Fewer Yellowstone wolves equals no wolf-on-wolf deaths

Fewer Yellowstone wolves equals no wolf-on-wolf deaths

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Yellowstone wolf

A wolf near Blacktail Pond in February 2006 in Yellowstone National Park.

YELLOWSTONE — For the first time in 24 years, Yellowstone National Park’s wolf project staff found no evidence in 2018 of wolves killing each other.

That’s unusual since such wolf-on-wolf deaths are the leading cause of natural mortality for the park’s big canines. There was also no evidence of wolves dying from any major diseases, even though mange was found in several coyotes and foxes in or near the park boundary.

These details about Yellowstone’s wolves, along with many other insights, are contained in the 2018 Yellowstone Wolf Project Annual Report, which can be found online. The annual report contains information on individual packs, pup survival, wolf project outreach as well as mortalities.

Seven wolf deaths were recorded among park wolves in 2018. Of those, three were shot by hunters outside the park’s boundary. The most well-known was 926F, a female wolf killed by a hunter near the small community of Silver Gate near the Northeast Entrance. That legal harvest prompted an outpouring of anger at the hunter, drawing national attention.

In an unusual incident, an older wolf from the Cougar Creek pack that was shot outside the park in February 2018 was a hermaphrodite, possessing both male and female sex organs. The wolf’s unique condition was discovered by the park staff as they were handling it during collaring operations. At the time, the team had assumed the wolf was the alpha female of the Cougar Creek pack. Given its condition, the wolf was identified as 1116U, the U denoting that the wolf was neither male (M) nor female (F).

According to Doug Smith, Wolf Project biologist, his team had never seen or heard of this before, and to their knowledge this is the first time it has ever been recorded.

Yellowstone wolf packs

All told, at the end of 2018 there were at least 80 wolves in nine packs with seven breeding pairs that were calling Yellowstone home. That’s down from the previous five years and the lowest number of wolves since 2012. Those lower wolf numbers may help explain why there were fewer pack conflicts over territory, as well as no transmission of disease — both of which are more likely when populations are denser.

“Overall, wolf numbers fluctuated little from 2009 to 2017 (83-108 wolves) but dropped slightly” in 2018, particularly in the park’s interior, according to the wolf report. That’s where one of what had been one of the park’s larger packs — the Mollie’s pack — lives. Once the largest pack in the park — in part because they needed more wolves to bring down the main winter prey of bison in Pelican Valley — Mollie’s had fallen to seven wolves, three of which were pups. That was the smallest the pack had been in five years. In 2017, the pack numbered 14 wolves, none of which were pups. The year prior, it consisted of 18 wolves.

Now the largest pack is the 19 member Wapiti Lake contingent, which consisted of 13 adults and six pups in 2018. The pack was even bigger at the start of that year after having two litters of pups, for a total of seven. But following a fight with the overlapping 8 Mile pack in late November, eight males from the Wapiti Lake pack broke away, staying on the Northern Range while the other wolves migrated south.

Wolf prey

Yellowstone wolves continue to dine mainly on elk, although they also took on a grizzly bear and cougar in 2018.

“Project staff detected 151 kills that were definitely, probably, or possibly made by wolves in 2018: 95 elk (62.9%), 25 bison (16.6%), 11 mule deer (7.3%), 3 deer of unknown species (2.0%), 2 coyotes (3.0%), 2 pronghorn (1.3%), 1 grizzly bear (0.6%), 1 mountain lion (0.6%), and 11 unidentified animals (7.3%),” the report stated. “The composition of wolf-killed elk was: 22.1% calves, 6.3% yearlings, 22.1% adult females, 37.9% adult males, 3.2% adults of unknown sex, and 8.4% of unknown sex and age.”


In another unusual tale in the Yellowstone wolf saga, a subordinate male of the Junction Butte pack — 996M — “showed an unusual infatuation with the small pups — at times he would play roughly and try to pick them up, and this led to the death of at least one pup and possibly more. The adult females were protective over the pups and sometimes aggressively pinned 996M when he was close, but otherwise he behaved as a normal subordinate member of the pack. Only three pups survived the summer, and it is unknown how the others died.”

The Junction Butte pack is well-known to wolf watchers since it sometimes dens along Slough Creek, making the site visible from the road to the Slough Creek Campground to wolf watchers with long spotting scopes. Four females in the pack were bred and produced pups in 2018, three of which denned at the popular site. “By late May, as many as 11 pups were counted at the Slough den, nursed by all three females. Only three of the pups survived the summer and it is unknown how the others died.”

Looking ahead, Wolf Project biologist Doug Smith said 2019 may have been a rebuilding year for Yellowstone’s wolves.

“We did see some big pup litters,” Smith said. “Three Northern Range packs did pretty well.”

Collaring wolves

Since the reintroduction of gray wolves to Yellowstone National Park in 1995 and 1996, radio collars have been used as the main tool for monitoring and research. Collaring efforts were never intended to be used as tool to locate wolves for public viewing. Now, 24 years, seven wolf generations, and 616 collars later, radio-collaring remains an important method to collect all kinds of data and has undergone its own technological evolution.

The collars used by the Yellowstone Wolf Project weigh approximately 500 grams, which amounts to 0.8-1.8% of the wolf’s total body mass in proportion to the collar.

Wolves wearing radio collars do not act any differently than wolves without radio collars — we have no evidence suggesting collars influence rates of dispersal, mortality, survival, breeding success, and leadership. And the collar does not seem to bother the wearer at all. The Wolf Project has not recorded increased scratching or rubbing for wolves wearing collars; the wolves seem to completely ignore their own collars.

A few packs have made collar-chewing a bit of a fun pastime — between 2017 and 2018, the anomalous Cougar Creek pack chewed off three of their six collars.


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