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1. Specificity of California mouse pup vocalizations in response to olfactory stimuli

   https://doi.org/10.1002/dev.22261  

   Wilson, Kerianne M. ; Wagner, Victoria A. ; Saltzman, Wendy ( March 2022 , Developmental Psychobiology)

   To investigate flexibility in vocal signaling by rodent pups, we examined whether olfactory stimuli influence characteristics of pup calls and how these calls may be affected by sex and litter size in California mice (Peromyscus californicus). Pups were isolated and recorded during a 3‐min baseline period followed by a 5‐min exposure to bedding containing scent from their home cage, scent from the home cage of an unfamiliar family, coyote urine, or no scent (control). Latency to call, call rate, and call characteristics (duration, frequency, and amplitude) were compared between the baseline and scent‐exposure periods and among olfactory conditions. Compared with the control condition, pups from two‐pup litters called more quietly when exposed to odor from a predator, whereas pups from three‐pup litters called more loudly. Additionally, pups showed nonsignificant tendencies to reduce call rates in response to odors from their home cage and to increase call rates when exposed to predator urine. Last, males produced higher‐frequency calls and more ultrasonic vocalizations than females. These results indicate that pup calling behavior in this species can be influenced by acute olfactory stimuli as well as litter size and sex. The flexibility of pup calling in response to these three variables potentially increases the communication value of pup calls and helps shape the parents’ responses.

    

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2. Playback of broadband vocalizations of female mice suppresses male ultrasonic calls

   https://doi.org/10.1371/journal.pone.0273742  

   Hood, Kayleigh E. ; Long, Eden ; Navarro, Eric ; Hurley, Laura M. ( January 2023 , PLOS ONE)

   Coleman, Melissa J. (Ed.)

   Although male vocalizations during opposite- sex interaction have been heavily studied as sexually selected signals, the understanding of the roles of female vocal signals produced in this context is more limited. During intersexual interactions between mice, males produce a majority of ultrasonic vocalizations (USVs), while females produce a majority of human-audible squeaks, also called broadband vocalizations (BBVs). BBVs may be produced in conjunction with defensive aggression, making it difficult to assess whether males respond to BBVs themselves. To assess the direct effect of BBVs on male behavior, we used a split-cage paradigm in which high rates of male USVs were elicited by female presence on the other side of a barrier, but which precluded extensive male-female contact and the spontaneous production of BBVs. In this paradigm, playback of female BBVs decreased USV production, which recovered after the playback period. Trials in which female vocalizations were prevented by the use of female bedding alone or of anesthetized females as stimuli also showed a decrease in response to BBV playback. No non-vocal behaviors declined during playback, although digging behavior increased. Similar to BBVs, WNs also robustly suppressed USV production, albeit to a significantly larger extent. USVs suppression had two distinct temporal components. When grouped in 5-second bins, USVs interleaved with bursts of stimulus BBVs. USV suppression also adapted to BBV playback on the order of minutes. Adaptation occurred more rapidly in males that were housed individually as opposed to socially for a week prior to testing, suggesting that the adaptation trajectory is sensitive to social experience. These findings suggest the possibility that vocal interaction between male and female mice, with males suppressing USVs in response to BBVs, may influence the dynamics of communicative behavior. 

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3. An acute dose of intranasal oxytocin rapidly increases maternal communication and maintains maternal care in primiparous postpartum California mice

   https://doi.org/10.1371/journal.pone.0244033  

   Guoynes, Caleigh D. ; Marler, Catherine A. ( April 2021 , PLOS ONE)

   Rosenfeld, Cheryl S. (Ed.)

