Billions of plastic pieces litter coral reefs off Asia and Australia
News and notes about science
Joleah Lamb began her career as a coral biologist on the Great Barrier Reef. Every now and then, she’d note a scrap of plastic as she swam through. But when she started studying reefs in Asia, she came across a completely different level of detritus.
“I don’t even know how to record this!” she remembers thinking. “It’s a chair! Where do I put ‘chair’? Or diaper? Or bottle?”
Through the years, Lamb, who is now a professor at Cornell University, and her collaborators assembled a formidable database of plastic pollution on 159 reefs in Australia, Indonesia, Myanmar and Thailand. In a paper released in the journal Science on Jan. 25, they estimate that reefs across the Asia-pacific region are littered with more than 11 billion pieces of plastic larger than 5 centimeters.
If those pieces were lined up next to each other, they would reach around the Earth nearly 14 times. To make matters worse, corals with plastic on them were 20 times more likely to be diseased than those that were not polluted.
In their survey of about 12,000 square meters of reef, the researchers noticed that countries known to have particularly poor methods of dealing with plastic pollution had the most plastic on corals. By combining the amount of plastic entering the ocean in each country — a known quantity from previous researchers’ work — with their own observations, they were able to estimate how much plastic was likely on reefs in 15 nations in the Asia-pacific region.
That gave them the stunning figure of 11.1 billion pieces, which they project will increase to 15.7 billion in the next seven years, as worldwide plastics entering the ocean are projected to increase tenfold.
Still, the study shows that it is possible to control the impact of plastic on reefs. Countries that take a great deal of care to keep plastic from entering the ocean — like Australia — see notably lower levels of it on reefs.
— Veronique Greenwood
Elephants’ fear of bees
Elephants are afraid of bees. Let that sink in for a second. The largest animal on land is so terrified of a tiny insect that it will flap its ears, stir up dust and make noises when it hears the buzz of a beehive.
Of course a bee’s stinger can’t penetrate the thick hide of an elephant. But when bees swarm — and African bees swarm aggressively — hundreds of bees might sting an elephant in its most sensitive areas, the trunk, mouth and eyes. And those stings hurt.
The threat of bees is so intensely felt by elephants that conservationists are using it to help prevent the kinds of conflict that put the behemoths at risk. The endangered animals have sometimes been shot by farmers trying to save their crops from elephants foraging at night for late-night snacks, or by poachers allowed access to help guard the fields.
Now there’s a weapon — and a mutually beneficial one — in the arsenal. In recent years, researchers and advocates have persuaded farmers to use the elephant’s fear of bees as a potential fence line to protect crops. By stringing beehives every 20 meters — alternating with fake hives — a team of researchers in Africa has shown it can keep 80 percent of elephants away from farmland.
In a new study published this past month, the same team, led by Lucy King, an Oxford University research associate, found that Asian elephants also are afraid of bees, though perhaps less so. It’s the first step toward showing that the control strategy can work in countries like Sri Lanka, India, Nepal and Thailand, where Asian elephants are 10 times more endangered than their African cousins.
In Africa, Save the Elephants, a nonprofit conservationist group, builds wire and beehive fences at a cost of about $1,000 for a 1-acre farm — roughly onefifth the cost of an electrified fence, King said. The farm gets protection against elephants and a modest new source of income from a twice-a-year honey harvest.
The fences also serve as a psychological barrier for the farmers, making them think twice before slashing and burning more forest for farmland, she said.
So far, the beehive fences are being used or tested in 11 countries in Africa and four in Asia.
— Karen Weintraub
Swatting at mosquitoes may help you avoid bites, even if you miss
If you keep swatting at a mosquito, will it leave you alone?
Some scientists think so. But it depends.
Some blood meals are worth a mosquito risking its life. But if there’s a more attractive or accepting alternative to feed from, a mosquito may move on to that someone or something instead. That’s because if you keep trying and missing, the mosquito may learn to associate your swatting vibrations with your scent, a study published Jan. 25 in Current Biology suggests. And it just may remember: This is not a person who will tolerate me.
Mosquitoes, which transmit diseases like Zika and malaria, do not just bite anything, said Jeffrey Riffell, a neuroecologist at the University of Washington who led the study. They prefer people over other animals, and some people over others. Attraction depends on how a person looks, smells or acts. But when a feeding situation isn’t favorable, a mosquito can switch preferences.
Riffell and his colleagues put mosquitoes and different odors into a vortex that creates vibrations similar to those created when a hand swats a forearm, but misses. In just 15 minutes, the mosquitoes learned to associate the odors with the vibrations. Some once-attractive odors became threatening signals that the mosquitoes learned to avoid. Rather than approach them again, the mosquitoes chose to approach a new odor instead. For at least 24 hours, they retained this memory.
Remembering the smell of a particularly defensive individual with a propensity to swat is important for a bug’s survival. One good smack to a mosquito stuck biting, and splat. Knowing who smells like a splat-maker means mosquitoes can seek out potentially less risky hosts instead. Riffell thinks learning about odors helps drives these decisions.
But just how the insect processes the more than 200 chemicals in a person’s scent signature isn’t fully understood. One thing that helps, the researchers determined, is dopamine, a chemical in the brain that contributes to learning in humans.
— Joanna Klein
This is how an impala can escape a cheetah
Imagine you’re in a highspeed car chase. You’re fast — but the 12-cylinder Lamborghini behind you is faster. Flooring the accelerator and going in a straight line only spells certain defeat.
So what’s your best bet for escape?
Drive along, not too quickly, and just as the other car is about to close in, make a sharp turn.
That’s the suggestion of a study published Jan. 24 in Nature, although instead of cars, it looked at high-speed pursuits between two pairs of predator and prey: cheetahs and impalas, and lions and zebras.
The study, done over many years in Botswana, is the first to gather stride-by-stride data on how these animals hunt and flee for survival in the wild, said Thomas Roberts, a professor of biology at Brown University who was not involved in the study.
In the new study, led by Alan Wilson, a professor of locomotor biomechanics at the Royal Veterinary College in London, researchers captured thousands of high-speed runs by fitting five cheetahs, seven impalas, nine lions and seven zebras with custom collars that could record each animal’s location, speed, acceleration, deceleration and turning performance many times per second.
Though cheetahs and impalas were universally more athletic than lions and zebras, both cheetahs and lions had a similar advantage over their prey — they were 38 percent faster, 37 percent better at accelerating, 72 percent better at decelerating and their muscles were 20 percent more powerful.
This makes sense because the predators are always a step behind, Wilson said. They have to run faster to catch up, but they must also be able to decelerate quickly in case their targets decide to suddenly slow down and turn.
The data also showed that impalas and zebras were typically moving at only half their maximum speed when running from their pursuers. To confirm why, the scientists created a computer model that simulated the last moments of a hunt, after a predator has closed in enough to capture its prey within two strides.
The model showed that impalas and zebras have the best chance of making a getaway if they run at moderate speeds, because that leaves more options for maneuvering away at the last second.
— Steph Yin