Why is forest loss making tropical heatwaves lethal for fruit bats?

During tropical heatwaves, the first signs are subtle. Flying foxes also known as fruit bats—remain motionless in full daylight, wings spread wide in a desperate attempt to regulate their body temperature. Normally nocturnal and active at dusk, they now hang silently from exposed branches, unable to escape the heat.
Across the Indian Ocean region, such scenes are becoming increasingly common. Heatwaves are not new in tropical environments. What has changed is the disappearance of forests—the natural climate buffers that once enabled flying foxes to survive extreme temperatures.

A keystone species under pressureFlying foxes play a critical ecological role across islands and coastal forests of the Indian Ocean. As long-distance pollinators and seed dispersers, they actively contribute to forest regeneration, biodiversity maintenance, and the recovery of degraded ecosystems.
Their survival depends on stable microclimates. Dense forest canopies provide shade, humidity, and air circulation—essential conditions for thermoregulation in these large-bodied bats. Unlike smaller species, flying foxes are particularly vulnerable to overheating when exposed to direct sunlight for extended periods.
When forests remain intact, heat rarely becomes fatal. When forests disappear, even moderate heatwaves can turn deadly.

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Deforestation in the Indian Ocean: a gradual erosion
In Madagascar, Mayotte, and other islands across the region, deforestation rarely takes the form of a single dramatic event. Instead, forests are progressively fragmented through fuelwood extraction, agricultural expansion, urbanisation, and infrastructure development.
Each cleared area may appear insignificant in isolation. Together, however, they dismantle the forest’s ability to function as a thermal refuge. Mature trees used for generations as communal roosts are felled or left isolated, forcing colonies into exposed landscapes with no viable alternatives.
In island ecosystems—where space is limited—this loss is particularly severe.

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Why heat becomes lethal without trees : Flying foxes regulate body temperature primarily through evaporative cooling and behavioural adaptations: seeking shade, adjusting roosting posture, or moving short distances to cooler areas. Without forest cover, these options vanish.
Exposed bats experience rapid dehydration and severe hyperthermia. During extreme heat events, individuals may fall from roosts or die while still clinging to branches. Mass mortality events—once rare—are now increasingly documented worldwide, with habitat loss consistently amplifying their scale.
In tropical regions, deforestation removes the final margin of survival against heat.

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When habitat loss turns species against each other: flying foxes and lemursForest loss does not affect a single species in isolation. In Mayotte, intense habitat fragmentation has forced species that once coexisted with little interaction to share an increasingly limited number of trees.
Lemurs (makis), themselves forest-dependent and emblematic of regional biodiversity, are now sometimes forced into direct competition with flying foxes for food resources and refuge trees. This inter-species conflict is not natural—it is the product of extreme habitat compression.
As space disappears, ecological balances collapse. Stress behaviours increase, temporal niches overlap, and protected species are pushed into conflict despite sharing the same underlying threat. The ecological crisis, in this case, creates conflict between victims—not between culprits and the innocent.

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Key figures: alarming population declines : The Mauritian flying fox (Pteropus niger) lost approximately 45–50 % of its population between 2015 and 2016, largely due to heat stress and large-scale culling campaigns sanctioned by the government of Mauritius. These actions, alongside ongoing illegal hunting and habitat degradation, were significant contributors to this rapid decline and were part of the reasoning behind the species’ uplisting to Endangered on the IUCN Red List. (decline of ~50 % since 2015 due to culls and other pressures) 
During the 2015 cull alone, over 30,000 individuals were killed, making it one of the largest documented removals of fruit bats in the world. (government-authorized national cull of over 30,000 individuals in 2015, with additional tens of thousands culled in the following years) 
The Livingstone’s fruit bat (Pteropus livingstonii), endemic to the Comoros archipelago and one of the world’s rarest megabats, is currently estimated at about 1,200–1,500 individuals in total across its limited range on the islands of Anjouan and Mohéli. (population estimates ~1,200–1,500) 
Globally, more than 70 % of large Old World fruit bat species (including many in the genus Pteropus) are now classified as threatened or near-threatened on the IUCN Red List due to a combination of habitat loss, hunting pressure, and climate-related stressors that are affecting their populations worldwide. (Pteropus species are widely listed as threatened due to these pressures) 

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The danger of the wrong narrative : As flying foxes move into exposed or human-dominated areas, they are increasingly labelled as pests, invasive, or dangerous. This narrative obscures the real cause of their displacement and often justifies ineffective or harmful responses such as culling or forced relocation.
Removing flying foxes does nothing to address the absence of functional forests. On the contrary, it undermines ecosystem resilience by eliminating a keystone species essential to forest regeneration—precisely when forests are most needed.
Killing bats treats a symptom, not the disease.

