Regulation of creche size by intercolonial migrations in the Japanese greater horseshoe bat, Rhinolophus ferrumequium nippon.

Abstract

Intercolonial migrations of mother-infant pairs in Rhinolophus ferrumequinum nippon were investigated during the summers of 1984 and 1985 by the banding-recapture method in the Izumo mines, Ishikawa Prefecture, Japan. About 50% of all lactating females migrated with their infants among several nursery colonies, and the nursery colonies were closely interconnected with each other through interchanges of mother-infant pairs. Emigration of mother-infant pairs increased with larger creche size (the term 'creche' referring to the infant cluster formed while mothers are feeding away from the colony). Creche size-dependent emigration contributes to the development of 'multi-divided and small-sized' nursery colonies, a particular characteristic of R. f. nippon. Such behavior may decrease the maternal costs of the selective nursing.