Sexual dimorphism in the loud calls of Azara’s owl monkeys (Aotus azarae): evidence of sexual selection?

Primates use different types of vocalizations in a variety of contexts. Some of the most studied types have been the long distance or loud calls. These vocalizations have been associated with mate defense, mate attraction, and resource defense, and it is plausible that sexual selection has played an important role in their evolution. Focusing on identified individuals of known sex and age, we evaluated the sexual dimorphism in a type of loud calls (hoots) in a population of wild owl monkeys (Aotus azarae) in Argentina. We found evidence of sexual dimorphism in call structure, with females and males only emitting one type of call, each differing in dominant frequency and Shannon entropy. In addition, both age-related and sex-specific differences in call usage were also apparent in response to the removal of one group member. Future acoustic data will allow us to assess if there are individual characteristics and if the structure of hoot calls presents differences in relation to the social condition of owl monkeys or specific sex responses to variants of hoot calls’ traits. This will provide deeper insights into the evolution of vocal mechanisms regulating pair bonding and mate choice strategies in this and other primate species.Leakey Foundation, Wenner-Gren Foundation, National Geographic Society, NSF, National Institute on Aging, University of Pennsylvania Research Foundation, Zoological Society of San Dieg

Terrestrial behavior in titi monkeys (Callicebus, Cheracebus, and Plecturocebus) : potential correlates, patterns, and differences between genera

For arboreal primates, ground use may increase dispersal opportunities, tolerance to habitat change, access to ground-based resources, and resilience to human disturbances, and so has conservation implications. We collated published and unpublished data from 86 studies across 65 localities to assess titi monkey (Callicebinae) terrestriality. We examined whether the frequency of terrestrial activity correlated with study duration (a proxy for sampling effort), rainfall level (a proxy for food availability seasonality), and forest height (a proxy for vertical niche dimension). Terrestrial activity was recorded frequently for Callicebus and Plecturocebus spp., but rarely for Cheracebus spp. Terrestrial resting, anti-predator behavior, geophagy, and playing frequencies in Callicebus and Plecturocebus spp., but feeding and moving differed. Callicebus spp. often ate or searched for new leaves terrestrially. Plecturocebus spp. descended primarily to ingest terrestrial invertebrates and soil. Study duration correlated positively and rainfall level negatively with terrestrial activity. Though differences in sampling effort and methods limited comparisons and interpretation, overall, titi monkeys commonly engaged in a variety of terrestrial activities. Terrestrial behavior in Callicebus and Plecturocebus capacities may bolster resistance to habitat fragmentation. However, it is uncertain if the low frequency of terrestriality recorded for Cheracebus spp. is a genus-specific trait associated with a more basal phylogenetic position, or because studies of this genus occurred in pristine habitats. Observations of terrestrial behavior increased with increasing sampling effort and decreasing food availability. Overall, we found a high frequency of terrestrial behavior in titi monkeys, unlike that observed in other pitheciids

Study of the spatial relations between young avocets on their rearing grounds

On montre, au sein d'une colonie d'avocettes, le caractère dynamique des relations spatiales entre jeunes non émancipés. Analyse du système d'espacement entre couvées; analyse du mode de progression d'une couvée dans l'espace, depuis sa naissance jusqu'aux regroupements des oiseaux, en fin de saison de reproductio

Une étude des relations spatiales entre jeunes avocettes sur leurs lieux d’élevage

This study examines the spatial organization in broods of young Avocets, Recurvirostra avosetta, on their rearing grounds. In order to describe the development of the ranging behaviour within the colony, detailed observations are reported on one of these broods (brood A), studied from hatching to 60 days of age. Before the young were fledged, there was a small overlap in the daily ranges of different broods, and these moved slightly on successive days. This brood spacing is achieved through the territorial behaviour of the parents. In contrast, interbrood disputes never arise. Brood movement in the colony occur when the parents lead their young away or when a resident family is forced to leave its area, after being supplanted by another. Home range size of brood A shows a discontinuous increase, up to 47 ha, as a result of the movements of the young which often shift around. During the pre-fledging period (40 days), brood A did not wander through its whole area ; instead, the home-range (including the nest-site) could be subdivided into five parts, each of which was used intensively for several consecutive days. After fledging of the young, a shift in the home-range use was observed. Between 40-52 days of age, two exclusive areas were visited in flight, with a pronounced daily variation. Moreover, a predominent activity (resting or feeding) was associated with each of them. From 53 to 60 days of age, brood A expanded its home range considerably, by using a new area 600 m apart from the rearing site. During the post-fledging period, territorial behavior became less consistent and the birds (adults and juveniles) gradually form small unstable flocks. Brood movements within the colony and social relationships between juveniles both emphasize the dynamics of the spatial organization in the Avocet colony.Adret Patrice. Une étude des relations spatiales entre jeunes avocettes sur leurs lieux d’élevage. In: Revue d'Écologie (La Terre et La Vie), tome 39, n°2, 1984. pp. 193-208

