Timing and environmental cues associated with triggering of reproductive activity in Atlantic forest marsupials

Abstract

Seasonal reproduction during the time when food availability is high is a widespread strategy in marsupials, which maximizes offspring survival. In Australian marsupials, reproduction is commonly synchronous among co-occurring species, the onset of reproduction being triggered by photoperiodic cues. In a subset of these species, partial semelparity with high mortality of males after reproduction is a common pattern. For Neotropical marsupials, however, environmental triggers of reproduction have been poorly studied despite some evidence of a seasonal synchronous reproduction, and semelparity has been described in few species. Using a capture–recapture dataset of co-occurring marsupials in the Atlantic forest sampled for two years, we aim to investigate the timing and triggering of reproductive activity as well as the occurrence of semelparity in Neotropical small marsupials. We evaluated which environmental cues (rainfall, photoperiod and temperature) best explain the age structure of the populations of Gracilinanus microtarsus, Marmosops incanus, Marmosops paulensis, Monodelphis americana, Monodelphis scalops and Monodelphis iheringi. For the most common species we also tested for the occurrence of semelparity by assessing if survival rate is affected by sex and mating period. Our results indicate that reproduction onset seems to be synchronous among species and driven by photoperiod cues. In all species, reproduction is seasonal with juveniles being born and lactation occurring in the period of highest food availability, the warm–wet season. Further, semelparity is likely to be the cause of a high population turnover in Marmosops incanus, and probably also in co-occurring marsupials.