Linda Thurston

Linda Thurston

Linda Thurston has been involved for over four years with the Yellowstone Gray Wolf Recovery Project, participating in capture, handling gray wolves and conducting predator-prey research. Linda spends long hours watching wolves at observation sites with high-powered scopes examining how they live; in particular, she has collected data over three seasons focusing on wolf denning behavior.

Ms. Thurston received a B.S. degree in 1995 from the University of California at San Diego in Ecology. Her experiences include studying Amazon parrots, black iguanas in Costa Rica, and coyotes in Wyoming. Linda received her master’s degree from Texas A&M University in Wildlife and Fisheries Sciences, with an emphasis in animal behavior. Her life goal is to pursue the study of animal behavior Her writings include Yellowstone Wolves: Predation , A History of the Rose Creek Wolf Pack, and A History of the Crystal Creek Wolf Pack.

Currently Linda and Nathan  run their company, the Wild Side, which provides personal guided trips into Yellowstone to study the Parks ecosystem and the behavior of its wolves, bears, and other diverse wildlife.  They also include interesting educational classes.

Linda and Nathan remain very active in working with Yellowstone Wolf Project and
other issues facing Yellowstone Park today.  www.Wolftracker.com


The Yellowstone Wolf Project: Observing Denning

Research by Linda Thurston

Particularly with the monitoring of endangered species and, in general, to know more about a species, denning behavior helps us to understand reproduction and pup survival. The reintroduction of wolves in Yellowstone provided one for the first opportunities scientists had really observe wolf denning behavior in the wild.

Previous studies on wolf behavior were done on captive wolves, but because wolves in the wild are able to travel up to 40 miles a day, confinement can alter the behavior of these mobile, highly social animals. The Yellowstone Wolf Project has taken advantage of this opportunity by collecting rarely observed behavioral data.

The Yellowstone Wolf Project examined wolf denning behavior for three years.

Den study would begin in early April with a crew of volunteers that monitor chosen packs for four months. The idea is to follow packs with radio tracking equipment to determine when the breeding (mother) females whelp (giving birth to wolf pups). Since scientists are able to observe some wolves breeding, the whelp dates of those females can be estimated based on a 63-day gestation period. Also, it becomes apparent when the female wolf stops traveling with her pack, staying in the vicinity of a den for a month. The packs which were monitored were selected on the basis of accessibility in the spring—this included the Rose Creek, Druid Peak, Leopold, and Chief Joseph Packs. Snow depth during winter and early spring months makes it extremely difficult to collect data on packs in the park’s interior.

In 1998, the Rose Creek Pack was the first pack to have pups, with two females both whelping on April 7 th. They shared the same den. The other three packs had their litters in the next two weeks. Once the packs had their litters, a team was assigned to each pack to monitor the den for 48 continuous hours once a week for three months. So their presence would not upset the wolves, observers were stationed a mile from the den. They observed wolf behavior using high-powered field scopes.

The study continued until the pups were about 15 weeks old. Duration of the study coincides with the weaning schedule of the pups: they begin to be weaned at approximately 5 weeks of age and are fully weaned by 10 weeks. A pup is weaned when it not longer depends on its mother’s milk.

For wolves to be removed from the federal endangered species list involves observing that 10 breeding pairs reproduced successfully for three successive years in three recovery areas. Those areas include packs located in northern Montana , central Idaho , and Yellowstone .

By noting factors affecting denning, the study Yellowstone Wolf Project has provided insight to the conditions under which packs are able to successfully raise litters. Key information collected included the date pups are born, litter size, and causes of pup mortality.

What was observed?

During 1998 the Rose Creek Pack had 11 pups between two females only one pup died during the first month of age. Possible causes of pup mortality include disease, predation, malnutrition, and territorial intrusions by neighboring packs. The cause of the Rose Creek Pack pup mortality was unknown; nevertheless the pack had high pup survivorship with the remaining 10. If, for example, packs were to loose many pups at approximately one month of age, canine disease would be suspected and managers could then decide what action needed to be taken.

Other information collected dealt with the nutritional condition of pups. The majority of pups observed in Yellowstone were vigorous and playful, an indication of good nutrition. If the available prey base were to change in the future making less food available to wolves, we might see more lethargic pups and lower survivorship.

Data on the placement of denning sites is also valuable information. When packs have selected dens near roads it has enticed visitors to approach too close to the den which interfered with pack movements. Detailed notes have been taken on human-caused disturbances and the resulting wolf behavior. One case of a mother wolf moving her den due to human intrusion was observed.

While observing denning behavior sometimes information may be gather that examines some theoretical questions. For example, if a lone female can successfully raise a litter of pups without the protection of other pack members, then why do wolves live in packs? While a rare occurrence, observation has shown that single mothers can be successful. In 1997 and 1998, Number16 of the Chief Joseph Pack was able to raise her pups without help from other wolves. But because Number 16’s 1997 litter did not fare well, it appears that pup survivorship is enhanced when helper wolves are available.

Information was also collected on the amount of time each pack member stays at the den and provides protection to the pups. One of these questions was: (1) are the subordinate wolves providing care to pups in the way of bringing food, providing protection, and playing the role of babysitter while the mother is away? Or (2) are some wolves merely near the den to intercept food brought back by other wolves? Simply do some wolves take a caring (self-sacrificing) role or merely greedy and opportunistic. Behaviors on both sides of these questions have been observed.

Other questions examined were:

How does the amount and type of care provided to pups differ between males and females within the same pack and among different packs?

How much does pup care vary depending upon pack size and social composition?

Preliminary findings to these questions are being analyzed and will be presented in Linda Thurston ’s graduate dissertation. It is only by collecting information over a long period that we will begin to see trends, and develop a better understanding of the denning ecology of wolves in the wild.