habitat was rapidly shrinking and introduced predators such as bullfrogs and largemouth bass (Micropterus salmoides) were just as rapidly proliferating.

By 1990, the turtles had been all but wiped out in Puget Sound and just two remnant populations existed in the Columbia Gorge. The dozen or so turtles remaining in South Puget Sound were brought to WPZ for a captive breeding program.

Laying the groundwork for turtles to return to the wild in South Puget Sound, WDFW fenced off a 12-acre turtle recovery area in Pierce County, digging three ponds, planting native trees and shrubs, and constructing a nesting hill in one corner of the enclosure.

The turtles have complex habitat requirements: They are primarily aquatic, but leave the water to lay their eggs, disperse, and sometimes to enter dormancy during the cold winter months or hot, dry periods in summer.

“Pond turtles need very specific nesting habitat,” says Katie Remine, Living Northwest Conservation Manager at WPZ. “It’s this certain kind of upland habitat, it has to be sort of a meadow. They have to be able to dig into the soil and lay their eggs, and it has to get enough solar radiation, but not too much.”

The turtles’ nesting habitat has characteristics similar to that of South Puget Sound prairies – open grasslands that Indigenous groups once maintained with fire and that are now one of the rarest ecosystems in the state. But the turtles are not as closely associated with prairie ecosystems as some other species such as the Oregon spotted frog, Mazama pocket gopher, or Taylor’s checkerspot butterfly; the turtles’ need for wetland habitat adds an extra wrinkle.

“Restoring Puget Sound prairies would support future management and recovery actions this species may need in Washington,” says Andrew Lavalle, a public affairs officer with the US Fish and Wildlife service, “but prairie restoration alone is not likely to meet all of this species’ needs, because it requires both wetland and upland habitats to support different aspects of its annual life cycle.”

SAFE zone

Releases of captive-bred turtles began at the Pierce County site in 1996. A second site on Washington Department of Natural Resources land in Mason County, where a 20-acre beaver pond anchors a wetland complex on abandoned farmland, began receiving turtles in 2005, but there have been no releases and or monitoring of the population there since 2013.

By 2010, turtles at the Pierce County site had begun nesting on their own, so WPZ shifted from captive breeding to the current headstarting program. It’s a year-round job: Eggs are collected from wild nests in May or June, placed into incubators set at 27.7 °C to ensure an equal number of male and female babies (in turtles and other reptiles, sex is determined by the temperature during a critical period of embryonic development), and hatch in July or August.

The young turtles are raised in the lab – a recently opened facility that places the turtles on public view for the first time in more than 30 years of the program – and released back into the wild the following summer.

In 2023, “within a day of releasing [the yearling turtles], we had hatchlings,” Sullivan says. “So we were never without a turtle in the lab, which was amazing.”

WPZ’s effort is part of the Association of Zoos and Aquariums Saving Animals from Extinction (SAFE) program and received the organization’s North American Conservation Award in 2016. A similar program at Oregon Zoo in Portland launched in 1998 to headstart turtles for release in the Columbia Gorge region; WPZ concentrates on Puget Sound.

Today, there are six populations of northwestern pond turtles in Washington – four in the Columbia Gorge and two in South Puget Sound. Statewide, about 800-1,000 turtles survive out of more than 2,200 that have been released into the wild over the years.

All the turtles in the Puget Sound region today are descended from the dozen involved in the captive breeding program in the 1990s, and most of the turtles statewide have been headstarted. “There’s only about 40 or so that have never spent any time in captivity,” says Julia Smith, Endangered Species Recovery Manager for WDFW. “So it’s mostly a population that has been completely held up by the work in captivity supported by zoos.”

New threats

While the headstarting programs have succeeded in bringing pond turtles back from the brink of extirpation in Washington, the problem is the state’s turtle populations remain dependent on these programs. Natural recruitment is still too low to maintain and grow them.

