Foraging patterns of arctic foxes at a large arctic goose colony

Arctic foxes (Alopex lagopus) are the main predators of many arctic-nesting birds, and such predation can have a large impact on the nesting performan ce of geese in some years and in some parts of the Arctic. We examined fora ging patterns of arctic foxes at a large lesser snow goose (Chen caerulesce ns caerulescens) colony on Banks Island, Canada, from 1996 to 1998 and were especially interested in the proportion of food that was cached for later use and the impact that fox predation had on goose productivity. Arctic fox es took mostly eggs when foraging among geese, and most of these eggs (97%) were cached for later use. Adult geese and lemmings were taken in low numb ers, and most of these foods (83% of geese and 75% of lemmings) were eaten immediately. In years with high fox abundance, the foxes spent considerable effort moving eggs from old caches. This behaviour may have resulted from high rates of cache pilfering, or foxes may have been moving caches to dete r cache pilfering. The impact of fox predation was low in all years, and fo xes look only about 4-8% of all eggs available at the colony during incubat ion each year. However, caching and use of cached eggs may influence the su rvival of arctic foxes by forming significant parts of their winter diet or by supplementing the diets of growing young: during nesting each year, fox es took on average 900-1570 eggs per fox.