In this study we classify call structures and compare vocalizations toward humans by captive red foxes Vulpes vulpes, artificially selected for behaviour: 25 domesticated, or “Tame” animals, selected for tameness toward people, 25 “Aggressive” animals, selected for aggression toward people, and 25 “Unselected” control foxes, representing the “wild” model of vocal behaviour. In total, 12,964 calls were classified visually from spectrograms into five voiced (tonal) (whine, moo, cackle, growl and bark), and three unvoiced, or noisy (pant, snort and cough) call types. The classification results were verified with discriminant function analysis (DFA) and randomization. We found that the Aggressive and Unselected foxes produced the same call type sets toward humans, whereas the Tame foxes used distinctive vocalizations toward humans. The Tame and Aggressive foxes had significantly higher percentages of time spent vocalizing than the Unselected, in support of Cohen & Fox (1976) hypothesis that domestication relaxes the selection pressure for silence, still acting in wild canids. Unlike in dogs, the “domesticated” Tame foxes did not show hypertrophied barking toward humans, using instead the cackle and pant. We conclude that the use of a certain call type for communication between humans and canids is species-specific, and not is the direct effect of domestication per se.
vocalization, domestication, vocal communication, nonlinear phenomena, articulation, red fox, Vulpes vulpes, Canidae