Adaptation to climate change: Great noctule bat – one of the largest native bat species – shift their wintering areas further north over successive generations, as a study shows. This adaptation to the warmer climate therefore takes place across generations. This behavior ensures the great noctule’s survival in times of increasing global warming.
Bats are endangered all over the world: modern agriculture and the intensive use of insecticides mean that flying mammals find fewer and fewer insects. In addition, suitable quarters such as old trees are becoming rarer. Modern buildings are unsuitable as hiding places for bats, and they can even become a deadly danger. The sound signals emitted by the flying animals are initially reflected away by the animals on smooth surfaces, creating the impression of a free flight path.
And the climate development is also causing problems for animals: Due to the rapidly increasing global warming, many species have to change their distribution areas so that they can still find suitable habitats and prey and thus ensure their survival and reproduction. Mobile species, such as seasonally migratory bats, relocate their summer and wintering habitats to the north or south, depending on the climate, in order to find consistently good conditions.
Wintering areas moved to the north
In the case of mammals in particular – such as bats – it is mostly still unknown how the species change their distribution areas due to global warming. Are the individual individuals moving to new areas? Or does this change take place over several generations, so that the offspring live a little further north or south than their parents? In order to get to the bottom of the mechanisms, Kseniia Kravchenko from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) has now investigated with an international team of researchers how the great noctule bat (Nyctalus noctula) is adapting its range to global warming.
In the last few years researchers have already observed that the wintering area of the great noctule has shifted further and further north. To investigate this more closely, Kravchenko and her team examined a bat population in the northern Ukrainian city of Kharkiv. Hibernating bats of this species have only existed in Kharkiv for about 30 years because they used to migrate further south to hibernate. Over a ten-year period from 2007 to 2016, the team of scientists has now collected data on the age and gender of almost 3,400 individuals wintering there.
Move over several generations
The result of the observations: The data showed that young males were more frequently represented in the initial phase of colonization of the new wintering area. Gradually, the ratio of males to females and of young to adult animals equalized. But had these animals moved to the new area themselves or did they already belong to a new generation? The researchers answered this question with the help of fur samples:
“With the help of the analysis of stable hydrogen isotopes in fur keratin, we examined the region of origin of the wintering noctule bat,” explains Kravchenko. “The data from almost 400 animals shows a clear trend: The number of remote trainers decreased in both females and males and across all age groups”.
This shows above all that in the early years of colonization the wintering guests came from the populations whose summer quarters are in the far north. Over time, however, more and more individuals who have their summer quarters nearby and no longer fly further south began to use the Kharkiv area for wintering. “For the noctule bat, we found that the shift of the wintering area to the north takes several generations of young animals,” says Kravchenko’s colleague Christian Voigt. “Especially young males, who usually migrate further from their place of birth than young females, are important when establishing new wintering areas.”
Not all species are fast enough
Great noctule swifts, which have a short life expectancy and a high reproductive rate, can presumably react relatively quickly to global warming in this way – even if the limit of distribution only shifts slowly from generation to generation.
The rapid generation change and the high migration potential of young male bats seem to be an evolutionary advantage of the noctule bat in times of climate change: “Our results indicate that the colonization of winter roosts in higher latitudes is promoted by generation changes, where especially males in the first Year of life are involved ”, sums up the team.
However, this form of adaptation is not feasible for all species: “Mammal species with a higher life expectancy and lower migration potential of the young certainly have a lot more difficulty keeping up with the speed of global warming,” the experts suspect. The future could not look so good for these animals in view of the ongoing global warming. “If the areas of these species also only change from generation to generation, it could be that they will become extinct if global warming continues,” say Kravchenko and Voigt be necessary.
Source: Forschungsverbund Berlin eV, specialist article: Biology Letters, doi: 10.1098 / rsbl.2020.0351