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The Big Picture
Nail varnish helps researchers pinpoint numbers of rare bats


Emma Huntley explains how researchers from the Zoological Society of London are using an inventive way to calculate bat populations

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It was time consuming giving each bat an individual manicure

Conservationists have been able to determine the population of a rare Cuban bat for the first time using manicures.

Following an expedition led by the Zoological Society of London’s (ZSL’s) Edge of Existence Programme, researchers have confirmed that less than 750 of the Cuban greater funnel-eared bats (Natalus primus) remain in the wild, confined to a single cave on the Guanahacabibes peninsula in Western Cuba.

In order to identify and count the bats, researchers opted for a unique approach – painting the bats’ ‘nails’ with four different colours of nail varnish (see inset picture). This allowed researchers to log thousands of potential combinations for distinctive markings, without harming the bats.

According to Jose Manuel De La Cruz Mora, a fellow at ZSL based at the Natural History Museum of Pinar del Río, marking of bats is usually done using leg rings, necklaces, or wing punches – but these techniques can alter the animals’ behaviour.

Given their small numbers, he explained that understanding the biology of these bats was fundamental and that it was important to keep things as ‘natural as possible’.

‘It was time consuming giving each bat an individual manicure. But it’s an incredible privilege to get up close to these amazing animals, and to discover more about them made all those hours painting their nails worth it!’ De La Cruz Mora said.

Until 1992 these bats were declared as extinct. They were rediscovered by Cuban scientists in the same cave they still inhabit – a cave known to the locals as ‘cueva la barca.’

N primus was thought to have once been a widespread species – fossils from the late Pleistocene (11,000 years ago) place them as inhabiting areas from the Bahamas to Grand Cayman.

The cause of their mass population decline is still unconfirmed, but their specific roosting habitat in hot caves is thought to have contributed to their significant population decline. However, factors such as human intrusion in caves, disease, and climate change are also considered to be contributing factors.

‘The story of the Cuban greater funnel-eared bat really resonated with me as it reiterates the absolute need to ensure underappreciated species don’t become lost to scientific history, simply because we forget to look [for them],’ said De La Cruz Mora.

‘Bats around the world are one of the most threatened group of animals due to destruction of their roosts, disease and even hunting – but they provide an enormous ecosystem benefit to people. By keeping insect populations down, they reduce the chance of disease risk and pests on farmers’ crops.

‘They’re particularly vulnerable to human disturbance, but now we have a rough estimate of how many are left, we can plan the best conservation action – including local community awareness campaigns to raise their profile.’

• More information about the ZSL’s EDGE of existence programme can be found at

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