Returning to our base in Jagna, our team quite literally stumbled upon a stranded beaked whale. The animal was long dead and although the sympathetic feeling for the end of a life, it offered an educational opportunity to learn more about this rare species. The details of the stranding and the necropsy can be found elsewhere in the LAMAVE blog.
A couple of days later while conducting a survey we stumbled again in a second beaked whales but this time the animal was breathing and healthy looking.
The animal was encountered nearby squid fishing lines, not surprisingly since this species is known to feed on cephalopods. Likely the animal enjoyed a succulent calamari’s dish before our arrival and it only allows us a quick sight before disappearing again in the sea to look for a second helping. There are several species of beaked whales and is very difficult to tell them apart, especially from a moving boat looking at a moving animal. Thanks to the help of technology, aka our fancy big camera lenses, we were able to determine that our new friend belonged to the Blainville’s species. At this stage we still don’t know whether this animal was in the same party of the one we found stranded on the beach. However this is a social species with an average group size of 3 to 4 individuals so we might have found the best buddy of the stranded whale.
Blainvilles’s beaked whales are called Mesoplodon densirostris highlighting the males’ middle tooth and the very dense bones that characterize the animal’s skull. They are commonly described alongside with the more famous Cuvier’s and although details on their behavioural ecology remain mysterious, some information has been collected by scientists. This deep dive cetacean can reach the astonishing depth of 3000 meters for one hour, in just one breath of air! To go so deep down and still being able to find their prey in the complete darkness, beaked whales evolved a very refined echolocation. When they echolocate odontocetes (dolphins and whales that have teeth) emit clicking sounds at a certain intervals, like sonar. These clicks are more frequent when a prey is detected forming what is known as feeding buzz trail. However more spaced clicks would allow to detect farther preys so the animals must choose if having a very precise image of one single prey or a more vague idea of its entire surroundings. Researchers found that Blainville’s whale change click frequency according to the distance of their prey. These animals produce slow rate clicks so that schooling fishes are not scared and when they get close the buzzing increase to precisely follow each prey. A possible explanation for this change in click rates relates to the small dimension of Blainville’s mouth that looks more aptly developed for sucking rather than chomping.
However the increasing presence of squid in Jagna waters is mouth watering not only for fishermen and beaked whales but also for several other species. The Bohol sea these days is in fact a sleeping ground where hundreds of animals may be found logging at the surface while recovering from night frenzy feeding sessions. Yesterday our team spent more than an hour with Short-finned Pilot whales, another deep diving species that feed on squids. Less rare than beaked whales and not as active as Fraser’s dolphins, they still excited us all as for many of us was the first encounter with this species. Another fulfilling day on the water for a bunch of action nerds with a devotion to large water animals.