The Today Show (several weeks ago) briefly touched on a study about how animals do not have memories (and they don't have future thoughts). As far as I can tell, from the brief reporting, the study was talking about memory in the sense of "thinking about the past".
Savanna Guthrie mentioned how this lack of memory didn't make sense to her because the Today Show puppy remembers tricks he had learned the day before. Here is the deal: memories and knowledge are generally thought of as two different things. Wrangler (the puppy) isn't lying in his crate remembering yesterday's training session. When he is asked the do the trick from the day before he also isn't having thoughts (memories) of yesterday's training session. He does, however, remember the trick- but he experiences it as knowledge, not as a memory. For example as you read this you know how to read, but you aren't remembering when you were 5 and learned how to read.
Matt Lauer mentioned that his childhood dog always met him at the bus stop. He wondered how the dog could know to come at that time without a memory. The dog must have been sensitive to his own biological clock and environmental reminders (such as daylight or the mailman's schedule) to know when to go the the bus stop. Of course the dog did not say to himself at 10 AM, "Oh I must go the the bus stop to meet Matt at 3 PM.
"My experience from asking animals about the past is that they never think about it unless something from the present moment is reminding them to recall their knowledge and experiences from the past. I do believe that animals, including dogs, absolutely have memories when they are triggered (by in the moment circumstances) but I do agree with the study that dogs don't have memories in the sense of thinking about the past on their own.I previously wrote about donkeys and their excellent memories. Reading that you can take the word "memory" and change it to "ability to retain knowledge", if you want to have a new way of thinking about what I wrote above.