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Zoo Researchers as Grassland Guardians

Nov 20, 2012

Calgary Zoo Researchers Study Complex Prairie Ecosystem

Gone from the Canadian prairies for more than 70 years, black-footed ferrets might get the most time in the spotlight since their reintroduction in 2009, but the Calgary Zoo's research team actually spends the majority of their time focusing on the larger ecosystem dynamics that make ferret survival possible. Researchers spend four times as much of their time monitoring black-tailed prairie dogs – a critical piece of the puzzle that will ultimately ensure the long-term survival of ferrets and several other species in Canada.

As the sun sets on Saskatchewan’s short-grass prairie, the Calgary Zoo’s Centre for Conservation Research team pulls off to the side of the road in Grasslands National Park and collects their equipment to head off into the gathering darkness.

Loaded down with headlamps, spotlights, spare batteries, reflectors, live traps and scanners, the team of eight divides the area into sections and heads out to the prairie dog colony in search of black-footed ferrets. During their late-night searches, researchers are collecting information about how ferrets are doing in their new prairie home.

"It's about finding balance and making sure things are working for all species that rely on this rare landscape."

Under the light of a full moon, when ferrets tend to be more active, researchers hike up to 28 kilometres a night, carefully avoiding burrows and shining their handheld spotlights in search of black-footed ferrets. The reward? A glimpse of green eye shine is a sure sign that a ferret has popped out of a prairie dog burrow. 

In Search of Eyeshine

“Every species has a distinctive eye shine,” explains Calgary Zoo Husky Energy Endangered Species Program researcher Tara Stephens. “When we’re monitoring ferrets in the dark, we’re looking for a brilliant emerald green reflection, but we can go entire nights without actually seeing one. When we do spot a ferret, it’s really exciting.”

Even on nights when they don’t catch a glint of emerald in their spotlights, Tara is quick to point out that not seeing a ferret doesn’t mean failure. "There are several reasons for not seeing ferrets – they could be underground in burrows, moved to another colony or not survived the winter. We always hope to find ferrets out there, but not seeing them also gives us important information about their survival, reproduction and use of the colony.

Even if ferrets aren’t on their radar on a given night, researchers are busy recording the presence of other animals that live on prairie dog colonies – predators, such as badgers and great horned owls, species at risk such as burrowing owls and swift foxes and other, more common, species including nighthawks, rabbits, mule deer, frogs, salamanders and porcupines. “Seeing the night life on the prairies helps keep researchers motivated and sheds light on other important members of the ecosystem,” says Tara.

Once researchers finally catch a glimpse of that elusive green eye shine, they quickly mark the location with their GPS, and make their way carefully and quickly to the burrow to place a trap or a round scanner over the hole. “It’s funny, but I almost always find myself talking quietly to the ferret who is watching me from its burrow as I approach,” says Tara. “Sometimes they’re really shy, other times they chatter at us and some of them will even run right up to our feet. They have a variety of personalities.”

The round scanners Tara mentioned are used to read a microchip that all captive-bred ferrets have implanted between their shoulder blades. During the surveys, veterinarians from the Toronto Zoo and Parks Canada vaccinated and microchipped the wild-born ferret kits that were located and trapped. The microchip is critical to helping researchers identify ferrets in future monitoring sessions and track their survival and reproduction. In addition to the microchips, the ferrets were also marked with temporary hair dye to keep track of individuals that had already been trapped that year.

This year, researchers searched a total of 12 colonies for a month during the late summer. In partnership with Parks Canada, the Toronto Zoo and volunteers, researchers found a total of 15 ferrets on five different colonies. These included three wild-born litters and three adult ferrets still surviving from the original 2009 reintroduction. One of the litters was a second generation of wild-born kits, which is an important measure of success in species recovery.

While the four weeks of ferret monitoring in 2012 was the biggest monitoring effort for black-footed ferrets ever in Canada, looking for ferrets is really just part of a larger story. 

Understanding the Prairie Dog Ecosystem

Tara explains that black-footed ferrets are only one element of an intricately-woven ecosystem that has prairie dogs at its very core. “We study what we call the prairie dog ecosystem – not just ferrets,” explains Tara. “Everything is interconnected in this unique ecosystem, so we are really looking at the bigger picture. Prairie dogs play a critical role as ‘ecosystem engineers,’ altering the landscape. They eat vegetation sparking new growth for grazers such as bison and pronghorn, they dig extensive burrow systems that provide shelter for other species such as burrowing owls, rattlesnakes and ferrets, and they are a concentrated prey source for  other predators such as ferruginous hawks and coyotes.”

Tara adds that the team actually spends more time studying prairie dogs than they do studying ferrets. “For most of the year, we are doing visual counts, mark and recapture, and burrow counts for prairie dogs. We trap prairie dogs by day starting in June and going right through the last week of July when we switch over to nights and start monitoring ferrets. Then we switch back to days and look at prairie dogs until the next ferret monitoring session at the end of August.”

Researchers also keep an eye on prairie dog colonies even when they are not in the field. Cameras that are triggered using motion sensors are placed throughout the colonies to help fill in some of the blanks. “It’s a bit like spying on all the residents of prairie dog colonies,” says Tara. “They allow us to estimate when prairie dogs go into and emerge from hibernation, and also give us an idea of how the relative presence of predators changes over time.”

An incredible amount of data is collected during the monitoring session. As the field data comes in, it is mapped and analyzed quickly using a complex mathematical model. As soon as the monitoring sessions end, Tara works with Parks Canada biologists to determine how many ferrets the year’s prairie dog numbers can support.  This ultimately determines how many ferrets can be released that year and where they should be placed.

Finding a Delicate Balance

And all of this happens quickly. In 2012, monitoring ended on September 9 and 17 days later, on September 26, an additional 11 captive-born ferrets were released into Grasslands National Park.

It’s a delicate balance. Release too many ferrets and prairie dog populations will suffer. “It all goes back to the interconnectedness of this prairie ecosystem. It’s about finding balance and making sure things are working for all species that rely on this rare landscape,” says Tara.

The black-footed ferret and black-tailed prairie dog component of the Husky Energy Endangered Species Program is also currently supported by the Canadian Wildlife Federation and WWF-Canada.

From the Winter 2012-13 issue of the Calgary Zoo’s Wild Life member magazine.

Photos by Tara Stephens, Solene Touzeau, Fiona Le Taro, Dennis Flaherty, USFWS, Gordon Court