Distribution and Broadscale Habitat Relations of the Wolverine in the Contiguous United States

Abstract

Conservation of the wolverine (Gulo gulo) at the southern extent of its North American range requires reliable understandings of past and present distribution patterns and broad-scale habitat relations. We compiled 820 verifiable and documented records of wolverine occurrence (specimens, DNA detections, photos, and accounts of wolverines being killed or captured) in the contiguous United States from museums, the literature, and institutional archives. We spatially referenced 729 records with areal precision 1 township (93.2 km 2 ) and temporal precision 10 years. Historical records were located primarily in the western mountains and Great Lakes region. However, our data suggest that the historical distribution of wolverines in the Cascade Range and Sierra Nevada was disjunct, contradicting previous interpretations. Our results indicate that wolverine range in the contiguous United States had contracted substantially by the mid-1900s. Current records (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) are limited to north-central Washington, northern and central Idaho, western Montana, and northwestern Wyoming. We investigated potential relations between wolverines and alpine vegetation, cold temperatures, and spring snow cover by comparing the distribution of historical wolverine records with Kuchler's potential natural vegetation types, Holdridge's climatic life zones, and EASE snow-cover maps during the latter portion of the wolverine denning period (15 Apr-14 May). In the western mountains, historical wolverine records generally occurred in or near alpine vegetation and climatic conditions, especially at the limits of their distribution in the Cascade Range, Sierra Nevada, and southern Rocky Mountains. However, the only habitat layer that fully accounted for historical distribution patterns was spring snow cover. Causal factors for the extirpation of wolverines from the southern portions of their range in the contiguous United States are unknown, but are likely related to high levels of human-caused mortality and low to nonexistent immigration rates.

Food storage in a changing world: implications of climate change for food-caching species

“…Studies on both the Gray Jays [171] and Wolverines [6,62] highlight how climate could be influencing population abundance but detailed demographic studies on caching species remain limited. It will also be important to consider what cached food is being used for during periods of low resource availability.…”

“…Seven percent (7%) stored both high-and low-perishability food and only 2% (four species: the Bull-headed Shrike Lanius busephalus, Gray Jay, Siberian Jay Perisoreus infaustus and Wolverine Gulo gulo) were both long-term cachers and relied exclusively on high-perishability food (susceptibility score of 9). Population declines at the southern edge of ranges have already been documented for both Gray Jays [171] and Wolverines [6] and studies on both of these species also suggest that climate change could be contributing to population declines [62,139,171].…”

Addressing biased occurrence data in predicting potential Sierra Nevada red fox habitat for survey prioritization

“…These changes will likely have a profound effect on the ranges, elevations, and associations of California's biota (e.g. Loarie et al 2008, Parra & Monahan 2008, Wiens et al 2009, Ackerly et al 2010, Forister et al 2010 The Sierra Nevada red fox may follow the pattern of another alpine-associated carnivore, the wolverine Gulo gulo, which disappeared from Califor-nia by the 1930s, with populations persisting only in higher latitude states such as Washington, Montana, and Idaho (Aubry et al 2007). Predicting the future range of Sierra Nevada red fox based upon its historic range and the anticipated climate changes is an important next step toward its effective conservation.…”

Reconstructing historical snow depth surfaces to evaluate changes in critical demographic rates and habitat components of snow‐dependent and snow‐restricted species

“…Although the small sample of wolverine locations prevented us from assessing how well wolverine locations matched snow depths annually, our simple predictive model of snow conditions that potentially benefit wolverines identified broad fluctuations in availability of this habitat component based on snow depths >1 m. This wolverine model excluded 14% of the wolverine locations that were encompassed by a map derived from the number of snow cover days, which possibly reflect differences in how these two snow metrics may account for dispersal records. As snow depth is important for the reproduction, dispersal and distribution of wolverines (Magoun & Copeland 1998;Balkenhol & Waits 2009), our snow depth model can help direct further investigations into the relationships of this increasingly limited resource and its role as a limiting factor on the demography, distribution and dispersal of this species (Aubry, McKelvey & Copeland 2007). Additionally, the estimated inter-annual persistence and annual availability of potentially suitable winter habitat can be coupled with genetic data to identify the importance of these environmental variables as predictors of population connectivity and viability (Balkenhol & Waits 2009;Schwartz et al 2009).…”

“…This species is dependent on deep, persistent snow for reproduction because females establish reproductive den sites and rear young where snow depths are ‡1 m in March (Magoun & Copeland 1998). In the absence of spatiotemporal snow depth data sets, models of wolverine distribution and investigations of habitat relationships over the past decade have focused on snow cover as a key habitat component (Magoun & Copeland 1998;Aubry, McKelvey & Copeland 2007;Copeland et al 2010).…”