Ambient temperature drives sex ratio and presence of pregnant females of Anoura geoffroyi (Phyllostomidae) bats living in temperate forests

Abstract

Phenology in animals is strongly influenced by seasonality that promotes changes in abundance of food resources and temperature. These changes may impose energetic constraints to organisms in certain seasons during the year, especially on those animals facing high energetic demands, such as nectarivorous bats. Seasonality in temperate forests could, therefore, promote migration of female nectarivorous bat to find warmer sites, thus enhancing breeding success. To test this hypothesis, we compared the proportion of females and the proportion of pregnant females of the nectarivorous bat Anoura geoffroyi, between months, in six different populations across temperate forests of Mexico. Bats were captured over a complete season cycle either with sweep or mist nets at the entrance or near their roosting caves, and their age, sex, and reproductive condition were recorded. We found that over 50% of bats present in the cave roosts across different populations in temperate forests of the Trans-Mexican Neovolcanic Belt of Mexico during the warmer and wetter months (April–September) were females, both pregnant and nonpregnant. In contrast, fewer than 30% of bats present in the roosting caves sampled in the colder and drier months (October–March) were females. In addition, we found that the temperature that favors the proportion of females at the studied sites was greater than 8°C. We concluded that seasonality affects sex ratio and phenology of A. geoffroyi in Mexican temperate forests. Our findings suggest females’ migrations to lowland warmer sites to improve prenatal development.

Intraspecific variability of nectar attracts different bats: the case of Pseudalcantarea viridiflora, a bromeliad with crepuscular anthesis

“…Taking into account that A. geoffroyi is a common species at Los Tuxtlas, and that it is the main pollinator of other sympatric bromeliads in the study site (i.e., Pitcairnia recurvata, Aguilar-Rodríguez et al 2019b), it is unclear why this species does not act as the main pollinator of P. viridiflora in this site. Recent studies in Mexican temperate forests show that seasonality affects the sex ratio and phenology of A. geoffroyi, promoting regional altitudinal migrations to favor reproduction in this species (Saldaña-Vazquez et al 2020), which might explain its lower abundance at the time when P. viridiflora is flowering at Los Tuxtlas. However, further studies are required to explain whether differences in pollinators are directly related to the floral reward, to pollinator population migrations or are produced by specific environmental conditions.…”

Aspectos Ecológicos De Duas Grandes Colônias De Morcegos Nectarívoros (Anoura Geoffroyi Gray, 1838) Residentes Em Cavernas No Brasil: Implicações Para Conservação

“…Sex segregation behavior is common among vertebrates and several factors can lead species to exhibit this behavior (Main & Cobientz, 1996, Ruckstuhl, 2007. Saldaña-Vázquez et al (2020) hypothesis to explain segregation in A. geoffroyi, is that pregnant females seek warmer shelters that have more suitable microclimatic temperature conditions for better prenatal development of their offspring. The authors of this study (Saldaña-Vázquez et al, 2020) observed that in six populations of A. geoffroyi evaluated in temperate forests of Mexico, seasonality affects sex ratio and phenology of the species.…”

“…Saldaña-Vázquez et al (2020) hypothesis to explain segregation in A. geoffroyi, is that pregnant females seek warmer shelters that have more suitable microclimatic temperature conditions for better prenatal development of their offspring. The authors of this study (Saldaña-Vázquez et al, 2020) observed that in six populations of A. geoffroyi evaluated in temperate forests of Mexico, seasonality affects sex ratio and phenology of the species. Shelters occupied predominantly by females had a temperature that was up to 8°C higher than the other colonies during the warmer and more humid months.…”