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OBJECTIVES: We quantified variation in fecal cortisol across reproductive periods in Azara's owl monkeys (Aotus azarae) to examine physiological mechanisms that may facilitate biparental care. Specifically, we evaluated evidence for the explanation that owl monkeys have hormonal mechanisms to mobilize energy during periods when each sex is investing heavily in reproduction, that is, the gestation period for females and the infant care period for males. MATERIALS AND METHODS: Between 2011 and 2015, we monitored 10 groups of Azara's owl monkeys from a wild population in Formosa, Argentina and collected fecal samples from 26 adults (13 males, 13 females). Using enzyme-linked immunosorbent assays, we quantified fecal cortisol as a proxy for evaluating stress responses, including energetic demands, on both sexes during periods of reproduction and parental care. RESULTS: Male cortisol was lowest during periods when they were caring for young infants (<3 months) compared with periods with older infants or no infant. Female cortisol was elevated during gestation compared with other periods. Mean fecal cortisol in both males and females was lower when an infant was present compared with when females were gestating. DISCUSSION: Our results do not support the hypothesis that owl monkey males have elevated fecal cortisol during periods when they need to mobilize energy to provide intensive infant care. Our findings are also inconsistent with the Maternal Relief hypothesis. However, results from studies measuring fecal cortisol must be interpreted with care and alternative explanations, such as seasonal fluctuations in diet and thermoenergic demands, should be considered when drawing conclusions.

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Agonistic behaviors are common in many group-living taxa and may serve a variety of functions, ranging from regulating conflicts over reproduction to defending food resources. However, high rates of agonism are not expected to occur among close relatives or individuals in established mating relationships, which are characteristics of monogamous groups. To contribute to our understanding of agonism within socially monogamous groups, we collected behavioral and demographic data from Azara's owl monkeys (Aotus azarae) in the Gran Chaco of Argentina over 14 years. We examined factors related to age, sex, kinship, and behavioral context to evaluate predictions of the hypotheses that agonism functions to regulate dispersal and that it mediates competition for food and/or mates. Intragroup agonism was relatively rare: the group rate was approximately one event every three and a half hours. Rates of agonism were generally similar for both sexes, but there were marked differences among age categories. Agonism performed by adults was more frequently directed at subadults than at younger offspring. In contrast, agonistic interactions involving infants were very rare. Among interactions between adults and subadults, adults were much more frequently the actors than the recipients, suggesting that agonism from adults may influence natal dispersal of subadults. Agonistic events were most frequent during foraging, but also occurred more frequently than expected during bouts of social behavior. Overall, our results suggest that agonism in owl monkeys serves as a mechanism for regulating dispersal, and also likely plays a role in mediating mating and feeding competition.

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In polygynous primates, a greater reproductive variance in males have been linked to their reduced life expectancy relative to females. The mortality patterns of monogamous pair-bonded primates, however, are less clear. We analyzed the sex differences in mortality within wild (NMales = 70, NFemales = 73) and captive (NMales = 25, NFemales = 29) populations of Azara's owl monkeys (Aotus azarae), a socially and genetically monogamous primate exhibiting biparental care. We used Bayesian Survival Trajectory Analysis (BaSTA) to test age-dependent models of mortality. The wild and captive populations were best fit by the logistic and Gompertz models, respectively, implying greater heterogeneity in the wild environment likely due to harsher conditions. We found that age patterns of mortality were similar between the sexes in both populations. We calculated life expectancy and disparity, the latter a measure of the steepness of senescence, for both sexes in each population. Males and females had similar life expectancies in both populations; the wild population overall having a shorter life expectancy than the captive one. Furthermore, captive females had a reduced life disparity relative to captive males and to both sexes in the wild. We interpret this pattern in light of the hazards associated with reproduction. In captivity, where reproduction is intensely managed, the risks associated with gestation and birth are tempered so that there is a reduction in the likelihood of captive females dying prematurely, decreasing their overall life disparity.

