Effect of Reproductive Status on the Diet Composition of Wolverines (Gulo gulo) in Boreal Forests of Eastern Finland

Abstract

Sex differences in foraging ecology have been found in a variety of taxa. We tested the hypothesis that breeding female wolverines (Gulo gulo), probably due to their smaller home ranges and higher energy demands because of gestation and lactation, are forced to rely more on food caches and carrion than other wolverines. The diet composition, as the percentage occurrence, was estimated for four breeding females and six males and non-breeding females by analyzing scat samples, all collected in eastern Finland. The most important food source for breeding female wolverines was human-and wolfkilled moose (55%), while the diet also comprised mountain hare (13%), domestic pig (13%) and grouse (11%). Mountain hare (52%) was the most utilized food source for males and non-breeding females. Moose (22%) and grouse (15%) were also important components of the diet. Our study highlights the importance of human-and wolf-killed carrion for breeding female wolverines in areas where the density of medium-sized ungulates is low.

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“…Wolverines (Gulo gulo) are known as "facultative scavengers" that alternate between hunting live prey, scavenging, and consuming previously cached food to fulfill their energy requirements (Magoun 1987;Banci 1994;Dijk et al 2008;Dalerum et al 2009;Koskela et al 2013;Mattisson 2016). In the Arctic, Wolverines generally switch from killing and consuming cached ungulate carrion (e.g., Caribou [Rangifer tarandus]) in the winter, to hunting small mammals (e.g., Arctic Ground Squirrel [Urocitellus parryii]) during the summer (Magoun 1987;Dijk et al 2008).…”

“…Information on the relative contribution of small prey such as cricetids, soricids, Snowshoe Hare (Lepus americanus), ptarmigan, and large prey in the Wolverines' diet across the Alaskan Arctic is lacking, but could contribute towards understanding how prey selection influen-ces Wolverine survival and reproductive success (Krebs et al 2004;Persson 2005;Koskela et al 2013). A lack of large ungulate prey coupled with dwindling food caches during early spring may force Wolverines to switch from ungulate carrion to other prey sources (Persson 2005).…”

Reproductive adaptations to reduce locomotor costs in viviparous fish (Poeciliidae)

“…Consequently, in some animals a shift to more easily obtainable food sources is observed during pregnancy. Pregnant wolverines (Gulo gulo Linnaeus, 1758) for instance, switch from preying on moose to easier to catch prey in Canada [118], and from consumption of self-captured prey to carrion in Finland [119].…”

“…A reduction in activity is also reflected in smaller home ranges, e.g. in sex-role-reversed seahorses [136] and in wolverines (G. gulo) [119]. In contrast, total active (foraging) time was found to 2 Chapter 2 | Locomotor costs of live-bearing and adaptations to reduce them be increased in pregnant bats (Myotis daubentoni Kuhl, 1817) compared to males, probably to accommodate the increased metabolic demand of pregnancy [137].…”

“…This is followed by contraction of the contralateral muscles, driving the fish forwards in a direction often different from its initial orientation [117,118]. Another type of fast-start, the 'S-start' in which the fish curves in an S-shape, is mainly exhibited by predatory fish to perform a strike [119].…”