11 December 2010 by Julienne du Toit

Eagle vs Dassie

If you’re looking for a splendid example of an evolutionary arms race, head for the mountains.

It’s here you’ll find the rock hyrax (also known as the dassie), which is the favoured food of the Verreaux eagle (formerly known as the black eagle).

A nesting eagle pair raising a youngster will typically devour nearly 400 dassies in a year. For millennia they have battled one another, first one winning, then the other.

To bypass the dassie’s vigilance, eagles used to attack like fighter jets, swooping down using the sun’s glare as cover. That worked well until dassies developed a unique lens in their retinas that allowed them to look directly into the sun. They remain the only mammals with such a light-shield.

Thwarted, the eagles have developed a different tactic. You’ll usually see them hunting in pairs now - one eagle distracts the dassies while the other attacks from the rear.

The dassies have simply upped their vigilance, and now usually venture no more than 12 metres from cover. They usually can squeak to safety in the time it takes an eagle to stoop from 150 metres up.

Even as you read this, the eagles are at the evolutionary drawing board, working out another tactic…

Category: Wildlife

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