Grey seals have different types of personality that affect the extent to which they guard and care for their young, according to new research.
Researchers from Durham University and the University of St Andrews, looking at seal colonies in Scotland, found that seal mothers are often unpredictable and adopt a wide variation of mothering styles when it comes to checking on their pups. Some are very attentive while others are not, the researchers found.
The Durham-St Andrews study shows, for the first time, the extent of personality differences in marine mammals in the wild. It shows how individual animals have differing behavioural 'styles', and how they may be limited in their ability to respond to different environments; a concern in a world of rapid environmental change and changing resources.
The study could have benefits for future conservation policy, habitat management and reveals new information about the process of evolution.
The first results are published in the journal Marine Mammal Science and will be presented at the 19th Biennial Conference on the Biology of Marine Mammals conference in Tampa, Florida, USA, November 27-December 2.
Researchers observed seals on the Scottish island of North Rona during the breeding season between September and November over two years. The team targeted seals in their natural habitat to analyse individual variation and consistency in behavioural response.
Using a remote controlled vehicle (RCV) with a fitted video camera, the researchers set up tests to assess how seals react to external stimuli and potential threats, including approaches by the RCV and wolf calls played from the vehicle, triggered by the operator controlling the car. The seals' responses ranged from disinterested to aggressive, however, the reasons for such a wide range of reactions are not clear, the researchers say.
The team checked the responses of seal mothers by recording the number of pup checks made (where the mother raises her head off the ground and moves it in the direction of her young to check their well-being) during a specific time period. The test worked particularly well with females because they tended to stay with their pups, which are relatively sedentary.
The researchers were able to observe behaviour over two years as many seals return to the same site to breed, and identification of particular individuals is relatively easy as seals have very individual patterns on their fur. The team ran an 11-minute test on 28 females during which they were approached by the RCV and the wolf call was played.
Female seals varied considerably in their responses to the RCV from almost completely ignoring its presence to pushing it with their muzzles.
Lead author, Dr Sean Twiss, School of Biological and Biomedical Sciences, Durham University, said: "Our findings show that there is no such thing as an average seal. Individuals behave differently and do so consistently. We found that some seal mothers are very watchful when something potentially threatening approaches them, while other mums barely check their pups at all.
"Why female grey seals express individually consistent patterns of pup checking is unknown. It might be expected that females should be able to change their behaviour according to the situation but the non-attentive mothers remained inattentive. Our results show large differences in response to the same potential dangers."
The researchers also checked the response of male seals to the RCV and logged a wide range of reactions from rapid retreat to approaching it in a threatening way (e.g. the use of open mouth threats). Some males, particularly the dominant ones, were consistently alert and aggressive, and challenged the RCV; others were much more cautious and immediately moved away from the vehicle.
In both male and female seals, behaviour was not linked to factors such as age or size. Further studies could help biologists to understand the nature and ecological consequences of individual variation in behaviour, and whether such individually consistent behaviour patterns limit the ability of individuals, and potentially species, to adapt to climate, resource or habitat change.
Dr Twiss said: "We can see that grey seals are individuals and we want to find out if having different personalities and behaviour helps seals and other animals in the wild, or whether it does limit their ability to cope with change."
Co-author, Dr Patrick Pomeroy, Sea Mammal Research Unit, University of St Andrews, said: "Our results show strong consistencies in behaviour of wild seals.. If maternal attentiveness contributes to fitness, one would be forced to ask why selection has not favoured a single optimum level of pup checking, or flexibility in terms of the number of checks made. Our next task is to find out if personality differences have fitness consequences."
There are approximately 460,000 grey seals in the world. About 40 per cent of the world's seal population can be found in the coastal waters of the UK and other major seal populations can be found in the coastal waters of Canada and the USA. The pups are born between September and November in the eastern Atlantic and January to February in the west. Seals can live into their late thirties and forties and reach weights of 250kg for adult females, and up to 350kg for adult males in breeding condition.
The study is funded by the Natural Environment Research Council (NERC) and the Esmée Fairburn Foundation.