Using Sounds to Conduct a Seal Census

Conducting head counts on various animal species is a very important aspect of biology. The data provide environmentalist groups and protection agencies with the necessary information they need to propose and sustain conservation programs. However, performing a census is not always easy. Some species prefer to remain secretive, or are simply very rare. But now Australian researchers have developed a new method of performing head counts, which relies on listening to the noises species make, rather than on observing the animals visually and directly, LiveScience reports.

The technique was developed by scientists at the University of New South Wales in Sydney, Australia, who refined it for leopard seals living in Antarctica. The researchers say they are now able to listen to the calls the animals make, and then translate them into fairly accurate estimates of population sizes. “Because they have this really stylized acoustic behavior, we can turn numbers of seals into numbers of sounds. [We can] use this technique to monitor over a long period to see if their populations are changing […] and where they are, whether that's changing or not,” explains the creator of the new model, UNSW ecologist Tracey Rogers.

With the help of the new acoustics-based approach, the scientist and his team managed to detect no less than 10 times more seals visual studies were able to count. “So it's not that they weren't there, they were there all the time, it's just we weren’t detecting them,” the researchers say. One of the reasons why surveying leopard seals with traditional methods is so difficult is the fact that they live on pack ice, which is a notoriously difficult environment to work in. Conducting research here requires a lot of equipment, preparations, as well as extensive funding, and most research teams do not benefit from such perks.

“If they're not out on the ice, and they're in the water – the dark seals in the dark water – you don't see them at all,” Rogers says of the 3-foot-long, 750-pound animals. “We’ve cracked their communication code, so we can use their own communication patterns just like they’re doing. To actually find a mate they tend to sing and call to each other, so they tend to have these very stereotyped calling behaviors,” the expert adds, saying that it's precisely these sounds that the new computer model deciphers and analyzes. The new head counts are based on this data, the team concludes.