Lisa in front of Daisy Farm Cabin
We just arrived back to the western end of Isle Royale after having spent 15 days in a small ranger cabin near the Daisy Farm campground on the eastern part of the island. During the summer, this is a busy place with hikers, canoeists, boaters and campers arriving and departing from the Daisy Farm dock. But in the winter, there is no one. It is silent, peaceful, wild, and isolated. Wildlife travels the snow covered hiking trails, browses the trees and shrubs surrounding the campground, and some even make a winter home under the wooden lean-tos used by so many visitors in the summer. Our small plane landed on the ice in front of the cabin on February 4th and after saying goodbye to Tim and Pat, the Forest Service pilots, we watched as they taxied down Moskey Basin and took off back to Ely, MN. Minutes later, the Isle Royale Wolf/Moose Study Flagship, piloted by Don Glaser, landed to make sure we had everything we needed for our two week stay.
Ky at the water hole – we use the antler to cover the hole so the otters don’t find it!
First order of business was to make sure the propane cook stove and heater would work (they did) and to cut a hole in the ice of Moskey Bay so that we could get some water (17 inches of ice later, we had all the water we would need). We unpacked the boxes of non-perishable food that had been left for us back in October, put away our gear, and settled in for our long stay. Over the next 15 days, we covered much of the area within a 3-4 mile radius of the cabin, skiing over frozen lakes and snow covered ridges, bushwhacking through thick balsam fir forests, tangled white cedar swamps, dense spruce regeneration, open deciduous forests, and windblown slopes.
One of the many island vistas. This one is in the drainage between Angleworm Lake and Lake Ojibway.
Our goal was to collect paired pellet/urine samples from as many different moose as possible for a study looking at winter moose nutrition. DNA on the surface of the pellet is used to identify individual animals, and the ratio of urine metabolites, specifically the ratio of urinary nitrogen to creatinine (UN:C ratio), tells us how healthy it is. In short, the more urinary nitrogen we find in relation to creatinine tells us that the moose is not able to get enough forage, is in a caloric deficit, and is now metabolizing its own muscle to make energy.
Ky in a pit he dug around frozen moose urine so that he could collect it without diluting it with too much snow. The urine is orange because this moose has been feeding on cedar.
In addition, if we were able to isolate an area of balsam fir where a single moose had been feeding, we took samples from both browsed (preferred) and un-browsed (not preferred) trees for a new study on plant secondary metabolites (PSMs).
Measuring where the moose have browsed the balsam fir
PSMs are chemical compounds created by plants as a defense from herbivores. It is thought that after moose browse a balsam fir, the tree produces more PSMs in its regenerating growth in the hopes that the moose does not find it very tasty the next time around. Indeed, the moose seem to shy away from the lush green shoots of the most recent years’ growth in favor of lower branches where concentrations of PSMs are less. It is thought that these chemical defenses of plants may be more important in the shaping of food chains than we thought. Here on Isle Royale researchers are specifically studying the wolf, moose, and balsam fir food chain.
Snow-covered balsam firs and white spruce
This year the island has had almost a record winter as far as snowfall and cold temperatures. We measure snow depth when we collect our samples and on average, the snow averaged 3.5 feet deep with some areas close to 4’ deep. The moose that we saw were struggling through the deep snow up to their bellies. It seemed especially hard on the calves who generally followed their mothers around by stepping into her exact tracks. We found many moose beds tucked into the shelter of conifers, indented deeply into the snow. With so much snow, the animals don’t move around as much as they normally would. Instead, they find an area with food, and then stay close by until they deplete their food supply. Like bison and elk in Yellowstone, the moose have been digging as much as 3’ into the snow to get to the bottoms of young fir trees-very unusual behavior for moose. There were areas of balsam fir, most especially on the western end of the island, where almost nothing remained of the sapling except for some sticks with a few needles. Some moose were chomping down on the main stem of trees to a diameter of almost ½” where a ¼” is usually the winter maximum. One might not think there is much difference between a fir and a spruce tree, but to moose there is a world of difference, and even under these food-stressed times for moose we have not seen one browsed spruce tree. Obviously the spruces have figured out a formidable defense against moose.
Balsam Fir on the left, White Spruce on the right
One of the tree species that stands out in the winter is the mountain ash. This beautiful hardwood is quite plentiful on the island and in the winter, its bright red berries make a beautiful contrast against the white of the snow. This year the trees put forth a bumper-crop of berries and the fruit laden crowns can even be seen from the air as we fly over in the plane. Moose love mountain ash, especially the tender saplings and new growth. As we travelled on our skis over Isle Royale this winter, most of the young mountain ash that we came across had been browsed by moose. The trees that escaped from the moose and have been allowed to mature, provide food in the winter for other wildlife. Along the shoreline of Moskey Basin, fox tracks cover the ground under mountain ash trees as foxes love to eat the juicy red berries when they fall from the tree. The trees also attract some of the winter bird species found on the island. We saw several American robins, a flock of 100 Bohemian waxwings, and multiple Pine grosbeaks eating the berries.
