Isolation call ontogeny in bat pups (Glossophaga soricina)

Bat pups produce isolation calls to solicit maternal care. During maturation, pup isolation calls may gradually develop into echolocation calls or exist in parallel to them, depending on the species involved. We studied the ontogeny of isolation calls in nectivorous bats, Glossophaga soricina. Isolation calls of G. soricina pups were frequency modulated calls uttered in bouts of varying length. Newborn pups already produced both isolation calls and echolocation call precursors (which developed into ` normal' echolocation calls), indicating that isolation calls of G. soricina pups occur independently and exist in parallel to echolocation calls during ontogeny. We found strong statistical evidence for an individual signature encoded in isolation calls. Moreover, we provide evidence for considerable changes in isolation call parameters over a short ontogenetic time span. Throughout ontogeny, the call interval decreased significantly whereas most frequency parameters increased significantly and call entropy rose (i.e., isolation calls became less tonal but noisier).