Bats in temperate and subtropical regions typically synchronize birth of a single young with peaks in resource availability driven by local climate patterns. In tropical rain forest, insects are available throughout the year, potentially allowing departures from seasonal monoestry. However, reproductive energy budgets may be constrained by the cost of commuting to foraging grounds from distant roosts. To test these hypotheses, we simultaneously tracked female reproductive activity of 11 insectivorous bat species, insect biomass, and local weather variables for 20 months in a Malaysian rain forest. Five species roost in forest structures and hence have low commuting costs, whereas six species depend on caves, which are limited in the landscape, and are presumed to incur higher commuting costs to foraging sites. Monthly insect biomass was positively correlated with monthly rainfall, and there was a significant relationship between insect biomass and lactation in cave‐roosting but not forest‐roosting species. Cave‐roosting species were seasonally monoestrus, with parturition confined to a two‐month period, whereas in forest‐roosting species, pregnancy and lactation were recorded throughout the year. Our results suggest that the energetic costs of commuting from roosts to foraging grounds shape annual reproductive patterns in tropical rain forest insectivorous bats. Ongoing changes in forest landscapes are likely to increase these costs for cave‐roosting bats, further restricting reproductive opportunities. Climate change is projected to influence the timing of rainfall events in many tropical habitats, which may disrupt relationships between rainfall, insect biomass, and bat reproductive timing, further compromising reproductive success.

Dietary studies on insectivorous bat species in Southeast Asia are relatively few. We studied diet of the intermediate horseshoe bat, Rhinolophus affinis, and the temporal variations in prey resource use. We also measured prey availability in order to explore whether this species is a generalist or specialist feeder. A total of 665 fecal samples were collected from 133 captured individuals from January to December 2019 in a tropical rainforest of Penang Island (Malaysia). A descriptive analysis of samples revealed a total of eight insect prey orders. The main taxon was Coleoptera (Percent Volume >50%), followed by Isoptera, Hemiptera, Lepidoptera, Hymenoptera and Diptera, respectively (5–15%). Neuroptera and Psocoptera were occasionally found in the samples (each <1%). This result exhibits a degree of dietary specialization on coleopterans although the diet composition was flexible and significantly varied over time (among months and within nights). Based on light trapping, Coleoptera, Hemiptera, Lepidoptera, Hymenoptera and Diptera were frequent insects in the study area, while Isoptera was seasonally abundant. The correlation between variation in the diet and light trap for each prey taxon was mostly not statistically significant, suggesting that R. affinis do not consume prey in proportion to abundance and alternatively may discriminate between prey items when foraging and take prey in rank order. Given this, we further investigated the heavy consumption of absolute abundance of Coleoptera (high‐ranking prey in diet). As a result, coleopterans were included in the diet regardless of the abundance of other prey showing a pattern of dietary specialization.

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