Deer mothers are sensitive to infant distress vocalizations of diverse mammalian species.

Acoustic structure, behavioral context, and caregiver responses to infant distress vocalizations (cries) are similar across mammals, including humans. Are these similarities enough for animals to respond to distress vocalizations of taxonomically and ecologically distant species? We show that mule deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus) mothers approach a speaker playing distress vocalizations of infant marmots (Marmota flaviventris), seals (Neophoca cinerea and Arctocephalus tropicalis), domestic cats (Felis catus), bats (Lasionycteris noctivagans), humans (Homo sapiens), and other mammals if the fundamental frequency (F0) falls or is manipulated to fall within the frequency range in which deer respond to young of their own species. They did not approach to predator sounds or to control sounds having the same F0 but a different structure. Our results suggest that acoustic traits of infant distress vocalizations that are essential for a response by caregivers, and a caregiver's sensitivity to these acoustic traits, may be shared across diverse mammals.