Call intercalation in dyadic interactions in natural choruses of Johnstone's whistling frog Eleutherodactylus johnstonei (Anura: Eleutherodactylidae).

Communal signaling increases the likelihood of acoustic interference and impairs mate choice; consequently, mechanisms of interference avoidance are expected. Adjustment of the timing of the calls between signalers, specifically call alternation, is probably the most efficient strategy. For this reason, in the present study we analyzed call timing in dyads of males of E. johnstonei in six natural assemblages. We addressed whether males entrain their calls with those of other males at the assemblage and if they show selective attention in relation to perceived amplitude of the other males' calls, inter-male distance, or intrinsic call features (call duration, period or dominant frequency). We expected males to selectively attend to closer or louder males and/or to those of higher or similar attractiveness for females than themselves, because those would be their strongest competitors. We found that most males intercalated their calls with those of at least one male. In assemblages of 3 individuals, males seemed to attend to a fixed number of males regardless of their characteristics. In assemblages of more than 3 individuals, the perceived amplitude of the call of the neighboring male was higher, and the call periods of the males were more similar in alternating dyads than in the non-alternating ones. At the proximate level, selective attention based on perceived amplitude may relate to behavioral hearing thresholds. Selective attention based on the similarity of call periods may relate to the properties of the call oscillators controlling calling rhythms. At the ultimate level, selective attention may be related to the likelihood of acoustic competition for females.

Behavioural Repertoires and Time Budgets of Semi-Free-Ranging and Captive Groups of Wedge-Capped Capuchin Monkeys, Cebus olivaceus, in Zoo Exhibits in Venezuela.

The behavioural repertoires and time budgets of 2 captive groups and 1 semi-free-ranging group of Cebus olivaceus were determined with the aim to assess the impact of the zoo environment on behaviour. The repertoires were qualitatively similar between groups and to those reported for wild troops, but the captive groups showed self-directed and stereotyped behaviours not reported in the wild. The differences in repertoires between groups were easily associated with the opportunity to interact directly with the visitors, with particularities of the enclosure and with the severity of confinement. Overall, females spent more time foraging than males in the 2 captive groups, and adults rested and watched more than subadults in all the groups. Time budgets were dominated by foraging, resting, movement and affiliative interactions, but their relative importance varied between groups, with foraging being especially prominent in the most confined group. The time budgets also varied qualitatively from those reported for wild troops. We conclude the species is behaviourally able to adjust to captivity, but the slight differences along the continuum from wild to semi-free to captive are suggestive of mild stress or social tension probably due to unstimulating environmental conditions, high visitor pressure and deviations from typical sex-age group composition.

Comportamiento social del mono capuchino común Cebus olivaceus (Primates: Cebidae) en tres exhibiciones zoológicas de Caracas, Venezuela

Social behavior of the Wedge-capped Capuchin Monkey Cebus olivaceus (Primates: Cebidae) in three zoological exhibits of Caracas, Venezuela. Captivity represents an extreme situation for primates, especially for those with large home ranges, and its effect on their behavior might be considerable. The Wedge-capped Capuchin Monkey Cebus olivaceus is the most common primate in Venezuelan zoos. To estimate the effect of confinement on C. olivaceus behavior, we analyzed the social behavior of three groups that differed in captivity conditions, in zoological exhibits in Caracas (Caricuao, Parque del Este, El Pinar). Caricuao’s group moved freely over a non-fenced area of 15 ha, Parque del Este’s and El Pinar’s groups lived in relatively small outdoor enclosures. Social behaviors were described using focal-animal sampling, group scans and ad libitum sampling. The frequency, duration and time devoted to each behavior (per focal period per individual) were estimated. Relative dominance between pairs of individuals was established as well as affiliative associations. The repertory of social behaviors was similar between groups and to which has been observed in nature, but the duration and frequency of affiliative and agonistic interactions differed between groups. Affiliative behaviors were less frequent but longer in Caricuao than in the other two groups, while agonistic behaviors were more frequent in El Pinar and Parque del Este. Differences between groups are explained by variation in captivity conditions. We suggest that confinement generates social tension and favors agonism, while affiliative encounters help reduce this tension. On the other hand, differences in agonism between captive and natural groups may result form prolonged association, restrictions to keep optimal spacing or leave the group. All groups had some social structure (e.g., dominance ranks, association and repulsion between individuals) but the social dynamic was partly disrupted. Dominance ranks were not clear throughout the group, the top male was not dominant over the top female, dominant individuals did not interact affiliatively more than other individuals, and females did not affiliate frequently with other females. All of these observations are contrary to which has been observed in nature. As a whole, C. olivaceus tolerates captivity well because its behavioral repertoire is similar to that in natural conditions, and abnormal or undesirable behaviors (e.g., self-mutilation, stereotyped actions), were not observed. Nonetheless, there is an effect of captivity, reflected in a disruption of the social dynamic. Rev. Biol. Trop. 56 (3): 1503-1520. Epub 2008 September 30.

El confinamiento es una situación extrema para los primates con áreas de vivienda extensas, y su efecto sobre la conducta puede ser considerable. Cebus olivaceus es el primate más común en los zoológicos de Venezuela pero su conducta en esta condición no ha sido documentada. Para estimar el efecto del confinamiento sobre el comportamiento social de C. olivaceus, observamos tres grupos en zoológicos de Caracas (Caricuao, Parque del Este, El Pinar), que diferían en las condiciones de cautiverio. El grupo en Caricuao, podía desplazarse libremente en un área no cercada, mientras que en Parque del Este y El Pinar estaban en fosas relativamente pequeñas. Se determinó el repertorio de conductas sociales y la frecuencia, duración y tiempo dedicado por individuo a cada comportamiento. Se realizaron observaciones focales de cada individuo, barridos del grupo y observaciones ad libitum. Se estableció la dominancia relativa y las asociaciones afiliativas entre individuos. El repertorio de conductas sociales fue similar entre grupos y respecto a lo observado en condiciones naturales. Sin embargo, las conductas afiliativas fueron menos frecuentes pero más largas en el grupo de Caricuao, mientras que las conductas agonísticas fueron más frecuentes en Parque del Este y El Pinar. Además, el agonismo fue menos frecuente en los grupos observados que en la naturaleza. Las diferencias entre grupos se explican por la condición del cautiverio. Sugerimos que con el confinamiento incrementa la tensión social y la probabilidad de encuentros agonísticos, en contraposición, la afiliación reduciría esta tensión. Por otra parte, la convivencia prolongada, la imposibilidad de mantener distancias individuales óptimas o de migrar del grupo promoverían la reducción del agonismo, a largo plazo, lo que explicaría las diferencias con los grupos naturales. En los tres grupos hubo cierta estructura social (relaciones de dominancia, afiliaciones y repulsiones entre individuos), pero algunos aspectos de la dinámica social están alterados. Los rangos de dominancia no fueron claros, el macho alfa no dominaba a la hembra de mayor rango, los dominantes no interactuaban afiliativamente más que otros individuos, y las hembras no se afiliaban preferentemente con otras hembras. Estas observaciones son contrarias a lo descrito en la naturaleza. Globalmente C. olivaceus tolera bien el cautiverio porque presenta un repertorio de conductas similar al observado en la naturaleza y no muestra conductas anormales (auto agresión, movimientos estereotipados); sin embargo la dinámica social es afectada.