Science in brief
This rat covers itself with poison that can take out an elephant
For a rodent that resembles the love child of a skunk and a steel wool brush, the African crested rat carries itself with a surprising amount of swagger. “[These rats] very much have the personality of something that knows it’s poisonous,” says Sara Weinstein, a biologist at the University of Utah and the Smithsonian Conservation Biology Institute.
In sharp contrast to most of their skittish rodent kin, Lophiomys imhausi lumber about with the languidness of porcupines. When cornered, they fluff up the fur along their backs into a tip-frosted mohawk, revealing rows of black-and-white bands that run like racing stripes down their flanks – and, at their centre, a thicket of specialised brown hairs with a honeycomb-like texture. Those spongy hairs contain a poison powerful enough to bring an elephant to its knees, and are central to Weinstein’s recent research, which confirmed ideas about how this rat makes itself so deadly.
Give them a chance and African crested rats will take nibbles from the branch of a poison arrow tree. It’s not for nutrition. Instead, they will chew chunks of the plants and spit them back out into their fur, anointing themselves with a form of chemical armour that most likely protects them from predators such as hyenas and wild dogs. The ritual transforms the rats into the world’s only known toxic rodents, and ranks
them among the few mammals that borrow poisons from plants. Weinstein’s research, which was published last month in the Journal of Mammalogy, is not the first to document the crested rats’ bizarre behaviour. But the new paper adds weight to an idea described nearly a decade ago, and offers an early glimpse into the animals’ social lives. People in east Africa have long known about the crested rat’s poisonous punch, which has felled many an overcurious dog. (Those that survive their encounters tend to give the rats a wide berth.)
For their paper, Weinstein and her team snared 25 rodents and filmed them in the lab. When offered cuttings of Acokanthera, some of the animals chomped on the bark then groomed it into their stripes. Scientists still aren’t sure how often the rats anoint, or even how they tolerate the toxins themselves, especially if some of it ends up going down their gullets.
Don’t get between a caterpillar and its milkweed
In the 1969 children’s book The Very Hungry Caterpillar, the tiny protagonist spends a week scarfing his way through a smorgasbord of fruits, meats, sugary desserts and, finally, a nourishing leaf. This familyfriendly tale was missing one crucial and far less G-rated plot element: the pure, unadulterated rage of an insect unfed. When food gets scarce, monarch butterfly caterpillars will turn on each other, duking it out for the rights to grub, according to a paper published in the journal iScience. The jousts don’t get bloody, but they do involve plenty of bumping, boxing and body-checking.
“I went to grad school with a guy who played rugby in college,” said Alex Keene, a neuroscientist at Florida Atlantic University and an author on the study. “A flying head butt is a fair assessment.” The study offers an in-depth look into the underappreciated phenomenon of caterpillar aggression. It could also aid entomologists racing to preserve monarchs and the milkweed plants they depend on, as populations of the fragile species continue to plummet.
In the lab, Keene and his team placed caterpillars in groups of four in tiny arenas with varying amounts of milkweed leaves. The less milkweed, the more the wriggling insects squabbled. “Some would just roam off and eat,” said Elizabeth Brown, a biologist in Keene’s lab. But if an insect spotted a morsel of food that was being monopolised by another, she said it would rear up and, with its head, make a lunge onto the body of the other caterpillar.
Sometimes the strikes landed near the recipient’s head. In other cases, it was a bit more like a punch in the gut, Brown said. Either way, the battered caterpillar would usually skulk away in defeat, freeing up the milkweed for the voracious victor. That’s a huge consequence for the loser, Keene said, because at this stage in their life, the larva were basically eating constantly. Newly hatched caterpillars are born famished, and as
they balloon in size, can strip entire plants bare of leaves in a matter of days. The older and larger the caterpillars got, the more their disdain for sharing grew, the researchers found. The greatest number of scuffles occurred among bugs in the final stage before metamorphosis, when the stakes of milkweed munching were probably especially high.
These shrimp leave the safety of water and walk on land. But why?
The parading shrimp of northeastern Thailand have inspired legends, dances and even a statue. (Locals also eat them.) During the rainy season, between late August and early October, tourists crowd the riverbanks with flashlights to watch the inch-long crustaceans climb out of the water and walk on land.
Watcharapong Hongjamrassilp first learned about the parading shrimp, and the 100,000 or more tourists who come each year to see them, about 20 years ago. When he started studying biology, he returned to the topic. “I realised that we know nothing about this,” he said. Hongjamrassilp, a graduate student at UCLA, decided to answer those questions himself. His findings appeared last month in the Journal of Zoology.
Working with wildlife centre staff members, Hongjamrassilp staked out nine sites along a river in Thailand’s Ubon Ratchathani province. They found shrimp parading at two of the sites – a stretch of rapids, and a low dam. The videos they recorded revealed that the shrimp paraded from sundown to sunup. They travelled up to 65 feet upstream. Some individual shrimp stayed out of the water for 10 minutes or more.
