Are migratory behaviours of bats socially transmitted?

Attraction to conspecific social-calls in a migratory, solitary, foliage-roosting bat (Lasiurus cinereus)

As a migratory, cryptic, foliage-roosting bat with a mostly solitary roosting behavior we have an incomplete understanding of the social behavior of the hoary bat, Lasiurus cinereus. In this species most social interactions between conspecifics are thought to involve mating behavior or territorial disputes. Developing a more complete understanding of the social behavior of this species would provide critical insight to address conservation challenges including high fatality rates from wind turbines during the period of fall migration. We tested the response of hoary bats to conspecific social call playback during the spring and fall migration to: (1) test whether conspecific social call broadcasting attracts or repels individual bats; (2) examine whether there are seasonal differences in these responses; (3) describe the structure and variation of recorded social calls; and (4) test whether conspecific social call playback can increase capture success. Hoary bats were attracted to social call broadcasting during both the spring and fall migration. Hoary bats produced social calls during the spring and fall migration, and when only males were present, suggesting a social function not associated with mating. While calls were variable in frequency and length, social calls tended to be a consistent upsloping shape. Attraction to social calls suggests social interactions not associated with mating behavior in hoary bats, and this technique proved successful as an acoustic lure to aid in capture and study of this elusive species.

PRINCIPLES AND PATTERNS OF BAT MOVEMENTS: FROM AERODYNAMICS TO ECOLOGY

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.

Memory, not just perception, plays an important role in terrestrial mammalian migration

One of the key questions regarding the underlying mechanisms of mammalian land migrations is how animals select where to go. Most studies assume perception of resources as the navigational mechanism. The possible role of memory that would allow forecasting conditions at distant locations and times based on information about environmental conditions from previous years has been little studied. We study migrating zebra in Botswana using an individual-based simulation model, where perceptually guided individuals use currently sensed resources at different perceptual ranges, while memory-guided individuals use long-term averages of past resources to forecast future conditions. We compare simulated individuals guided by perception or memory on resource landscapes of remotely sensed vegetation data to trajectories of GPS-tagged zebras. Our results show that memory provides a clear signal that best directs migrants to their destination compared to perception at even the largest perceptual ranges. Zebras modelled with memory arrived two to four times, or up to 100 km, closer to the migration destination than those using perception. We suggest that memory in addition to perception is important for directing ungulate migration. Furthermore, our findings are important for the conservation of migratory mammals, as memory informing direction suggests migration routes could be relatively inflexible.