The party continues! Today you get a double-dose of Monday Pets. Here's one from the archives. Later today, you can expect a new one.

This post was chosen as an Editor's Selection for ResearchBlogging.orgResearchBlogging.orgI often write about animals that the average person does not interact with all that much on a day-to-day basis. Today, I introduce something I like to call "Monday Pets". The focus of Monday Pets will be the animals that we intentionally bring into our lives as pets. Sometimes those animals are even considered part of the family. Ever notice some weird behavior that you notice your pets doing? Want to know more about it? Email me. Always wanted to know if your pet goldfish can count? Ask me. If there's research out there, I'll do my best to find it. If there's not, I'll make something up.

I hope that reading about the cognitive lives of these animals make your Mondays just a little bit happier. Not that you should be reading blogs at work! know who you are.

So, without further ado. Consider the dog.

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Figure 1: The family dog, Argo.

You might be walking the dog or taking the dog to the dog park, and your beloved Border Terrier (or whatever) meets another dog. They carefully inspect each other. They sniff each other's butts, because that's what dogs do. And then the fight begins.

But is it really a fight? Is it just rough play? How can you tell the difference between play and true aggression? When is it okay, and when should you pull your poor dog out of there? And - forgetting about you for a moment - how does your DOG know whether or not he or she is engaged in play or in a brawl? Seems like pretty important information to know.

Actions called play signals have been observed in many species which appear to engage in play. It is generally accepted that these behaviors serve as signals to communicate the initiation ("I want to play") of play. One behavior that is used a LOT by dogs (and their evolutionary cousins, wolves and coyotes) is the bow.

Dr. Marc Bekoff (who blogs at Psychology Today) from the University of Colorado, Boulder wondered if the bow was used as a play signal, and how it functioned. He hypothesized that the bow might serve an additional function beyond initiation; it might support the maintenance ("I still want to play") of ongoing social play.

Figure 2: The bow, more or less (it is surprisingly hard to get a dog to pose for you).

Argo is crouching on his forelimbs, the hindlimbs remain fully extended, and he wags his tail and barks. Typically the head is lower than Argo's head is in a formal bow. The bow is a stable posture from which the dog can move in multiple directions. It also allows for the stretching of the leg muscles before and during play, and places the dog's head lower than the head of the other dog, in a non-threatening position.

The types of actions used in play are also used in other contexts, such as during aggressive, predatory, or sexual behaviors. Dogs engaged in play often bite and shake their heads back and forth, like Argo does to his toy squirrels. (Dude! I've bought him new squirrels like EVERY week!) Sometimes they mount the animal from behind, as they might in a sexual encounter.

At first glance, the use of bows in play may appear random. They do not occur every N actions, or every N seconds. But it turns out that the bow has a very important function: the bow is regularly used before and/or after other actions that could be misinterpreted by the other dog, and could disrupt the social play. For example, bows were used either immediately before or after bites during play 74% of the time in infant and adult domesticated dogs, 79% in infant wolves, and 92% in infant coyotes.

In addition to communicating "I want to play," bows performed during the play sequence itself seem to mean "I still want to play despite what I am going to do or just did." It's like what your Mom used to tell you - it's always fun until someone gets hurt. The dogs seem to have internalized that rule, and continually make it clear that any damage done was all done in good fun. No hard feelings. (What I learn from this is: if my brother had simply bowed to me when we were kids, there wouldn't have been any fights in the first place. Right?)

Why do the coyotes seem to need to use the bow so much more often than the dogs and wolves? Bekoff thinks that social play in coyotes - different from dogs and wolves - happens only after dominance relationships have been firmly established, and it is clear which individual is dominant and which is submissive in a given pair. Coyotes, therefore, need to make a greater attempt to maintain the play atmosphere, and also need to communicate the intention to play more clearly before the play begins in the first place.

These findings suggest that the bow is not used to stretch the muscles, or because it is a good position from which to increase the range of movement. Instead, it seems to serve a particular social communicative function. Social play depends on the mutual sharing of the play mood between both participants; when there is a greater chance of play-fighting escalating into real fighting (as with infant coyotes, especially), the bow is used more often to maintain playtime.

In a sense, the dogs' use of the bow functions as social punctuation - behaviors that clarify the meaning of subsequent or previous behaviors.

Bekoff, M. (1995). Play Signals as Punctuation: the Structure of Social Play in Canids. Behaviour, 132 (5), 419-429. DOI: 10.1163/156853995X00649