“It is an awe-inspiring experience to be faced with a 3-metre-long, 500 kilogram predator, the size of a racehorse, as it launches itself out of the water and slides on its belly for a couple of seconds, coming to a halt barely a metre away from where I stood, without any barrier between me and it.”
That was how Erich Fitzgerald met Sabine the leopard seal.
Leopard seals are like the lions of the Antarctic. They are huge, powerful predators, known for their brutal killing strategy. They bite penguins and seal pups with their big canines, and thrash them onto the surface of the water to flay and dismember their prey.
But Fitzgerald, David Hocking and Alistair Evans have shown that these predators can take smaller prey in a very different way. They suck krill and small fish into their mouths and sieve them in the manner of whales, by passing their mouthfuls of water through tightly interlocking teeth. It’s astonishing behaviour that allows them to dine from the top and bottom of the food chain. As Fitzgerald told me: “This is equivalent to a lion hunting down zebras, but also regularly feasting on ants or termites.
I’ve written about the story for Nature News. Head over there for the full details.
The cheetah’s spots look like the work of a skilled artist, who has delicately dabbed dots of ink upon the animal’s coat. By contrast, the king cheetah – a rare breed from southern Africa – looks like the same artist had a bad day and knocked the whole ink pot over. With thick stripes running down its back, and disorderly blotches over the rest of its body, the king cheetah looks so unusual that it was originally considered a separate species. Its true nature as a mutant breed was finally confirmed in 1981 when two captive spotted females each gave birth to a king.
Two teams of scientists, led by Greg Barsh from the HudsonAlpha Institute for Biotechnology and Stanford University, and Stephen O’Brien from the Frederick National Laboratory for Cancer Research have discovered the gene behind the king cheetah’s ink-stains. And it’s the same gene that turns a mackerel-striped tabby cat into a blotched “classic” one.
Back in 2010, Eduardo Eizirik, one of O’Brien’s team, found a small region of DNA that seemed to control the different markings in mackerel and blotched tabbies. But, we only have a rough draft of the cat genome, they couldn’t identify any specific genes within the area. The study caught the attention of Barsh, who had long been interested in understanding how cats get their patterns, from tiger stripes to leopard rosettes. The two teams started working together.
Earlier this year, I wrote about a new study showing that polar bears split off from brown bears around 600,000 years ago – already making them four times older than previously thought. Now, a new study pushes the date of that split back even further, to between 4 and 5 million years ago. The exact date is probably going to shift again in the future, and if anything, it’s the least interesting bit of the new paper.
Webb Miller, Stephan Schuster and Charlotte Lindqvist have taken a whirlwind look at the history of the polar bear. For a start, they sequenced its genome – that detail would be the centrepiece of other papers, but gets mentioned halfway through this one. They started looking at the genetic changes that have made polar bears lords of the Arctic, and they reconstructed the bears’ population history across the many climate upheavals it must have lived through. Finally, they found evidence that polar bears carry a lot of brown bear DNA in their genome (and vice versa) – a sure sign that the two species repeatedly bred with each other after diverging, in much the same way that our ancestors had sex with Neanderthals and other ancient humans.
I’ve written about the study for The Scientist. Head over there for the full story.
Photo by Alan Wilson
It looked like we had the polar bear’s origin story nailed down. Genetic studies suggested that between 111 and 166 thousand years ago, a group of brown bears, possibly from Ireland, split off from their kin. In a blink of geological time, they adapted to the cold of the Arctic, and became the polar bears we know and worry about. Fossils supported this story: the oldest polar bear bone is between 110 and 130 thousand years old.
But according to Frank Hailer at the Biodiversity and Climate Research Centre in Frankfurt, this story is wrong in two important ways. First, the polar bear aren’t just a branch of the brown bear family tree. They’re a separate lineage in their own right. Second, they around four times older than anyone had thought, arising around 600 thousand years ago.
If this new vision is right, the bear’s journey to polar dominance wasn’t a speedy sprint, but a more leisurely stroll. As a species, polar bears have seen many ice ages. Rather than being a symbol of extraordinarily fast evolution, they’ve actually had plenty of time to adapt to life in the freezer.
