Madagascar is an island that’s no stranger to natural disasters, in particular cyclones. This is because it’s located in the south-west Indian Ocean cyclone basin, a region of the Indian Ocean where tropical cyclones typically form and develop.
Madagascar has experienced 69 cyclones between 1912 and 2022, although cyclones have been a pressure on the island for much longer – estimates range from hundreds to more than thousands of years. This regular exposure has resulted in a uniquely harsh and unpredictable environment.
Madagascar is also the only place in the entire world where lemurs, a group of primates, are naturally found. It’s home to over 100 species of lemurs.
Due to ongoing threats of disaster impacts, hunting and deforestation, lemurs are the most endangered group of mammals in the world. According to the International Union for Conservation of Nature (IUCN), 98% of lemur species are threatened with extinction, 31% of which are critically endangered.
It is therefore important to understand future threats to lemurs so as to protect them.
Lemurs are unusual among primates. They show a higher degree of traits associated with resilience to living in a disaster-prone environment. For example, very few species rely on a diet of fruit, which is one of the first food items to disappear after a cyclone. Over half of lemur species rely on leaves as their main food item.
They also exhibit a high degree of energy conserving behaviours, including hibernation and torpor – a shorter period of inactivity characterised by a lower body temperature and metabolic rate.
It has long been believed that these behaviours are a result of Madagascar’s frequent cyclones. Living in an unpredictable environment over multiple generations could lead to different features being beneficial for survival. Some evolutionary adaptations may happen within a few decades, others could form over thousands of years.
However, there is variation among species in these traits and, to date, no one has tested whether the unique behavioural features of lemurs actually occur more frequently in species that have experienced more cyclones, or if there may be a different explanation. Our research wanted to clear this up.
In our study, my colleagues and I found no association between cyclone impact and how resilient lemurs are. We did however find a positive association between cyclone impact and body size. This suggests that the more a lemur species is affected by cyclones, the smaller they are.
Given the increase globally in disasters, this type of work allows us to better understand the most and least resilient species to prepare for conservation efforts into the future.
How resilient are lemurs?
My research focuses on how animals, particularly primates, respond to the threat of climate change and disaster exposure. Previous work my colleagues and I did with howler monkeys showed that historical hurricane exposure was significantly linked to the evolution of behavioural adaptations, like small group size and energy conserving behaviours.
We set out to design a specific study for lemurs. We wanted to determine whether the variation in behavioural traits in lemurs could be accounted for by the variation in cyclone exposure across the island.
To carry out this research, we first made a map showing how cyclones affect different parts of Madagascar. We used weather patterns, past cyclone paths, how strong the cyclones were, and how much rain they brought. Data used for this came from the past 58 years, which is the data that was available, although Madagascar has been hit by cyclones over a much longer time period.
We then placed a map of where lemurs live on top of our cyclone map to see how much cyclones affect each lemur species’ home. Our study covered the 26 species for which enough data was published to be able to determine their overall behavioural traits.
For each of these species, we created a “resilience score”. To create this score, each species got one point for each behavioural trait they exhibited that is associated with living in a cyclone-prone area. For example, a species that shows hibernation got one point and a species that does not got 0 points. The resilience traits we used included: energy conserving behaviours; habitat use; group size; fruit in the diet; home range size; geographic range; and body size.
We then added up the score across all resilience traits and compared the resilience score of each species with their habitat range cyclone score. This helped us see if species in high-impact areas had higher resilience. If so, it would strongly suggest that resilience traits evolved as an adaptation to frequent cyclones.
Our results found no relationship between cyclone impact and overall resilience score. This may be because the historical cyclone data we had access to covered only the past 58 years. This may not be an accurate proxy for longer term cyclone activity associated with evolutionary adaptations.
It could also be that the traits linked to cyclone resilience may have already existed in the last common ancestor of lemurs due to rapid environmental change on the African continent. Recent research suggests this ancestor rafted to Madagascar from Africa on floating vegetation. These traits could have helped it survive the journey. They’re also seen in other wildlife believed to have rafted to their island habitats and that may have been crucial for island colonisation.
While overall resilience scores were not associated with cyclone impact, we did find that lemur species with smaller bodies experienced greater cyclone impacts. The north-east of the island was found to experience higher cyclone activity compared to the south-west. This aligns with previous research suggesting that larger primates, which require more food and space and reproduce more slowly, are less resilient and more likely to die after habitat disturbance.
Importance for conservation
Ours was the first study to try to find a quantitative link between cyclone exposure and the evolution of behavioural adaptations in lemurs and only the second to do so in primates.
While results did not show a link to overall resilience, they did provide a template for future studies to explore the concept on other primates at a global scale. The study also provides a cyclone impact grid that could be used to assess impacts on other wildlife in Madagascar.
In addition, our work has highlighted the importance of body size as a factor associated with less resilience to disaster.
This research helps us to understand more about how species responded to cyclones in the past, which improves our understanding of the sorts of behavioural flexibility needed to survive severe environmental change. This then improves our ability to predict the effects of future events and mitigate impacts through more effective and targeted conservation. This is particularly true in island ecosystems, such as Madagascar, where endemic species are confined.
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The post “Madagascar’s lemurs live with the threat of cyclones – has this shaped their behaviour?” by Alison Behie, Professor of Biological Anthropology, Australian National University was published on 03/05/2025 by theconversation.com