by Steve Westerman

Wharfedale Naturalists Society

wharfedale-nats.org.uk

AS the footballer, Eric Cantona once famously said to the press, “When the seagulls follow the trawler it’s because they think sardines will be thrown into the sea”. I was put in mind of this phrase while watching an otter progress along the edge of the river, feeding as it went. It passed under a kingfisher that was sitting on a branch, looking for a meal in the water below. Initially the kingfisher was unnerved and moved a little distance away. But then it was back, perching close to the otter, seemingly following its path, and diving periodically a little distance behind. Perhaps it was just coincidence, but I wondered whether the otter was disturbing small fish that were hiding in the vegetation; fish that were too small or too swift to interest the otter, but that were just right for a hungry kingfisher. So, just as seagulls may benefit from the activities of trawlers ….

The diet of otters is varied and depends on the availability of prey. Eels can be favoured, but their numbers have been in alarming decline for some time. So, in the Ilkley stretch of the Wharfe, perhaps other fish are a more likely targets, supplemented by amphibians, small mammals, water birds, and crayfish.

It has been suggested that discarded crayfish claws, at places along the banks of the Wharfe, are evidence of otters feeding – and I have seen it written elsewhere that otters land crayfish before consuming them. Maybe this is sometimes, or even usually, the case, but I don’t think either of these propositions always applies.

I have seen a gull feeding on crayfish while standing amongst disassembled parts of, what I assume were, previous victims. Recently, I also watched a small otter feeding on crayfish and, as far as I could tell, it was consuming them in one go. It didn’t obviously dissect them. Instead, it would surface with an unfortunate crayfish in its mouth. A bite or two probably dispatched it. The otter then threw its head back and seemingly swallowed the crayfish, whole, just as it would a small fish. The accompanying photograph shows a Signal Crayfish in the jaws of the otter (in the Wharfe).

Just to return, somewhat obliquely, to where I started, and the idea of ‘gulls following trawlers’, it is interesting that gulls will occasionally ‘mob’ an otter, swooping down at it and encouraging it to find somewhere else to hunt. Presumably they view them as unwelcome competition.