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High mortality rates have been observed in Teleost during early developmental stages, as well as great variations in reproductive tactics, which are related to adaptations towards environmental conditions and ecological niches for which different species have a specific response. The objective of this study was to describe reproductive tactics related to the survival of Cichlasoma orientale offspring, including aspects of body size, parental care, fecundity, oocyte size and spawning patterns. Samples were performed monthly from August 2011 to July 2013, in lentic and lotic environments at Curu river basin, Brazilian Northeastern semiarid region. Individual behavior (n=113) was observed underwater for over 50 hours by ad libitum sampling and focal-animal sampling. Collected individuals (males n=185, females n=95) were evaluated regarding the standard length, batch fecundity, oocyte size and spawning pattern. In females with mature ovaries, oocyte groups at different developmental stages were observed, these cells were counted and measured, and fecundity was estimated by the gravimetric method. Our results showed that the species displayed biparental care behavior and, on average, males were larger than females. Based on 46 ovaries, the average batch fecundity was 2 052±849 (range: 254-3 389). Standard length and batch fecundity were positively correlated, but no correlation was found between oocyte size and standard length. The maximum diameter observed in the most developed oocytes was 1.8mm. The observed distribution of oocyte size classes indicated synchronous oocyte development in three groups: previtellogenic, vitellogenic and mature, showing that C. orientale is a multiple spawner. Differences in the amount of oocytes among the three groups were observed, with the most developed group showing the smallest number of oocytes. The combination of low fecundity and large egg size is characteristic of demersal spawners due to a greater environmental stability. Multiple spawning increases chances of survival mainly because of increased fecundity per reproductive season, and the reduced competition among the offspring. We concluded that C. orientale makes a heavy investment in larval survival in detriment of the offspring number. Survival is favored by the large size of oocytes, large yolk reserve, biparental care and multiple spawning pattern.

Las altas tasas de mortalidad se han observado en teleósteos durante las etapas iniciales del desarrollo, así como una gran variación en las tácticas reproductivas, que están relacionados con adaptaciones a las condiciones ambientales y nichos ecológicos con cada especie que presenta una respuesta específica. El objetivo de este estudio fue describir las tácticas reproductivas relacionadas con la supervivencia de la descendencia de Cichlasoma orientale, incluyendo aspectos tales como el tamaño corporal, el cuidado parental, la fecundidad, el tamaño de los ovocitos y los patrones de desove. Las muestras se recolectaron mensualmente desde agosto 2011 hasta julio 2013, en ambientes lénticos y lóticos en la cuenca del río Curu, región semiárida del noreste de Brasil. El comportamiento individual (n=113) se observó bajo el agua durante más de 50 horas por un muestreo ad libitum y muestreo de grupos focales. Para los individuos recolectados (n=185 machos, hembras n=95) se evaluó: la longitud, la fecundidad por camada, el tamaño estándar de los ovocitos y el patrón de desove. En las hembras con ovarios maduros, se observó la cantidad de grupos de ovocitos en diferentes etapas de desarrollo y estas células fueron contadas y medidas y la fecundidad se estimadó por el método gravimétrico. Las especies muestran un comportamiento de cuidado biparental y, en promedio, los machos son más grandes que las hembras. Con base en 46 ovarios, la fecundidad promedio de lotes fue de 2 052±849 (254-3 389). Longitud estándar y fecundidad parcial se correlacionaron positivamente, pero no se encontró correlación entre el tamaño de los ovocitos y la longitud estándar. Los oocitos más desarrollados miden 1.8mm. La distribución observada de las clases de tamaño de los ovocitos indica desarrollo de los ovocitos sincrónico en tres grupos: pre-vitelogénicos, vitelogénicos y maduros, lo que demuestra que C. orientale es una especie con desova múltiple. Se observaron diferencias en la cantidad de ovocitos entre los tres grupos, con el grupo más desarrollada que muestra el menor número de ovocitos. La combinación de la baja fecundidad y gran tamaño del huevo es una característica de los reproductores demersales, debido a una mayor estabilidad del medio ambiente. Múltiples desoves aumenta las posibilidades de supervivencia, principalmente debido al aumento de la fecundidad por temporada reproductiva y reducción de la competencia entre la descendencia. Llegamos a la conclusión de que C. orientale hace una fuerte inversión en la supervivencia de las larvas en detri- mento del número de descendientes. La supervivencia se ve favorecida por el gran tamaño de los ovocitos, gran reserva de yema de huevo, cuidado biparental y patrón de desove múltiple.

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