describes (about)

"About" is absolutely not need. It's wrong.

"About" is wrong after "describes".

She describes the animals.
She gives a description of the animals.
She talks about the animals.

But..

The ethologists know the behavior she describes about the animals in captivity..

No?

One would use 'in'.

Do you mean:

The ethologists recognise the behaviour (which she describes) as occurring in or among captive animals?

If so, then:

The ethologists know of the behavior she describes in the animals in captivity..

The naturalist described mating behaviour in chimps. My Grandmother blocked her ears.