For grey seals, breeding is stressful. Leaving the sanctuary of the water, females haul out for a month, giving birth and raising their pups as quickly as they can, before mating with the big, boisterous males that chance their luck through the whole season. The resulting pups will be born a year later.
Now, as seal watching becomes more popular in the UK, a team from Durham University and the University of St Andrews’ Sea Mammal Research Unit is investigating whether human disturbance adds to the seals’ stress.
Their study site is the Isle of May, a craggy outcrop in the Firth of Forth, home to the largest breeding colony of grey seals on Scotland’s east coast.
The team is noting stress responses in female seals to both natural stimuli, for example the arrival of a large male at the colony, and man-made stimuli, such as the approach of a researcher or unfamiliar noises played by a remote-control car driven into the colony.
For each stressful situation, the behavioural and physiological responses are recorded by means of observation and heart-rate monitors. Full analysis of the data will take time, but a few things are becoming clear.
First, seals seem to get as stressed by anthropogenic stimuli as they do by natural ones. Lead scientist Sean Twiss points out that even though seals may appear calm when approached by a well-meaning tourist, there is a good chance they are not, because “observed behaviour doesn’t always reflect the stress state of the seal.”
Second, the team have noticed that seals react differently to stress. “Some are inherently more responsive, others less so,” Twiss says. In other words, they have personalities.
The research may eventually show that the personalities of seals in this population are changing. The simple presence of humans may be affecting which seals breed and thus which behavioural traits are passed on – something to bear in mind on your next trip to the coast.
Chris Howard is series producer of BBC Springwatch.