[LINK] Two animal intelligence notes

[rfmcdonald]

Older elephants, it turns out, have accumulated the experience necessary to outsmart lions.

In natural history films, lionesses are usually portrayed as the hunters of the pride, while male lions mope around under shady trees. But males are no layabouts – they’re effective killers in their own right, particularly when they target larger prey like elephants and buffalo. Aside from humans, lions are the only predators powerful enough to kill an elephant. The males, being 50% heavier than the females, are especially suited to the task. It typically takes seven lionesses to kill an elephant, but just two males could do the same.

Even a single male can overpower a young elephant. Between 1994 and 1997, Dereck Joubert found that the lions of Botswana’s Chobe National Park were getting better and better at hunting elephants. He wrote: “In one notable case, a single male lion ran at nearly full speed into the side of a 6-year-old male calf with sufficient force to collapse the elephant on its side.”

Male lions clearly pose a great threat, and older elephants know it. Karen McComb from the University of Sussex has found that older matriarchs – the females who lead elephant herds – are more aware of the threat posed by male lions. If they hear recordings of male roars, they’re more likely to usher their herd into a defensive formation. Their experience and leadership could save their followers’ lives. “Family units led by older matriarchs are going to be in a position to make better decisions about predatory threats, which is likely to enhance the fitness of individuals within the group,” says McComb.

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McComb studied 39 groups of elephants at Amboseli National Park, including hundreds of animals who are all individually known. Approaching the herds in vehicles, she played the recorded roars of lions – either one or three, and either all males or all females. She filmed their responses (and asked an independent colleague to confirm her interpretations).

McComb’s videos showed that, unsurprisingly, the elephants responded more strongly to the roars of three lions than the sound of a singleton. The matriarch was more likely to raise her head and ears, and the others were more likely to quickly draw towards her in a tight huddle. All of the herds reacted in the same way, but only those with older leaders (60 years or more) twigged to the greater danger posed by the fake male roars. They were more likely to draw together, they did so more quickly, and they were even more likely to aggressively mob the lions.

The older the matriarchs were, the more sensitive they and their group were to the sound of male lions. They didn’t react in the same way to lionesses, so it wasn’t that they were becoming generally more panicky in their dotage.. Instead, they had become better at discerning the most dangerous roars.

And Israeli ravens use vultures to crack open the eggs they can't break themselves.

Ostriches lay their eggs in a single nest. The dominant female goes first, laying around 15 to 20. Her subordinates follow with 3 to 4 of their own. However, the top pair of ostriches can only incubate around a dozen eggs effectively, and they roll the rest away from the nest. This creates a ring of nutritious treats for any bird skilful enough to break into the eggs.

The Egyptian vulture does so with a special technique – it uses a tool, and is one of the few birds to do so. It picks up rounded stones in its beak and uses them to hammer the egg shells until they crack. Even ostrich eggs eventually give way. But the vultures don’t always get to enjoy the fruits of their labours. Yosef found that on at least three occasions, a pair of ravens, watching nearby but hidden behind a bush, quickly flew in and drove the vultures away.

Yosef thinks that the ravens he saw are the same individuals – they behaved in virtually the same way from one robbery to the next. Their behaviour suggests a keen intelligence. Yosef writes, “Most apparent in the ravens is their innovative thinking and ability to predict the actions of the potential host or prey.”

He thinks that the ravens recognise that ostrich eggs are valuable food but that they cannot break through the shell. They seem to understand the vultures’ technique. They know they have to hide and “be patient”, waiting till the vulture has broken the egg before showing themselves. They know that by hunting together, they can effectively exploit a source of food that they would never be able to reach.

This is possibly overstating the case, at least without putting the birds through any experiments. Animal intelligence is a notoriously tricky thing to study and many previous claims have been overplayed. For example, are they biding their time for the vultures to finish, or are they simply attracted to the glisten of exposed egg whites?

Nonetheless, it’s hardly far-fetched to claim that the ravens are acting intelligently. They and their relatives – crows, rooks, jays and bowerbirds – have demonstrated impressive feats of behaviour time and again. In the same nature reserve, Yosef has found that brown-necked ravens cooperate to hunt a local lizard called a mastigure. When the lizard is away from its burrow, a pair of ravens circles in and blocks the entrance. With its escape route cut off, the lizard is attacked by the other ravens. Only when the lizard is dead do the burrow-blockers join the feast.