By Gina Maffey
Adventurous water voles (the beloved Ratty of “The Wind in the Willows”) are doing their bit to increase the species’ chances of survival in a fragmented habitat in the Scottish Highlands.
“And to think, a road goes past my very door, and I only know a mile or two of it,” said Ratty. No longer.
Fragmented habitats, due to human influence, are increasingly common throughout the UK and can cause problems for species, as populations are squeezed into smaller and more distant areas.
Connected habitats are critical for genetic exchange and disease resistance, and fragmentation has a profound effect on the likelihood of extinction of a species.
A study by Professor Xavier Lambin and Chris Sutherland at the University of Aberdeen have shown that adventurous ‘lonely heart’ teenage water voles leave their family group to avoid incestuous relationships, and embark towards unknown habitats in search of others.
Where some individuals are able to find new colonies of water voles, others sequentially visit different suitable habitats in the hope of meeting another departing water vole at the same time.
Despite being a small species, around the size of a large hamster, dispersing individuals regularly travel huge distances with some being tracked at distances 15km away from their original population.
However, the efforts of these lonely heart heroes that come from already failing colonies of water voles may inadvertently be increasing the risk of population extinction by creating a ‘wave of death’.
It is known that decreased habitat size leads to a decreased population size and a subsequent increased likelihood of extinction, and there is much discussion around creating wildlife corridors for increased connectivity between populations.
In some instances dispersing water vole individuals are able to rescue failing colonies by increasing numbers, but in situations where a colony is already failing the loss another individual can cause the group to collapse.
This extinction burden can then be shared around surrounding groups in a wave of death.
This wave can radiate as far as 3km, destroying populations and being magnified according to the size of the colony and the distance from its closest neighbours.
Professor Lambin’s and Sutherland’s research has demonstrated the necessity for networks among populations. It has also highlighted the need to understand the optimal degree of connectivity between colonies to prevent increasing extinction risk.