CONICET | Buscador de Institutos y Recursos Humanos

Reproductive states involve high nutritional requirements for female primates and may influence on their feeding patterns. Lactation is considered the most energetically expensive part of mammalian reproduction. In order to compensate the nutritional cost of lactation, female primates generally increase their nutritional intake, consuming more high-quality food items, and/or spend significantly more time foraging than nonlactating females. The goal of this study was to investigate whether female reproductive states in wild Alouatta caraya is associated to fluctuations in feeding patterns at two nearby study sites in Northeastern Argentina. One was a flooded forest in Isla Brasilera,Chaco province (27° 20' S; 58° 40' W), and the other site a gallery forest in mainland northwestern Corrientes province (27° 30´ S; 58° 41´ W). We collected data from 22 adult females and 10 adult males belonging to 8 groups of black and gold howler monkeys, using a 2-min scan sampling technique every 10 minutes, we recorded age, sex, reproductive state, and activity of each individual. We completed a total of 720 hours of observation between September 2008 and February 2009. We compared thetime invested in feeding activities in adult females across different reproductive states (gestating, lactating, and cycling), and between adult females and males. We found that lactating females spent significantly more time feeding than gestating or cycling females (Kruskal ? Wallis Test, H (2, N= 18) = 6.87, p < 0.05). When we comparedlactating females with adult males, the feeding frequencies were also higher for females during lactation (Kruskal ? Wallis Test, H (1, N= 12) = 6.58, p < 0.05). These results suggest a possible dietary adaptation to reproductive costs in Alouatta caraya females, indicating that lactation is the energetically most demanding reproductive state.

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