The disappearance of Quolls, small carnivorous marsupials, in many parts of northern Australia has been blamed at least in part on cats, foxes and dogs.
But Robbie Wilson, a biologist at the University of Queensland, believes there could be other not so obvious reasons.
Quolls would be expected to run as fast as they can when trying to escape but this ignores the fact that there are huge costs for fleeing at top speed.
“It’s likely that an animal running at top speed will not be able to turn or manoeuver as quickly,” Wilson says.
Wilson and colleagues captured 66 quolls on Groote Eylandt, an island off Australia’s northeastern coast, as test subjects.
As the team expected, quolls crashed more frequently when they approached a corner at high speed and when running around tighter corners.
When the team analysed footage of the running animals, they found that average turning speed decreased as the magnitude of the turn angle increased. When negotiating 135 deg turns, quolls decreased their running speeds to around one-third of their straight line speeds.
“We expected that larger animals would find it harder to get around tighter corners,” says Wilson.
But the team found that foot length was the strongest predictor of manoeuvrability.
“It appears that it’s the foot size of the animals that constrains their ability to negotiate a corner successfully,” Wilson says. “The larger the foot size, the greater their grip.”
The team concludes that an animal’s running speed constrains its ability to make quick, rapid turns.
“This means that an animal should modify its speed when running away from a predator, optimising its combination of speed and manoeuvrability to maximise its chances of success,” says Wilson.
Quolls most likely to survive attacks by introduced predators are those who master the optimal compromise between speed and agility.
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