Michael Viney: Why secret of everlasting youth might lie in bats

The little corpse at the edge of the path was the merest scrap of fur with a squiggle of a tail. To come upon it at the back end of winter was no great surprise. Ireland’s smallest mammal, the pygmy shrew, has a frantic, insect-munching lifestyle that rarely lasts much longer than 13 months.

Compare that with the common pipistrelle, the tiny bat of so many Irish roof spaces. Its body size, at the heart of those flickering wings, is much the same as the shrew – it will, as one scientist friend put it, “fit on the end of your thumb”. Its feeding schedule, too, can be hectic: as much as 3,500 insects in one night. But the pipistrelle may live as long as 15 years.

The extreme longevity of bats seems to counter the rule that bigger animals live longer. Of the 19 mammals that live longer than humans, all but one are bats. This has led one Irish geneticist to a line of research that now has a keen global following.

Deep in the DNA that gives bats their longevity, hopes Prof Emma Teeling of University College Dublin, "may lie the secret of everlasting youth".

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In 2012, this conclusion startled a 2,000-strong Dublin audience at a TED Talk about the evolutionary characteristics of bats. Since then, in research that warranted the cover of Nature, she and the team at her UCD “Bat Lab” have been exploring the bat genome that gives them their “unique and peculiar adaptations”.

Forty-two years

A key species for the research, with blood sampled at roosts in a village in Brittany, has been the greater mouse-eared bat, Myotis myotis. It lives as long as 37 years. Another species, Brandt’s bat, a vagrant visitor to Ireland, sets the record at 42 years.

With more than 1,400 species identified so far, bats make up a fifth of the world’s mammals. Their consumption of flying insects (in annual thousands of tonnes) and pollination of many tropical fruits make them vital to the planet’s ecosystems.

Bat DNA tolerates viruses toxic to people and other mammals. It may also hold genes secure against blindness and deafness

Of possibly huge importance to humans, bat DNA gives the animals a unique immune system and longevity. It tolerates viruses toxic to people and other mammals. It may also hold genes secure against blindness and deafness. The chance of insights into such woes of human ageing is the big drive to research.

It also makes even more absurd the common human attitudes to bats. Born within a parish or two of Bram Stoker, Teeling forgives the vampire narratives. And the generous flow of fair hair around her shoulders disdains another cultural myth.

The nonsense about bats entangled in women's hair particularly incensed Prof James Fairley, now long retired from NUI Galway to his native Belfast. In the 1980s, as Europe's zoologists were sounding alarm on the wide decline of bats, Fairley launched a wave of student interest in Ireland's species and enthusiastic research by a group of young women.

Threatened

Among them was Dr Kate McAney, later cofounder of Bat Conservation Ireland (BCI) and head of Irish conservation for the UK-based Vincent Wildlife Trust. Her special concern was for the welfare of the threatened lesser horseshoe bat, for whom roosts in caves, old farm buildings and big-house attics of Ireland's western seaboard have been an important refuge.

The hibernating bat in my drawing was hanging from the wall of an old mine shaft on a Connemara hillside, to which McAney had guided me. The lesser horseshoe, now numbering some 13,000 individuals, leads the nine resident Irish bats described in a new identification guide published by the National Biodiversity Data Centre and the BCI.

Prepared by Niamh Roche and Andrew Torsney and well-crafted for the pocket, it pictures key features of animals held in the hand and gives sonograms of their calls as recorded on bat detectors.

The echolocation calls of night-flying bats are pitched too high for human hearing and have to be tuned in, as to a radio station. The booklet offers downloadable, distinctive sound files for each species and a commentary offers much field experience.

The brown bat, for example, is nicknamed the whispering bat and “can usually only be detected within 5m to 8m”, whereas the call of Leisler’s bat “sounds like chi-chi-chi-chop-chop when tuned in at 25Hz”.

Yearly trends

With funding from the National Parks and Wildlife Service, a cross-border Centre for Irish Bat Research studies three rare woodland bats.d BCI volunteers have tracked yearly trends in key species since 2003.

All seem to be stable or increasing, despite loss of traditional roosts and hedgerows. Newer threats come from the spread of over-intense LED lighting and wind farm development.

The first Irish research into the impact of wind turbines on bat populations, involving years of fieldwork, launched Dr Una Nealon as yet another woman expert in chiropterology.