Taking our leave of the Mediterranean, we head south to meet up with Risso's researcher, Karin Hartman from Nova Atlantis Foundation. Karin is studying the Risso's dolphins to be found in and around the island archipelago known as the Azores. Once again I have to note how jealous i am of their weather conditions (that make for outstanding photographs) ... I guess that's what being closer to the equator does for you!!
A message from a big rock in the Atlantic Ocean: Pico Island, Azores archipelago.
I am currently living here to study Risso’s dolphins and am conducting a PhD project titled: “Long term patterns of social behaviour and ecology of Risso’s dolphins, (Grampus griseus) off Pico Island. More than a decade ago we “discovered” a Risso dolphin hot spot by chance in the Bay of Ribeiras off the south coast of Pico. A Dutch based Foundation was created two years later in order to study and protect this cetacean rich area. Besides Risso’s dolphins, a variety of about 20 other cetacean species can be observed both from land and at sea. The reason for this species’ richness is related with the presence of food! The upwelling from deep-sea waters against the steep marine (volcanic) walls, the nutrient run off from the Islands itself and the circulation of the Gulf Stream along the Islands in general provides and creates food in a relatively poor high sea. In general we started working on Risso’s since there is not a lot know of their social behaviour and life history patterns and they seemed to be one of the most seen species in our study area.
Risso’s dolphins feed predominantly on squid just like pilot, sperm and beaked whales. In the Bay and around the Azores, it seems that there is food for all, and everybody can be observed feeding at their own “depth” line. Due to the availability of prey in a relatively deep but coastal place we were able to observe the animals (land-based) from dawn to dusk, following them at rather strange hours. This method gave us general insights in how and when the dolphins use the area.
But to answer more detailed questions like: How do males and females life? How is their social structure? Who is with whom? When and where are they here? How long stays a calve with the mother? - you need to go to the ocean and identify the dolphins. Photo Identification has therefore been our main research method and after the digital camera’s were introduced we were able to study the group compositions directly. Until today, we have identified 1248 individuals during eleven years of research. This is the largest ID catalogue in the world for this species. After taking thousands of pictures, cropping the dorsal fins, matching these with the catalogue and finally analyzing the connecting behavioral and spatial data, it seems that Risso’s dolphins off Pico Island cluster in highly stable pods of 3 to 12 individuals.
Since the presence of calves of most long term followed pods were missing we assumed that these animals were males. These pods may work together (second order alliances) with other stable groups but mainly if they feel the need to defend their habitat towards other squid eating species. This already indicates that we are dealing with a resident population! But… many times we see some guys hanging behind groups of females. Sometimes they escort a female or a female and calf. When the female is fertile more male pods may come and sometimes they fight and get very wild. During these social events they wound each other and leave their tooth marks in the rival’s or the female’s skin. In general the females seem to life separated from the males, clustering together in nursery groups. They babysit for each other when it’s time to forage in the deep. Sometimes one female is taking care of 3 calves! A newborn baby is a fragile and under serious threat: pelagic sharks do attack and eat them! The coastal waters around Pico seems a very important nursery ground since they also find some shelter (to lactate and rest) and have food available in near shore and shallow waters.
I am currently trying to come up with proof and numbers that we indeed have a resident population around Pico. This is very important since Risso’s and 4 other species’ are locally targeted for swimming with dolphin tourism. In other words: our residents are frequently exposed to very close and long encounters of the commercial whale watching industry. In another study we found that the Risso’s change their resting schedule during high season: They rest only between 13:00 and 15:00, when all boats are back in the harbours for lunch… In low season they rest at other hours, over the day. Since this species’ is feeding mainly at night they need to rest during the day. Wasting their energy by travelling away from vessels may have a serious impact on their day to day survival.
In general Risso’s deserve special attention: They show the social aspects of bottlenose dolphins and chimps, are driven by the diet of a deep diving beaked whale and have their own special looks! Because they are so well recognizable and tolerant we have been able to study them intensively and part by part the secrets of their complex social life are becoming visible. And of course: more questions are arising since we cannot follow them to the bottom of the ocean or on their inner or outside island migrations.
Keep on Gramping!
Greetings form Pico,
Nova Atlantis Foundation