“I was so surprised,” Hongjamrassilp said, “because I never thought that a shrimp can walk that long.” Staying in the river’s splash zone may help them keep their gills wet, so they can keep taking in oxygen. He also observed that the shells of the shrimp seem to trap a little water around their gills, like a reverse dive helmet.
Most parading shrimp that Hongjamrassilp captured were young. Observations and lab experiments showed that these shrimp probably leave the water when the flow becomes too strong for them. Larger adult shrimp can handle a stronger current without washing away, so they’re less likely to leave the water. Walking on land is dangerous for the little shrimp, even under cover of darkness. Predators including frogs, snakes and large spiders lurk nearby, Hongjamrassilp said. “Literally, they wait to eat them along the river.”
And the shrimp can survive on land for only so long. If the parading crustaceans lose their way, they may dry out and die before they get back to the river. Leaving the water when the swimming gets tough may have helped these animals spread to new habitats over their evolutionary history, Hongjamrassilp said.
Hawaii’s fresh water leaks to the ocean through underground rivers
There are few things on the island of Hawaii that are more valuable than fresh water. This is not because the island is dry. The trouble is that there is tremendous demand for this water and much of it that does accumulate on the island’s surface disappears before it can be used. New research by marine geophysicists reveals that underground rivers running off the large island’s western coast are a key force behind this vanishing act.
Fresh water is often pumped on the island from aquifers formed from rain at higher elevations where it is easy to access. The drawback is that if too much water gets pumped to meet demand, little remains to travel through rocks to farms and fragile ecosystems that depend upon it. To make matters worse, recent studies of this water have revealed that these aquifers are also heavily leaking somewhere else.
“Everyone assumed that this missing fresh water was seeping out at the coastline or travelling laterally along the island,” said Eric Attias, a postdoctoral researcher at the University of Hawaii, who led the new study published last week in Science Advances. “But I had a hunch that the leak might be subsurface and offshore.”
Attias’ work shows that within the rock of the island below the waves, there are underground rivers of fresh water flowing 2.5 miles out into the ocean. These rivers are flowing through fractured volcanic rock and surrounded by porous rocks that are saturated with salt water. Between all of this salt water and the flowing fresh water are thin layers of rock that appear to be impermeable and thus keeping the two types of water separated. In total, these rivers appear to contain enough fresh water to fill about 1.4 million Olympic swimming pools.
To access this water, Attias proposes a system similar to an offshore oil platform. “The water is already under high pressure, so little pumping would be needed and, unlike an oil pump, there would not be any threat of pollution. If you have a spill, it’s just fresh water,” he said. Attias speculates that the discovery could be relevant to other islands, too. “Given that Reunion, Cape Verde, Maui, the Galápagos and many other islands have similar geology, our finding could well mean that the water challenges faced by islanders all over the world might soon become a lot less challenging,” he said
Burning fossil fuels helped drive Earth’s most massive extinction
Paleontologists call it the Permian-Triassic mass extinction, but it has another name: the Great Dying. It happened about 252 million years ago, and 96 per cent of all life in the oceans and, perhaps, roughly 70 per cent of all land life vanished forever. The smoking gun was ancient volcanism in what is today Siberia, where volcanoes disgorged enough magma and lava over about 1 million years to cover an amount of land equivalent to a third or even half the surface area of the United States.
But volcanism on its own didn’t cause the extinction. The Great Dying was fueled, two separate teams of scientists report in two recent papers, by extensive oil and coal deposits that the Siberian magma blazed through, leading to combustion that released greenhouse gases such as carbon dioxide and methane.
“There was lots of oil, coal and carbonates formed before the extinction underground near the Siberian volcanism,” said Kunio Kaiho, a geochemist at Tohoku University in Sendai, Japan, and the lead author of one of the studies, published in November in Geology, which presented evidence for the burning of ancient fossil fuels by magma. “We discovered two volcanic combustion events coinciding with the end-Permian land extinction and marine extinction.”
The findings solidify the Great Dying as one of the best examples of what a changing climate can do to life on our planet.
Kaiho and his team retrieved samples from rock deposits in south China and northern Italy that formed around the time of the extinction, and they detected spikes of a molecule called coronene. That substance, Kaiho said, was produced only when fossil fuels combusted at extremely high temperatures – such as those you might find in magma. The team’s findings are backed up by a Nature Geoscience study published in October that presents chemical evidence for the acidification of the oceans after the fossil fuel combustion and greenhouse gas release.
As the planet warmed, the oceans absorbed more and more carbon dioxide. This caused waters to acidify to the point that organisms such as corals would have dissolved, said Hana Jurikova, a biogeochemist at the University of St Andrews in Scotland who led the study. While you may be tempted to draw an analogy between the Great Dying and today’s warming climate, there are significant differences. For one, the greenhouse gases emitted during the Permian-Triassic events were far greater than anything humans have produced.