CHAPTER 2; AFFECIT.D ENVIRONMENT 



declined and poor recruitment was attributed to winterkill. USFWS believes that the significant decline in 

 natural prey availability led to the record high number of livestock depredations and subsequent lethal 

 control. Wolf depredations on livestock in 1997 alone accounted for 50% of all depredations in 

 northwestern Montana between 1987 and 1999. Smaller prey populations likely translated to decreased 

 wolf pup survival in 1997 and 1998, compared to 1996. Ungulate populations rebounded in recent years 

 and the wolf population is also nearing its 1996 level. 



Newly reintroduced wolves in the GYA and central Idaho exceeded all expectations for reproduction and 

 survival (Bangs et al. 1998). Populations became established in both areas within two years, rather than 

 the predicted three to five years. Pup production and survival in the GYA has been high. The average 

 annual growth rate for the GYA from 1996-2000 is 35%, based on the minimum count as of December 31 

 and including pups (USFAVS et al. 2001). However, population growth in the GYA slowed in 1999 after 

 the rapid increase in the first three years post-reintroduction (Smith et al. 2000). 



It is likely that population growth rates will slow for both the core Yellowstone and central Idaho 

 populations because of declining availability of suitable, vacant habitat. However, these populations will 

 be a source of founders for new packs outside the YNP and central Idaho recovery areas and within the 

 state boundaries of Montana, Idaho, and Wyoming. Therefore, wolf numbers and distribution outside 

 core areas are expected to increase rapidly in the next few years. 



Pack membership typifies the predominant manner in which a wolf exists in the wild. The pack is the 

 mechanism by which wolves reproduce and populations grow. However, in most wolf populations, some 

 lone, nomadic individuals exist as dispersers - looking for vacant habitat, waiting to be found by a 

 member of the opposite sex within a new home range, or searching for an existing pack to join. Up to 10- 

 15% of a wolf population may be comprised of lone animals. 



This is a temporary transition. Wolves in northwestern Montana usually found other wolves in an 

 average of 66 days (range 2-202 days) (Boyd and Pletscher 1999). Occasionally, lone wolves get into 

 conflict with people and/or livestock, ultimately being lost to the population through legal or illegal 

 means. For a wolf to make a contribution to the population, it must affiliate with other wolves. Until 

 they affiliate with a pack, lone wolves are generally counted separately or omitted from total population 

 counts altogether because they do not contribute to population growth and are difficult to detect by 

 routine monitoring activities. 



Interactions with Other Species. The relationships between carnivores and other species, and the 

 ecosystems in which they live, could be the most poorly understood and controversial dimension of 

 carnivore ecology (Estes 1996). The real question is not whether carnivores play important, unique roles 

 in the natural functioning of ecosystems, but rather how they go about it, to what degree, and at what 

 scale (Mech 1996). 



Some researchers believe wolves could function as a "keystone species," which exists at relatively low 

 abundance, whose effect on its community or ecosystem is relatively large and involves multiple levels on 

 the food chain (Power et al. 1996, Estes 1996). Despite volumes of published literature on gray wolves, 

 however, there is remarkably limited evidence of the precise nature, degree, and mechanisms by which 

 wolves affect ecosystems. 



Wolves kill ungulates, but the effects on ungulate populations are varied. Scavenging species, such as 

 coyotes, common ravens, and wolverines feed on wolf kills. A wide variety of scavengers and other 

 carnivores benefit from carrion being readily available year round, rather than just a pulse in the early 

 spring because of winterkill (Stabler et al. 2001 ). Wolves may directly or indirectly compete for food 

 with other carnivores (e.g. mountain lion) by selecting similar prey, or by usurping kills (Kunkel et al. 



21 



