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Abstract Potential of ultrasonic vocalizations (USVs) to reflect a degree of discomfort of a caller is mostly investigated in laboratory rats and mice but poorly known in other rodents. We examined 36 (19 male, 17 female) adult yellow steppe lemmings Eolagurus luteus for presence of USVs during 8-min experimental trials including 2-min test stages of increasing discomfort: isolation, touch, handling and body measure. We found that 33 of 36 individuals vocalized at isolation stage, i.e., without any human impact. For 14 (6 male and 8 female) individuals, a repeated measures approach revealed that increasing discomfort from isolation to handling stages resulted in increase of call power quartiles and fundamental frequency, whereas call rate remained unchanged. We discuss that, in adult yellow steppe lemmings, the discomfort-related changes of USV fundamental frequency and power variables follow the same common rule as the audible calls of most mammals, whereas call rate shows a different trend. These data contribute to research focused on searching the universal acoustic cues to discomfort in mammalian USVs.

Abstract Objectives This is the first study of the sonic and ultrasonic vocalization in a Dipodidae rodent. For the small-sized quadrupedal northern birch mouse Sicista betulina, phylogenetically related to the bipedal jerboas (Dipodidae), we report null results for ultrasonic vocalization and investigate the acoustic cues to individual identity, sex and body size in the discomfort-related high-frequency tonal sonic calls. Results We used a parallel audio recording in the sonic and ultrasonic ranges during weighting adult northern birch mice before the scheduled hibernation in captivity. The sonic (audible) high-frequency tonal calls (ranging from 6.21 to 9.86 kHz) were presented in all individuals (7 males and 4 females). The ultrasonic calls lacked in the recordings. Two-way nested ANOVA revealed the effects of caller individual identity on all 10 measured acoustic variables and the effects of sex on four out of 10 measured acoustic variables. Discriminant function analyses with 10 acoustic variables included in the analysis showed 85.5% correct assignment of calls to individual and 79.7% correct assignment of calls to sex; both values significantly exceeded the random values (23.1% and 54.3%, respectively) calculated with randomization procedure. Body mass did not differ between sexes and did not correlate significantly with the acoustic variables.

Begging behaviour is an important element in the parent-offspring conflict; it has been studied in many avian species. However, the majority of the studies have been entirely based on the call counts, and they agreed that vocal activity was a good indicator of chick's nutritional need and/or condition. Fewer researches were dedicated to the temporal-frequency variables of the begging calls themselves and they showed contrary results. Here begging behaviour in three burrow nested, uniparous species of auks (Alcidae) was studied. These objects provide an opportunity to study the signalling value of begging calls in the absence of important confounding factors such as nestling competition and predation pressure. I recorded calls of individual chicks in two conditions: during natural feeding and after experimental four-hour food deprivation. I found that almost all measured acoustic variables contain information about the chick's state in all studied species. The hungry chicks produced calls higher in fundamental frequency and power variables and at higher calling rate compared to naturally feeding chicks. The effect of food deprivation on most acoustic variables exceeded both the effects of individuality and species. In all studied species, the frequency variables were stronger affected by hunger than the calling rate and call durations. I suppose that such strong change of acoustic variables after food deprivation can be explained by absence of vocal individual identification in these birds. As parents do not need to check individuality of the chick in the burrow, which they find visually during the day time, the chicks could use all of the acoustic variables to communicate about their nutritional needs.