Can Dogs Tell Time

Welcome Back to Science Sunday

"C'mon get off the couch it's time for my supper." We have all seen or heard of stories about dogs knowing when the school bus is due, or when it's time for their daily walk, but obviously they do not understand clock time in the same way that we do. So how do they understand the passage of time? There has been surprisingly little research into this fascinating topic. 
Without clocks even we do not have a very good sense of time. If we are engaged in some activity we are interested in, time seems to fly by, while on the other hand if we are stuck with some mundane task we abhor, it seems to take forever. But that forever is related to a clock. If we didn't have a clock we would not have any idea how long each of these events actually took. So how can dogs know when they spend most of their time sleeping?  
I think we need to distinguish between two aspects of time, time of day and duration of events.
Knowing when the school bus is due requires dogs to know the time of day. There are several theories about how they do this. 
 Dogs, like most mammals, have a circadian rhythm, an internal sense that tells them when to sleep or when to be active. Perhaps it’s their bodies, not their minds, that can detect roughly what time it is. So if in the mid-afternoon your dog is used to getting her food, her body gets hungry around this time each day. 
Another theory expands on dog's amazing ability to pick up on external cues and associate them with another event. For example maybe you start getting dinner ready just before the school bus arrives or another bus passes every day just before the kids get home.
There have been studies on how dogs perceive duration of events, specifically how they greet you when you have been gone for a period of time. 
We have all seen that they don't get too excited when we come back from getting the mail but on the other hand if we have been gone for more than two hours we get quite a happy greeting. One researcher attributes this to their well know sense of smell. The longer you have been gone, the more your scent in the house diminishes. They tested this by leaving the owners' scent around the house and evaluate the return greeting after various lengths of time. The dogs did not respond the same as long as the scent was present.
​At any rate there does not seem any need to purchase a Rolex for Fido just yet.

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References:	​How do dogs perceive time? Jane McGrath, howstuffworks.com
	Do Dogs Understand Time? Megan Sullivan, petmd.com 21 April 2017
	​What's Up With That: Why Does Your Dog Seem to Know What Time It Is? Adam Mann, Wired