What exactly is 'fixed action pattern?'

Question

I mean, the definition given in my textbook is this: A fixed action pattern is a highly sterotyped sequence of behaviors that, once begun, is usually carried out to completion.

I really want to understand the concept, so I was wondering if you could further explain this topic.

Answer 1

Absolutely.  A fixed action pattern (hereafter, FAP) is a type of instinct, which means that an animal is born with it; they don't have to learn FAPs.  An FAP is triggered by some outside event and causes the animal to go through the exact same routine everytime.  This routine usually has some purpose, but even if it becomes impossible to reach that purpose, the animal will still carry on the motions of the FAP.

An example: greylag geese lay eggs in nests.  If a mother goose spots an egg that has rolled out of the nest, she will begin a series of movements with her beak intended to push the egg back into the nest.  Here's the thing, if you remove the egg from her before she manages to return it to the nest, she will STILL continue the beak motions, pushing a now-imaginary egg.

Furthermore, the FAP can be triggered by any egg-shaped object placed in the vicinity of the nest.  Again, the goose will continue the motions, even past the point where she should have realized that the object was not really an egg.

Another example:  male stickleback fish recognize other males by their red underbellies.  If a male sees another male entering his territory, he will mount an aggressive response.  The male will actually begin an aggressive FAP when he encounters ANY object with a red underside, even if that object only remotely resembles another fish.  The aggressive behavior is highly ritualized and, like the goose's egg-rolling maneuvers, is carried to completion each time.

I hope that helps.  Good luck!