How do banded mongooses locate and select anvils for cracking encased food items?

Banded mongooses (Mungos mungo) extract encased food items by throwing them against anvils. Observations indicate that their chosen anvils are generally hard enough to crack open casings, suggesting an understanding of the physical properties that render an anvil suitable for cracking. We report results from two field experiments investigating spatial and physical aspects of anvil selection in a wild group of banded mongooses. Mongooses rapidly carried prey items to nearby anvils in their environment, without simply returning to the last anvil they passed, suggesting a detailed knowledge of anvil locations. Moreover, in choice experiments with hard or soft anvils, they always chose the appropriate anvil when both anvils were natural but chose indiscriminately when they were synthetic. These results support a recent suggestion that mongooses lack a generalized understanding of the functional properties of anvils but also indicate that they may mediate their decisions on the basis of familiarity. Together, our experiments suggest that mongooses employ simple rules of thumb that, in most cases, result in the selection of appropriate anvils. Where environmental problems are limited and predictable, selection will favor the evolution of such rules of thumb rather than a more generalized understanding of functional properties.