The structure, meaning and function of yellow-bellied marmot pup screams

The function and structure of alarm signals may vary with the caller's age, and some of this variation may be because young may have to attract the attention of their caregivers. The structure of calls may reveal this function. Yellow-bellied marmot, Marmota flaviventris, pups utter a novel vocalization, an elongated scream, which often contains nonlinear acoustic characteristics, 6% of the time when handled within about a week of emergence from their natal burrow. With a single exception in over 4000 captures, only pups uttered these unique vocalizations. Acoustically, pup screams are more than an order of magnitude longer than pup alarm calls and a majority of the screams have at least one type of nonlinearity. Playback experiments showed that average-length screams elicited higher-level responses than adult alarm calls and that elongated and average-length screams elicited higher-level responses than shortened screams. The acoustic structure of screams makes them especially evocative, and they may function to allow pups to recruit their mothers to help them fend off predators. More generally, an examination of nonlinearities in vocalizations of other species suggests that nonlinearities may be an honest indicator of arousal, and this honesty elicits heightened responses in receivers.