The Sound Signals of the Adult Avocet Recurvirostra A Vosetta During the Perinatal Phase

International audienceRecordings of Avocet vocalizations were collected from three pairs, using a microphone placed close to nests at the end of incubation in a colony on the French Atlantic coast, in Vendée.From sonagraphic analyses, ten vocal structures were identified and described. Particular attention is given to the internal components of each call in an attempt to demonstrate structural relationships. In terms of general melodic features, three vocal groups are identified: chuckle calls, ascending chirping calls and sustained calls with whistled components. The existence of numerous gradation forms is emphasized.Verification of gestural behaviour at the time of the recordings additionally allows the context of emission to be clarified. It is distinguished thus: parental calls, calls concerned in the maintenance of individual distance and calls produced in the presence of predators.Finally, the Avocet sound signals are compared with those of other species, mainly waders

Airborne vs. radio-transmitted vocalizations in two primates: a technical report

<p>Elucidating the structure and function of joint vocal displays (e.g. duet, chorus) recorded with a conventional microphone has proved difficult in some animals owing to the complex acoustic properties of the combined signal, a problem reminiscent of multi-speaker conversations in humans. Towards this goal, we set out to simultaneously compare air-transmitted (AT) with radio-transmitted (RT) vocalizations in one pair of humans and one pair of captive Bolivian grey titi monkeys (<i>Plecturocebus donacophilus</i>) all equipped with an accelerometer – or vibration transducer – closely apposed to the larynx. First, we observed no crosstalk between the two radio transmitters when subjects produced vocalizations at the same time close to each other. Second, compared with AT acoustic recordings, sound segmentation and pitch tracking of the RT signal was more accurate, particularly in a noisy and reverberating environment. Third, RT signals were less noisy than AT signals and displayed more stable amplitude regardless of distance, orientation and environment of the animal. The microphone outperformed the accelerometer with respect to sound spectral bandwidth and speech intelligibility: the sounds of RT speech were more attenuated and dampened as compared to AT speech. Importantly, we show that vocal telemetry allows reliable separation of the subjects’ voices during production of joint vocalizations, which has great potential for future applications of this technique with free-ranging animals.</p

Response of Bolivian gray titi monkeys (Plecturocebus donacophilus) to an anthropogenic noise gradient: behavioral and hormonal correlates

Worldwide urban expansion and deforestation have caused a rapid decline of non-human primates in recent decades. Yet, little is known to what extent these animals can tolerate anthropogenic noise arising from roadway traffic and human presence in their habitat. We studied six family groups of titis residing at increasing distances from a busy highway, in a park promoting ecotourism near Santa Cruz de la Sierra, Bolivia. We mapped group movements, sampled the titis’ behavior, collected fecal samples from each study group and conducted experiments in which we used a mannequin simulating a human intrusion in their home range. We hypothesized that groups of titi monkeys exposed to higher levels of anthropogenic noise and human presence would react weakly to the mannequin and show higher concentrations of fecal cortisol compared with groups in least perturbed areas. Sound pressure measurements and systematic monitoring of soundscape inside the titis’ home ranges confirmed the presence of a noise gradient, best characterized by the root-mean-square (RMS) and median amplitude (M) acoustic indices; importantly, both anthropogenic noise and human presence co-varied. Study groups resided in small, overlapping home ranges and they spent most of their time resting and preferentially used the lower forest stratum for traveling and the higher levels for foraging. Focal sampling analysis revealed that the time spent moving by adult pairs was inversely correlated with noise, the behavioral change occurring within a gradient of minimum sound pressures ranging from 44 dB(A) to 52 dB(A). Validated enzyme-immunoassays of fecal samples however detected surprisingly low cortisol concentrations, unrelated to the changes observed in the RMS and M indices. Finally, titis’ response to the mannequin varied according to our expectation, with alarm calling being greater in distant groups relative to highway. Our study thus indicates reduced alarm calling through habituation to human presence and suggests a titis’ resilience to anthropogenic noise with little evidence of physiological stress