WDC’s Sarah Dolman reports on her final days in the Azores where she helped carry out field work for a local research organization, Nova Atlantis, this summer.
In my 4 weeks on Pico we saw more pods of Risso’s dolphins than any other species! In the 15 years that the study has been underway, Nova Atlantis have photographed 1,250 individual dolphins, about 150 of which live in the survey around. The rest have a wider home range and are just passing through.
Nova Atlantis have discovered that Risso’s dolphins don’t have the same social structure as bottlenose dolphins or pilot whales. As the males age, they form more stable pods with other males. This is rare in the animal world and it’s thought that these alliances may help them to get females and also to defend their habitat. We saw this first hand when a small group of local male Risso’s scared off both northern bottlenose whales and pilot whales – both larger pods and larger animals than resident Risso’s.
The females form looser groups, but they cluster together when they have young calves, we assume to enable mutual protection, for example from sharks, and to enable more productive foraging. These females stick closer to the shore when their calves are very young.
Nova Atlantis have been investigating the scar patterns on Risso’s dolphins to understand their ages better, more scars means older animals. It seems there is lots we can learn from them including that the scars are stable and remain over time. This helps us to identify individuals from one survey year to another. Risso’s dolphins mainly eat gelatinous cephalopods (squid), which don’t require teeth to capture or eat, so the teeth may be a sign of ‘male quality’ and the older and more scratched a male is, the more attractive he is to a potential mate. The females are also less scratched on their bodies than the males, which may mean they are more peaceful in their interactions. This work on aging has also shown us that Risso’s dolphins can live for 50 years!
We also had amazing encounters with lots of other incredible species whilst I was in the Azores. Here is some underwater video footage that we were lucky enough to collect of false killer whales and spotted dolphins when they came to interact with our survey vessel.
It’s two weeks since I returned from my trip to Pico to learn about the Risso’s dolphins and I’m now on the Isle of Lewis, back at WDC’s own field study, where we have had pods of Scottish Risso’s dolphins already! But more about that in another blog to follow…