They are small, have a high reproductive rate and live in the forests of Madagascar: mouse lemurs are among the smallest representatives of the lemurs. Now a long-term study shows that climate change threatens to destabilize populations of even these normally adaptable and non-endangered primates. Although the mouse lemurs have increased their reproduction rate in adapting to the changed conditions, there is always a high mortality rate.
Climate change is shifting climate patterns around the world. Temperatures and the resulting climate zones are shifting, while at the same time extremes are intensifying: droughts and heavy rain are becoming more frequent and more intense. In regions with pronounced seasonal fluctuations, for example in the form of dry and rainy seasons, climate change has different effects depending on the area: In some regions, the seasonal differences are becoming greater and this means that the dry seasons are more intense and the rainy seasons stronger. In others, however, the differences are weakening. In both cases, this requires an adaptation of nature to these changes.
Mouse lemurs in view
Arpat Ozgul from the University of Zurich and his colleagues have investigated how well this works using the example of the mouse lemur in Madagascar. Climate data show that the rainy season there has become increasingly drier over the past 30 years and the rather cool dry season has become increasingly warmer. For the lemurs native to Madagascar – one of the most endangered mammal groups in the world – this means a change. According to current theory, long-lived animals with a low reproductive rate in particular have difficulties adapting to environmental changes. Small mammals with a high reproductive rate, on the other hand, are considered to be relatively adaptable and have therefore hardly been researched in connection with climate change.
Therefore, the research team has now studied a primate species that has a high reproductive rate: the gray mouse lemur (Microcebus murinus). These lemurs, which weigh only around 60 grams and are 15 centimeters long, eat fruit, blossoms and insects depending on availability and often survive the cool, dry, nutrient-poor season in a kind of hibernation. During the rainy season, which lasts about five months, female mouse lemurs can give birth to several young once or twice, depending on the climate and food. Therefore, compared to larger lemur species, they are considered primates with a high reproductive rate. The mouse lemur populations of Madagascar have been monitored and researched by researchers from the German Primate Center since 1994.
Large population fluctuations despite adaptation
For their study, Ozgul and his colleagues from the German Primate Center have now compiled data from 26 years to record changes in mouse lemur age structure and populations in response to the changing climate. It turned out that the small lemurs increased their reproduction rate slightly during this period, but mortality also increased at the same time. “While these opposing trends prevented the mouse lemur population from collapsing, they led to population destabilization as the animals’ already fast life cycle was further accelerated,” says co-author Claudia Fichtel from the German Primate Center. At the same time, however, population fluctuations have increased significantly.
According to the researchers, these fluctuating population sizes due to climate change pose a great threat to the animals and, in extreme cases, could even lead to the species becoming extinct. “Our results show that even an animal species that supposedly can easily adapt to changing environmental conditions thanks to a high reproduction rate is threatened in its survival by climate change,” says co-author Peter Kappeler from the Primate Center. His colleague Fichtel adds: “In the future, data on the demographic stability of a population should also be included when classifying the endangerment status of an animal species.” an alarming warning sign of potential biodiversity loss in the tropics.
Source: Deutsches Primatenzentrum GmbH – Leibniz Institute for Primate Research; Specialist article: Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2214244120