Hormonal Monitoring of Reproductive Status in Monogamous Wild Female Owl Monkeys (Aotus azarai) of the Argentinean Chaco

Abstract

The Neotropical owl monkeys (Aotus spp.) are a good model for evaluating the hypothesis that monogamy may arise if female reproductive cycles limit the mating potential of males. To evaluate this hypothesis, we first needed to assess the feasibility of using fecal sampling for monitoring the reproductive status of females. We collected fecal samples (n = 242, from 7 females) from wild adult Aotus azarai females in the Gran Chaco forests of Argentina during 3 years. Fecal estrone-1-glucuronide (E₁C) and pregnenadiol-3-glucuronide (PdG) tended to rise in parallel during the luteal phase. The average cycle length was 22 ± 3 days (n = 5 females, 10 cycles). We identified 2 conceptive cycles and characterized the E₁C and PdG profiles of 2 pregnancies. This report is the first of its kind on wild female owl monkeys. Despite the difficulties in sample collection and processing in the field and providing a species-specific validation in the laboratory, we show that fecal samples from A. azarai can be used for monitoring female reproductive status and function.

Hormonal correlates of development and natal dispersal in wild female owl monkeys (Aotus azarae) of Argentina

“…We utilized feces to monitor females’ reproductive hormones, because feces are the only medium that we can reliably obtain from wild individuals without repeated capturing (Fernandez-Duque et al, 2011). We collected fecal samples systematically from five juveniles, seven subadults that had not yet dispersed from their natal groups, and four subadults that had dispersed from their natal groups within the previous 12 months and were ranging solitarily.…”

“…We followed a sampling schedule previously utilized to monitor the reproductive status of adult female owl monkeys at our field site (Fernandez-Duque et al, 2011). Under this schedule, we sampled each female, on average, every 3.5 days (typically 2–4 days (85% of samples), absolute range: 5–7 days).…”

“…We monitored individuals an average of 129 ± 16 consecutive days (range: 31–220 days) between May and December in three consecutive years (2013, 2014, 2015), with the exception of two females who were sampled during July and August in 2011 (Table 1). The average cycle length for wild adult reproductive A. azarae females is approximately 22 ± 3 days (range 18–25 days) when computed using consecutive peaks in E1C from 12 cycles, and 24.0 ± 1.6 days (range 20–26 days) when computed using E1C nadirs from 10 cycles (Fernandez-Duque et al, 2011). Thus, the time when each female was monitored encompassed at least one full potential ovulatory cycle.…”

“…We performed diethyl ether extractions on all samples using established methods (Fernandez-Duque et al, 2011; Strier and Ziegler, 1994). Briefly, we transferred 1 mL of the liquid portion of each sample into a glass culture tube and then added 1 mL of DI water and 5 mL of diethyl ether to the tube.…”

“…Very little is known about the development and sexual maturation of wild owl monkeys, though ovulatory cycles of wild adult females have been described (Fernandez-Duque et al, 2011). In captivity, Aotus nancymaae females as young as 20.5 months may be capable of conceiving (Gozalo and Montoya, 1990).…”