The (turtle) battle of Mill Lake

Two types of turtles call Mill Lake Park in Abbotsford home. One belongs there, and one does not.

The western painted turtle is BC’s only native freshwater turtle. Seven or eight of them live in the park, laying eggs and basking in the sunlight as the seasons turn.

For decades, their peaceful existence has been threatened by a faster-growing, distant cousin: the red-eared slider. Native to parts of the U.S. the turtle arrived in BC—and in Mill Lake’s quiet waters—by way of pet store tanks beginning in the 1960s. Many locals bought them as pets only to later release them into the wild, said Aimee Mitchell, the executive director of Coastal Partners in Conservation, an organization that has been studying Mill Lake’s turtles.

“We used to hear arguments that ‘Oh, they’ll all just die,’ But they won’t.”

Initially, red-eared sliders couldn’t successfully hatch eggs after colder BC winters. But that has changed as the climate warmed. In 2015, the first red-eared slider hatchlings were recorded, and the species was officially deemed invasive.

Western painted turtle populations—including the small group in Mill Lake—were an endangered species until a few years ago. Now, they’re recovering under the watchful eye of conservationists. Warming winter temperatures will give the sliders an edge—but they won’t hurt the western painted turtles.

Mill Lake’s resident turtles

Mill Lake is the crown jewel of urban parks in Abbotsford, if not the entire valley. It’s surrounded by two kilometres of walking trail, a playground and clusters of culs-de-sac on one side, and a shopping mall on the other. Its dark waters fill with plants in the summer. As the city clambers upwards around it, the lake remains one of the last nearby homes for BC’s native freshwater turtle.

“Often [parks are] where our native turtle remains—in these lakes that are available after extensive wetland draining and habitat loss from development,” Mitchell said.

The lake may not be the only place where a western painted turtle or two survives, but it’s the only place in Abbotsford with a surveyed and studied population. The turtles’ Lower Mainland population has recovered from endangered to threatened over the course of a decade.

While the preserved lake is a pretty decent habitat for the western painted turtle, the popularity of the park isn’t necessarily safe for the reptiles. They’re at risk for poaching and being taken home as pets.

More commonly, though, it’s not what visitors take from the park but what they leave behind that presents a risk to the native turtles.

The sliders living in the park were almost all pets at one point and were “freed” into Mill Lake when their owners no longer wanted them. It’s a common move, Mitchell said. When the turtles are sold—plenty of them, she said, from the two pet stores in the mall right next to the lake—they’re tiny. Then they grow up.

“People buy these little baby pet turtles and they think they're so cute, they're only the size of a loonie,” she said. “But they will grow to be potentially a foot long.” Once they get large enough to need a tank the size of a large coffee table, they’re hard to look after and keep healthy.

Pet turtles released into parks have been a problem for as long as turtles have been popular pets—on and off since the 1960s. Their popularity spiked in the 1980s and ‘90s, an event that BC SPCA blames, at least in part, on the Teenage Mutant Ninja Turtles. But the battles between the released pets and their native counterpart don’t involve swords, sewers, or skateboards—or much violence at all.

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The nature of the competition

Red-eared sliders don’t eat or attack their native cousins. They just grow bigger and faster.

But size, when it comes to cold-blooded creatures who depend on sunlight for energy, is the difference between life and death. Both turtles need places to bask on logs or shorelines and Mill Lake has only so many spots for turtles to hang out in the sun. So when bigger turtles take more space, the smaller native turtles get less. The turtles use the energy from that warmth to fuel their immune and digestive systems. It’s also important for the turtles’ reproduction. Laying eggs takes lots of energy.

The sliders also introduce new illnesses to Mill Lake’s western painted turtles.

Sliders can spread parasites, bacterial and fungal shell diseases, and viruses—especially when they’re released after (often deteriorating treatment in) captivity.

“One of the issues is that people have these pet turtles and they often don't take care of them well enough,” Mitchell said.

The illnesses are passed on to western painted turtles. When a native turtle is brought into a vet from a place with a high percentage of sliders (like Mill Lake), it’s more likely to be sick than a similar turtle in an area without the invasive species, Mitchell explained.

