Lack of food means lonely dolphins

Dolphins in the Moray Firth in Scotland are spending less time socialising because of a scarcity of food, reports The Scotsman newspaper. Mirroring changes in human society, the bottlenose dolphins are seeing less of their extended families because they are too busy working to feed themselves.

As a result of the findings, scientists say attempts to manage the declining population will have to be adapted to their new, more isolated, lifestyles.

The world’s leading cetacean body, the Whale and Dolphin Conservation Society (WDCS), said it was “urgent” that more is done to protect whales and dolphins in the Moray Firth. The waters are home to about 130 dolphins.

However, in 1999, a mathematical model, based mainly on data collected from the Firth, predicted an annual decline of almost 6 per cent. In effect, this would lead to extinction in a little under 50 years.

The dolphins of the Moray Firth are the most northerly population of bottlenose dolphins.

Because of the cold water they are larger than populations found elsewhere in the world – and draw thousands of wildlife tourists each year.

The new research, which was conducted over 12 years and led by a team of scientists based at the Lighthouse Field Station, University of Aberdeen, found the resident population of bottlenose dolphins is made up of two interconnected communities that had different movement patterns.

One of the social groups was only observed within the inner Moray Firth, while the other was ranging more widely all the way to the Firth of Forth.

The team found there had been a decrease in the amount of time spent in the Moray Firth by one of the groups, giving the dolphins less time to mix with each other and exchange important information about food.

The research, which was partly funded by the WDCS, also discovered that all dolphins have preferred companions, yet they will spend much of their life surrounded mainly by what appears to be more casual acquaintances.

Since the number of dolphins present in a school is related to the abundance of prey in the area, this feature of the population’s social structure could help the dolphins to find out quickly where food is, the scientists said.

David Lusseau, of the Lighthouse Field Station, said: “Three-quarters of the members of a school will not spend much time together, typically less than a day at a time, and therefore individual dolphins will often join others that came from other schools.

“This means that knowledge about food location could quickly spread throughout the whole population just by word of mouth.

“This is a very advantageous social structure when food is patchy both in space and time.”

The scientists said the findings have important implications for dolphin population management in general, and in particular for the Special Area of Conservation designated for this population.

Currently, the population is managed as an integrated unit. The researchers said the new findings about the social structure of the population show that the situation is more complex and that the needs of both social communities might differ.

Source: The Scotsman