Bechstein's Bat Is Forest Specialist
May 28, 2013

Bechstein’s Bat Is Forest Specialist

Lee Rannals for — Your Universe Online

A new study sheds a little light on the origins of the Bechstein's bat, which tends to be thought of as a Euro-Siberian species.

The Bechstein's bat is distributed from the Iberian Peninsula to the Caucasus, and is even seen as far south as Scandinavia. Moreover, the species is regarded as rare, despite its abundance in the fossil records of the late Pleistocene and Holocene periods.

Fossil records show that the start and consolidation of the bat species' decline coincides with the deforestation caused by the intensification of agriculture. This decline has been linked to cold temperatures and greater humidity.

The Bechstein's bat has also been spotted on very few occasions in the Mediterranean area. Now, a team at Elhuyar Fundazioa's Department of Zoology and Animal Cell Biology revealed that Bechstein's original habitat could be more Mediterranean than previously thought.

"That led us to revisit the traditional dogma that the M. bechsteinii is a Euro-Siberian species, restricted to the temperate forests of Central and Western Europe, and to ask whether its current distribution could respond more to the history of deciduous forestloss in part of its original range," explains Dr. María Napal, leading author of the paper published in Forest Ecology and Management. "In fact, during the Holocene the vegetation evolved differently in the Mediterranean compared with the rest of Europe. In the Mediterranean, the intensity of human activity, linked to great aridity, led to the substitution of the deciduous vegetation by the typical xerophytic vegetation."

The team studied the ecology of the species in the Mediterranean and Atlantic climate domains of the Iberian Peninsula. They followed bats for several nights to discover their roosts and specify their hunting areas. The team also documented their diet on the basis of their droppings.

Napal's team found that Bechstein's bat prefers carved out trunks in living oak trees inside the forest, which is a habitat less conditioned in the Mediterranean. She said the colonies were more flexible in terms of the variables relating to the microclimate of the cavity, even though the presence of water was a more limiting factor.

Bats observed in both the Atlantic and Mediterranean hunted in the middle of the forest, but the distances covered between their roosts and their hunting grounds were longer in the Atlantic. Napal believes this could be explained by a greater fragmentation of their habitat or its inferior quality.

The team's study helps confirm that Bechstein's bat is a forest specialist with a narrow ecological niche, and it adapted to hunting and roosting in temperate deciduous forests.

"Both areas of study offer conditions that meet the ecological needs of the species, and it could also be said that, contrary to our expectations and based on the distribution area and data on the ecology of the species available to date, in the Mediterranean localities the conditions are even more lax than in the Atlantic," Napal said.

She added that their data suggests the current distribution of the bat in Europe reflects not only the climate changes that have taken place, but also the severe loss and degradation of the deciduous forests in the Mediterranean.

"We reckon the species could still find optimum conditions in some locations in the Mediterranean area if these forests were still present," she said. "This is a clear demonstration of the effect that a prolonged history of deforestation and degradation of the forestry systems can have on the populations of forestry specialists, like the Bechstein's bat."

According to Napal, the study constitutes an example of how the historical processes in the landscape may confuse or distort the apparent relationship between the distribution of the species and eco-geographical factors.

"It is not always easy to distinguish between the effect of current and historical factors, but ignoring this reality may lead us to draw wrong conclusions about the ecological needs of certain species, and therefore to design inappropriate conservation measures," concludes Napal.