Yellowstone wolf population is hit hard this year. Reasons not certain-
Back in 2005 after years of major population growth tapering off to stability, the Yellowstone wolf population suddenly crashed when all but 20% of that year’s wolf pups died. While the cause was not determined for sure, most think it was due to canine distemper.
The next two years, however, saw a rebuilding of the wolf population with high wolf pup survival rates. 2008 began with what appeared would be more growth with reports of very high pup counts, e.g., 24 pups in the Leopold Pack.
The first signs of trouble came, however, from the Slough Creek Pack which had a number of pregnant female wolves, but only one pup was seen. As the summer wore on, many packs seemed to have lost all of their pups and most at least some. Currently only the Gibbon Pack has a large number of pups left — ten — and it is the largest wolf pack inside the Park with 25 or more members. Despite its size it is not commonly seen. Its territory is not close to the Park roads.
Not only have more than half the pups died, but interpack strife is high with fights between wolf packs and attacks on by packs on lone wolves taken by surprise.
Finally, canine distemper, which might be the cause of the pup loss (this has not been proven) does attack older wolves too. It is less deadly with older wolves but for those in poor nutritional status mortality can be high. Nutritional stress could be present given the decline of the elk population in the Park.
Wolves born in 2005 or earlier in the Park probably have antibodies to distemper, but the 2006-7 young adults probably do not. If distemper is around, it may have taken wolves older than pups.
Distemper is spread by saliva and is carried by wolves, dogs, coyotes, fox, skunks and other animals.
I should caution that distemper has not yet been proven as the cause, and the pup loss might be due to one or more entirely different factors.
The following packs seem to have lost all their pups as of October
Slough Creek, Agate, Oxbow, Canyon, and Cougar Creek.
Update: Canyon still has one pup. RM
The Delta Pack, which was the Park’s largest last year, appears to still have 2 pups (the alpha female is old and she may not have had more than that).
The Druids went from possibly 18 pups down to a current 5. The Druid Pack still has 21 members and dominates the area.
After an attack by the Agate Pack, the Oxbow Pack is down to just the alpha pair, and maybe not even that.
The Canyon Pack, which formed from a Hayden female and a Molly’s male (replacing the disrupted Hayden Pack) lost one, or maybe 2 pups. I think it has 4 or 5 members, including a surviving pup.
Mollies Pack size is unknown. It has 2 or 3 pups.
The Leopolds are on the brink of extinction. They are the Park’s oldest wolf pack and have long been one of the biggest. At the beginning of the summer it looked like they might have 30 or 40 members. However, all but 3 of their 24 pups disappeared. The alpha male was killed in an attack by other wolves and only 3 adults are now collared and seen regularly. So the pack might be down to 6 or even less.
The Slough Pack lost all its pups, and in repeated attacks by other packs lost its alpha and beta females. Now just one female is left, “Hook,” a surviver of the 2005 pup dieoff, is the sole and alpha female. The pack seems to have 8 adult male wolves.
The Slough Creek Pack lost all of its pups, and in repeated attacks by other wolf packs it lost its alpha female and beta female this summer.
Now the alpha female is “Hook”, a surviver of the 2005 pup dieoff. The Slough pack is female, not male-heavy. All the pack members are females except for one male. There are about 11 pack members.
One new wolf pack has formed. Wolf 470F, born to the Leopolds, and who became a founder of the Oxbow Pack, has gathered some other wolves and may have a few pups. Her pack is called the Mt. Everts Pack, based on their primary range.
I will be in Yellowstone and hope to return with more information.