Are hallucinations common in people with Alzheimer's?

My mom, she 78, insists that she saw a some animal(wild animal) in the backyard yesterday.
So is it cause of Alzheimer
I did found a similar question here
http://www.caring.com/
but still wondering if i can get some more advice.

Hi,

I can imagine that it is very common, because the brain 'pathways' in a person with Alzheimer's become rather garbled (for want of a better word), and therefore memories can become crossed. So, whilst it might not be an hallucination per se, it is a pseudo-hallucnation in that it's a number of different memories being joined into one, and that makes it seem weird. Think of it as a dream, where many different memories are brought together.

Kevin