Minsmere’s mystery of the ‘weird’ otters

There’s a mammalian mystery at Minsmere that is baffling even the best of brains in naturalists’ circles.

Something “completely weird” is happening in the intensively studied otter population in the famous RSPB reserve’s fresh water habitats, the conference was told.

Suffolk Otter Group member Nicky Rowbottom told delegates Minsmere’s otters were, unusually for the species, active both in the day and in hours of darkness. Activity levels were assessed as being 72% in daytime and 29% at night – distinctly different from other populations that hunt in fresh water mainly in darkness and also those that feed on fish taken from salt water, which were often active mainly in daylight.

Ms Rowbottom was standing in at the conference for Suffolk otter specialist Richard Woolnough who could not attend the event due to ill health.

In an attempt to establish if such unusual behaviour as was being recorded at Minsmere related to the otters’ fish prey items and the times at which they are easiest to catch, the group had set up a team of spraint analysts – a “Suffolk Spraint Appreciation Group”.

More than 3,000 sweet-smelling otter spraints had so far been analysed – but there were “no clear differences that would make you think why they are going out in daytime and the question keeps coming back as to why on Earth are they going out in the day,” she said.

The otters were not feeding in the sea and there was no artificial feeding. There had been suggestions that it may be due to a lack of daytime disturbance on the reserve or “habituation” to the benign presence of people who observe mainly from hides.

RSPB habitat management for Minsmere’s bitterns had benefitted otters and it might be that the reserve’s otter population had reached a density whereby individuals were “spacing themselves out” during daylight and darkness “to avoid conflict” but there was still much to learn about them, said Ms Rowbottom.

Read more: Suffolk Mammal Conference brings top naturalists together