What Ahab never saw: the secret life of diving mammals
Leaping bottlenose dolphins in St Andrews Bay.
'Bottlenose dolphins have been shown to use whistles that are almost as versatile as human names, a type of vocal communication that has never before been seen in animals apart from humans. These animals live in dark, cold, high pressure conditions,' explains Vincent Janik, a Royal Society University Research Fellow at the St Andrews Sea Mammal Research Unit (SMRU). 'In such an environment, it is crucial that they have an effective and fail-safe system to stay in touch with each other.'
Through recording the signature whistles of bottlenose dolphins and then observing the response of other dolphins to the recorded whistles, it had already been established that dolphins recognise one another. However, it was not known whether this was due to voice quality or the specifically learned frequency modulation of the whistle. 'The recognition system could have been based on the overall quality of the dolphin's whistle, like recognising someone's voice on the telephone,' says Vincent. By recording signature whistles, stripping out parts of the signal that reflect voice and then monitoring other dolphins' responses, Vincent discovered that there is something key to the whistle that enables one dolphin to recognise another. 'Dolphins develop their own unique modulation pattern. You could compare this to a name,' says Vincent. 'You can identify someone by their name regardless of how it is said, this seems to be what the dolphins are able to do.'
Detailed long term studies of known individual seals carried out by SMRU have uncovered other complex and unexpected social interactions. 'In a study of breeding female grey seals, clear links between females were observed. Female seals pair up and remain paired when relocating to a different breeding site,' says Paddy Pomeroy. 'These associations weren't the result of similar preferences for particular types of habitat, although this also occurs. More importantly, seal friends don't seem to be close kin. Exploring these relationships can tell us more about the evolution of social behaviour,' says Paddy.
Tracking devices that record sound, photos and video are a further means of studying the secret life of sea mammals. Archival tags store all the data collected over a period of anything from a few hours to many months but they need to be recovered from the animal. Telemetry transmitter tags do not need to be recovered as they send the data back via an orbiting satellite. Recent devices allow us to understand how animals use the marine environment but also to monitor this environment for other purposes, such as estimating the effects of global warming', explains Ian Boyd.