On April 29th, Ross Dorendorf and I swung our legs over our snow machines and gave each other a thumbs up; it was time to head home. We had just completed the initial season of the first ground-based collaring effort for wolverines on Alaska’s North Slope in 35 years – the second ever – and were pleased to call it a success. For fifty days we ran four traps, complemented by ten bait stations, covering approximately 500 square miles of tundra near the oil camp of Umiat. It was the first effort to shed light on how wolverines use deep snow as a structural feature of their habitat, and it was very much a pilot season, one of several to come. In a landscape where woody plants are scarce, we had no way to know what the wolverines would think of our wooden traps constructed of commercial 4x4s, but we hoped that the animal’s characteristic curiosity and namesake gluttony would overcome any reservations it had about jumping in.
Though slow to start, we ultimately captured four different wolverines (possibly five – one got away before we reached the trap), and collared three. With the generous aid of the Alaska Department of Fish & Game, we were able to deploy two more collars, for a total of five wolverines now out on the tundra, transmitting data. Two are lactating females.
But this figure is only a part of what allows us to claim success. In our seven weeks there, we also collected 88 scats for diet analysis and genetic information, followed over 40 miles of wolverine tracks to understand where the animals traveled, remotely observed what may be the first GPS documentation of a wolverine traveling on sea ice, and deployed 13 motion activated cameras on snow-holes created by wolverines.
This last number is worth expounding. With the aid of aerial observers Tina Laird, Mark Keech, Pat Valkenburg, and Audrey Magoun, we located and investigated around twenty holes dug by wolverines in the snow. On the surface, these holes are unassuming. Some are accompanied by scat or food remains (often caribou or moose bones), while others are meticulously clean. Some have dozens of tracks coming and going, while others appear to have only been used once. At some, the opening is small – often a mere 7-8”—while at others a wide entrance leads into a large (~2′ diameter) cavern. Some are created in relatively shallow snow, while others are dug into meters-deep drifts, often on the lee of cut banks or lake shores.
We are intensely curious about these holes. Around the world, wolverine distribution is strongly correlated with snow that persists late into spring, but no one fully understands why. In the Lower 48, where increasingly warm winters mean less late-season snow, this relationship may put the species in peril. On the tundra, wolverines seeking some sort of structure (for protection from predators, to raise their kits, to store food, or for any number of other reasons) have little choice but to dig holes in the snow. Unlike wolverines in most other places, these animals live above treeline, and cannot hide under boulders (for the most part – there are few here), root wads, or downed timber. They must entirely create their own structure.
We think that snow on the North Slope may play a crucial role in the life of a wolverine, and that coming to understand this role may unlock if and how the changing climate will impact wolverines in the Lower 48, and around the world. In three weeks, I will return to the study area to collect our thirteen cameras, which we hope hold a first glimpse into this mystery.
In the meantime, our aerial observers are back at it, investigating whether GPS-clusters transmitted by our collared animals might be dens or other snow structures. Very little is known about how wolverines use snow for structure, and we hope to change that.
Written by Tom Glass, WCS Wolverine Research Technician. April 2016.