Quantitative evaluation of individual food intake by insectivorous vespertilionid bats (Chiroptera, Vespertilionidae)

Abstract

Insectivorous bats provide important ecosystem services, especially by suppressing and controlling the insects’ biomass. To empirically quantify the amount of insects consumed by European vespertilionid bats per night, we estimated their ratio of dry mass of feces to mass of consumed insects. This study combines the results of feeding in captivity and the data obtained in field surveys; dry mass of feces was measured in both cases. In captivity, we analyzed the effect of species, age and sex of bats, species of insects consumed and the mass of food portion on the dry mass of feces. Using coefficients of the regression model, we estimated the amount of insects consumed by free-ranging bats based on dry mass of their feces. According to our estimates, on average, one individual of one of the largest European bat species, N. noctula, consumes 2.2 g (ranging from 0.5 to 8.5 g) of insects per one feeding night, while the smallest European bats of genus Pipistrellus consume 0.4 g (ranging from 0.1 to 1.3 g), further confirming the importance of insectivorous bats for ecosystem services. This publication offers the novel method for the estimation of insects’ biomass consumed by bats.

Are Animal Disease Reservoirs at Risk of Human Antiviral Exposure?

“…Antivirals in surface waters could potentially expose bats to therapeutic concentrations , corresponding to a human daily defined dose (DDD) (Table ). In our first model, the fraction of a human DDD that bats would be exposed to is a combination of (1) published estimates of concentrations of pharmaceuticals used to treat COVID-19 in aquatic ecosystems, , (2) an estimated range of antiviral bioaccumulation factors (BAF) by aquatic insects, , and (3) estimated rates of insect consumption by bats. For the antiviral remdesivir, if BAF = 1, small and large bats may consume 0.23% and 0.28% of a human dose, respectively (Table ) from eating emerged aquatic insects.…”

“…We then calculated the consumption of antivirals by bats ( C in ng g –1 day –1 ): C = ( B × I ) / M normalb where I is the ingestion rate of insects by bats (in g d –1 ), and M b is the mass of the bats. Average insect consumption by bats ( I ) is 0.4 and 2.2 g d –1 ,and M b is 6 and 28 g for small and large species, respectively …”

“…In the second model, we calculated the therapeutic concentration in bats (Bat DDD ) based on the corresponding human therapeutic dose for each drug: normalB normala normalt DDD = DDD 70 × 0.028 where human DDD is adjusted for the body weight of bats assuming 70 kg for humans and 28 g for bats . Using an average daily consumption of 2.2 g of invertebrates by bats, eq yields the concentration needed in invertebrates to achieve a daily dose for exposed bats: I n v Load = true( normalBatDDD 2.2 true) × 1000 where Inv Load is the load of pollutants in invertebrates needed to achieve a Bat DDD in μg/g, based on the previous assumptions. The predicted environmental concentration in the water (PEC in ng L –1 ) necessary to achieve the relevant contaminant load in invertebrates is PEC = ( I n v Load / BAF ) × 1000 × 1000 where Inv Load is calculated above, and BAFs were either modeled (see Table S2) or set to 1 and 1000.…”

“…In the second model, we calculated the therapeutic concentration in bats (Bat DDD ) based on the corresponding human therapeutic dose for each drug: where human DDD is adjusted for the body weight of bats assuming 70 kg for humans and 28 g for bats . Using an average daily consumption of 2.2 g of invertebrates by bats, eq yields the concentration needed in invertebrates to achieve a daily dose for exposed bats: where Inv Load is the load of pollutants in invertebrates needed to achieve a Bat DDD in μg/g, based on the previous assumptions.…”

“…28 Some bat species are estimated to consume at least a third of their body weight per day of prey, on the order of hundreds to several thousands of insects per individual per night. 29 Many bats forage over water bodies, especially on evenings with high aquatic insect emergence. 30 Some species feed over wastewater treatment lagoons.…”