Biologists Are Using ‘Mission: Impossible’ Techniques to Save the World’s Wildlife
Sometimes the best way to understand nature is to get as far away from it as possible. The 19th-century popularization of binoculars was a step in that direction, allowing people to back off and observe wild animals without disturbing them. Camera traps, left unattended in the field for weeks at a time, have more recently also minimized the intrusion while revealing unexpected worlds of animal behavior.
Scientists have lately begun to deploy a host of new remote sensing techniques to solve some of the most challenging problems in wildlife conservation. I’ve written here before about iDNA, a novel technique for finding out what birds and mammals live in a habitat by sequencing the DNA from the latest blood meals leeches and mosquitoes have taken from them. Even better, eDNA does the same thing for aquatic species by sequencing DNA from a water sample.
But let’s say you don’t have a DNA sequencer at hand and must rely instead on sound. Here is your mission, if you choose to accept it: Count how many seabirds are nesting on a sheer cliff face on a remote island, with raging seas crashing on the rocks just below. Bear in mind that ornithologists have demonstrated an alarming penchant over the past few centuries for plunging to their deaths while studying such birds. Naturally, you want to know if you could (please, please, please) just use binoculars to do a visual count from a boat. But the birds often nest out of sight, in burrows or under rocks, and some species take flight only under cover of darkness.
The solution? To figure out how populations of Cory’s shearwaters are surviving, despite the introduction of cats and rats, on an island in the Azores, 900 miles west of Portugal in the North Atlantic, European scientists recently turned to a microphone array. First, they set out microphones in lower-elevation areas where they could count all nests within recording distance. That gave them a baseline figure for how much noise a given number of nests produces in breeding season.
Then came the climbing—though a lot less than would be required to count individual nests on the cliffs, some of them almost 2,000 feet high. The roped-up researchers placed a series of recording devices on the cliff faces. Then they left the birds alone for the five-month breeding season.
Anybody who has ever visited a nesting colony will spot the apparent flaw in this technique: Colonies of nesting birds can make a hellacious, Hitchcockian racket. To break down five months of noise into analyzable chunks, the researchers pulled out brief samples from nighttime periods when the phase of the moon and weather conditions were uniform. Then big data technology came to the rescue, with an automated call recognition algorithm. The researchers say the technique needs further tinkering to achieve the necessary precision, but they estimate that the test island of Corvo is home to more than 6,000 nesting pairs of Cory’s shearwaters.
Other forms of eavesdropping have lately proved useful with creatures as disparate as dolphins and honeybees. A team led by Elena Papale of the University of Torino didn’t know at first if it could make sense of how different dolphin populations and species whistle underwater. The whistling varies according to a population’s genetic characteristics and adaptations to a particular environment, but these differences are small, and they may also shift over time.
The researchers studied three dolphin species in the Atlantic and the Mediterranean, recording the whistling of different groups as they observed them visually. When they later analyzed recordings by their acoustic structure alone, they found they were able to assign 82 percent of the calls to the correct dolphin species. With further refinement, Papale believes, scientists will be able to employ underwater microphone arrays for “constant and continuous monitoring” of dolphin populations.
Finally, a study being published today in the journal Current Biology used honeybees to answer a complicated question: Over the past two decades, the European Union has spent $56 billion on schemes to make farms more hospitable to birds, butterflies, and other wildlife. Was it money well spent?
The new study relied on one of the most astonishing behaviors in the insect world: Honeybees returning to the hive do “waggle dances” to map out the route to a particularly appealing patch of flowers. Researchers at the University of Sussex recorded 5,484 such dances over two years. Then they deciphered them to see where honeybees were foraging in a 36-square-mile mixed rural and urban area on the southeast coast of England.
“Imagine the time, manpower, and cost to survey such an area on foot, to monitor nectar sources for quality and quantity of production, to count the number of other flower-visiting insects to account for competition, and then to do this over and over for two foraging years,” said lead author Margaret Couvillon. “Instead, we have let the honeybees do the hard work of surveying the landscape and integrating all relevant costs and then providing, through their dance communication, this biologically relevant information about landscape quality.”
It turned out the honeybees liked the environmentally friendly areas created under EU agri-environment schemes, and because bees are good indicators of habitat for other wildlife, that suggests the schemes are working as intended. (On the other hand, the bees avoided areas created under organic farming schemes, possibly because of mowing or other management practices.)
Together, these three studies bring to mind an adage of the celebrated war photographer Robert Capa. “If your photographs aren’t good enough,” he once said, “you’re not close enough.” But with wildlife, the opposite seems to be true: If your science isn’t good enough, maybe you need to get farther away.