Current packs in Yellowstone

At the end of 2010, at least 97 wolves in 11 packs and 6 loners occupied Yellowstone National Park (YNP). This is nearly the same size population as in 2009 (96 wolves) and represents a stable population. Breeding pairs increased from six in 2009 to eight in 2010. The wolf population declined 43% since 2007, primarily because of a smaller elk population, the main food of northern range wolves. The interior wolf population declined less, probably because they augment their diet with bison. The severity of mange declined in 2010 and there was no evidence of distemper being a mortality factor as it was in previous years (1999, 2005, and 2008). Pack size ranged from three (Grayling Creek) to 16 (Mollie's) and averaged 8.3, slightly higher than in 2009 (7.1), but lower than the long-term average of 10 wolves per pack. Eight of the 11 packs reproduced (73%). The average number of pups per pack in early winter (for packs that had at least one pup) was 4.8, compared to the 2009 average of 3.8. A total of 38 pups in YNP survived to year end.

For more information, please visit the NPS wolf webpage.

 

Reintroduction History

The gray wolf (Canis lupus) is the only top carnivore to be extirpated from the American West by the 1930s. Nearly 60 years later, the wolf was reintroduced to YNP and CID in 1995 and 1996 as part of wolf restoration to the Northern Rocky Mountain Region (see US Fish and Wildlife Service Annual Reports on the Wolf Recovery). A founding stock of 31 wild-born individuals were captured from two genetically distinct wolf populations in northwestern Canada and translocated to YNP and CID to establish a breeding population. The YNP founding population was further augmented by an additional 10 wolf pups translocated from northwestern Montana due to control action. In the years following the reintroduction, wolves have recolonized the 8991 km2 park and several portions of the 72,800 km2 Greater Yellowstone Area (GYA).

Currently, there are over 300 wolves in GYA and have affected many aspects of the local ecosystem. This remarkably successful reintroduced population provides a unique opportunity to study the natural history, genetics, and social structure of a keystone carnivore.

Soft-release of a founder in Yellowstone National Park (1995-1996)

 

The genealogy of three packs of varied structure

The Nez Perce pack genealogy (1995-2004): Two full-sibling members of this pack (29M and 37F) received 10 orphaned pups from the Sawtooth pack in northwest Montana. The pups were successfully accepted into the pack. Later, the pack dissolved, with a new Nez Perce pack forming naturally (unlike the other founder packs, which were translocated from Canada). The new pack was lead by female 48F, and Sawtooth male 72M became the dominant breeding pair. They soon became the dominant pack in the Madison-Firehole area, a tough place for wolves to inhabit. This was the first pack to prey upon bison in addition to elk. After many years of tenure, 70M (the brother of 72M) inherited the dominant male position when his brother died in 2004. However, Nez Perce genetics extend beyond the pack. Genetic analysis confirmed that 534M (offspring of 48M and 72M) usurped the long-time breeding male (2M) of Leopold pack, forcing him out by 2004.

 

 

The Leopold pack genealogy (1995-2004): This pack has one of the longest-tenured pairs noted; wolves 7F and 2M were a monogamous breeding pair for 7 years. We have genetically documented over 30 pups by this pair. 7F and 2M met as singletons, dispersing from their respective founder packs (Rose Creek and Crystal Creek), joining up in 1996. Leopold pack's lineage has split into many new packs by solitary female dispersers (e.g. Swan Lake and Cougar Creek packs). This pack also exemplifies a mechanism by which one daughter of the dominant female inherits the dominant position upon vacancy. With the loss of 7F in 2002, her daughter 209F became the new dominant female, soon to be joined by Nez Perce disperser 534M as her mate. Leopold can be considered one of the most stable packs during the tenure of wolves in Yellowstone. They were a picture of constant nature and habit, using traditional den/rendezvous sites with a regularity unlike many of the other packs in YNP. Until their end, Leopold defended their territory despite disease and interpack clashes. Despite the great loss of this pack, their genetics remain trickling through the generations, as one can see by 302M's lineage (section below).

 

The Druid Peak pack genealogy (1995-2004): This pack exemplifies a highly complex, multiple-breeding structure with higher levels of genetic diversity maintained by the variety of breeding strategies (e.g. subordinate females breeding new dominant male). For example, the male immigrant (21M) filled a vacant breeding position created by the death of previous dominant male, 38M in 1997. As a new dominant male, 21M was very successful in mating many of the females (as many as seven: 40F, 41F, 42F, 103F, 105F, 106F, and 286F) in the pack to whom he was unrelated until the pack split in 2001. Extra-pack copulations were genetically documented between Druid Peak pack females and an interloping male (214M from Nez Perce), pairing temporarily with the Druid Peak females but ultimately not joining the pack. Additionally, genetic paternity of three pups confirmed that Leopold wolf 302M (offspring of 7F and 2M) had bred with two subordinate Druid Peak females before he joined the pack in 2004.