Felines surrendered by their owners are more stressed, fall ill more easily and are therefore euthanized more often than their stray counterparts at the shelter, according to new research by Kathryn Dybdall at the University of Nebraska in Omaha, US.

Dybdall studied 86 shelter cats and discovered that owner-surrendered cats were more likely to hide at the back of their kennel with their heads down and eyes wide, rather than resting comfortably on their sides as strays were more apt to do. Additionally, the records of 260 cats that developed an upper respiratory infection at the shelter revealed that surrendered cats become ill faster.

And sick, stressed-out cats were less likely to be deemed adoptable and were more likely to be put to sleep as a result.

Dybdall presented her research on Tuesday at the Animal Behavior Society meeting in Snowbird, Utah.

Biologist Rebecca Fox at the University of California in Davis, US, rated the personalities of about 20 cockatiels in an aviary, using 45 adjectives, including “gentle”, “bold”, “agreeable”, “feisty” and “selfish”.

When the birds were mixed, these different personalities sized each other up and began courting. Both male and female cockatiels take an active role in the process.

By measuring how much time each bird spent near each of its peers – a good proxy for preference – Fox compared the personalities of the birds with those of their potential paramours. Instead of hunting for a mate they have a lot in common with, the cockatiels sought out their opposites.

“This is an area we just don’t know a lot about,” says behavioural ecologist Denis Réale at the University of Quebec at Montreal, who was not involved in the study.

It would be interesting to see personality included with many of the well-studied traits that are important in mate choice, such as courtship display, colouring and song, he adds.

Fox’s research was presented on Monday at the Animal Behavior Society meeting in Snowbird, Utah.

One study involved killer whales at Marineland in Niagara Falls in Ontario, Canada. An inventive male devised a brand new way to catch birds, and passed the strategy on to his tank-mates. The 4-year-old orca lures gulls into his tank by spitting regurgitated fish onto the water’s surface. He waits below for a gull to grab the fish, then lunges at it with open jaws. “They are in a way setting a trap,” says animal behaviourist Michael Noonan of Canisius College in Buffalo, New York, who made the discovery, “They catch three or four gulls this way some days.”

“The orca lures gulls into his tank by spitting regurgitated fish into the water. He waits for a bird to grab the fish and then lunges”

Noonan had never seen the behaviour before, despite three years of observations for separate experiments. But a few months after the enterprising male started doing it, Noonan spied the whale’s younger half-brother doing the same thing. Soon the brothers’ mothers were enjoying feathered snacks, as were a 6-month-old calf and an older male. Noonan presented the research this month at the US Animal Behavior Society meeting in Snowbird, Utah.

Wild dolphins off the west coast of Australia were the first marine mammals in which cultural learning was observed. They apparently learn from group-mates how to use sponges to protect their snouts while scavenging (żěè¶ĚĘÓƵ, 11 June, p 12). But the evidence from killer whales is much more conclusive because the process was observed from start to finish.

Some researchers have suggested that many purported examples of cultural transmission can instead be explained by individuals discovering the skill on their own rather than following another’s lead. But because the gull-baiting behaviour is so unusual, “it would be hard to argue that it is individual learning”, says ethologist Janet Mann of Georgetown University in Washington DC, one of the authors of the dolphin sponging study. Behavioural scientist Andrew Whiten of the University of St Andrews in the UK agrees, “This is a particularly clear set of observations.”

Whiten and his colleagues have meanwhile shown in a separate study that when chimpanzees learn a skill from their peers, they tend to stick with that method even if it isn’t the most effective. Whiten’s team taught two female chimps how to get food from a complicated feeder using a stick to move a barrier. One chimp learned to lift the barrier while the other was taught an apparently more efficient poking method. The chimps’ group-mates were then allowed to watch their respective experts at work.

The chimps followed the lead of their own expert chimp – the poker’s group preferred to poke and the lifter’s group lifted (Nature, DOI: 10.1038/nature04047).

And even when some lifters learned to poke, the majority reverted to the group’s original lifting strategy.

GETTING THE MESSAGE

Chimpanzees appear to be capable of communicating using sounds that refer to specific objects, according to a study of sounds made in response to different foods. It is the first time this ability has been demonstrated in chimps.

Primatologist Katie Slocombe of the University of St Andrews, UK, recorded the grunts made by chimps at nearby Edinburgh Zoo as they collected food at two feeders. One dispensed bread, considered a high-quality treat, and the other doled out apples, a much less sought-after snack.

Slocombe then played back the recordings and watched the reactions of a 6-year-old male named Liberius. The results were striking. After hearing a bread grunt, Liberius spent far more time searching around the bread feeder, while an apple grunt would send him hunting under the apple feeder. Slocombe presented the work at the US Animal Behavior Society meeting in Snowbird, Utah, this month.

This is the first convincing evidence of “referential communication” in chimps, says primatologist Amy Pollick of Emory University in Atlanta, Georgia. Earlier research with a close cousin of the chimpanzee – a male pygmy chimpanzee, or bonobo, named Kanzi – showed that he made specific sounds for four different things: bananas, grapes, juice and yes. But the researchers did not test if the sounds conveyed any meaning to other bonobos, and the same experiments have never been done in chimpanzees.

