World's biggest fish gets a black-box flight recorder

The project is the result of a collaboration between two Laureates of the Rolex Awards for Enterprise – Australian Brad Norman who set up the world’s first photo-ID system for identifying whale sharks and Briton Rory Wilson, who has developed the world’s most sophisticated device for monitoring the activity of animals in the wild.

Wilson says his logger, which weighs only 30-48 grams, is like an aircraft black-box flight recorder that monitors changes in speed, altitude and heading. At its heart is a tiny electronic device that measures changes in an animal’s acceleration in every direction – forward/back, up/down or sideways. This accelerometer measures motion along all three axes up to 32 times a second, and, combined with a compass, determines the animal’s speed, direction and position. It can do many things that widely-used animal tracking systems using GPS (Global Positioning System) cannot, such as operate in dense forest, underground or in the ocean.

All animals spend energy to keep warm, digest food, and maintain vital functions like breathing and pumping blood – but movement requires energy expenditure ten times higher. “An animal that’s not expending energy is dead,” Wilson says. Animals burn glucose to generate energy, consuming oxygen in the process, so by measuring an animal’s oxygen intake in a sealed chamber called a respirometer, scientists can estimate how much energy it consumes just staying alive and warm, and how much it requires while walking, running or swimming.

Wilson and his colleagues have already used the logger to record energy expenditure in wild cormorants, and were thrilled when their data corresponded to the figure predicted from trials determining the average oxygen consumption of five great cormorants tested in a respirometer. Zoologists can now use Wilson’s black box to estimate how much energy an animal expends flying, swimming, hunting, digging, feeding, fighting or mating. Adding these figures to the baseline energy needed to stay alive and warm gives a reliable estimate of the species’ total energy expenditure.

This information will revolutionise wildlife studies. By measuring the energy content of a species’ natural diet, zoologists will know how much time a carnivore must spend hunting, or how long a herbivore must graze, to keep up its strength, grow and successfully breed – the ultimate aim of the game of life. “A successful animal,” says Wilson, “is one that takes in a lot more energy than it expends. Many conservation issues involve animals that are expending too much energy. Energy for an animal is like money for a human, but if an animal overdraws its budget, it dies. We haven’t had a way of measuring energy expenditure in wild animals before.”

Data about animals’ energy expenditure will help conservationists understand what constitutes poor, average or optimum living conditions, or what minimum area is needed for an individual or population of animals to survive and do well. The logger could help resolve important conservation questions - such as whether climate change, predation or over-fishing in its hunting grounds is responsible for an observed decline in the case of of the African penguin.

Wilson and fellow zoologists have recently tested the black box on species in Argentina, including imperial cormorants and armadillos. The device has also been trialled on wild beavers in Norway and the badgers of Wytham Woods in Oxfordshire, England. And closer to home, Wilson’s own the family pet, a Border Collie named Moon, has been the "guinea pig" in providing a conveniently co-operative test animal.

The importance of Wilson’s device is highlighted by the insights gained on the Oxfordshire badgers, which are of interest to those studying the evolution of social behaviour. Professor David Macdonald, of Oxford University’s Wildlife Conservation Research Unit, has been observing these badgers since the 1970s, making them amongst the world’s most intensively studied carnivores, but Macdonald has always had difficulty tracking their detailed movements at night and observing their behaviour underground.

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