image: In this image from April 2021, an emaciated and nutritionally stressed bull moose -- who is also severely impacted by winter ticks -- beds down on the island.
The COVID-19 pandemic halted the in-person wintertime survey of wolves and moose on the island for the first time in 63 years. Consequently, there are no estimates of wolf or moose abundance for 2021, and the next estimates are scheduled in February 2022. But though the Isle Royale Winter Study didn't happen quite as planned, researchers were still able to visit the remote national park in the spring.
Now, fieldwork has resumed and Michigan Technological University researchers have already uncovered new information about these two iconic wildlife populations. In particular, wolves produced at least two litters of pups, and moose appear poised for decline.
In the Isle Royale Winter Study, Michigan Tech researchers share other significant developments about curating the world's largest moose bone collection, advances in understanding of wolf foraging behavior and the nutritional health of the moose population.
Key points:
The Isle Royale wolf population is likely growing. "We recovered footage of a group of four wolf pups taken in January 2021 by remote cameras at the east end of Isle Royale," said Sarah Hoy, research assistant professor in Michigan Tech's College of Forest Resources and Environmental Science (CFRES). "Additionally, observations of tracks and scats left by wolf pups last fall at two different locations suggest that there were probably two different litters of pups living at the east end of the island in September 2020."
Wolves are specialized foragers. "Wolf foraging behavior seems driven by minimizing the risks associated with killing large prey, like moose, even when the differences in vulnerability among individual moose might seem relatively subtle compared to when predators are choosing between different prey species," Hoy said.
Nutritional stress stacks the deck against moose, which holds significant implications for how moose will handle a warming climate. "We found that the nutritional health of moose was importantly influenced by how hot it is during the summer, and also by how deep the snow is in winter," Hoy said. "Moose tended to be more nutritionally stressed during winters with deep snow, which may be because deeper snow makes it more difficult for moose to move around and find food."
The moose population is likely declining. "Moose really struggled to find enough food this past winter," Hoy said. "Because there have been such large numbers of moose on the island over the last five years and moose ate branches faster than the trees can recover and replace them, the amount of food available to moose during winter has been getting progressively worse each year since 2017.
Winter ticks are worse than usual this year, as evidenced by moose with very little fur left in spring -- having scratched or bitten off almost all of their winter coats in an effort to rid themselves of the blood-sucking parasites. This is significant because blood loss to ticks can exacerbate the detrimental effects of food shortage. Despite the mild winter, depleted food supplies and ticks made life harder for the island's moose this year.