Some rodents produce ultrasonic vocalizations (USVs) for social communication using an aerodynamic whistle, a unique vocal production mechanism not found in other animals. The functional anatomy and evolution of this sound production mechanism remains unclear. Using laryngeal airway reconstruction, we identified anatomical specializations critical for USV production. A robust laryngeal cartilaginous framework supports a narrow supraglottal airway. An intralaryngeal airsac-like cavity termed the ventral pouch was present in three muroid rodents (suborder Myomorpha), but was absent in a heteromyid rodent (suborder Castorimorpha) that produces a limited vocal repertoire and no documented USVs. Small lesions to the ventral pouch in laboratory rats caused dramatic changes in USV production, supporting the hypothesis that an interaction between a glottal exit jet and the alar edge generates ultrasonic signals in rodents. The resulting undulating airflow around the alar edge interacts with the resonance of the ventral pouch, which may function as a Helmholtz resonator. The proposed edge-tone mechanism requires control of intrinsic laryngeal muscles and sets the foundation for acoustic variation and diversification among rodents. Our work highlights the importance of anatomical innovations in the evolution of animal sound production mechanisms.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.170976

Laryngeal airway reconstruction indicates that rodent ultrasonic vocalizations are produced by an edge-tone mechanism

The bat fauna of Alaska and northwestern Canada remains poorly known, principally due to a lack of dedicated surveys To better assess the diversity of bats in the region, we conducted full-spectrum acoustic surveys at several sites in Yukon, Canada During our surveys we obtained the 1st acoustic records of Hoary Bat (Lasiurus cinereus) and Long-Legged Myotis (Myotis volans) in Yukon Neither species had been documented previously in the territory, but one or both species were known from adjacent Alaska, British Columbia, and Northwest Territories Characteristics of certain echolocation calls of Hoary Bats and Long-legged Myotis are difficult to confuse with other species that might also occur in the region In addition, we made other noteworthy recordings; however, species identification for these other echolocation calls was ambiguous These 1st records significantly increase our knowledge of the ranges of these bat species in Yukon, Canada Further acoustic surveys, coupled with live capture

https://bioone.org/journals/Northwestern-Naturalist/volume-95/issue-3/13-08.1/Acoustic-Surveys-Reveal-Hoary-Bat-iLasiurus-cinereus-i-and-Long/10.1898/13-08.1.pdf

Acoustic Surveys Reveal Hoary Bat (Lasiurus cinereus) and Long-Legged Myotis (Myotis volans) in Yukon

Ultrasonic vocalizations (USV) of laboratory rodents may serve as age-dependent indicators of emotional arousal and anxiety. Fast-growing Arvicolinae rodent species might be advantageous wild-type animal models for behavioural and medical research related to USV ontogeny. For the yellow steppe lemming Eolagurus luteus, only audible calls of adults were previously described. This study provides categorization and spectrographic analyses of 1176 USV calls emitted by 120 individual yellow steppe lemmings at 12 age classes, from birth to breeding adults over 90 days (d) of age, 10 individuals per age class, up to 10 USV calls per individual. The USV calls emerged since 1st day of pup life and occurred at all 12 age classes and in both sexes. The unified 2-min isolation procedure on an unfamiliar territory was equally applicable for inducing USV calls at all age classes. Rapid physical growth (1 g body weight gain per day from birth to 40 d of age) and the early (9-12 d) eyes opening correlated with the early (9-12 d) emergence of mature vocal patterns of USV calls. The mature vocal patterns included a prominent shift in percentages of chevron and upward contours of fundamental frequency (f0) and the changes in the acoustic variables of USV calls. Call duration was the longest at 1-4 d, significantly shorter at 9-12 d and did not between 9-12-d and older age classes. The maximum fundamental frequency (f0max) decreased with increase of age class, from about 50 kHz in neonates to about 40 kHz in adults. These ontogenetic pathways of USV duration and f0max (towards shorter and lower-frequency USV calls) were reminiscent of those in laboratory mice Mus musculus.

/pdf/rapid-development-of-mature-vocal-patterns-of-ultrasonic-28i8caub1o.pdf

Rapid development of mature vocal patterns of ultrasonic calls in a fast-growing rodent, the yellow steppe lemming (Eolagurus luteus).