The Pierce County site hosts one of two turtle populations in the state to have reached a benchmark size of 200 individuals set out in a 1999 WDFW recovery plan for the species. But the Pierce County population needs to not just sustain itself; it’s also expected to be the source of turtles to establish future new populations elsewhere in South Puget Sound. The 2022 South Puget Sound Wildlife Area Management Plan calls for attaining a population of 500 turtles at the site.

Complicating the work is the fact that the Pierce County site does not provide set-it-and-forget-it habitat. Both the ponds and the nesting hill require yearly weeding and removal of invasive plants to maintain suitable conditions for the turtles. "The sites that we have are not wild sites,” Sullivan says. “The ponds that we're releasing them to now are very managed sites."

Meanwhile, new threats are emerging. A shell-rot disease that causes pitting and soft spots began to be recognized in the early 2010s. A 2013-2014 survey showed that 29 - 49 percent of the turtles in each of the six populations were affected. And when scientists looked back at old photos of the turtles, they found the disease had been present at least since 2003.

Sometimes disease that appears mild on the outside can involve significant lesions internally, with nodules growing into the lungs and spinal cord. “It looks awful,” Smith says. “If you look at these CT scans of these turtles, clearly, it's got to create at the very least, discomfort for them. Because it looks like these big Swiss cheese holes in their shells.”

Scientists are not yet sure how the disease affects turtle survival and reproductive success. Nor is the cause of the disease certain: a fungus, Emydomycese testavorans, is associated with the disease, but hasn’t been definitively shown to be the cause. The relationship with captivity is also an open question: the disease appears to affect mostly headstarted animals but is sometimes found in wild turtles too.

“One of the difficulties is that [pond turtles] grow very slowly, they reproduce slowly,” Smith says. “Everything with turtles is slow and so takes a long time to get some of these answers."

The emergence of the new disease has forced agencies and organizations working on the turtle’s recovery to reorganize their plans. In the mid-2010s, WDFW evaluated more than 12,000 potential sites in South Puget Sound where new turtle populations might be established, but does not plan to proceed with more introductions until the shell disease is better understood.

"Right now, we're very, very focused on shell disease and understanding how that is affecting turtles,” Smith says. “A lot of our resources and time goes toward that effort."

Making the list

The proposed federal ESA listing of the northwestern pond turtle comes in response to a petition and lawsuit from the Center for Biological Diversity. As well as experiencing steep declines in Washington State, northwestern pond turtles have declined by 99% in the Willamette Valley in Oregon and have disappeared from many sites in California’s Central Valley, the Center has noted.  

USFWS has also proposed listing the closely related southwestern pond turtle (A. pallida), which ranges from Monterey County, California to Baja California, Mexico, as threatened. Until 2014, the two were considered a single species, known as the western pond turtle.

The proposed listing of the two species has generated more than 16,000 public comments – an unusually large number for a relatively low-profile species, Lavalle says (in comparison, the recent proposed listing of a salamander generated comments in the single digits). In early April, the agency reopened the public comment period for an additional 30 days.

A final decision on the listing could come as early as this fall, Lavalle says.

If the listing goes through, it will trigger an effort to designate critical habitat for the northwestern pond turtle. "A major hurdle we face with this species is the lack of available suitable habitat in South Puget Sound,” Lavalle says.

WDFW and WPZ are also waiting to see how a listing might affect their recovery efforts. A proposed “4(d) rule” would enable activities that support conservation of the species to continue. "We're optimistic that we'll still be able to do some head starting and help out in the way that we're helping out," says Sullivan.

If the listing goes through, " There is the potential for sources of federal funding to open up for the Northwestern pond turtle,” Smith says. “But one of the sticky parts of that is that just because funding opens up for a federally listed species, it doesn't make the whole pot of money bigger, it actually just cuts it into smaller slices."

Either way, pond turtles will likely need focused attention from humans for the forseeable future in order to persist, Smith says. “And unfortunately, that's true for many of our rare and imperiled species,” she adds. Species that, like the turtle, are dependent on very specific ecosystems and habitat conditions “are, in many cases, conservation reliant. Many of our species require this intensive effort.”