Mountain Ash laden with fruit
Isle Royale is a very unique place in that much of the vegetation is similar to surrounding mainland areas in Minnesota, Ontario, and northern Michigan, but the wildlife diversity is much sparser. There is only one species of deer on the island, the moose. At one time there were caribou but they have long since disappeared. No whitetail deer have made it across the 15-20 miles separating the island from the mainland. The deer would have to swim, as hooves don’t make for good traction on ice, and it is believed that because of their relatively smaller body size (with more surface area to body mass than moose) that they would succumb to hypothermia in the cold Lake Superior water and die before they got here. Researchers had found one whitetail carcass years ago washed up on the shore. There are no coyotes or black bears, only wolves and red foxes. There are red squirrels but no gray or flying squirrels. There are snowshoe hares, otters, and pine martens. There are no porcupines, or raccoons, or skunks. There is only one species of mouse, the deer mouse, and no voles, shrews, or rats.
Because we find ourselves bushwhacking through many different kinds of habitat, we often see tracks from snowshoe hares, especially when the vegetation is thick and impenetrable. They have elaborate networks of trails from beneath downed trees to feeding sites, where they feed on spruce and cedar twigs, and the bark of hardwood trees. Over the last month we have seen several during our travels. This year, they seemed particularly plentiful. Call me a crazy bunny lady, but if you talk to them as they are hopping away, they generally stop and sit still, not moving a muscle until you continue on your way. Their fur is mostly white, their winter camouflage coat, and their large back feet seem almost comically big as they propel themselves over the deep snow. We use the density of bunny tracks in areas –especially white cedar swamps- as a litmus test for how bad the bushwacking is going to get. When the tracks get thick, pull up jacket hoods, shorten up the adjustable ski poles, and keep a positive attitude because it gets ugly!
Isle Royale Wolves – photo courtesy of John Vucetich
Last year, we were incredibly fortunate to see three of the island’s eight wolves. These were three un-collared animals who were traveling past Daisy Farm and stopped to investigate our water hole. This year, we were not so lucky. We never even saw a track during all of our travels around the island. Wolves are an integral part of the Isle Royale ecosystem as they help to keep the moose numbers in check, which in turn helps to keep the vegetation from becoming too over-browsed. Unfortunately, the number of wolves on the island have decreased to an all-time low and these wolves are all quite closely related (which keeps them from breeding with one another), which will eventually lead to their extinction unless new genes are introduced into the population – either naturally by wolves crossing to the island from the mainland, or artificially by transplanting wolves from the mainland. There is great controversy brewing over what to do about the wolves and there are three scenarios that are being debated. The first is to do nothing and let the wolves die out or repopulate on their own (which is not likely given the lack of an ice bridge in recent years). Scientists who have been studying the island’s ecology for many years, warn that doing nothing (unless the wolves can get to the island on their own) would be disastrous as it would lead to an unsustainable increase in moose numbers. Another option would be to wait and let the wolves die out and then introduce new wolves to the island.
Isle Royale wolves hunting. Photo courtesy of John Vucetich
This would be a viable option but it may take a while before the last wolf is gone and by that point, vegetation would have suffered under the increasingly burgeoning moose population. The last option, is to introduce a few new wolves into the existing population in order to inject new genes into a struggling population. Over the years that wolves have been established on the island, there have been quite a few instances where an ice bridge has formed between the island and the mainland, giving the animals an opportunity to travel onto or off of the island. But recently, those ice bridges have been less frequent (there was one this year and the one before that was in 2008). Consequently, it is likely the wolves will need human help to rescue their struggling populations. Hopefully, Isle Royale park managers will make the decision to rescue this isolated population that is on the brink of extinction before it is too late.
**We just learned a few days ago, that “Isabelle”, one of the breeding females from Isle Royale, was found dead in Grand Portage, MN. If any of you read the Isle Royale Winter Study blog last winter, she had been repeatedly and brutally attacked by two females who were accompanying her brother. She managed to make it through the summer and she had last been seen by the Isle Royale Project’s crew from the plane on the 21st of January 2014, just before an ice bridge formed. She took the first chance she got and fled the island. No one knows how she died, but she was five years old and of prime breeding age, so in addition to escaping her difficult life on the island she may also have been looking for an opportunity to breed.
Isle Royale NP – Cow moose with twin calves. Courtesy of John Vucetich.
This year, it seemed as if there were fewer moose on the island than last year based on the amount of moose and moose sign we were seeing. However, we won’t know for sure until the final aerial moose count has been completed. It could be that they were more concentrated due to the heavy snows and we were missing pockets of them, or it could be that the combined effect of winter ticks and a prolonged winter last year caused more to die than was originally thought. One thing we did observe, was that bulls were holding their antlers longer than normal. We did come across several freshly dropped antlers in our travels, when usually, these would have all been dropped by late December and buried deep in the snow. We did have several instances where we sampled a cow moose with twins. It is always a treat to come across their beds tucked up into the conifers – the larger mom’s bed, and the two calves nearby, usually one bigger than the other. Perhaps the male twin is larger than the female twin or one was just more aggressive when nursing from their mother. In some places, you could see where the young ones had pounced around in the snow, wrestled with branches, and pulled vegetation everywhere. Their tracks often lead us through tree-wells where adult moose never travel.
Three moose beds – moms bed with pellets and two smaller calf beds