Academic journal article The American Midland Naturalist

Wolverine (Gulo Gulo) Food Habits in Greater Yellowstone

Academic journal article The American Midland Naturalist

Wolverine (Gulo Gulo) Food Habits in Greater Yellowstone

Article excerpt

Introduction

The wolverine (Guio guio) is a large terrestrial weasel (8-18 kg) that has a circumboreal distribution and occupies a cold relatively unproductive niche (Copeland and Whitman, 2003; Inman et al, 2012a, b). Across its range the species naturally exists at extremely low densities (~5/1000 km2) and average annual reproduction is very low (~0.7 young/female >3 y of age; Persson et al, 2006; Golden et al, 2007; Lofroth and Krebs, 2007; Inman et al, 2012a). Wolverines were extirpated from large areas of their historical distribution (Persson, 2003; Aubry et al, 2007), in part because they are relatively vulnerable due to small population sizes and limited capacity for growth. While populations have recovered in some areas, the species is considered vulnerable or endangered in Scandinavia and warranted for listing as threatened in the contiguous United States (Gärdenfors, 2010; Kâlâs et al, 2010; United States Fish and Wildlife Service, 2013). Starvation is a significant natural cause of wolverine mortality in some populations (Krebs et al, 2004), and reproductive rates are strongly influenced by food abundance (Persson, 2005).

Wolverines are opportunistic feeders. Reported food items include reindeer/caribou (Rangifer tarandus), moose (Alces alces), mountain goats (Oreamnos americanas), sheep (Ovis spp.), beaver (Castor spp.), marmots (Marmota spp.), ground squirrels (Spermophilus spp.), hares (l^epus spp.), voles (Microtus spp.), lemmings (Lemmus spp.), fox (Vulpes vulpes), birds, bird eggs, frogs, insect larvae, berries, and marine mammals (Rausch and Pearson, 1972; Magoun, 1987; Samelius et al, 2002; Copeland and Whitman, 2003; Lofroth et al, 2007). Wolverines will scavenge carrion, including bones and hide, and caching is known to be common. Scavenging of ungulate carrion is often reported to be the primary means of obtaining food (Haglund, 1966; Myhre and Myrberget, 1975; Band, 1994; Lofroth et al, 2007; Dalerum et al, 2009). However the vast majority (=94%) of wolverine food habits observations have been made during winter when the use of ungulate carrion predominates. Litde is known of the summer food habits of the species, but summer foods may be at least as critical for reproductive success (Inman et al, 2012b). We are not aware of any reports of the species using rotted meat in any season.

Because wolverines occupy cold, often snow-covered areas, the species may be impacted by a warming climate (e.g., Peacock, 2011; McKelvey et al, 2011). As species ranges shift due to climate change, the foods available to wolverines and the competition for that food may also change. Information on wolverine food habits at the southern periphery of their range is limited (Copeland, 1996) but may be more representative of what could be expected in the larger more northern core areas of wolverine distribution as climate warming occurs. Our objectives were to: (1) document the food items used by wolverines at the southern periphery of the species distribution, (2) determine if the general pattern of scavenging ungulates during winter and preying upon small prey during summer existed in our study area, and (3) determine if the field observation technique was biased in its ability to detect ungulates vs. small prey relative to scat samples.

Study Area and Methods

Our research occurred in the Greater Yellowstone Ecosystem (GYE), a 108,000 km2 area that includes the Yellowstone Plateau and 14 surrounding mountain ranges in Idaho, Montana, and Wyoming (Fig. 1). The GYE is one of the southernmost points of wolverine distribution, and our work occurred from approximately 43.0°-46.0°N latitude and - 109.0°-114.0°W longitude. Elevations ranged from 1400-4200 m. Rainfall increased with elevation and varied from 32-126 cm per year (National Oceanic and Atmospheric Administration, 2007; Natural Resources Conservation Service, 2007). Snow usually fell as dry powder and depths at higher elevations were often in excess of 350 cm. …

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