It’s Easter. For some of people, this means they can take up all the vices they gave up for Lent, and binge on chocolate till they feel sick. For the hyenas of northern Ethiopia, it means it’s time to stop hunting donkeys.
Spotted hyenas are unfussy eaters and incredible opportunists. They can feast on rotting meat, anthrax-infected corpses, garbage and dung. They digest their food so completely that their droppings tend to consist of hair, hooves, and white powder made from broken-down bones. Unsurprisingly, they do rather well near urban environments, where humans provide them with a bonanza of scraps, leftovers, and livestock. The hyenas of northern Ethiopia get almost all of their food by scavenging on such sources.
Local humans tolerate the hyenas, which are affectionately known as “municipal workers”. The animals clean the waste from butchers, households, and even the local veterinary college. They’re seen and heard almost every night, and they almost never attack humans. Instead, they have come to depend on the Ethiopians for their food.
But that changes in the run-up to Easter. For 55 days, the local Orthodox Christians go through a period of fasting. Meat goes off the menu, and few animals are slaughtered. This lack of demand creates supply problems for the hyenas. Gidey Yirga from Mekelle University in Ethiopia has found that they sate their hunger by hunting instead.
Imagine a world without sweetness, where you couldn’t taste the sugary rapture of cakes, ice cream or candy. This is what it’s like to be a cat. Our feline friends carry broken versions of the genes that build sugar detectors on the tongue. As such, they’re completely oblivious to the taste of sweet things.
So are Asian otters. And spotted hyenas. Sea lions and dolphins too. In fact, Peihua Jiang from the University of Zurich has found that a wide variety of meat-eating animals can’t taste sugars. The genomes of these carnivores are wastelands of broken taste genes.
A cat-like animal explodes from the long grass and leaps onto an antelope. Its huge bulk drags the target to the ground and its muscled forelegs pin it down. With two long sabre-shaped canine teeth, it stabs its victim in the throat, just the once, severing its blood vessels and windpipe. Death comes quickly.
The hunter could be Smilodon, a sabre-toothed cat that lived throughout North and South America, around one or two million years ago.
Or, it could be a nimravid, another group of hunters that looked like cats, but belonged to a separate, closely-related family. Some of them had sabre-teeth too, and they wielded these weapons between 42 and 7 million years ago, well before Smilodon or its relatives did.
Or, it could be Barbourofelis, a member of yet another group of sabre-toothed not-quite-cats, which lived between 16 and 9 million years ago. Its long sabres slipped into long grooves in its lower jaw, which looked like it was about to melt away.
It’s been a week since the last full moon on 15th July. During this time, the odds of being attacked by a lion are highest than at any other point in the month, which is why I’ve been walking around the neighbourhood with two guard bears and a platoon of ninjas. The fact that I live in a leafy suburb of London is inconsequential. You can never be too careful. Constant vigilance.
Of course, lion attacks are more of a problem in other parts of the world. In Tanzania, lions have attacked more than a thousand people between 1988 and 2009, and eaten around two-thirds of them. Now Craig Packer from the University of Minnesota has shown that the frequency of these attacks is tied into lunar cycles.
One animal’s cure can be another animal’s poison. Take aspirin – it’s one of the most popular drugs on the market and we readily use it as a painkiller. But cats are extremely sensitive to aspirin, and even a single extra-strength pill can trigger a fatal overdose. Vets will sometimes prescribe aspirin to cats but only under very controlled doses.
The problem is that cats can’t break down the drug effectively. They take a long time to clear it from their bodies, so it’s easy for them to build up harmful concentrations. This defect is unusual – humans clearly don’t suffer from it, and neither do dogs. All cats, however, seem to share the same problem, from house tabbies to African lions.
Now, Binu Shrestha from the Tufts University School of Medicine has found that cats may have developed their strange sensitivity because of their lifestyle as specialist hunters. Their penchant for meat could have ultimately turned aspirin into their kryptonite.