The pond bat in the Netherlands. Energetic challenges during foraging, pregnancy, lactation, mating and hibernation.

Friday 29 September 2023, 12:30 pm
PhD student
A.J.M. Haarsma drs.
prof. dr. H. Siepel, prof. dr. B. Gravendeel
dr. ir. E. Jongejans

Pond bats live in buildings. They make use of gaps under roof tiles and in cavity walls. They need habitats of varying temperatures. Just like most European bats, the pond bat is heterothermic: it can choose between self-regulating its body temperature or determining its temperature by its environment. 
Male and female pond bats live in separated areas for the entire year. The females live in maternity colonies and have their own areas for food and habitation. The males live in the vicinity of the females as well as along large rivers in areas only visited by the females in autumn. Pond bats thrive on this LAT (living-apart-together) relationship. 
As insect eaters, pond bats must survive a period of extreme food scarcity every year. They can survive the winter with minimal fat reserves by hibernating in safe locations with a stable temperature. Before and after hibernation, the bats must divide their energy between mating, giving birth to and raising their young, migrating and gaining weight for hibernation. The timing and expected energy expenditure of these events are different for males and females. The living spaces and food habitat preferences of both sexes therefore also differ. 
This PhD dissertation substantiates how the differences in energy needs between both sexes explain the LAT relationships of pond bats. 
Renovation and the demolishing of living environments mainly affect female pond bats. Depending on the varying availability of food, their young grow quicker or slower: for fast growth, a warm habitat is desired; for slow growth, a cool habitat. Well-insulated houses are too uniform regarding temperature, as a result of which reproduction problems arise. As a consequence, the pond bat population in the Netherlands has been in decline for years. Unfortunately, no sufficient replacement habitats for pond bats have yet been created. Insights from this PhD dissertation could accelerate the construction of alternative pond bat habitats. To save energy in the Netherlands, and to achieve our national climate targets as well as biodiversity goals, the accelerated construction of pond bat habitats is necessary. 

Anne-Jifke Haarsma is an authority when it comes to pond bats in the Netherlands. She has been researching the pond bat since 2002, and has already written many publications. She has also been coordinating the national monitoring of the pond bat since 2002. She has mapped out the national distribution of the species and has since captured multiple thousand pond bats, of which at least 200 have been fitted with a transmitter (for telemetric research). As a result, she is the absolute expert on the species in the Netherlands and in Europe as a whole. Haarsma is also one of the founders of the bat capturing system; a method considered the standard for capturing bats in the Netherlands. As a researcher, she is affiliated with Naturalis Biodiversity Center and Radboud University.