Trail-Camera Research Unlocks Carnivore Mysteries
Hidden cameras solve crimes, track fugitives and prove mountain lions visit Wisconsin, but they haven’t found Bigfoot or verified Elvis is alive and well.
In other words, motion-activated cameras are reliable and credible, which is why researchers like using them for low-impact wildlife studies. If a critter truly exists and moves regularly, it will eventually walk in front of a trail camera and into the news or scientific journals.
For example, a collaborative three-year study by Northland College in Ashland, the University of Wisconsin-Madison and the National Park Service recently used over 160 trail cameras to document 10 of Wisconsin’s 12 land-dwelling carnivores on Lake Superior’s Apostle Islands.
Researchers placed the cameras on 19 of the Apostles’ 22 islands, and found carnivores on 15 of these remote “rocks,” which range in size from tiny Eagle Island to the 15.6-square-mile Stockton Island.
The only land-based Wisconsin carnivores not detected on the islands were badgers and striped skunks. The cameras documented bobcats, coyotes, fishers, raccoons, weasels, gray fox, red fox, black bears, American martens and a gray wolf.
Researchers baited the “camera traps” with a stinky commercial substance that smells like “rotting skunk,” said former UW-Madison graduate student Morgan Morales. When animals stopped to sniff, the cameras clicked.
The biggest surprise came in 2015 when trail-camera photos found American martens on Stockton Island, where they hadn’t been documented since 1969. Cameras subsequently snapped marten photos on six more Apostle islands: Bear, Cat, Manitou, Otter, Outer and Rocky. The Manitou photos weren’t so shocking. In 2014, a visitor snapped a photo of a marten running between his legs.
Although American martens are endangered in mainland Wisconsin, they were the third most commonly photographed carnivores on the Apostles from 2014 to 2016, behind only black bears and coyotes. The lone gray wolf photographed was on Stockton Island in 2015. Morales said they later found a dead wolf there and assume it was the same animal, so it’s possible no wolves currently roam the Apostles.
From 2014 to 2017 the research cameras clicked 203,385 photos, of which 7,291 showed wildlife, of which 1,970 showed carnivores. For those keeping score, carnivores appeared in less than 1 percent of the photos.
The cameras detected black bears on 12 of the 19 islands, coyotes on nine islands, and red fox on eight islands. Morales described the Apostles’ black bears as incredibly healthy, with photos often showing sows accompanied by two or three cubs.
The largest island in the study, Stockton, was home to all 10 carnivore species identified in photos. Oak Island, which lies between mainland Bayfield County and Stockton Island, lacked only wolves, martens and weasels. Basswood, which lies between the mainland and Madeline Island, was home to five carnivore species: bear, bobcat, coyote, fisher and gray fox.
Morales and Professor Erik Olson at Northland College were also intrigued by which islands held martens. Based on a branch of biology called “biogeography,” they were expecting the most carnivore “richness and diversity” to occuron islands closest to the Bayfield Peninsula’s mainland.
Instead, they found martens only on the next two rows of islands – Stockton, Manitou, Otter and Bear – and Rocky, Cat and Outer. Further, martens apparently share only two islands with their fisher cousins: Rocky and Stockton. Another family member, weasels, were found only on Stockton and Devils islands. Devils is a small island northwest of Rocky Island.
“We’re still trying to figure out why we only detected martens on islands separated from the mainland by other islands,” Morales said. “That’s not what you’d expect, but there really hasn’t been much research on tundra islands. Tropical islands are usually the biological diversity hotspots.”
The marten’s distribution is also intriguing because the only way to reach the Apostles’ middle islands is to cross several miles of ice in winter, or swim for it the rest of the year. Bears have no problem swimming long distances, and coyotes often travel far over ice, but both travel options would seemingly test a marten. As Olson notes, “The lake is the boss.” No matter the season, even humans can’t dictate travel to the Apostle Islands.
If individual martens aren’t moving back and forth from the mainland, and each island has unique marten populations, they could conceivably die out from inbreeding. Therefore, researchers are studying marten hair samples for DNA to learn if the islands’ martens have always been out there, if they’re relics of restocking efforts on Stockton Island during the 1950s, or if they’re recent immigrants from restocking efforts in the Chequamegon-Nicolet National Forest from 1975 through 2010.
“It’s fairly conjectural at this point,” Morales said, “but it seems unlikely they’re a holdover population.”
Either way, without dedicated researchers and all their strategically placed cameras, we probably wouldn’t be speculating about the martens’ origins. We’d just assume they’re rare or nonexistent on the Apostles.
Photos and Map Submitted by Morgan Morales, University of Wisconsin-Madison.