Movement ecology: the role of environmental cues and sensory mechanisms in bat navigation

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Bats are one of the most enigmatic groups of animals. The only flying mammal, they are nocturnal which means we rarely see them. Nevertheless, across Europe, every night through the spring, summer and autumn, bats range out from their roosts in caves, trees and buildings to forage for insect prey. They detect these by producing sonar calls ("echolocation") that are at a frequency high above the human range of hearing. They may range hundreds of kilometers in a night, but must return to their roost before sunrise to avoid predators. How they achieve these remarkable feats of navigation is still a mystery. If action is not taken soon it may remain a mystery as bat species are declining across Europe, despite legislation to protect them. Bats provide a vital service that is not often recognized: that of insect pest control. It has been estimated that the economic value of the reduction of insects by bats may be in excess of millions of pounds in terms of savings in pesticides alone. Like many other species, bats are vulnerable to habitat destruction and other human induced environmental changes. Ironically, one measure introduced to mitigate human change to environmental conditions is causing a reduction in their numbers. Bats are vulnerable to collisions at "green power" wind turbines. Still we do not understand fully why they do this, and it is surprising given the precision with which they can detect a small flying insect that they are unable to avoid such large structures. Understanding more about their movement behaviour and the sensory systems and environmental cues that bats use for navigation, as well as the environmental conditions that induce them to forage or return to their roost will help to mitigate these threats. This is challenging though, as bats have proven hard to study in the wild and so we understand little about their navigation behaviour on foraging or migration trips. Being nocturnal they are far more difficult to observe than birds and so standard techniques for studying their navigational ability are less useful. However advances in technology have allowed us to make the first steps in understanding how bats move about their environment and have the potential to discover which environmental cues are most important to them. This project will study the navigation behaviour of bats by manipulating their perception of environmental cues such as the sun and the magnetic field to understand how they interact to tell the animal which direction to fly when it needs to return to its roost. By understanding the sensory systems that bats use to navigate, we can understand which environmental cues are important for their movement. This knowledge can be used to help mitigate some of the human impacts on bat abundance. Understanding their behaviour will allow us to predict when and where they move, which will enable better placement and activity of wind turbines to minimize disruption to bats. It will also allow us to understand the patterns of movement of bats in terms of the availability of environmental cues, which will aid in predicting their temporal patterns of activity and habitat requirements. While bats are rarely seen and never heard, if we lose this vital cog in the balance of the environment, we would surely miss them. It is thus vital that we understand their movement behaviour in order to allow us to take action to avoid further decline in the number of bats that patrol our night skies.