Ambient temperature is more important than food availability in explaining reproductive timing of the bat Sturnira lilium (Mammalia: Chiroptera) in a montane Atlantic Forest

Abstract

Reproduction of bats is determined by a suite of endogenous and exogenous factors. Among exogenous influences, special attention has been given to the influence of food availability. However, in highland forests, severe decreases in temperature during the cold and dry season may also play an important role. In the present study we tested the influence of ambient temperature and food availability on the timing of reproduction in the frugivorous bat Sturnira lilium (E. Geoffroy, 1810). We conducted a 15-month mist-netting sampling in a mountain area of the Brazilian Atlantic Forest during which time we assessed the bats' diet through fecal samples, monitored fruit production of the main food plants, and recorded variations in ambient temperature. Sturnira lilium fed almost exclusively on Solanaceae. Similarly to the lowlands, reproduction was bimodal, but reproductive season tended to be shorter in the highlands and peaked in the warmer months of the year. Overall, 44% to 53% of the reproductive pattern was explained by variations in ambient temperature, while the relationship with food availability was nonsignificant. We conclude that variations in ambient temperature in tropical mountains may be a stronger selection pressure than food availability in determining reproductive timing of bats.Résumé : La reproduction des chauves-souris est déterminée par une série de facteurs endogènes et exogènes. Parmi les facteurs exogènes, on a porté une attention particulière à l'influence de la disponibilité de nourriture. Cependant, dans les forêts des terres hautes, les grandes chutes de température durant la saison froide et sèche peuvent aussi jouer un rôle important. Dans notre recherche, nous testons l'influence de la température ambiante et de la disponibilité de la nourriture sur le calendrier de la reproduction chez la chauve-souris frugivore Sturnira lilium (E. Geoffroy, 1810). Nous avons fait une échantillonnage pendant 15 mois dans une région montagneuse de la Forêt atlantique brésilienne; nous avons déter-miné le régime alimentaire des chauves-souris par prélèvement de fèces, suivi la production de fruits des principales plantes nourricières et enregistré les variations de la température ambiante. Sturnira lilium se nourrit presque exclusivement de Solanaceae. Comme dans les basses terres, la reproduction est bimodale, mais la saison de reproduction tend à être plus courte dans les terres hautes et elle atteint un sommet durant les mois plus chauds de l'année. Les variations de la température ambiante expliquent globalement 44 % à 53 % du patron de reproduction, alors que la relation avec la disponibilité de nourriture n'est pas significative. Nous en concluons que dans les montagnes tropicales, les variations de la température ambiante peuvent exercer une pression de sélection plus grande que la disponibilité de nourriture dans la dé-termination du calendrier de reproduction des chauves-souris.[Traduit par la Rédaction]

Reproductive biology of the bat Sturnira lilium (Chiroptera, Phyllostomidae) in the Atlantic Forest of Rio de Janeiro, southeastern Brazil

“…Some authors say that testes location is not a good indicator of male reproductive activity, since the spermatic activity is continuous (Fabián and Marques, 1989;Moraes, 2008). Other authors suggest the use of other external indicators of active reproduction, such as behavior, glands, and odors Mello et al, 2009). However, in the present study, the higher proportion of males with scrotal testes was synchronized with the proportion of potentially receptive females (lactating and post-lactating), indicating that the more females are in estrus, the more males will show maximum sperm production.…”

“…Mello et al (2009) observed that, although S. lilium did not have its reproduction synchronized with rainfall nor fruit availability, births occurred in the rainy season. These authors suggest that temperature has the strongest influence on the reproduction of S. lilium in montane forests.…”

“…However, there was no relationship between the percentage of lactating females and climate variables. In a study on S. lilium in southeastern Brazil at a subtropical latitude, Mello et al (2009) observed a relationship between temperature and the number of pregnant and lactating females. In the present study, the highest proportions of pregnant and lactating females were observed in the months with highest rainfall.…”

“…Mello et al (2008aMello et al ( , 2009 observed, in a montane rainforest in southeastern Brazil, a positive relationship between temperature, reproduction and population size of S. lilium. The purpose of our study was to analyze reproductive data of S. lilium from longterm sampling carried out in several sites in Rio de Janeiro, southeastern Brazil.…”

“…Although the reproductive biology of S. lilium has been well studied in other countries, it is still poorly known in Brazil, since it is based on local data (Mello et al, 2009), small samples (Stoner, 2001;Estrada and Coates-Estrada, 2001; Kaku-Oliveira et al, 2010) or short-term sampling (Sipinski and Reis, 1995). Mello et al (2008aMello et al ( , 2009 observed, in a montane rainforest in southeastern Brazil, a positive relationship between temperature, reproduction and population size of S. lilium.…”