Gannets' have extraordinary optical powers: Study


As it plunges into the water, the New Zealand gannet has the ability to transform its vision in an instant to see its prey.

That was one of the findings of research which involved an elaborate experiment using underwater videography near the gannet colony at Cape Kidnappers, near Napier.

Massey University researcher Gabriel Machovsky-Capuska says the coastal bird is one of the most efficient hunters in the animal kingdom and he has uncovered reasons why.

His study of the bird in Napier has found that its ability to adjust its vision between air and water makes its accuracy impeccable.

Mr Machovsky-Capuska, a biologist at the Institute of Natural Sciences' Albany campus, says it is the gannet's extraordinary optical powers that have earned it praise as a fierce hunter.

While other species such as penguins and seals can also adapt their vision between air and water, the gannet is unique in the speed with which the lens of its eyes change from oval to spherical the instant it touches the water.

Mr Machovsky-Capuska, aided by University of Haifa biologist Professor Gadi Katzir and Professor David Raubenheimer of Massey University, discovered it took 80 milliseconds for the bird's eyes to make that transition.

"This kind of research has been done in the past with animals that were trained. What we did, we were crazy and we went to the wild," Mr Machovsky-Capuska said.

"The uniqueness of the results are related to the diving strategy these animals have.

"These guys need to search and detect their prey from the air and then they decide within a second to dive into the water.

"They enter the water with high impact, their eyes open, and then they switch to underwater vision in 80 milliseconds."

Gannets are successful at catching their prey 72 per cent of the time, which Mr Machovsky-Capuska says is pretty high in comparison to its peers.

The researchers used sophisticated photographic devices, including underwater videography, to film the birds as they dived into the water.

The research features on the cover of the latest Proceedings of the Royal Society of Biological Sciences journal, published in the United Kingdom.

Mr Machovsky-Capuska is now turning his focus to why gannets are social hunters.

"It's very rare to see one gannet diving," he said.

"Usually they gather socially in these big events, you see them diving together.

"We're trying to explore what are their advantages of diving together."

- Hawkes Bay Today

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