Mosquito Consumption by Insectivorous Bats: Does Size Matter?

Abstract

Insectivorous bats have often been touted as biological control for mosquito populations. However, mosquitoes generally represent only a small proportion of bat diet. Given the small size of mosquitoes, restrictions imposed on prey detectability by low frequency echolocation, and variable field metabolic rates (FMR), mosquitoes may not be available to or profitable for all bats. This study investigated whether consumption of mosquitoes was influenced by bat size, which is negatively correlated with echolocation frequency but positively correlated with bat FMR. To assess this, we investigated diets of five eastern Australian bat species (Vespadelus vulturnus Thomas, V. pumilus Gray, Miniopterus australis Tomes, Nyctophilus gouldi Tomes and Chalinolobus gouldii Gray) ranging in size from 4-14 g in coastal forest, using molecular analysis of fecal DNA. Abundances of potential mosquito and non-mosquito prey were concurrently measured to provide data on relative prey abundance. Aedes vigilax was locally the most abundant mosquito species, while Lepidoptera the most abundant insect order. A diverse range of prey was detected in bat feces, although members of Lepidoptera dominated, reflecting relative abundance at trap sites. Consumption of mosquitoes was restricted to V. vulturnus and V. pumilus, two smaller sized bats (4 and 4.5 g). Although mosquitoes were not commonly detected in feces of V. pumilus, they were present in feces of 55 % of V. vulturnus individuals. To meet nightly FMR requirements, Vespadelus spp. would need to consume ~600-660 mosquitoes on a mosquito-only diet, or ~160-180 similar sized moths on a moth-only diet. Lower relative profitability of mosquitoes may provide an explanation for the low level of mosquito consumption among these bats and the absence of mosquitoes in feces of larger bats. Smaller sized bats, especially V. vulturnus, are likely to be those most sensitive to reductions in mosquito abundance and should be monitored during mosquito control activities.

Insectivorous bats selectively source moths and eat mostly pest insects on dryland and irrigated cotton farms

“…Bats also frequently consumed soft‐bodied flies, but these do not contribute greatly to overall diet in terms of volume, as found in similar studies (Gonsalves, Bicknell, Law, Webb, & Monamy, ; Rydell, McNeill, & Eklöf, ; Wetzler & Boyles, ). Small prey items such as mosquitoes and gnats were most common in the diet of V. vulturnus (the smallest species of bat), while larger prey items (such as crickets) were most common in the diet of C. gouldii (a larger aerial‐hawking bat) and N. geoffroyi (a gleaning bat).…”

“…The ability of these bats to detect insect prey is constrained by echolocation call structure and explains the variation in prey choice (Waters, Rydell, & Jones, ). Smaller bats tend to use high‐frequency‐modulated “soft” echolocation and are restricted to detecting smaller prey items, typically dipterans and moths 5–10 mm in length (Gonsalves, Bicknell, et al, ; Møhl, ; Robert & Brigham, ). However, several studies on larger aerial‐hawking bats that echolocate using low‐frequency and long‐duration calls show that they consume a range of prey sizes (Waters et al, ).…”

Effects of the removal or reduction in density of the malaria mosquito, Anopheles gambiae s.l., on interacting predators and competitors in local ecosystems

“…Maturation in both sexes, and feeding and resting in males, are largely disaggregated activities that reduce the predictability of adults as a resource to predators. Additionally, adults are harder to locate and catch relative to larvae and are of low resource value compared with other flying prey such as Lepidoptera (butterflies and moths) (Gonsalves et al ., ). Much of 20th century vector control success with ITNs and IRS was based on post‐mating aggregation in females as they sought to feed on sleeping humans and then to rest in houses.…”

What you need is what you eat? Prey selection by the batMyotis daubentonii

“…While black flies are abundant in the habitat, they may be either too small for M. daubentonii to detect (Barclay & Brigham ) or nonprofitable as a food items (Gonsalves et al . ). Nonetheless, they are regularly detected in bat diet in low quantities, confirming that bats are indeed able to discover and catch them (Flavin et al .…”