Final Activity Report Summary - ORIENTATION IN BATS (Orientation in bats: from migration to spatial memory)
Every year billions of small bats, birds and insects move thousands of miles between breeding and wintering grounds, but we know very little about how they do this. Much of the work on the behaviour of small flying animals during migration has been done in a laboratory, observing animals hop around in a cage. How this corresponds to the large journeys they make in the wild is hard to determine, but it has generally been difficult to study the behaviour of small (<200 g) flying animals in the wild. This means that we know very little indeed about how bats are able to navigate. Despite having one of the few biological sonar systems, these animals need other mechanisms to find their way on long migratory journeys, as their echolocation is only short range (maximum 30 m). Little is known about bats as they do not show any laboratory based behaviour that correlates with migration. It was the aim of this project to study orientation and navigation in bats in the wild, to discover what cues and mechanisms they use to find their way home over long distances.
To do this, the project 'Orientation in bats: from migration to spatial memory' (ORIENTATION IN BATS) used the technique of radio tracking, where the animal had a small transmitter attached to its back (light enough not to affect its behaviour). This can be detected by a radio receiver as long as it is in range. To keep in contact the animals were tracked using an aircraft. Using this technique it was discovered that bats use the Earth's magnetic field as a compass to tell them which direction to fly. A further experiment demonstrated that the bats detect the Earth's magnetic field with tiny iron oxide particles called 'Magnetite' which are contained in their cells.
These discoveries would not have been possible without the ability to track their movement in the wild. No laboratory based behaviour had been used successfully to tell us how bats navigate. The technique that was developed to track their movement allowed developing experiments to also study the migratory orientation of small songbirds in the wild. It was discovered that these small birds can still recognise the correct direction to fly to reach their wintering grounds, even when they are displaced across the entire continent of the United States. A follow up experiment indicated that their sense of smell may play a role in this ability. The ability to follow small animals in a natural setting is crucial to a complete understanding of their behaviour and the methods we have pioneered will allow the study of small migratory animals to be carried out in a natural setting, finally allowing us to understand their role in the ecosystem and their impact on the globe.
To do this, the project 'Orientation in bats: from migration to spatial memory' (ORIENTATION IN BATS) used the technique of radio tracking, where the animal had a small transmitter attached to its back (light enough not to affect its behaviour). This can be detected by a radio receiver as long as it is in range. To keep in contact the animals were tracked using an aircraft. Using this technique it was discovered that bats use the Earth's magnetic field as a compass to tell them which direction to fly. A further experiment demonstrated that the bats detect the Earth's magnetic field with tiny iron oxide particles called 'Magnetite' which are contained in their cells.
These discoveries would not have been possible without the ability to track their movement in the wild. No laboratory based behaviour had been used successfully to tell us how bats navigate. The technique that was developed to track their movement allowed developing experiments to also study the migratory orientation of small songbirds in the wild. It was discovered that these small birds can still recognise the correct direction to fly to reach their wintering grounds, even when they are displaced across the entire continent of the United States. A follow up experiment indicated that their sense of smell may play a role in this ability. The ability to follow small animals in a natural setting is crucial to a complete understanding of their behaviour and the methods we have pioneered will allow the study of small migratory animals to be carried out in a natural setting, finally allowing us to understand their role in the ecosystem and their impact on the globe.