Working with ferrets

A black-footed ferret sits in the entrance to a burrow.

The high-pitched chatter of black-footed ferrets has once again fallen silent on the Saskatchewan prairie, but efforts are continuing to reintroduce this endangered species to Grasslands National Park.

A total of 74 ferrets were released in the park over a four-year period from 2009 to 2012, but they have not been seen for several years and it is assumed they have all died.

Sherri Clifford, manager of resource conservation at Grasslands National Park, said the recovery strategy for black-footed ferret has been put on hold for the moment.

“We're learning all the time,” she noted. “I think what I've learned from all of this is that once a species is gone, recovering it is extremely difficult and indeed it's heartbreaking at times.”

The black-footed ferret is North America’s only native ferret species and before their near extinction they were found throughout the short grass prairie. Their habitat became increasingly fragmented due to human activities and their main food source, black-tailed prairie dogs, were also disappearing.

The last wild black-footed ferret in Canada was seen in 1937 and for some time conservationists thought the species had become extinct in North America. In 1981 a small population was found near a ranch in Meeteetse, Wyoming. Several ferrets were trapped and they were used to start a successful captive breeding program.

“Captive bred descendants of those ferrets were released into the wild in Wyoming, Montana and South Dakota, and then the Toronto Zoo began breeding in 1992,” she said.

Their reintroduction to Canada took place in 2009, when 34 were released in Grasslands National Park. Additional animals were released in the following three years, starting with 15 in 2010, another 15 in 2011, and 10 in 2012.

One of the highlights of the recovery strategy occurred early on, when wild-born ferrets were observed in 2010.

“That demonstrated to us that it was possible for captive born animals to reproduce and that we could have truly wild litters in the park,” she said. “So that was really encouraging and a big highlight.”

A confluence of factors over several years created concerns about the welfare of the ferrets in the park, and that caused the suspension of any additional ferret releases after 2012. Eventually the monitoring program was also put on hold in 2016 after there were no further ferret sightings.

“During those four years of releases we had two severe droughts,” she said. “Those droughts resulted in a low winter survival and then low reproduction of prairie dogs in the year following the drought, and this is a predator-prey system. The ferrets are dependent on the prairie dogs.”

The black-tailed prairie dog population in the park experienced a further decline after sylvatic plague, a bacterial disease in wildlife, was detected in 2010. 

“We think that it's something that harbours in the environment all the time, and then sometimes we have an outbreak,” she said. “We suspect that one of the factors that leads to those outbreaks can be things like drought followed by higher precipitation, different stressors in the environment, and so we're monitoring for that all the time.”

That sylvatic plague outbreak helped to reduce the main food source of the ferrets and at the same time they were also susceptible to the disease. All of this happened too soon after the reintroduction of the ferrets to Grasslands National Park, and they did not have enough time to increase their population. 

“Then the other thing is just that they have a really short lifespan,” Clifford said. “We estimate that they probably live in the wild for three to four years. So they really need to be augmented in order to have any chance of establishing a wild population.”

One of the challenges for conservationist when they want to create good habitat conditions for ferrets is that they require a lot of space. Each breeding female ferret needs about 55 to 80 hectares of habitat to meet her requirements to feed and raise her litter.

“So that would mean that we would need to have about 4,000 hectares of habitat for a small but viable ferret population, and we currently have 1,000 hectares,” she said.

The intention is to resume the recovery strategy for black-footed ferrets in the future, but only after there is greater certainty that their habitat needs can be met. Parks Canada has therefore decided to focus on creating a healthy black-tailed prairie dog population, because they are such an important part of the ferret habitat. There are currently 18 prairie dog colonies in Grasslands National Park, and there are also two colonies outside the park on community pasture lands.

“We're committed to black-footed ferret recovery in a funny roundabout way, but first we have to focus on the black-tailed prairie dog population and distribution objectives that were outlined in that management plan,” she said. “Grasslands National Park also has a multi-species action plan and we collaborate with a lot of partners, both in Canada and the United States. So we switched our focus to black-tailed prairie dog with the hope that we can eventually circle back to considering releasing ferrets again, but we have to make sure that all of those factors are looked after before we try it again.”

The black-tailed prairie dog’s status in the Species at Risk Act has been increased from special concern to threatened due to increasing threats such as drought and sylvatic plague. This recommendation was made by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), and Parks Canada is preparing a recovery strategy for prairie dogs, which must be completed by 2020. This is done in collaboration with species experts, including the Calgary Zoo, conservation biologists, climate change ecologists, park managers and local ranchers.

“The intent of the process is to assess threats to prairie dog survival, estimate the probability of persistence of the species in light of a changing climate, and identify options available for the recovery of black-tailed prairie dog in Canada,” she noted.

The feasibility of any future releases of black-footed ferrets in Grasslands National Park will therefore depend on the outcome of these efforts to create a healthy and sufficient black-tailed prairie dog population.

“It remains to be seen,” she said. “The prairie dog recovery strategy and subsequent action plan will directly influence the feasibility of recovery for black-footed ferret. We have to make informed, evidence based, responsible decisions on both. It is a balancing act that we take very seriously.”

For Clifford these ongoing efforts to give future visitors to Grasslands National Park an opportunity to again hear the chatter of black-footed ferrets will hopefully serve as an important reminder to protect species and their habitat before it is too late.

“Once they're gone, bringing them back can be exceptionally difficult,” she said. “That's why conservationists work as they do every day in the hopes that you never get to that point. “I think some people also have the misconception that because we're successfully breeding them in captivity, then releasing them into the wild means that they're just going to be a success story. It's not. Living in captivity versus living in the middle of Grasslands National Park is something very different.”

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