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Similar concerns existed for the relatively small founding population reintroduced to YNP and central Idaho. But 

 wolves were trapped from two distinct source populations in Canada. The genetic variation among reintroduced 

 wolves (and the .source populations from which they came) was also high (Forbes and Boyd 1997). Overall, 

 heterozygosity was similar among samples of natural rccolonizers, reintroduced individuals, and the Canadian 

 source populations. Field studies of wolf dispersal and migration distances supported the genetic results (Ream et 

 al. 1991, Boyd et al. 1995, Boyd and Pletscher 1999). Wolf populations in the northern Rockies should not suffer 

 from inbreeding depression. 



An underlying tenant of the wolf recovery and restoration program is that each state's wolf population is 

 functionally connected so that genetic material can be exchanged among all three. In isolation, none of the three 

 populations could maintain its genetic viability (USFWS 1994a, Fritts and Carbyn 1995). 



Population Growth 



Wolf populations increase or decrease through the combination and interaction of wolf densities and prey densities 

 (Keith 1983, Fuller 1989). Actual rates of change depend on whether the wolf population is pioneering vacant 

 habitat (as in YNP and central Idaho) or whether the population is well established (as in northwestern Montana). 

 The degree and type of legal protection, agency control actions, and regulated harvest also influence population 

 trends. Once established, wolf populations apparently can withstand human-caused mortality rates of up to 28-35% 

 without declining (Keith 1983, Fuller 1989). 



If protected, low density wolf populations can increase rapidly if prey is abundant. Keith ( 1983) speculated that a 

 30% annual increase could be the maximum rate of increase for any wild wolf population. Once densities were high 

 enough, social interactions probably intensify. Intraspecific conflict and increased competition for food eventually 

 cause the population to level off or decline (Keith 1983, Fuller 1989). 



Wolf populations in the GNP area (northwestern Montana and southeastern Alberta) increased an average of 23% 

 annually from 1986-1993 (Fritts et al. 1995). After 1993, the population leveled off (Pletscher et al. 1997). Those 

 packs produced dispersers that eventually colonized vacant habitats in western Montana (USFWS unpubl. data). 

 Some packs which formed in the Northwestern Montana Recovery Area since the early 1990s persisted, but others 

 did not. Packs have been lost due to illegal mortality, control actions where livestock depredation was chronic, and 

 for other unknown reasons. 



The average annual rate of increase from 1992 to 2000 in northwestern Montana was 4.7% (USFWS et al. 2001 ). In 

 1992, the minimum mid-winter count (including pups) was 41 wolves. Sixty-two wolves were counted in 2000. 

 The highest count was 70 wolves, at the end of 1996. The population grew in some years, but declined in others. 

 Some of the variation probably reflects true changes wolf numbers, but some variation may be due to monitoring 

 inaccuracy or decreased monitoring effort. 



Prey populations influenced recent wolf population dynamics in northwestern Montana. White-tailed deer 

 populations expanded from the late 1970s through the mid 1990s, in part precipitating and sustaining increases in 

 wolf numbers and distribution. However, the winter of 1996/97 was exceptionally severe, and white-tailed deer 

 populations declined significantly (Sime, unpubl. data). Other prey populations also declined and poor recruitment 

 was attributed to winterkill. The USI^S 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%j 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. 



Wolf populations in the GYA and central Idaho areas exceeded all expectations for reproduction and survival 

 (Bangs et al. 1998). Populations became established in both areas within 2 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 3 1 and including pups (USFWS et al. 2001 ). 

 However, population growth in the GYA slowed in 1999 after the rapid increase in the first three years post- 



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