Disparate defences


I think that I am on safe ground to suggest that prey prefer not to be eaten.

Yesterday I watched two prey animals which had adopted rather different methods of defending against predators. They were a mountain goat and a ruffed grouse.

The mountain goat is a large animal, but not so large that it cannot be overcome by a cougar. Despite being conspicuous, the goat makes no attempt to prevent being seen; rather it attempts to prevent access. The goat’s defence against being eaten is to go where the cougar is loath to tread: cliff faces. Consequently, mountain goats have developed a great agility to navigate nearly vertical surfaces.

The ruffed grouse faces a different problem in avoiding predators. It is small enough that it can be eaten by both land predators, such as coyotes, and aerial predators, such as eagles and hawks. So, it tries to be inconspicuous by hiding in the undergrowth and has developed camouflage and stealth. Its plumage resembles the dappled pattern of light on the forest floor and by moving slowly, it looks like a shifting pattern of sun flecks through leaves. The problem is that the grouse maintains the same defence strategy even when the background isn’t dappled, such as when crossing snow or gravel.

A mountain goat is safely perched on a narrow ledge half way up a 300 metre cliff.

Perhaps the funniest (non) defence by the normally camouflaged grouse is when it slowly crosses a plain surface. Now conspicuous, it would be better for it to flush.


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7 Responses to Disparate defences

  1. Helen says:

    Great photos, and mysteries solved! I always wondered why grouse are so reluctant to hurry–I guess they have limited ability to change to suit the circumstances!

    • Alistair says:

      Helen, apparently the stealth strategy serves the species well, but not necessarily the individual. I have seen a grouse flush when chased by a dog, but its normal tempo is marked largo.

  2. H. Borland says:

    Looks most proud!

  3. Lorna Surina says:

    That is such a beautiful picture Alistair. The colours surrounding that big goat. Just love it.

  4. Mr. Homburg says:

    Poetry is a grouse on the plain. The flush is the exuberance which is irrespective of any ground.

  5. Karen Pidcock says:

    Delightful marching grouse!

  6. Christine says:

    Succinctly portrayed! And then there are the American coots, protecting themselves against two eagles swooping down on a raft of approximately 30 individuals on Green Lake open water a week ago. Tightly bunched, all flapping their wings in unison, they were a true “commotion”!

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