Female Barbary macaque (Macaca sylvanus) copulation calls do not reveal the fertile phase but influence mating outcome

In a number of primate species, females utter loud and distinctive calls during mating. Here we aim to clarify the information content and function of Barbary macaque (Macaca sylvanus) copulation calls by testing (i) whether or not copulation calls advertise the female fertile phase and (ii) whether and how copulation calls influence male ejaculatory behaviour. In order to do this, we combined hormone measurements with acoustic analysis and behavioural observations. In contrast to a previous study implying that the structure of copulation calls indicates the timing of the fertile phase, our results, using objective endocrine criteria for assessing ovulation, provide evidence that the structure of copulation calls of female Barbary macaques does not reveal the timing of the fertile phase. More importantly, females seem to influence the likelihood of ejaculation by calling versus remaining silent and by adjusting the timing of call onset. Females make use of this ability to influence mating outcome to ensure ejaculatory matings with almost all males in the group. In addition, calls given during ejaculatory copulations differ from those during non-ejaculatory copulations, providing information about mating outcome for listeners. We conclude that in this species, copulation calls apparently serve to enhance sperm competition and maximize paternity confusion.     

Correspondence between evoked vocal responses and auditory thresholds in Pleurodema thaul (Amphibia; Leptodactylidae)

Thresholds for evoked vocal responses and thresholds of multiunit midbrain auditory responses to pure tones and synthetic calls were investigated in males of Pleurodema thaul, as behavioral thresholds well above auditory sensitivity have been reported for other anurans. Thresholds for evoked vocal responses to synthetic advertisement calls played back at increasing intensity averaged 43 dB RMS SPL (range 31–52 dB RMS SPL), measured at the subjects’ position. Number of pulses increased with stimulus intensities, reaching a plateau at about 18–39 dB above threshold and decreased at higher intensities. Latency to call followed inverse trends relative to number of pulses. Neural audiograms yielded an average best threshold in the high frequency range of 46.6 dB RMS SPL (range 41–51 dB RMS SPL) and a center frequency of 1.9 kHz (range 1.7–2.6 kHz). Auditory thresholds for a synthetic call having a carrier frequency of 2.1 kHz averaged 44 dB RMS SPL (range 39–47 dB RMS SPL). The similarity between thresholds for advertisement calling and auditory thresholds for the advertisement call indicates that male P. thaul use the full extent of their auditory sensitivity in acoustic interactions, likely an evolutionary adaptation allowing chorusing activity in low-density aggregations.     

Echolocation calls produced by Kuhl's pipistrelles in different flight situations

Flexibility in the echolocation call structure of bats can improve their performances, because, in some situations, some signal designs are better than others. Hence, at least some bats should adjust their echolocation calls according to the setting in which they are operating but also to the specific task at hand, that is their behavioral intention. We studied variation in the echolocation calls of Pipistrellus kuhlii emitted during four flight situations that were similar in setting but differed in behavioral context: emergence from a roost, commuting to and from foraging sites, foraging and returning to a roost. Echolocation calls produced by P. kuhlii differed significantly according to the flight situation. Call types differed most distinctly between foraging and commuting. We also found a high variance in the emergence calls we recorded, perhaps reflecting pre- and post-takeoff calls. Discriminant function analysis on calls emitted while foraging, commuting or returning to the roost classified the calls to the correct group 73.3% of the time. The differences between bats' echolocation calls in different flight situations might indicate an intrinsic change in the bat's behavior. Recognizing these differences could be crucial when using call variables to identify bat species.     

Acoustic Niches of Siberut Primates

The loud calls nonhuman primates use in long-distance communication have supposedly been selected for efficient information transfer in the habitat. The differential effects of scattering and reverberation and the masking effects of background noise predict that loud calls produced in rain forest habitats should be low-pitched and whistle-like with low-frequency modulation. Callers may also use particular calling posts or times of day with reduced background noise to increase the efficacy of sound transmission. We studied the loud calls of the 4 sympatric primate species on Siberut Island. Only Kloss gibbons (Hylobates klossii) fulfilled the predictions regarding both the structure and use of calls. Though the other 3 species —Mentawai macaques (Macaca siberu), pig-tailed langurs (Simias concolor), and Mentawai leaf monkeys (Presbytis potenziani)— also concentrated their main energies in the spectral window with the lowest background noise, their calls were not adapted to long-range transmission. All 4 species produced loud calls exclusively no lower than 18 m above ground, but food abundance and shelter in the canopy may also be factors. Though all 4 species produced the majority of loud calls in the morning, it was not the only time of day with reduced background noise. We suggest that phylogenetic inheritance may better explain the structure of calls than adaptation to the habitat. In sum, the observed usage of spectral and temporal niches is not solely an adaptation to the sound profile of the habitat, though it clearly improves their transmission.     

