I don't know squat about deer memory. But this thread and its talk about age and memory got me to thinking about something I learned a long time ago.

Up to a certain age, people don’t realize the idea of permanence. Here’s how it manifests. Take a very young child and tell him you are going to hide a toy. Right in front of him, take the toy and put in under a pillow on the couch. Then, while the child watches, take the (same) toy from under the pillow and hide it under a different pillow. The child will search under the first pillow first, even though they saw you take the toy from there and put it under the second pillow.

I can’t remember the cutoff age for this, but I think it is either 6 months old or 2 years old.