Stoat's dainty steps a vital part of the great dance of life
ANOTHER LIFE:Such animals offer an insight into the link between biodiversity and our own health
The tracks at the tideline were those of tiny feet: a sinuous line of marks in the sand, now being licked away by foamy wavelets pushing up the strand.
I am used to seeing tracks of fox scavenging at first light well ahead of me, but this was finer stitching altogether: two little paws together at the front, the others spaced aslant in the length of one wellington-boot print – about 30cm.
The skipping gait of a stoat suddenly sprang to mind, an idea that would have taken longer to arrive some years ago. Among the earliest observations to Eye on Nature was that of a Co Clare naturalist who had watched a stoat circling a little pocket of rock-pool in the limestone shore of the Burren. The tide had left a small fish – perhaps a blenny – locked up in the pool, and the stoat, by this account, had mesmerised it by its circling before pouncing to hook it out.
I was, perhaps, a tad sceptical at the time, but others offered similar stories of stoats haunting the shore for prey or fresh carrion. The beachcombing fox, too, helped my education. And the tracks of the stoat now reminded me of Paddy Sleeman’s island badgers.
Dr Sleeman, a zoologist with UCC, has spent years studying badgers as part of research towards a vaccine to protect them from bovine TB. Among them are animals that have colonised offshore islands – two off Donegal, others off Sligo, Cork and Waterford. The badgers seem simply to have walked to them, on short causeways at low spring tides, and decided to stay, sometimes making their setts in sand dunes. And their food, analysed from droppings, is rich in sandhoppers, crab and other marine life – the reason, perhaps, they wandered out on the shore in the first place.
This is interesting in itself. Badgers are supposed to eat earthworms, beetles and frogs. This is certainly their staple menu on pastures of intensive farming, where cattle and ryegrass dominate the local ecosystem. But Ireland’s mustelid mammal family – of which the badger is the largest, the stoat the smallest, the otter somewhere in the middle – also includes the pine marten, notoriously omnivorous in its food, eating everything from squirrels and birds to berries and bees.
The island badgers are fine and healthy – not one of them with TB. That you might expect from their glorious isolation, remote from dairy cattle. But Sleeman is one of the legion of scientists alert to every nuance of the link between biodiversity and the general health of the world, not least of its human population.
A recent manifesto is the weighty (but attractive and engaging) book Sustaining Life: How Human Health Depends on Biodiversity (Oxford, 2008), in which Harvard Medical School enlisted 100 scientists to spell out the consequences of the current cascade of extinction.
The value of “ecosystem services” to human life, such as clean water, breathable air and nourishing crops, may now be broadly appreciated, but nature’s complexity and fragility are not.
The interplay of biodiversity and the spread of infectious diseases has captured Sleeman’s special interest. Many such diseases are spread by biting insects, such as malaria by mosquitoes, and where biodiversity is rich these have a wider choice of animals to bite. Gabon, in west Africa, still has plenty of trees and monkeys, and the level of malaria is low; Ivory Coast is denuded of forests, and the only biteable primates are people, so malaria is widespread. Haiti and the Dominican Republic offer similar contrasts, even as they share one island.