Staggering results from a study into harbour porpoises reveal that the species hunts with a 90% strike rate – one of the best in the animal world – and eats constantly, digesting up to 10 fish per minute.
During the study, an international research team adhered suction capped-audio monitors to five harbour porpoise (Phocoena phocoena) to observe their hunting activity.
The machines monitored the echolocation sounds made by porpoises – a series of deep, resounding clicks – and the echoes that rebounded off prey, to establish how frequently each animal was attempting to feed.
The research team, led by Danuta Maria Wisniewska of Aarhus University in Denmark, published the findings in Current Biology which establish harbour porpoise as an extreme forager.
“Our results show that porpoises hunt small fish, typically less than five centimetres, nearly continuously day and night at ultra-high rates, attempting to capture up to 550 fish per hour,” says Wisniewska, “and frequently more than 10 per minute with a remarkable success rate of more than 90%.”
This intense feeding regime is necessary to sustain the harbour porpoise, the smallest of the cetacean family of marine mammals. Growing to just 80cm in length, the species resides in the cooler waters of the North Atlantic, North Pacific and Black Sea.
Because of its small size, it uses a lot of energy to keep warm in its chilly habitat, and is generally at high risk of starvation – hence the constant eating.
The harbour porpoise is known for its high energy requirement, but details of its foraging habits were not known. Its impressive hunting schedule came as a shock, even to the researchers.
Amy Middleton is a Melbourne-based journalist.
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