Landscape structure influences the use of social information in an insectivorous bat

Abstract

In anthropogenic landscapes, aerial insectivores are often confronted with variable habitat complexity, which may influence the distribution of prey. Yet, high mobility may allow aerial insectivores to adjust their foraging strategy to different prey distributions. We investigated whether aerial‐hunting common noctules Nyctalus noctula adjust their foraging strategy to landscapes with different habitat complexity and assumingly different prey distribution. We hypothesized that the movement behaviour of hunting common noctules and changes of movement behaviour in reaction towards conspecifics would depend on whether they hunt in a structurally poor cropland dominated landscape or a structurally rich forest dominated landscape. We tracked flight paths of common noctules in northeastern Germany using GPS loggers equipped with an ultrasonic microphone that recorded foraging events and presence of conspecifics. Above cropland, common noctules hunted mainly during bouts of highly tortuous and area restricted movements (ARM). Bats switched from straight flight to ARM after encountering conspecifics. In the forested landscape, common noctules hunted both during ARM and during straight flights. The onset of ARM did not correlate with the presence of conspecifics. Common noctules showed a lower feeding rate and encountered more conspecifics above the forested than above the cropland dominated landscape. We conjecture that prey distribution above cropland was patchy and unpredictable, thus making eavesdropping on hunting conspecifics crucial for bats during search for prey patches. In contrast, small scale structural diversity of the forested landscape possibly led to a more homogeneous prey distribution at the landscape scale, thus enabling bats to find sufficient food independent of conspecific presence. This suggests that predators depending on ephemeral prey can increase their foraging success in structurally poor landscapes by using social information provided by conspecifics. Hence, a minimum population density might be obligatory to enable successful foraging in simplified landscapes.

An agent-based algorithm resembles behaviour of tree-dwelling bats under fission–fusion dynamics

“…Although this computational algorithm has the unique ability to solve complex problems 67 – 70 , its formal description was solely inspired by echolocation properties during group foraging. The grouping mechanism in foraging individuals is completely different from group roosting, while group foraging is associated with even less investigated reasons for sociality in bats 71 , 72 . The most important features of a swarming algorithm applied in the SkyBat model are its ability to find a solution in a limited time and its independence from the environment and specific relationships among individuals.…”

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

“…We analyzed the effect of sex, age, genus of bats and time of catching (1–3 or 4–8 h after sunset) on mass of feces (with log conversion) from free-ranging N. noctula and genus Pipistrellus by building a LM followed by multiple regression analysis. We took into account the high food passage rate through the digestive tract in bats ( Kovtun and Zhukova, 1988 ; Staliński, 1994 ) and time of most active foraging (the latest studies for N. noctula , Roeleke et al, 2018 , 2020 ) and evaluated the difference between the first three night hours (the first part of a night) versus other night hours (the second part of a night). No significant difference was found (see Results).…”

Drivers of European bat population change: a review reveals evidence gaps

“…Agricultural expansion and intensification affect bat fitness and activity by reducing insect prey availability (Roeleke et al 2020), increasing pesticide exposure, degrading foraging areas or reducing access to them (Department for Environment Food and Rural Affairs 2005), and reducing habitat connectivity (Frey-Ehrenbold et al 2013). Intensive management of agricultural land was identified as negatively impacting six bat species by Burns et al (2016).…”

“…Loss of linear landscape elements that are identified as important bat foraging and commuting habitats, such as hedgerows, treelines, and canals (Vaughan et al 1997, Russ & Montgomery 2002, Frey-Ehrenbold et al 2013, is a common consequence of agricultural intensification. Increasing energy expenditure and decreasing foraging opportunities affect bat fitness (Russ & Montgomery 2002, Roeleke et al 2020. Nyctalus noctula uses direct flight more in cropland-dominated landscapes where insect prey is more ephemeral than in complex forest-dominated landscapes (Roeleke et al 2020).…”

“…Increasing energy expenditure and decreasing foraging opportunities affect bat fitness (Russ & Montgomery 2002, Roeleke et al 2020. Nyctalus noctula uses direct flight more in cropland-dominated landscapes where insect prey is more ephemeral than in complex forest-dominated landscapes (Roeleke et al 2020). A higher amount of semi-natural habitat had a positive impact on Tadarida teniotis and Pipistrellus kuhli activity in Mediterranean agroecosystems (Kahnonitch et al 2018).…”