In a study of gerbils with contrasting social and mating systems (group-living monogamous Mongolian gerbil Meriones unguiculatus, solitary nonterritorial promiscuous midday jird M. meridianus, and solitary territorial promiscuous pale gerbil Gerbillus perpallidus), we employed partner preference tests (PPTs) to assess among-species variation in sociability and pair-bonding patterns and tested whether the nature of contact between individuals: direct contact (DC) versus nondirect contact (NDC) affected our results. We measured male preferences as the time: 1) spent alone, 2) with familiar (partner), and 3) unfamiliar (stranger) female in the 3-chambered apparatus. Gerbil species differed strongly in sociability and male partner preferences. The time spent alone was a reliable indicator of species sociability independent of the nature of contact, whereas the pattern and level of between-species differences in male partner preferences depended on contact type: DC PPTs, unlike NDC-tests, discriminated well between monogamous and promiscuous species. In the DC-tests, stranger-directed aggression and stranger avoidance were observed both in the highly social monogamous M. unguiculatus and the solitary territorial promiscuous G. perpallidus, but not in the nonterritorial promiscuous M. meridianus. In M. unguiculatus, stranger avoidance in the DC-tests increased the time spent with the partner, thus providing evidence of a partner preference that was not found in the NDC-tests, whereas in G. perpallidus, stranger avoidance increased the time spent alone. This first comparative experimental study of partner preferences in gerbils provides new insights into the interspecific variation in gerbil sociality and mating systems and sheds light on behavioral mechanisms underlying social fidelity and pair-bonding.
The questions of individuality and stability of cues to identity in vocal signals are of considerable importance from theoretical and conservation perspectives. While individuality in alarm calls has been reported for many sciurids, it is not well-documented that the vocal identity encoded in the alarm calls is stable between different encounters with predators. Previous studies of two obligate hibernating rodents, speckled ground squirrels Spermophilus suslicus, and yellow ground squirrels Spermophilus fulvus demonstrated that, after hibernation, most individuals could not be identified reliably by their alarm calls. Moreover, in most speckled ground squirrels, individual patterns of alarm calls changed progressively over as little as 2 weeks. However, these previous data have been obtained using the collection of alarm calls from trapped animals. Here, we examined ten free-ranging dye-marked yellow ground squirrels to determine whether their alarm calls retain the cues to individuality between two encounters of surrogate predators (humans), separated on average by 3 days. Discriminant function analysis showed that the alarm calls of individual yellow ground squirrels were very similar within a recording session, providing very high individual distinctiveness. However, in six of the ten animals, the alarm calls were unstable between recording sessions. Also, we examined ten dye-marked individuals for consistency of acoustic characteristics of their alarm calls between the encounters of humans, differing in techniques of call collection, from free-ranging vs trapped animals. We found differences only in two variables, both related to sound degradation in the environment. Data are discussed in relation to hypotheses explaining the adaptive utility of acoustic individuality in alarm calls.
Blood analysis has recently become a popular tool to assess the welfare of the wild cats. However, the estimates of blood parameters may depend on the sampling method. We have tested (1) if the sampling procedure influences blood parameters and (2) what parameters are the most efficient in assessing the physiological status in wild cat species. We assessed the effect of handling time on red blood cells (RBC) and white blood cells (WBC) counts, the ratio of neutrophils to lymphocytes (N/L ratio), and serum cortisol level within 1 hr after the capture of the animal in six far-east wild cats (Prionailurus bengalensis euptilura). Also, we analyzed literature data in 17 cat species to assess the effect of place of study, type of immobilization, and handling time on WBC count and N/L ratio. Serum cortisol level varied significantly with the handling time. RBC and WBC counts were strongly affected by the handling time. N/L ratio was very robust and did not depend on the handling time. However, the analysis of literature data has shown that the prolonged handling time (over 1 hr) and the type of immobilization significantly influence the N/L ratio, whereas the WBC count does not depend on any of considered factors. We conclude that while most blood parameters of cats are affected by routine handling time, the N/L ratio does not vary if the samples are collected within 1 hr after the capture of the animal. All other tested parameters should be treated with caution.
In female terrestrial mammals, vocal aging has only been studied in humans and pandas. In cervids displaying convergent sex dimorphism of vocal apparatus with humans, vocal aging is only investigated in males. This cross-sectional study examined acoustic variables of nasal (closed-mouth) and oral (open-mouth) contact calls of 32 farmed Iberian red deer hinds (Cervus elaphus hispanicus) aged of 4-18 years and their relationships with caller´s age, weight, social discomfort score (bites of other hinds on hind pelt) and body condition score (fat reserves). Decrease of fundamental frequency was associated with age in both oral and nasal calls, but more prominently in the nasal calls. An increase in call duration, peak frequency and power quartiles was associated with a higher degree of bites due to social aggression. Weight and body condition weakly influenced acoustic traits. We discuss that vocal aging of hinds parallels that of vocal aging in human females.
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