PRINCIPLES AND PATTERNS OF BAT MOVEMENTS: FROM AERODYNAMICS TO ECOLOGY

Abstract

Movement ecology as an integrative discipline has advanced associated fields because it presents not only a conceptual framework for understanding movement principles but also helps formulate predictions about the consequences of movements for animals and their environments. Here, we synthesize recent studies on principles and patterns of bat movements in context of the movement ecology paradigm. The motion capacity of bats is defined by their highly articulated, flexible wings. Power production during flight follows a U-shaped curve in relation to speed in bats yet, in contrast to birds, bats use mostly exogenous nutrients for sustained flight. The navigation capacity of most bats is dominated by the echolocation system, yet other sensory modalities, including an iron-based magnetic sense, may contribute to navigation depending on a bat's familiarity with the terrain. Patterns derived from these capacities relate to antagonistic and mutualistic interactions with food items. The navigation capacity of bats may influence their sociality, in particular, the extent of group foraging based on eavesdropping on conspecifics' echolocation calls. We infer that understanding the movement ecology of bats within the framework of the movement ecology paradigm provides new insights into ecological processes mediated by bats, from ecosystem services to diseases.

Keywords: biomechanics; cognition; echolocation; emerging infectious diseases; energetics; migration; mutualism; sociality.

Figure 1. Schematic Pictures of Two Contrasting Movement Patterns Suggested For a Temperate Zone Bat

Long-distance migration between summer and winter roosts (A) and short foraging flights around the summer roosts (B). Note differences in spatial and temporal scales between A and B. Depicted migratory movements include several seasonal trips during subsequent years, whereas depicted foraging movements include trip during several consecutive days. See the online edition for a color version of this figure.

Figure 2. Schematic Picture of Two Contrasting Movement Patterns Observed in Common Noctule Bats (Nyctalus noctula)

Suggested combined exploratory and foraging flight (A) and commuting flights with area restricted foraging at a resource dense patch (B). Modified from Roeleke et al. (2016). See the online edition for a color version of this figure.

Figure 3. Wake Vortices of a Flying Bat

Vortices generated by the body and wings of a 20 g nectar-feeding bat, Leptonycteris yerbabuenae, flying from left to right (as indicated by the arrow) in a wind tunnel, as seen from three different perspectives: (A) side view, (B) top view, and (C) oblique top view. Vortices represent surfaces of equal absolute vorticity, indicated in dark gray for downwash and light gray for upwash movements. Reprinted with permission from Hedenström and Johansson (2015). See the online edition for a color version of this figure.

Figure 4. Metabolic and Mechanical Flight Power (W) of a Bat in Relation to Flight Speed

Flight power of a 20 g Carollia perspicillata in a wind tunnel at varying wind speeds. From von Busse et al. (2013). See the online edition for a color version of this figure.

Figure 5. Schematic Picture About the Role of Echolocation Calls as Inadvertent Cues for Promoting Hunting Efficiency Via Group Foraging

Bats may gain information about the location of ephemeral patchily distributed prey (e.g., swarms by eavesdropping on echolocation calls of conspecifics). The range from which a conspecific can be heard is much larger than the range from which prey can be detected and bats can thus benefit from searching individually while remaining in a range that allows eavesdropping on nearby individuals. Reprinted with permission from Cvikel et al. (2015a).

Figure 6. Conditions Required For Bat Virus Spillover, Illustrated For Hendra Virus in Australia

First, the pathogen reservoir must be present; second, bats must be infected and, in most cases, shedding pathogen; third, the viruses must survive outside of its reservoir host (if transmitted indirectly), with access to the recipient host; fourth, recipient hosts must be exposed to the source of the virus in sufficient quantity for an infection to establish; and, finally, recipient hosts must be susceptible to the virus. The area depicted in the layers is southeastern Queensland, Australia. The dark areas over layer 1 correspond to 20 km foraging zones around known bat roost sites. Locations of the four horses on the bottom layer correspond to those of Hendra virus spillover events in 2011. From Plowright et al. (2015). See the online edition for a color version of this figure.