Sickness, though, is not only a problem for the western painted turtles. Though red-eared sliders can survive in an Abbotsford winter, they aren’t adapted to it and struggle with illness themselves. Mitchell wants pet owners to remember that before setting a pet turtle free.

“They're just chronically sick, the pet turtles,” she said, when they’re released. “They're not living a great life being constantly ill.”

Climate Change and turtle sex

While sliders have been a concern for conservationists for decades, they only began garnering real attention as an invasive species when they started reproducing in the wild. And that has taken the help of climate change.

As winters get warmer, the sliders are getting more comfortable—and more of their hatchlings are surviving.

“Climate change is a contributing factor to making it more likely and more frequent that sliders are going to be successful,” Mitchell said.

But warmth is also important to the western painted turtles, Mitchell pointed out. Rising temperatures will help the sliders more in the long run. But that weather will also have a weirdly useful effect on the native turtle’s recovering population.

That’s because western painted turtles have temperature-dependent sex determination.

“Hotter temperatures will actually create females and cooler temperatures create males,” Mitchell said. And more females are better for a recovering population: a higher ratio of females to males leads to more nests full of hatchlings and a stronger population in the future.

But higher temperatures carry more risks for the native turtles. Droughts during hot weather can harm habitats and dehydrate western painted turtle eggs. “It’s a fine line,” she said.

Saving (both) the turtles

Instead of releasing a pet turtle into a wilderness they don’t belong in, advocates suggest finding a shelter to take them. But those, both in the Fraser Valley and BC as a whole, are few and far between.

Justin DeMerchant runs the Okanagan Turtle Adoption Program, a non-profit that finds new homes for pet turtles. Laws that determine what is and isn’t wildlife in the province can complicate an adoption process, DeMerchant said, but rehoming an unwanted slider is still very possible.

Not only is releasing a slider into the wild potentially harming native creatures, it’s also illegal, DeMerchant said.

“A lot of times when people can't figure out what to do with their turtle [it] ends up in the lake or pond but it's against the law to release them into the wild,” he said. “It's also against the law to catch them from the wild and rehome them.”

Though sliders are an invasive species, they’re still wildlife who’s removal or rescue is best left to professionals. Pet red-eared sliders surrendered to DeMerchant’s program go through a long process of quarantine and health checks before they’re put up for adoption, but he doesn’t take sliders from the wild to rehome as pets.

Though shelters that can take reptiles are often inundated with surrendered pets, DeMerchant isn’t pushing hard for more programs like his.

“While I want to say yes, it would be good to have more similar programs, at the same time it worries me a little bit,” he said. Operations, whether shelters or sanctuaries, that look after turtles well can get technical and expensive. He would rather see them done well than done often.

Mitchell says a lot of the shelters that would otherwise take in a surrendered slider are overwhelmed. And other options, which involve contacting animal control, are grim for previously beloved pets.

A role in recovery

The growing awareness of native turtles—and efforts to keep sliders out of BC’s ponds—are paying off.

Back at Mill Lake, the western painted turtle continues its slow rebound year after year, with help from both conservation workers and members of the public.

Coastal Partners in Conservation, the society Mitchell runs, works to ensure the native turtles are not only studied, but also assisted when possible.

“It’s a big operation [at Mill Lake] hunting, finding, monitoring turtles,” Mitchell said. Staff and volunteers play census-taker, ambulance driver, and construction worker for the turtles. They know how many turtles there are, ensure sick turtles get to veterinarians for treatment, and protect nests with special cages. When spring comes, staff wait for the eggs to hatch and, sometimes, help hatchlings make it safely into the cold waters of their ancestral home.

The society also deputizes the public where it can. A series of signs ask visitors to snap photos of turtles they see and send them in (via email or facebook messenger) to the society in real time.

While the actions of people have threatened the western painted turtle, humans—both professionals and passerbys—have a role in solving it.

“That's what people can have a direct impact on—[helping to keep] turtles and their nests and hatchlings protected,” Mitchell said. “That's wonderful.”