Resource availability and roosting ecology shape reproductive phenology of rain forest insectivorous bats

Abstract

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.

Reproductive Ecology of Wrinkle-Lipped Free-Tailed Bats Chaerephon plicatus (Buchannan, 1800) in Relation to Guano Production in Cambodia

“…This is because insect biomass and thus food availability for insectivorous bats such as C. plicatus correlates positively with rainfall [19,20], and consequently peaks during the wet season in the seasonal tropics of Southeast Asia [36,37]. Conversely, the progressive decline we observed in the live-weights of male bats from December 2015 through April 2016 suggests that these may experience increasing energetic stress as the dry season (November-April) progresses each year.…”

“…Both are consequently described for indicative purposes below. Because the two caves are situated ≈8 km apart, it was assumed their C. plicatus colonies would exhibit the same climate-driven patterns in reproductive phenology and seasonal body condition [14,19,20].…”

“…Although a wide variety of reproductive patterns have been described for molossid bats [14], the similar climate and monsoon seasons of Thailand and Myanmar [15] led us predict that reproductive phenology of C. plicatus in Cambodia would match patterns documented in these countries [16][17][18]. Due to the influence of climate and specifically rainfall on insect biomass and hence food availability for insectivorous bats [14,19,20], we further hypothesized that differences in the latter between the dry and wet seasons in Cambodia would be reflected in seasonal differences in body condition and consequently permit identification of periods when the species may be subject to energetic stress. Lastly, we quantified guano harvests at the largest known and most closely Because cave-roosting bats are vulnerable to human disturbance during critical reproductive periods (late pregnancy, lactation and weaning) [4], documentation of these periods has clear conservation relevance [13].…”

Assemblage and Species Threshold Responses to Environmental and Disturbance Gradients Shape Bat Diversity in Disturbed Cave Landscapes

“…Likewise, future studies should consider the role of human disturbance in altering interactions among species (e.g., competition, predation), particularly when differences in the sensitivity to human disturbances differ among species. For example, reproductive timing in cave-roosting bat species in Malaysia is strongly linked with increased insect biomass driven by seasonal monsoons, unlike foliage-roosting bat species [57]. Consequently, the reproductive success of cave-roosting bat species would be more severely compromised by increased spatio-temporal variability in rainfall patterns predicted by climate change projections.…”

The First Record of Coelopsfrithii (Blyth, 1848) for Penang, Malaysia, with anAcoustic Note of the Species

“…These data were exclusively from intact lowland forest, suggesting the species might be highly associated with undisturbed forest such as its conspecifics in Taiwan (Fang & Cheng 2011). However, there has been no update of the occurrence of the species since then, despite several intensive surveys in forest (Kingston et al 2003a, Struebig et al 2008, Lim et al 2014, Nurul-Ain et al 2017 have been conducted in the region in the last two decades. Species in genus Coelops are predicted to be sensitive to the loss and fragmentation of forest (Struebig et al 2009, Furey et al 2016 as well as disturbances to cave roosts (Fang & Cheng 2011).…”