Potential Effects of Global Warming on Calving Caribou.

摘要

Calving grounds of barren-ground caribou (Rangifer tarandus) are often in the portion of their range that remains covered by snow late into spring. We propose that global warming would alter the duration of snow cover on the calving grounds and the rate of snowmelt, and thus affect caribou population dynamics. The rationale for this hypothesis is based upon the following arguments. For females of the Porcupine Herd, one of the few forages available before and during early calving are the inflorescences of cotton grass (Eriophorum vaginatum), which are very digestible, high in nitrogen and phosphorus, and low in phenols and acid-detergent fiber. The nutritional levels of the inflorescences are highest in the early stages of phenology and decline rapidly until they are lowest at seed set, about 2 weeks after being exposed from snow cover. The high nutritional level of cotton grass inflorescences is important to post-paturient caribou attempting to meet nutritional requirements of lactation while minimizing associated weight loss. The pattern of weight regain in summer is important to herd productivity as female body weight at mating influences conception in late summer and calving success in spring. Therefore, temporal changes in snowmelt may have major effects on nutritional regimes of the female.