Bats threatened by climate change
Climate change threatens the future of a significant number of bat species.
Bats have already suffered due to changing temperatures, according to a study published in Mammal Review.
That change is "alarming" say the report's authors, but worse is expected as temperatures rise further.
The foraging and feeding, roosting, range sizes and reproduction of bats will all be affected, while extreme weather and disease will also impact many bat species, they say.
More than one in five mammal species are bats, which are considered ecologically and economically important, due to their ability to pollinate and disperse the seeds of a great many plants.
European Bat week begins on 25 August 2012
Mathieu Lundy, Hayley Sherwin and Ian Montgomery of Queens University, Belfast, UK reviewed the scientific literature for observed impacts that climate change has had on bat species.
They then looked to see how many of the bat species living across Europe and North America might be impacted by further temperature rises.
They found numerous examples of how bats will be affected.
For example, climate change is expected to impact the foraging ability of bats.
Firstly bats, particularly lactating females, may have to fly further to drink. Bats are more vulnerable to dehydration than other mammals of a similar size, especially in arid areas, as they lack specific adaptations to retain water and it evaporates at a high rate from the large surface area of their wings.
Aerial-hawking bats, which take insects on the wing, may also have to travel further to find food.
The researchers write that 38 of the 47 species of European and North American bat species investigated would be at risk from these factors.
Bats may also wake more quickly from hibernation or torpor, as temperatures increase. Free-living greater horseshoe bats spend less time in torpor, a form of sleep that helps animals conserve energy, when the outside temperature warms. Captive eastern red bats, and other species of wild tree-roosting bats do similar.
Eleven species that roost in caves or trees are at risk.
Bat reproduction is unlikely to be impacted, say the authors. It is an area that needs more study, they say, but warmer climates may even benefit females by allowing them to give birth and wean their young earlier, leaving more time for the mothers to store fat reserves in preparation.
Although bats can fly, and thus move greater distances than terrestrial mammals, rising temperatures may also severely impact the range size of many species.
In Australia, for example, grey-headed flying foxes now live in the Royal Botanic Gardens in Melbourne, despite historical records suggesting it was once too cold for them there.
The common vampire bat (above) has altered its range in Costa Rica, moving into the Monteverde Cloud Forest as local temperatures have climbed by 2ºC
For many bat species that already live at high latitudes and altitudes, however, climate change will leave them with nowhere to move to.
Extreme weather events triggered by climate change, such as a higher frequency of drought and heat waves, could also wipe out local bat populations: over 30,000 flying foxes, one the largest types of bat, died during 19 episodes of extreme temperature in Australia, the study's authors report.
Perhaps worst of all, these risk factors are not mutually exclusive, and may combine to affect species.
All the bat species examined by the researchers that are currently listed by the International Union for Conservation of Nature as "Near threatened", "Vulnerable" or "Endangered" will fare worse as a result of climate change, they say.