By Kyrmyzy Turebayeva
Only about 30 percent of gray wolf pups survive their first year of life even though the wolf population in the region remains stable, according to a new study by researchers at the University of Minnesota.
The study was conducted from 2019 to 2025 in the Greater Voyageurs Ecosystem, a forested region surrounding Voyageurs National Park in northern Minnesota.
Over those six years, researchers monitored 33 wolf packs to determine how many pups survived to one year of age.
“We had wanted to study wolf pup survival for a long time because it is one of the most challenging aspects of studying wolves in the wild,” said Thomas Gable, a researcher at the university and one of the authors of the study.
Minnesota’s gray wolf population is listed as “threatened” under the federal Endangered Species Act. Approximately 2,300 wolves lived in the state as of 2025, according to the Department of Natural Resources.
“Wolf pups are very difficult to observe, especially in forested ecosystems, so until now there has been limited knowledge about how many of them actually survive to one year old,” Gable said.
According to Gable, this is an important measure because pup survival largely determines how populations change from year to year. If more pups survive to adulthood, the population can increase. If the number of survivors declines, the population may remain stable or decrease over time.
This study is one part of the university’s larger Voyageurs Wolf Project.
To determine pup survival, researchers monitored wolf packs in the region.
First, they located dens using adult wolves that had been fitted with GPS collars.
These devices allowed researchers to track animal movements and identify locations where the adults regularly returned.
Those locations were where wolf dens with pups were typically found.
After locating dens, researchers counted the number of pups to determine how many were born at the beginning of the year.
Researchers also placed remote cameras throughout each pack’s territory, including along forest trails and roads and in other areas where wolves were most likely to travel.
“The biggest challenge was choosing good locations for cameras where we could be confident that wolves would regularly pass through,” Gable said.
“Wolves occupy very large territories, so even 15 to 20 cameras per pack is not that many,” he said. “If cameras are placed in poor locations, it is simply impossible to collect high-quality data. You need to understand animal behavior well and be able to anticipate where they are likely to appear.”
According to Gable, remote cameras were a key part of the study because directly observing wolves in a forest environment is nearly impossible.
Combining data from den visits and remote cameras allowed researchers to determine how many pups remained alive by the end of the year.
Lack of food is likely a main cause of pup mortality, Gable said.
Adults must obtain enough food not only for themselves but also for their offspring.
When prey is limited, some pups do not receive enough nutrition and die.
According to Gable, prey size plays an important role in determining how many pups a pack can successfully raise.
In areas where wolves hunt larger animals, such as moose or elk, a single kill provides more food for the entire pack. Under those conditions, more wolf pups typically survive.
White-tailed deer are the primary prey of gray wolves in the Greater Voyagers Ecosystem, but their smaller size means there is less food to go around.
“When wolves are hunting smaller prey, such as white-tailed deer, one deer is often not enough to feed a large number of pups and adults. As a result, fewer pups survive,” Gable explained.
In areas where the main prey are smaller animals, wolf packs can compensate by maintaining smaller territories.
That allows more packs to exist in the same region, but fewer pups typically survive in each pack.
Despite the fact that most wolf pups die during their first year, that does not mean that populations are at risk.
“Wolves can have low pup survival and still maintain stable and high-density populations,” Gable said.
According to him, the wolf population in the Greater Voyageurs Ecosystem has likely reached the maximum level that can be supported by available food resources.
This limit is known in ecology as biological carrying capacity.
This does not mean that the number remains unchanged, but rather that the population can fluctuate around a level that the ecosystem is able to support.
The fact that about seven out of 10 pups die during their first year of life is not a sign that wolves are disappearing; it is a natural process that reflects the limits of the ecosystem, Gable said.
“Many people believe that wolves can increase their numbers indefinitely and reach very high levels, causing strong negative impacts on their prey species because their populations cannot be controlled,” he said.
“But our research shows the opposite. There are factors that limit how many wolves can exist in a given area. The main one of these factors is food availability,” Gable said.
The study appeared in the journal Wildlife Biology.