Humpbacks share new feeding technique

Published: 25 April 2013 at 10:13

Anglia Ruskin scientist shows how whales adapt when favourite dish is taken off the menu

Scientists studying humpback whales in the Atlantic Ocean have shown for the first time how a new feeding technique has spread through a large social network.

The research by academics at Anglia Ruskin University, the University of St Andrews and the Whale Center of New England is published in the latest edition of the journal Science.

This new technique, called ‘lobtail feeding’, was first observed in 1980, at a time when herring, previously the main food of the humpback whales, was suffering a serious decline in numbers.

In the Gulf of Maine, bubble-feeding is a common foraging technique used by humpback whales (Megaptera novaeangliae), which is characterised by bubble production 20-25m below the surface, underneath and around a prey school, followed by a lunge through the bubbles.

Lobtail feeding consists of striking the surface of the water one to four times with the ventral side of the fluke (tail), followed by a bubble-feeding sequence.

At the same time as herring numbers were declining, sand lance stocks went through a boom, and it seems the innovation is specific to that particular prey, as its use is concentrated around the Stellwagen Bank off the coast of Massachusetts, a spawning ground for this particular fish.

Using a database containing 73,790 sighting records, gathered over 30 years by Mason Weinrich of the Whale Center of New England, the researchers were able track the spread of the behaviour.  By 2007, nearly 40% of the humpback whale population in the area was using the lobtail feeding method.

The team, also including Dr Will Hoppitt from Anglia Ruskin University and Jenny Allen and Dr Luke Rendell from the University of St Andrews, used a new technique called “network based diffusion analysis” to demonstrate that the use of lobtail feeding followed the network of social relationships within the population.

The new feeding behaviour spread through cultural transmission, the same process used by humans and primates, and the scientists believe their results strengthen the case that cetaceans (whales and dolphins) have evolved sophisticated cultural capacities.

“Our study really shows how vital cultural transmission is in humpback populations – not only do they learn their famous songs from each other, they also learn feeding techniques that allow them to buffer the effects of changing ecology,”

said Dr Rendell.

Dr Hoppitt said:

“Lobtailing, which is smacking the surface of the water, has previously been seen as a social signal, but this is the first time it has been recorded in feeding behaviour."
“Although the purpose of adding a lobtail to the beginning of a bubble-feeding dive sequence is unknown, the link with contemporaneous prey dynamics suggests some function specific to foraging for sand lance, perhaps causing a tightening of the prey school before bubble entrapment."
“The use of lobtail feeding spread rapidly in the Stellwagen Bank area.  Given the numbers involved and the short time span, it’s clear that this isn’t a genetic change, passed on from generation to generation, but is learned behaviour."
“Our results show that social transmission played a crucial role in the spread of lobtail feeding behaviour.  It can therefore be considered a tradition, and because humpback populations are known to also carry vocal traditions in the form of song, this population can be considered to carry multiple traditions.”

The skills, knowledge, materials and traditions that humans learn from each other help explain how we’ve come to dominate the globe as a species, but how we evolved the capabilities to transmit such knowledge between ourselves remains a mystery that preoccupies biologists, psychologists and anthropologists.

Dr Hoppitt added:
“We can learn more about the forces that drive the evolution of culture by looking outside our own ancestral lineage and studying the occurrence of similar attributes in groups that have evolved in a radically different environment to ours, like the cetaceans.”