Ecology and catastrophic mortality in wild horses: implications for interpreting fossil assemblages.

The identities, sexes, and reproductive status of groups of wild horses (Equus caballus) living in the Great Basin Desert of North America were known prior to their deaths on ridgelines. Another group of very young horses died on a quagmire. Snow accumulation or drought was apparently responsible for the mass deaths. These data have implications for reconstructing some aspects of the social structure of fossil mammals on the basis of skewed sex or age ratios in bone assemblages.