Survival rate of experimental food caches: implications for arctic foxes

Abstract

Avoiding cache loss is critical to food-hoarding animals. Arctic foxes ( Alopex lagopus (L., 1758)) scatter-hoard thousands of eggs annually at large goose colonies, and we examined how survival rate of experimental caches were influenced by (i) nesting density by geese, (ii) relative proportion of two sympatric goose species, (iii) departure by ca. 1 million geese and their young after hatch, and (iv) age of cache sites. Survival rate of experimental caches was related to age of cache sites in the 1st year of the study (0.80 and 0.56 per 18-day period for caches from new and 1-month-old cache sites, respectively) and departure by geese in the 2nd year of the study (0.98 and 0.74 per 18-day period during and after goose nesting, respectively). These results suggest that food abundance and deterioration of cache sites (e.g., loss of soil cover and partial exposure of caches) were important factors affecting cache loss at our study site. Furthermore, annual variation in the importance of these factors suggests that strategies to prevent cache loss are not fixed in time but vary with existing conditions. Evolution of caching behaviours by arctic foxes may, thus, have been shaped by multiple selective pressures.