Peromyscus is a diverse group of mice that exhibits important and extensive natural variation across many traits and is ideal for studying ultrasonic vocalization (USV) behavior. Early work established that Peromyscus males in the laboratory use USVs for modulation of sexual behavior. Recent work from laboratory and field studies, focusing on the California mouse (Peromyscus californicus), has investigated the effect of changing behavioral contexts on USVs. The studies included research on both males and females as well as endocrine and social control of vocal emission and animal response to playbacks. In adult Peromyscus, four USV types have been described as: sustained vocalization (also termed “syllable” vocalization), bark, simple sweep, and complex sweep. Evidence is presented for the differential use of these USV types under affiliative (pair bonding, courtship) and aversive (inter- and intrasexual aggression) contexts. We argue that field studies in wild Peromyscus should complement laboratory experiments and suggest future directions of investigations.

Ultrasonic Vocalizations of Young Mice in the Genus Peromyscus

Ultrasonic vocalizations (USVs) of laboratory rodents indicate animal emotional arousal and may serve as models of human disorders. We analysed spectrographically USV calls of pup and adult fat-tailed gerbils Pachyuromys duprasi during 420-s tests, including isolation, touch and handling. Based on combination of six different USV syllable contour shapes and six different note compositions, we classified 782 USV syllables of 24 pups aged 5-10 days to 18 types and 232 syllables of 7 adults to 24 types. Pups and adults shared 16 of these 26 USV types. Percentages of USV syllables with certain contour shapes differed between pups and adults. The contour shape and note composition significantly affected most acoustic variables of USV syllables in either pups or adults. The 1-note USV syllables were most common in either pups or adults. Pup USV syllables were overall longer and higher-frequency than adult ones, reminiscent of the USV ontogenetic pathway of bats and distinctive to rats and mice. We discuss that the USV syllable types of fat-tailed gerbils were generally similar in contour shapes and note compositions with USV syllable types of mice and rats, what means that software developed for automated classifying of mice ultrasound might be easily adapted or re-tuned to gerbil USV calls. However, using fat-tailed gerbils as model for biomedical research including control of USV vocalization is only possible since 6th day of pup life, because of the delayed emergence of USV calls in ontogeny of this species.

/pdf/ultrasonic-vocalization-of-pup-and-adult-fat-tailed-gerbils-5c428xvdco.pdf

Ultrasonic vocalization of pup and adult fat-tailed gerbils (Pachyuromys duprasi).

Anecdotal reports of ultrasound use by flying squirrels have existed for decades, yet there has been little detailed analysis of their vocalizations. Here we demonstrate that two species of flying squirrel emit ultrasonic vocalizations. We recorded vocalizations from northern (Glaucomys sabrinus) and southern (G. volans) flying squirrels calling in both the laboratory and at a field site in central Ontario, Canada. We demonstrate that flying squirrels produce ultrasonic emissions through recorded bursts of broadband noise and time-frequency structured frequency modulated (FM) vocalizations, some of which were purely ultrasonic. Squirrels emitted three types of ultrasonic calls in laboratory recordings and one type in the field. The variety of signals that were recorded suggest that flying squirrels may use ultrasonic vocalizations to transfer information. Thus, vocalizations may be an important, although still poorly understood, aspect of flying squirrel social biology.

/pdf/ultrasonic-vocalizations-emitted-by-flying-squirrels-3ir7wncqc5.pdf

Ultrasonic Vocalizations Emitted by Flying Squirrels

It can be challenging to understand the evolution of sociality, particularly the occurrence of co-operation by non-kin. Southern flying squirrels (Glaucomys volans) are an interesting example of non-kin co-operation because of the mutual benefits obtained by social thermoregulation during winter. Because group survival confers benefits to the entire group, flying squirrels may also follow an aggregation economy, whereby co-operative foraging during winter is advantageous. However, the extent of such social foraging in flying squirrels is unknown. We tested for social foraging of southern flying squirrels, and also for relatedness among foraging groups. To determine the structure of foraging groups, we set up and remotely monitored feeding stations and nest cavities. All squirrels at the study site were tagged with passive integrated transponder (PIT) tags and nests and feeding stations were monitored with automated PIT-tag recorders for a 24-month period. Squirrels were found most often foraging alone. Squirrels that were recorded foraging together comprised unrelated individuals that were also found to share nest cavities. Squirrels were also recorded travelling farther distances between nest cavity and feeding station in the winter season than in the summer season, suggesting that, during winter, squirrels trade-off proximity to food caches for membership in a nest group. Our data suggest that squirrels forage and cache alone in their summer home range and make solitary returns to this summer range to collect their cache during the winter months, despite exhibiting social winter nesting. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 1126–1135.

Meghan N. Murrant

Papers

Ultrasonic Vocalizations Emitted by Flying Squirrels

A test of non‐kin social foraging in the southern flying squirrel (Glaucomys volans)