Liberius, on the other hand, was able to take cues from apple and bread grunts made by at least three different chimpanzees.

Slocombe plans to expand her study to include chimps at the Leipzig Zoo in Germany and hopes to confirm whether the grunts refer to specific foods or to their relative quality.

Betsy Mason

Chimpanzees have behavioural traditions that vary between groups in the wild but, so far, direct experimental evidence of how these traditions are spread and maintained has been lacking. So Andrew Whiten of St Andrews University, UK, led a team that sought to show a chimpanzee proclivity for cultural conformity in a population of captive animals.

Whiten demonstrated cultural learning in chimps by introducing two different tool-use techniques to two separate groups of captive chimps at the Yerkes National Primate Research Center in Atlanta, Georgia, US.

The team taught two female chimps how to get food out of a complicated apparatus using a stick. One learned to poke a barrier with the stick, and the other to lift the barrier with the stick. Then the chimps’ groups got to watch the new experts use their skills. When the rest of the groups were allowed to try their own hand at freeing the food, they followed the lead of their own expert chimp – the poker’s group preferred to poke and the lifter’s group tended to lift.

Although the poke method was more effective – as shown by the fact that some lifters independently learned to poke – the majority of lifters-turned-pokers nevertheless reverted to their group’s original lifting strategy, conforming socially.

Journal reference: Nature (online publication)

Australia’s giant carnivorous kangaroos, seven-metre-long lizards, marsupial lions and enormous flightless birds all died off between 45,000 and 55,000 years ago. Most scientists agree that people arrived in Australia somewhere between 50,000 and 55,000 years ago.

This suspicious coincidence of timing has led some to conclude that overzealous hunting by humans caused the extinctions. But others claim that we could not have cleared the entire continent of so many species in such a short time.

Geologist Gifford Miller of the University of Colorado at Boulder and an international team analysed hundreds of eggshell fragments of an extinct flightless bird called Genyornis, dating from 130,000 to 50,000 years ago. They compared them with the eggshells of emus, dating from 130,000 years ago to the present day.

Last grass

Carbon isotopes in the eggshells reveal what the birds were eating when they laid the eggs. The team found that emus consumed either grasses, shrubs and trees, or a mixture, until 50,000 years ago, when grasses all but disappeared from their diet.

But Genyornis ate a narrow diet that always included grass – and then died out, Miller told an International Union for Quaternary Research meeting in Reno, Nevada, last week.

Climate change is too slow to have killed off most of the grasses, argues Miller. The best explanation is that people began burning the landscape.

Bert Roberts of the University of Wollongong in New South Wales, Australia, says that giant marsupials became extinct around the same time, and the reason could be that burning affected the entire ecosystem.

Animal behaviourists usually expect males to compete with each other for mates, with females preferring the larger, more aggressive or better-endowed winners. But this is not so for certain salmon and quail.

Some male coho salmon, known as jacks, stop growing earlier in their lives and remain smaller than their larger cousins, known as hooknoses, says behavioural ecologist Jason Watters of the University of California, Davis. When the salmon migrate from the Pacific Ocean to inland rivers to spawn, hooknoses dominate jacks and compete aggressively with each other to mate with females.

But contrary to what biologists had assumed, the females prefer to mate with jacks if they get the chance. “That shakes up everybody’s point of view a little,” says evolutionary biologist Steve Shuster of Northern Arizona University in Flagstaff.

Watters tracked the mating experiences of 15 female coho salmon in a Californian coastal stream. The females work harder on their nests and spawn longer with jacks than with hooknoses, Watters told an Animal Behavior Society meeting in Boise, Idaho, last week.

The female salmon may prefer jacks because their earlier maturation could be a sign of increased quality and success. Other males have to spend an extra year growing into hooknoses before they can mate.

The females may also prefer to avoid the physical abuse of mating with aggressive males. “Hooknoses were the only ones that chased or bit females,” Watters says. “Jacks pull up beside females and wiggle. They don’t touch them, they just advertise.”

Exceptionally aggressive

Female Japanese quail have similarly contrary tastes, animal behaviourist Alex Ophir of McMaster University in Ontario, Canada, told the meeting. Male Japanese quail are exceptionally aggressive towards each other, and this abuse often spills over into courtship and mating.

To see how the females feel about this, Ophir let female quail watch a fight between two males, and then separated the combatants and placed them on opposite sides of a female’s cage to see which one she would gravitate towards.

Virgin females tended to prefer the dominant males that had won the fight, but females with a little sexual experience were more likely to choose the loser. “People just expect the dominant guy to win,” says Ophir. “But females learn through personal experience that these males can be hurtful.”

Shuster thinks the idea that females may not always prefer dominant males will catch on. “Conventional wisdom is that males should always try to be these macho aggressive guys,” he says. “But this shows there is also a place for the nicer guys.”