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Within-population acoustic variation of European red deer Cervus elaphus follows two empirically established common rules: Rule 1: suggesting similar-pitched stag and hind calls because of potential prevalence of natural over sexual selection on call pitch; and Rule 2: predicting lower-pitched calls in adults, because larger vocal folds normally produce lower-pitched calls in mammals. We found that both rules were supported for native Pannonian red deer from Central Europe. All fundamental frequency () parameter values of hind contact calls (for the exclusion of the beginning ) were indistinguishable from those of stag rutting roars. These results agree with published data on vocalization of male and female American and Asian wapiti Cervus canadensis. Calls of adults of either sex were lower in frequency than calf calls. These results disagree with data collected from adult and young American wapiti producing same-frequency calls, probably because of a distinctive mechanism of sound production (whistling).

Relationships between individualization and the acoustics of contact calls in ungulate mother and young are different between taxa. We compared the acoustic variables and individuality of adult female and neonate goitred gazelles Gazella subgutturosa. Discriminant function analysis based on six acoustic variables of nasal (closed-mouth) contact calls similarly accurately classified calls to neonate and adult individuals in spite of the prominent differences in the acoustic resonances (formants) and the mean fundamental frequency of their calls. In addition, we found prominent differences in duration, mean fundamental frequency and frequencies of the first four formants between nasal and oral (open-mouth) contact calls within and between adult and neonate age-classes. We discuss the effects on the acoustics of call production mode (oral versus nasal) and the relationship of acoustic differences and individuality in mother and young contact calls across species of ruminants (Bovidae and Cervidae).

Summary Voice breaking is a process associated with puberty of human males that also occurs in adolescence in some birds. This study reports the jump-like vocal changes occurring during voice breaking in adolescent red-crowned cranes (Grus japonensis). We investigated acoustic parameters of chirp and trill calls during vocal ontogenesis from hatching to the age of 1.5 years in 17 male and 31 female captive red-crowned cranes and compared them with definitive calls of 5 male and 8 female conspecific adults. During voice breaking, trills and chirps of both sexes contained two non-overlapping independent fundamental frequencies: the upper one, representing the retained juvenile frequency, and the lower one, the newly attained adult frequency. Before voice breaking, the calls contained only the upper frequency, whereas after it only the lower one. Voice breaking occurred between the age of 7 and 11.5 months. We test whether sex, dates of birth and body mass gain are associated with voice breaking and speculate whether voice breaking triggers the disruption of the parent‐ chick bond or vice versa, or both events are driven by a third, yet unidentified trigger.

Summary The hypothesis of similarity in trends of acoustic characteristics regardless of the sign of emotional arousal, positive or negative, has been advanced based on human vocalizations. For non-human mammals, testing is complicated because the same stimulus cannot evoke opposite (positive and negative) internal states, to trigger the respective vocalizations. To resolve this concern, we designed an experimental procedure using Tame and Aggressive strains of silver foxes, with genetically predetermined positive or negative emotional responses to humans respectively. We analyzed features of vocalizations produced by callers at different fox‐human distances, assuming changes in vocal responses reflect the shifts of human-related positive arousal in Tame foxes and human-related negative arousal in Aggressive foxes. Both strains showed similar trends for changes in calling rate and proportion of time spent vocalizing toward higher levels in response to greater emotional arousal, positive in Tame foxes and negative in Aggressive foxes. At the same time, strains showed distinctive trends for the proportions of different call types and maximum amplitude frequency. We infer that the variables with similar trends reflect the strength of emotional arousal, regardless of triggering internal states, whereas variables with distinctive trends are specifically related to the sign of emotion in silver fox.