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Forests as living climate infrastructure : Forests are often discussed primarily as carbon sinks. Yet their role as local climate regulators is equally critical.
For flying foxes, forests are far more than simple habitat. They create the microclimates that buffer extreme heat, retain humidity during droughts, and provide the spatial complexity these large, highly social bats need to roost, thermoregulate, and survive. In a warming world, protecting forest ecosystems is therefore not an abstract conservation ideal  it is one of the most immediate and effective defenses against climate-driven mass mortality.
The solutions are neither speculative nor technologically complex. They already exist, and they are well understood: safeguarding the last remaining roost trees, restoring forest corridors that reconnect fragmented populations, preserving native large-canopy species that offer shade and thermal stability, and integrating wildlife requirements into land-use and agricultural planning. What is missing is not scientific knowledge, but political will and sustained local engagement. When forests are allowed to stand and regenerate, flying foxes are given back their most powerful ally against a rapidly destabilizing climate.

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Conclusion: a warning written on living bodiesIf flying foxes disappear, the heat they endure today will become our own reality tomorrow. What these animals experience first is not a biological anomaly, but the symptom of ecosystems stripped of their capacity to regulate climate extremes.
Flying foxes serve as early indicators: without forests, tropical regions lose their ability to buffer heat—affecting wildlife and human populations alike. As forests vanish, heatwaves will become more frequent, more intense, and harder to survive.
Protecting forests is therefore not just about saving a misunderstood species.
It is about preserving the conditions that will allow life—human and non-human—to endure in a warming world.

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At dawn, the lagoon of Wallis shimmers in soft pastel tones, the crow of roosters echoing through coconut groves. Soon, the steady toll of church bells drifts across the humid air, calling villagers to morning mass. On this small Polynesian island in the South Pacific, faith and tradition are inseparable from the rhythm of everyday life.

An island anchored in faithCatholicism arrived with missionaries in the 19th century, and today it remains the heartbeat of Wallisian identity. Every village has its own church, often perched by the water’s edge, its spire rising above breadfruit trees. On Sundays, families dressed in bright lavalava fill the pews, their polyphonic hymns lifting into the rafters. Religion here is more than private devotion — it is the collective pulse of the island.

The power of customAlongside the church stands another pillar of Wallisian society: la coutume. Rooted in Polynesian tradition, it dictates respect for hierarchy, rituals of welcome, and the authority of chiefs. At its centre is the Lavelua, the customary king. Wallis is the only French territory where a monarchy still exists, coexisting with the institutions of the Republic. Though the king holds no political power in the French state, his moral and symbolic authority is immense. It is a reminder that here, tradition has not bowed to modernity.

Wealth measured in pigsOn Wallis, prosperity is not counted in banknotes but in livestock. Pigs are the ultimate currency of respect and social standing. During major ceremonies, families present them as gifts — the more pigs offered, the greater the prestige. To raise pigs is to invest not only in food, but in reputation and influence.

A lagoon of endless bluesBeyond the villages, the lagoon unfurls in shades of turquoise and cobalt, dotted with tiny motu fringed with coral. Outrigger canoes glide silently across the shallows, fishing nets trailing behind. Life moves slowly here: coconuts fall, waves lap basalt shores, and the outside world feels far away.

The mystery of Lake LalolaloInland, hidden by dense forest, lies a perfect circle: Lake Lalolalo. This volcanic crater, its cliffs plunging more than thirty metres down to dark waters, is steeped in legend. Some say it is bottomless, others that it shelters spirits or mythical creatures. Even today, the lake has a gravity of its own — a silence broken only by the call of birds. For visitors, it offers a striking counterpoint to the brilliance of the lagoon: the secret, more enigmatic face of Wallis.

Where time holds steadyAs night falls, the island gathers once more — for prayer, for kava, for shared meals where roast pig feeds dozens and laughter echoes under the stars. Wallis may be a French territory, but it is first and foremost a Polynesian homeland, where religion, custom, monarchy and community are deeply interwoven. Time seems to hold steady here, anchored in faith and tradition, while the rest of the world rushes ever faster.