Some whales love mountains. New Caledonian humpbacks migrating between their breeding and feeding grounds pull over for days on end in waters around underwater mountains 鈥� though no one yet knows why.
Such mountains could be frequented by whales in other oceans, too, meaning that the habitats should be considered for conservation efforts, says a team led by Claire Garrigue and her team at Op茅ration C茅tac茅s in Noum茅a, New Caledonia.
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It may also mean that we鈥檝e been underestimating the size of whale populations, because sea mountains have not been well-studied or considered important habitats for these animals so far.
Garrigue鈥檚 team tracked 34 humpback whales migrating between breeding waters in southern New Caledonia and feeding areas in Antarctica for up to 110 days using satellite tags.
The first surprise was that not all whales took the same, or most direct routes.
鈥淲hat I really like about this paper is that it starts to challenge a little bit of the dogmatic thinking that we have about how humpback whales migrate and how they are very metronomic animals,鈥� says Ari Friedlaender of Oregon State University in Newport.
Another surprise was their prolonged stops of between three and 22 days around seamounts 鈥� underwater mountains that rise from the sea floor.
Conservation focus?
The importance of seamounts to whales has not previously been documented with such robust data, says Howard Rosenbaum of the Wildlife Conservation Society in New York. He says the new findings suggest that seamounts might merit special conservation.
鈥淭hrough this work, we now have the access to get a glimpse into the lives of whales along the migration route, find out how important seamounts are, and then consider them for areas in need of special protection,鈥� he says.
It is not yet clear what draws whales to the seamounts 鈥� but the team speculates that they may use them as navigation cues or spots for breeding activities such as singing by males. 鈥淢aybe they stop there to relax and to rest a little bit because they have lots of miles to go to Antarctica,鈥� says Garrigue.
Or they may simply use the waters for feeding, with seamounts rich in biodiversity. 鈥淚f you are spending several months of the year on a breeding ground not eating, as soon as you leave and are heading back, if you could find food along the way, it makes sense that you would want to stop and snack a little bit,鈥� says Friedlaender.
Intriguingly, other big marine organisms such as tuna and seabirds have also been spotted hanging around seamounts, says Tony Pitcher of the University of British Columbia in Vancouver, Canada.
鈥淭here are all sorts of very odd observations 鈥� things like hammerhead sharks aggregating on seamounts,鈥� he says. But again, it is not obvious what all these animals are doing there, he adds.
Journal reference: Royal Society Open Science, DOI:
Image credit: Yohann Djerahian
Read more: 鈥�Deep sea special: The undiscovered oceans鈥�;