   Maternal-offspring communication and care are essential for offspring survival. Oxytocin (OXT) is known for its role in initiation of maternal care, but whether OXT can rapidly influence maternal behavior or ultrasonic vocalizations (USVs; above 50 kHz) has not been examined. To test for rapid effects of OXT, California mouse mothers were administered an acute intranasal (IN) dose of OXT (0.8 IU/kg) or saline followed by a separation test with three phases: habituation with pups in a new testing chamber, separation via a wire mesh, and finally reunion with pups. We measured maternal care, maternal USVs, and pup USVs. In mothers, we primarily observed simple sweep USVs, a short downward sweeping call around 50 kHz, and in pups we only observed pup whines, a long call with multiple harmonics ranging from 20 kHz to 50 kHz. We found that IN OXT rapidly and selectively enhanced the normal increase in maternal simple sweep USVs when mothers had physical access to pups (habituation and reunion), but not when mothers were physically separated from pups. Frequency of mothers’ and pups’ USVs were correlated upon reunion, but IN OXT did not influence this correlation. Finally, mothers given IN OXT showed more efficient pup retrieval/carrying and greater total maternal care upon reunion. Behavioral changes were specific to maternal behaviors (e.g. retrievals) as mothers given IN OXT did not differ from controls in stress-related behaviors (e.g. freezing). Overall, these findings highlight the rapid effects and context-dependent effect a single treatment with IN OXT has on both maternal USV production and offspring care. 

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4. Testosterone pulses at the nest site modify ultrasonic vocalization types in a monogamous and territorial mouse

   https://doi.org/10.1111/eth.12812  

   Timonin, Mary E. ; Kalcounis‐Rueppell, Matina C. ; Marler, Catherine A. ; Ebensperger, ed., L. ( October 2018 , Ethology)

   Modulation of baseline testosterone (T) via long‐lasting T implants alters territorial, sexual, and social behavior of animals in the field. Transient T increases occur in numerous species after social interactions, but these transient increases in T have not been manipulated in the field. In the laboratory, these T increases can influence future behavior for days, causing changes in social behavior and inducing preferences for specific locations. We manipulated transient increases in T in the field at the nests of the monogamous and territorial California mouse (Peromyscus californicus) to examine long‐term (>24 hr) changes in ultrasonic vocalizations (USVs). Males of bonded male–female dyads (=pair) were administered a T injection (vs. saline) three times over seven days and USVs of the male–female dyad were measured for three days after the last injection. At T nests, the male–female dyad produced significantly more 1SV (one call SV: an SV is a sustained vocalization that is long in duration and low in modulation) and 4SV (four call SV) type USVs than controls, but no significant changes in aggressive barks. Overall, male–female dyad mice at T nests produced a greater diversity in call types such that 1SV, 4SV, 5SV, and a complex sweep were produced at T nests but not control nests. There were significantly more USVs produced at T nests on night 2 after the final injection. There were no differences in spectral characteristics of SV calls or aggressive barks between T and control nests. The function of the changes that occurred is unknown, but is consistent with increased long‐term changes in behavioral interactions with nest mates and may reflect T‐induced conditioned place preferences to the nest site. Significantly, transient increases in T influence future acoustic communication under field conditions with competing biotic and abiotic stimuli.

    

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5. Two conserved vocal central pattern generators broadly tuned for fast and slow rates generate species-specific vocalizations in Xenopus clawed frogs

   https://doi.org/10.7554/eLife.86299  

   Yamaguchi, Ayako ; Peltier, Manon ( May 2023 , eLife)

   Across phyla, males often produce species-specific vocalizations to attract females. Although understanding the neural mechanisms underlying behavior has been challenging in vertebrates, we previously identified two anatomically distinct central pattern generators (CPGs) that drive the fast and slow clicks of maleXenopus laevis,using an ex vivo preparation that produces fictive vocalizations.Here, we extended this approach to four additional species,X. amieti, X. cliivi, X. petersii, and X. tropicalis,by developing ex vivo brain preparation from which fictive vocalizations are elicited in response to a chemical or electrical stimulus. We found that even though the courtship calls are species-specific, the CPGs used to generate clicks are conserved across species. The fast CPGs, which critically rely on reciprocal connections between the parabrachial nucleus and the nucleus ambiguus, are conserved among fast-click species, and slow CPGs are shared among slow-click species. In addition, our results suggest that testosterone plays a role in organizing fast CPGs in fast-click species, but not in slow-click species. Moreover, fast CPGs are not inherited by all species but monopolized by fast-click species. The results suggest that species-specific calls of the genusXenopushave evolved by utilizing conserved slow and/or fast CPGs inherited by each species.

    

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