Following the Wolf Pack
By JOHN VUCETICH
Chippewa Harbor wolves resting after an unsuccessful night of hunting.John Vucetich, a wildlife ecologist from Michigan Technological University, leads the wolf-moose Winter Study at Isle Royale National Park.
Thursday, Feb. 2
We see two wolves sleeping with full bellies in the bright sun. Two others — each with bones braced between their paws — crunch and gnaw for the rich marrow inside. The last two wolves are not visible. Presumably, they are asleep beneath nearby spruce.
The Chippewa Harbor wolf pack is feeding on their moose carcass for the third day. They’re spreading bones, blood, stomach remnants and hair over larger and larger areas every day. There seem to be enough remains to keep these wolves eating for another couple of days. After observing the wolves, Don and I go prospecting from one inland lake to another. This is the most efficient way to find wolves or tracks of wolves you don’t know are there. We get lucky, finding two wolves walking the shoreline southwest from Hay Bay. Loping at four miles an hour, they clearly have a destination in mind. Don flies circles high overhead while we watch and wonder. Who are these wolves? Did a lone wolf hook up with a successful emigrant from the Chippewa Harbor Pack? Are they the reconstituted remnants of Middle Pack? Or something else altogether?
.After crossing the mouth of the Big Siskiwit River, the larger of the two wolves stops at a rock poking through the snow, sniffs, turns, raises his tail, arches his back and deposits a big scat. He scratches the snow and moves on. The second, smaller wolf walks over and scent-marks the same rock with a raised leg. Whoever these wolves are, this is their territory, and they are defending it. We could have figured out who this wolf was, had a raven not stolen that scat before we could get to it.“I want that scat,” I say to Don. The DNA in the scat will tell us who these wolves are. But it’s late, and the sun is fading fast. Maybe tomorrow we can snowshoe in from Lake Halloran to get it.
Friday, Feb. 3
The weather looks like it could change for the worse before we can retrieve that wolf scat. No one wants to spend a night in the bush because of excessive enthusiasm for a scat. But the weather is good for counting moose (no wind, low morning sun), so we go moose-counting. During the afternoon flight, Don and Rolf observe that the Chippewa Harbor Pack is continuing to feed and rest at the kill site for the fourth day. So they go prospecting for wolves or wolf tracks that we haven’t seen before. No new clues.
Saturday, Feb. 4
Rolf and I review all our field notes: which wolves were seen where and when? And where were they in relationship to the various sets of fresh tracks we’d observed? We realize that the two wolves we saw southwest of Hay Bay may be the alpha pair of the Chippewa Harbor Pack. All future observations will be weighed for or against the hypothesis that the Isle Royale National Park wolf population now comprises just a single pack.
On the fifth day at the kill site, four wolves are play-wrestling among themselves, tails wagging, front legs flailing. After several minutes of self-generated excitement, it is time to abandon this kill site. When they leave, they head west. We get a clear view when the pack comes out of the forest at McCargoe Cove. They are led by a strong, proud wolf, his tail pointing high to the sky. At the head of the cove, he scent-marks a stump: the exclusive privilege of an alpha wolf.
The wind is building, grabbing the wings of the Flagship, jerking with increasing violence, side-to-side, up-and-down. It is time for some work on the ground. Don sets us down on Lake Halloran. There, we strap on snowshoes and head north through alder, spruce and aspen, then downhill and onto the beach of Siskiwit Bay. After about a mile, we reach that rock poking through the snow, the one that held our scat. But we find nothing but a bare rock — and the tracks of a raven. Hop, hop, then the impression of flight feathers in the snow. A raven has stolen our scat.
Wolves eat very large prey. To minimize losses to scavengers like ravens, they are adapted to eat and digest food very quickly. Consequently, much of the protein in moose meat remains in wolf scat, more than enough to satisfy a raven’s hunger.
On our trek back to the plane, I can see that the moose’s shins are beginning to bleed. It is starting to show in their tracks. Temperatures fluctuating around the freezing mark have created a crust on the surface of the snow. Hair is thin on the front of a moose’s shin, and they get abraded from repeatedly punching through the crust. From now on, moose will begin to spend more time in thicker stands of conifer, where the snow is not so deep.
Cow and calf moose being chased by the Chippewa Harbor wolf pack.By late afternoon, the receding wind grants us an opportunity to catch up with the Chippewa Harbor Pack. They have left McCargoe Cove to hunt moose. Before nightfall, they find a cow and calf. There are moments of terror for the moose, no doubt, but the wolves never even come close.
Sunday, Feb. 5
The wolves have traveled all night, mostly in single file, and sometimes through snow that is chest deep. They passed through one swamp after the next, all country they’d been through many times before. Though they passed several moose, none were vulnerable enough to take down. After an unsuccessful hunt, the Chippewa Harbor Pack sleeps throughout the morning in a clearing beneath the warm sun. Southwest winds are building, sending us home long before we want to leave.
NOTE ABOUT THE NY TIMES SCIENCE BLOG
This blog is the modern version of a field journal, a place for reports on the daily progress of scientific expeditions — adventures, misadventures, discoveries. As with the expeditions themselves, you never know what you will find.
Are there scientists you would like to see write about their field work? Are you a researcher interested in writing about your own field work? Send an e-mail to scientistatwork@nytimes.com. If you are nominating yourself, please include a description of your field work and samples of your writing and photographs.
Posts
No comments:
Post a Comment