Gender identification using acoustic analysis in birds without external sexual dimorphism

Zoo and wildlife management faces a problem with bird sexing,as many bird taxa have indiscernible gender differences in size and coloration.Problematic groups are geese,cranes,rails,raptors,owls,parrots,doves,auks,shearwaters and some passerines.Commonly accepted invasive sexing techniques based on genetics,laparoscopy,morphometric and on cloacal inspection,are all needed in bird capturing and handling.Capturing and subsequent manipulations may be inapplicable for free-ranging birds,whereas distant voice-based sexing is relevant for many species.This review evaluates the potential for noninvasive sexing by separate calls or duet calls,for adult birds of 69 species from 16 orders and for chicks of 11 species from 7 orders.For adult birds of 25 species,a single call per individual was sufficient for 100 % reliable sexing by ear or using spectrographic analysis.For chicks,the potential for voice-based sexing seems to be very limited.For birds calling rarely or unpredictably,we propose a simple way of provoking vocalization using playbacks of species-specific calls that are available from sound libraries.We conclude that sexing by voice may represent a feasible alternative to the classical sexing techniques,both in the wild and in captivity.

Humans identify negative （but not positive） arousal in silver fox vocalizations： implications for the adaptive value of interspecific eavesdropping

The ability to identify emotional arousal in heterospecific vocalizations may facilitate behaviors that increase survival opportunities. Crucially, this ability may orient inter-species interactions, par- ticularly between humans and other species. Research shows that humans identify emotional arousal in vocalizations across multiple species, such as cats, dogs, and piglets. However, no previ- ous study has addressed humans＂ ability to identify emotional arousal in silver foxes. Here, we adopted low- and high-arousal calls emitted by three strains of silver fox--Tame, Aggressive, and Unselected--in response to human approach. Tame and Aggressive foxes are genetically selected for friendly and attacking behaviors toward humans, respectively. Unselected foxes show aggres- sive and fearful behaviors toward humans. These three strains show similar levels of emotional arousal, but different levels of emotional valence in relation to humans. This emotional information is reflected in the acoustic features of the calls. Our data suggest that humans can identify high- arousal calls of Aggressive and Unselected foxes, but not of Tame foxes. Further analyses revealed that, although within each strain different acoustic parameters affect human accuracy in identifying high-arousal calls, spectral center of gravity, harmonic-to-noise ratio, and F0 best predict humans＇ ability to discriminate high-arousal calls across all strains. Furthermore, we identified in spectral center of gravity and F0 the best predictors for humans＇ absolute ratings of arousal in each call. Implications for research on the adaptive value of inter-specific eavesdropping are discussed.

A blind climber:The first evidence of ultrasonic echolocation in arboreal mammals

The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(translated as“the blind mouse”)is incapable of object vision:the retina is folded and retains no more than 2500 ganglion cells in the focal plane,and the optic nerve is subject to gliosis.Hence,Typhlomys has no other means for rapid long-range orientation among tree branches other than echolocation.Ultrasonic vocalization recordings at the frequency range of 50-100 kHz support this hypothesis.The vocalizations are represented by bouts of up to 7 more or less evenly-spaced and uniform frequency-modulated sweep-like pulses in rapid succession.Structurally,these sweeps are similar to frequency-modulated ultrasonic echolocation calls of some bat species,but they are too faint to be revealed with a common bat detector.When recording video simultaneously with the ultrasonic audio,a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated.Our findings of locomotion-associated ultrasonic vocalization in a fast-climbing but weakly-sighted small mammal ecotype add support to the“echolocation-first theory”of pre-flight origin of echolocation in bats.

Sociability and pair-bonding in gerbils: a comparative experimental study

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 part ner pref ere nee 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 pref ere nces as the time: 1) spe nt 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 indepe ndent of the nature of con tact, whereas the pattern and level of betwee n-species differe nces in male partner preferences depended on con tact type: DC PPTs, un like NDC-tests, discriminated well betwee n monogamous and promiscuous species. In the DC-tests, stranger-directed aggression and stranger avoidanee were observed both in the highly social monogamous M. unguiculatus and the solitary territorial promiscuous G. perpallidus, but not in the non territorial promiscuous M. meridianus. In M. unguiculatus, stranger avoidanee 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, stran ger avoidance in creased the time spe nt alone. This first comparative experimental study of partner prefere nces in gerbils provides new in sights into the in terspecific variation in gerbil sociality and mating systems and sheds light on behavioral mechanisms un derlyi ng social fidelity and pair-b on ding.

Phylogenetic relationship and variation of alarm call traits of populations of red-cheeked ground squirrels(Spermophilus erythrogenys sensu lato)suggest taxonomic delineation

Distribution area and taxonomic borders within the species complex Spermophilus erythrogenys sensu lato re­main questionable.Early evidence suggests that red-cheeked ground squirrels of Southeast Kazakhstan are re­markably different in terms of the acoustic structure of their alarm calls from the red-cheeked ground squirrels of the Kurgan region in Russia.In this study,we analyzed the differences in the acoustic structure of the alarm call and mitochondrial DNA(complete control region,1005-1006 bp and complete cytochrome b gene,1140 bp)in 3 populations of red-cheeked ground squirrels(Tara,Altyn-Emel and Balkhash),all located within ar­eas isolated by geographical barriers in Southeast Kazakhstan.We found that the alarm call variables were sim­ilar between the 3 study populations and differed by the maximum fundamental frequency(8.46±0.75 kHz)from the values(5.62±0.06 kHz)reported for the red-cheeked ground squirrels from the Kurgan region of Rus­sia.Variation in mtDNA control region was only 3%and variation in cytochrome b gene was only 2.5%.Phylo­genetic trees based on cytochrome b gene polymorphism of 44 individuals from the study area and adjacent ter­ritories indicated 3 clades with high(98-100%)bootstrap support:“intermedius,”“brevicauda”and“iliensis”).We conclude that the 3 study populations in Southeast Kazakhstan belong to the clade intermedius and suggest a taxonomical revision of the species complex Spermophilus erythrogenys sensu lato,including analyses of nu­clear DNA and alarm calls for populations of the brevicauda and iliensis clades.