Caribou Feeding Sites in Relation to Snow Characteristics in Northeastern Alaska

Abstract

ABSTRACT. Caribou select areas of relatively shallow snow for winter feeding, and do so on at least two levels: broad area and microsite.

Cratering behaviour and faecal C:N ratio in relation to seasonal snowpack characteristics in a High-Arctic ungulate

“…This corresponds well with previous values reported for Svalbard reindeer (Hansen et al 2010) as well as caribou in Alaska (e.g., Collins & Smith 1991) and on Coats Island, Canada (Adamczewski et al 1988). Although Pruitt (1959) and LaPerriere & Lent (1977) suggested that caribou crater in snow with thickness up to around 50-60 cm, and Johnson et al (2000) found craters up to 1 m deep, Bergerud & Nolan (1970) Table 2). In ( craters in our study were well within these limits.…”

“…In a study of Arctic tundra caribou (R. tarandus) on southern Baffin Island, Canada, Ferguson et al (2001) found mean IRH in feeding craters to vary spatially between 160 and 601 kg cm. Similar values were reported by LaPerriere & Lent (1977) for caribou in north-eastern Alaska, while reindeer in mainland Norway were feeding on ridges with on average 357-2297 kg cm IRH (Nellemann 1996). This comparison with other Rangifer populations may indicate that, because of the extremely sparse-growing vegetation in the High Arctic, the energy expenditure threshold for cratering is low compared with lower latitude areas.…”

“…In contrast to snow depth, however, we found no effect of ice thickness on faecal C:N ratios, and on average there was no fine-scale selection against ice thickness. This study therefore indicates that during 'normal' precipitation winters with (in a Svalbard context) little ROS and icing -the conditions more typically faced by lowerlatitude Rangifer populations (LaPerriere & Lent 1977;Nellemann 1996;Ferguson et al 2001) -Svalbard reindeer feeding choices and diet quality are constrained by total snowpack depth rather than the few and overall thin ice layers present in the snowpack. The record high number of animals counted in Adventdalen during the annual monitoring in the following summer (Ims et al 2014) suggests that mortality during the study winter was low and that the winter feeding conditions supported a high subsequent reproduction rate, as expected in the absence of ground ice (e.g., Stien et al 2012;Hansen et al 2014).…”

“…This sedentary behaviour reduces their energy demands for locomotion, which can be substantial in other caribou and reindeer populations travelling longer distances (Fancy & White 1987). Like other reindeer and caribou (Tushinskii 1949, in Bergerud & Nolan 1970Bergerud 1974;LaPerriere & Lent 1977), the Svalbard reindeer show a remarkable ability to detect ice-free microhabitat under the snowpack, which has been attributed to their olfactory senses (Hansen et al 2010). The concave-shaped hooves have sharp foreedges, with which they can break through ice layers and scrape away the snow while feeding (Skogland 1978).…”

Factors influencing the distribution of Bathurst barren-ground caribou (Rangifer tarandus groenlandicus) during winter.

“…Maximum snow-depth thresholds for effective cratering (foraging for ground vegetation by pawing through snow) by caribou are 50 -80 cm (Pruitt 1959), and particularly deep or wind-hardened snow can decrease the availability of forage by up to 90% (Collins and Smith 1990). Numerous studies have shown that caribou select foraging sites with relatively lower snow depth, snow hardness, or both (LaPerriere and Lent 1977, Cichowski 1993, Johnson et al 2001. At a larger spatial scale, some barren-ground herds have likely adapted to the long-term variation in snow depth across their winter ranges.…”