Hoarding Strategies Research Articles

The Effect of Travel Costs on Food Hoarding in Gerbils

Hoarding strategies range between scatterhoarding (small multiple hoards) and larderhoarding (large single hoard). We hypothesized that spatial distribution of food affects hoarding strategy of 2 nocturnal psammophilic rodents, Gerbillus pyramidum and G. allenbyi. We used a modular arena to test the prediction that hoarding strategy would tend toward scatterhoarding as travel distance during foraging increases. We manipulated travel distance and studied its effect on hoarding behavior. G. allenbyi, as predicted, tended to scatterhoard as travel distance increased. G. pyramidum, however, reacted to changes in travel distance by moving the location of its larderhoard but did not scatterhoard. We suggest that hoarding strategy may be scale dependent and that gerbils will increase their number of hoards when energy costs of travel are sufficiently high.

Foraging currencies and the load-size decision of scatter-hoarding grey jays

Food-hoarding animals are assumed to maximize total storage while meeting their own energetic requirements. To maintain energetic balance, a hoarder must also devote some time to feeding. The predicted choice of hoarding strategy depends on the net rate at which a hoarder is able to feed itself. Rate-maximizing hoarding is favoured when the net self-feeding rate is high, as it was during our experiment. (At lower net self-feeding rates, the hoarder should behave more efficiently.) To evaluate the expectation of rate maximization, we examined load-size decisions (number of raisins collected for storage) made by hoarding grey jays, Perisoreus canadensis. During each visit to an experimental food source, the subject was forced to wait for access to the food. Following this delay, the jay collected a load, transported it for storage, and returned to the source. The predicted size of rate- and efficiency-maximizing loads diverged with increases in the delay. As predicted by both currencies, the jays collected larger loads following longer delays. The magnitude of the observed adjustments indicates that the jays closely approached the maximal rate of hoarding.

Age-Related Hoarding Strategies in the Crested Tit Parus cristatus: Should the Cost of Subordination be Re-Assessed?

1. In a population of crested tits Parus cristatus in northern Belgium, living in group territories outside the breeding season, food was mainly stored during October and November, a time when territorial flocks are split up in age-specific subflocks. 2. First-year flock members frequently stored in the upper and outermost parts of the trees, whereas adults consistently hoarded and foraged in protected sites near the trunk. The outermost, predator-exposed sites were only used by first-year foragers in mixed-age winter flocks with adults, as a result of site competition within flocks on cold days. 3. Consequently, the overlap between foraging sites (protected) and hoarding sites (exposed) of first-year birds was small during autumn, but large during winter