Variation in chick‐a‐dee calls of bridled titmice (Baeolophus wollweberi): Frequent use of non‐combinatorial calls in a combinatorial calling system

Chick‐a‐dee calls of Poecile (chickadee) and Baeolophus (titmouse) species are complex in terms of the structural composition of note types and the diversity of messages. Studies so far have mainly focused on the calls of various chickadee and just one titmouse species—the tufted titmouse (B. bicolor). To begin to address this lack of titmouse data, our study investigated variation in note composition of calls of bridled titmice (B. wollweberi). We obtained calls from 26 flocks in the Chiricahua Mountains of Arizona in the overwintering flocking period. Bridled titmice produce proportionally more non‐combinatorial call variants than combinatorial call variants. The number of the single noted calls furthermore exceeded the number of multinote calls. In general, structural variation in the combinatorial calls appears to be comparable to calls of better‐studied chickadees and of tufted titmice, although bridled titmice appear to have a unique call length distribution. We also analyzed some behavioral associations with call variation and found that flight behavior and close interactions between individuals were associated with use of specific note types. Finally, we found microgeographic variation in note type use in these calls. We discuss some possible explanations for call complexity in this species.     

Discomfort-related changes in pup ultrasonic calls of fat-tailed gerbils Pachyuromys duprasi

Rodent pups vocalize when placed in social isolation. We apply a method of “joint calls” for examining discomfort in rodent pup ultrasonic (>20 kHz) calls. Previously, this method has been developed for audible calls of fur farm mammals. Using a repeated measures design to exclude effects of individual identity and age on the analysed variables, we compared the ultrasonic call variables produced by 8–40-day pups of fat-tailed gerbils Pachyuromys duprasi during two subsequent experimental stages, the Isolation Stage and the Handling Stage. We considered that discomfort-related negative emotional arousal increased towards the Handling Stage compared to the Isolation Stage because of cumulative effects of handling and time of pup isolation from the nest. At the Isolation Stage, the call rate (calls/s) was higher from 10 to 18 days of age, whereas both the maximum amplitude frequency and power quartiles of joint calls were lower than at the Handling Stage from 20 to 32 days of age. At the same time, in audible (<20 kHz) vocalizations of a wide range of mammalian species, both the higher call rate and the upward shift of the maximum amplitude frequency and power quartiles indicate the discomfort-related increase of negative emotional arousal. We discuss the advantages of the method of joint calls for express-analyses of power variables for large sequences of ultrasonic vocalizations of complex acoustic structure during experimental trials.     

同一山洞中五种蝙蝠的回声定位比较及生态位的分化

对同一山洞中5种蝙蝠的回声定位叫声和外部形态作了比较分析,根据蝙蝠回声定位叫声,形态特征与捕食策略之间的联系,并结合部分的野外观察研究,推断其捕食生境及捕食策略,并对洞中5种共栖蝙蝠的生态位分化进行了分析;研究结果如下：（1）南蝠（Ia io)在地面或树冠中间的开阔空间捕食个体较大的昆虫;（2）大鼠耳蝠（Myotis myotis)主要以掠食性方式（gleaning) 捕食森林或草地地表面的昆虫;（3）黄大蹄幅（Hipposideros pratti)主要在树冠周围或树冠上方进行捕蝇器式（Fly-catching)（即倒挂于一固定枝条或地点,探索周围飞行或接近的昆虫,探索到后捕捉回原倒挂地点再进食）或飞行捕食,它主要捕食个体较大的甲虫;（4）角菊头蝠（Rhinolophus cornutus)主要在较密集树木中（枝叶间）,农田及树木周围捕食型较小的翼拍动昆虫;（5）三叶蹄幅（Aselliscus wheeleri)是在树木,灌丛或在其周围空间内捕食较小的翼拍动昆虫,但其食性可能菊头蝠不同,根据以上研究结果,认为这5种蝙蝠的取食生态位存在着明显的分化。     

Influence of Female Copulation Calls on Male Sexual Behavior in Captive Macaca fascicularis

We investigated the function of copulation calls—vocalizations by females during mating—in captive groups of long-tailed macaques. We tested predictions of the contest-competition, sperm competition, synchronized orgasms, mate again, alpha-male notification and graded-signal hypotheses. We observed 371 copulations of 36 females wherein the presence or absence of a copulation call was clear. Females call equally often with different males and shortly after ejaculation. Copulation calls occurred equally with copulations with and without ejaculation. Calls did not incite disruptions of the mating. Following calls females mated again, more often than expected, with their mating partner. Both pregnant and fertile females uttered copulation calls. Two females conceived and mated mainly with the alpha male then. We conclude that copulation calls do not incite male contest competition for sexual access to females and that it is unlikely that calls synchronize male and female orgasms. Several hypotheses remain plausible, but not all predictions are borne out unequivocably. This alerts us to the possibility that the calls could have multiple beneficial effects; natural selection might strike a compromise among functions. Investigation of the mate again, sperm competition and alpha-male notification hypotheses, and of hypotheses not tested in our study concerning female breeding overlap and female-female agonism, is required.