The more you study natural history the more surprising it becomes. Creatures do not always behave as the books prescribe – in fact their behaviour can be astonishing. Two striking examples of this have recently been brought to my attention.
Take the wood mouse – a common British mammal – the wee sleekit cow’ring timorous beastie of Burns’ famous poem. We often get a close look at one when our mammal recorder opens the humane traps used for monitoring the rodent population at the Otley Wetlands Reserve. True to form the captive sits quivering in the box then races off with great kangaroo leaps into the nearest cover – pretty timorous, I’d say. Then a friend sent me a cutting from British Wildlife reporting observations from a naturalist walking near Fewston. He came across a wood mouse in broad daylight- surprising in itself. However there’s more – instead of cowering the mouse strolled around and allowed itself to be picked up. It was perfectly healthy but extremely laid back. Once released it made a beeline for the corpse of a dead toad and began to nibble with every sign of enjoyment. Even when offered sunflower seeds it returned to its toad-meal looking more spaced-out by the minute. Toads secrete various chemicals in their skins to make them unpalatable to predators: our commentator could only conclude that the mouse was happily getting high on some psychotropic ingredient of this cocktail. Alas, a junkie mouse is not likely to survive long – if the addiction doesn’t kill him, a predator surely will.
A happier but equally bizarre story came from a WNS member living in Ilkley. When drawing her curtains one evening recently she glanced out at the garden and was amazed to see what looked like a small lobster sidling across the lawn. On closer examination it proved to be the lobster’s freshwater relative, a large signal crayfish. After taking a photograph she and her grandson picked it up (rather gingerly, I guess, as they have a nasty nip) and took it to the nearest stream where it scuttled off into deeper water.
I discussed this rare observation with our Aquatic Life expert: what could an aquatic creature possibly be doing there and how could it survive so long out of water. The answers surprised me. It must have been a rainy evening and the crayfish could continue to breathe so long as it remained wet. Given such conditions crayfish can, and do, make their way to new territory across land. Unfortunately the specimen in question was a signal crayfish – recognisable by its large size and red colouration on the claws – an alien form which is rapidly taking over our river system and causing the native crayfish population to dwindle. I had often wondered how the signal managed to escape from fish farms and invade rivers like the Wharfe. Now I know. All it takes is a very wet night and a spirit of adventure. I’m still wondering if our friend’s visitor was actually intent on leaving the stream to which she so carefully returned it!