An invasive turtle species has taken over the BioPond and a group of professors sees no other option than to euthanize them.
Biology professor Arthur Dunham estimated 75 red-eared sliders — a mid-size turtle native to the southern regions of the United States and an invasive species in Pennsylvania — are currently living in the pond, and it appears they have all but eclipsed the species of turtle native to the pond, the painted turtle. Dunham is a herpetologist who has written papers on turtle conservation and a member of the James G. Kaskey Garden Committee.
The red-eared sliders can survive in many environments, including polluted waters, which makes them susceptible to carrying disease and spreading it. Minor risks to a population’s health and the health of other populations are increased when there is overpopulation, said Biology professor and Department Chair Brenda Casper, another member of the James G. Kaskey Garden Committee.
The turtles are responsible for creating a stinky odor around the pond by allowing its nutrient load to skyrocket. They stir up sediments at the bottom of the pond, and they feed off of the plants in the pond that are meant to keep the nutrients at an ecologically sustainable level. Recent algal blooms have also contributed to the odor. Over the summer, one visitor to the park mistook the odor for a gas leak and called the fire department.
Though plans have not yet been finalized, members of the Committee and the garden/greenhouse who have worked with consulting veterinarians and live animal research specialists at Penn, consider euthanasia of the red-eared sliders to be the most ethical and legal way to resolve the overpopulation issue and restore the health of the pond.
Some members of the Committee, including Casper, Dunham, the manager of the garden and the associated greenhouse have considered various solutions to the overpopulation issue.
“We thought a lot of what to do with them,” Casper said.
One such option included transplanting the red-eared sliders back to their natural habitats, but was rejected for fear of introducing new genetic combinations and potential diseases to the native population, Casper said.
Dunham added that giving the turtles away to willing pet owners would not have been sustainable either. The risk of humans contracting salmonella from interacting with a turtle is very high, and he predicted that if they were to just give away the babies, they’d probably end up back in the BioPond again or in another non-native ecosystem when they grew too large.
“Invasive species are really a threat to biodiversity, it’s one of the biggest threats worldwide to biodiversity, and I think that we have a responsibility to make sure that we’re not releasing invasive species in the wild and we’re not helping propagate them, right. So that’s where we’re coming from,” Casper said. “And we haven’t finalized the plans yet, we have no date, we’re still planning this. But we see no other option. This is the most humane and the most ecologically appropriate course of action.”
The overpopulation has been attributed to irresponsible pet owners who introduced the red-eared sliders to the pond once they grew to a shell length of greater than four inches, Casper said. The introduction of the turtles began between 10 and 15 years ago, Dunham said. The red eared slider and the painted turtle were cohabiting the pond at the time of the pond’s last restoration, about a decade ago, but nothing was done at the time because the balance of the ecosystem was not perceived to be a threat, they said.
Release of any non-native species into the wild is illegal in Pennsylvania. The Food and Drug Administration banned purchasing any turtle with a carapace of shorter than four inches in 1975 in an attempt to stem the spread of salmonella, an easily communicable bacterium to humans that can cause fatal illness. Exceptions to the ban included the purchasing of such turtles for an educational or scientific purpose.
Despite the ban, turtles fewer than four inches long continue to be sold illegally online.
Along with the euthanization of the turtles, the BioPond will also be removing the overpopulation of koi fish, which Dunham estimates number in the several hundreds. The large size of the fish and their high population density prevents the pond from maintaining a stable nutrient load because the koi also feed off of the vegetation. Dunham added that the turtles could help maintain the ecological balance of the pond if they were eating more of the baby koi at a higher rate.
The committee has located a volunteer to keep all of the koi once they have been removed from the pond. The koi will now be kept in a koi pond where they will swim out their days instead of being placed in another natural ecosystem. Following the koi’s removal, more plants will be put in the pond, Casper said. Dunham added that the native painted turtles and native species of fish will gradually be added to the pond as well.
The garden will post signs around the pond expressly prohibiting the introduction of animals into the pond. The prohibition is already on the James G. Kaskey’s Memorial Garden’s website.
Casper added in an emailed statement that other species, such as cats, are sometimes released into the Kaskey Garden at the end of the Spring semester. On one occasion, lab rats were found in the garden, she added.
College junior Annie Freeman, co-president of Penn Animal Advocacy, emphasized the complexity of the issue and assigns part of the blame for this decision to the irresponsible pet owners who initially abandoned their turtles in the pond, but she still opposes the euthanasia.
“I do understand that this is kind of nuanced situation, but that isn’t really important in the case of each of these individual turtles’ lives...They should do everything in their power to find an alternate option,” she said.
Dunham and Casper believe that they already have. “I don’t like this any more than anybody else does but we don’t really have any ethical or legal alternatives,” Dunham said.
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