Bat babies are getting bigger than ever. Here’s why

Bat babies are getting bigger than ever. Here’s why

These ‘extreme mammals’ are crucial for the health of the environment, but we've hated them for far too long.

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Photo credit: Getty

Published: November 10, 2024 at 8:00 am

Bats are far from crowd favourites – from the rumours that they’re vampires, to the myths that they’ll tangle themselves in your hair. They also got a bad reputation after the coronavirus pandemic, as they’re thought to be implicated in the spread of viruses.

But the screeching, flying mammals are some of the most unfairly treated animals on the planet. According to Rodrigo Medellìn, a bat ecologist from the Institute of Ecology, University of Mexico, “Bats are our best friends”.

They’re fundamental for the well-being of entire ecosystems. And now that climate change is killing them off in large numbers, we might have learned to appreciate them a little too late.



Bats can be thought of as extreme mammals. They sleep upside down, they have muscular hands that evolved into wings and are such agile, masterful fliers that some species can reach speeds of 100 miles per hour.

They are the longest-lived mammals on the planet, relative to their body size. And, despite their longevity, bats stay healthy throughout their entire lives. They have a very low incidence of cancers and can contract otherwise deadly viruses without ever getting sick.

They also have fine-tuned biosonar capabilities that enable them to chirp out ultrasound vocalisations that bounce back from surrounding objects and give them an acoustic image of their environments – it’s like seeing with one’s ears. 

Bats can also ramp down their metabolism for days, or even weeks, to overcome periods of food scarcity. And when food is available, they have an extremely varied diet: some species eat birds, mammals, or even other bats. Three species drink blood.

Some have a penchant for eating juicy fruits, this habit means they pollinate seeds for around 550 species of plants. “Bats are the gardeners of tropical forests around the world,” says Medellìn.

“Forest regeneration strongly depends on bats dispersing the seeds of both pioneer and old-growth seeds,” says Medellìn. “They not only jump-start the recovery after a forest clear-cut but also continue to transport seeds of big trees away from the parent plant, ensuring the future of forests.”

Most bats, though, like to snack on insects and tiny invertebrates. This is one of their biggest superpowers, says bat ecologist Danilo Russo from Università degli Studi di Napoli Federico II.

“Bats are super pest predators in our culture, and I think that's the highlight for the usefulness of bats to humans,” he says.

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Russo’s own research in forests in central Italy found that species of forest bats protect beech trees from insects that cause damage to both forests and agriculture.

Bats also keep corn free from the larvae of corn earworms that eat away at the corn’s insides and keep corn-damaging fungi at bay too. A single colony of 150 big brown bats (Eptesicus fuscus) in Indiana can eat up to 1.3 million pest insects each year.

“Despite the fact that nowadays we use pesticides, pesticides count just for a small fraction of pest control,” says Russo. “Most pest control is still carried out by natural enemies, including birds, predatory insects, and bats.”

This has a measurable economic impact – both because of the damage that’s avoided and the cost of pesticides that’s saved — saving up to $173 per acre (or £350 per hectare) in some agricultural landscapes, and more than $3.7bn (£3bn) per year across agriculture in the USA alone.

It also affects our health, as suggested by the September 2024 Science study that found that as bat populations declined due to a deadly fungus infection, agricultural workers had to amp up their pesticide use by up to 30 per cent.

“It’s the wonders of the ecosystem services,” says Russo. “Initially, you might not find the link. But if you don't preserve bats, you will die.”

But many of bats' benefits risk being undermined by the fact that they are being heavily hit by the burdens of climate change. While most of the data about the relationship between bats and climate change comes from predictive models, the picture doesn’t look promising.

Warming temperatures are making some bat populations move north. While this means they’re flexible enough to adapt to new environments to escape the warmth, scientists don’t yet know what repercussions this might have on local ecosystems. Some bat species are disappearing entirely from areas they used to inhabit.

Crucially, some areas have seen an increase in bat die-offs as temperatures have reached new highs. Russo’s studies suggest a correlation between heat waves and the number of bats admitted into rescue centres in Italy, with bats potentially dying from thermal shock and acute dehydration.

Warming also has the potential to turn bat roosts into ecological traps, says Russo. Since bats seek out warm roosts to reproduce in because heat helps with embryo development, heatwaves “turn roosts into ovens,” he says.

Climate change is also affecting bats in more subtle ways. Russo’s work suggests that some bats have increased their offspring’s body size due to warming temperatures.

“This sounds okay,” says Russo. “But then, these bigger bats will have greater feeding requirements, and insects are declining worldwide, so it might be a deadly combination.”

So, how can we counteract the effects of climate change to keep bat populations healthy, so they can continue to provide their ecosystem services to the world? “It’s a million euro question,” says Russo.

The solutions are multipronged: protecting and managing bat habitats, reducing the use of pesticides, making urban areas more bat-friendly, preserving nature corridors, reducing artificial light, and more.

“If we protect bats better than we do today, we can assure them a brighter future, even under a climate change scenario,” says Russo.

About our experts

Rodrigo A. Medellìn is a senior professor of ecology at the Institute of Ecology, University of Mexico. He’s known as Mexico’s “Batman” because he’s been advocating for the preservation of these flying mammals for decades. He is the founder of the Program for the Conservation of Bats of Mexico, and the founding director of the Latin American Network for Bat Conservation.

Danilo Russo is a bat ecologist, ethologist, and conservation biologist from the Università degli Studi di Napoli Federico II in Italy. He is the editor-in-chief of the journal Mammal Review, and the chair of the Management Committee of “CLIMBATS”, a network of 27 countries evaluating the benefits brought about by bats in agriculture and how these will change in response to climate change.

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