Dog Behavior Blog

Why Dogs Eat Grass

These summer days, when I take my Standard Poodle Raja for a walk, he always wants to stop and eat grass. Not just any grass. The leaves have to be the right size and shape. Although there are other grasses nearby, he always heads for wheatgrass (Agropyron), with its broad green leaves.

I have read that dogs eat grass because they want to vomit or because they are having digestive troubles.

Raja hates to vomit. He will do anything to keep from vomiting, so that doesn't seem to be the answer, at least as far as he is concerned.

I feed him premium wet food, and he digests it very well, with well-formed stools (I get to sample these on walks, picking them up with my plastic bags). Digestive troubles do not seem to apply to Raja either.

So because the two explanations I have read do not seem to be relevant to Raja, I decided to dig a little bit into the scientific dog literature to see what I could find.

Surprisingly little has been written in scientific journals about why dogs eat grass.

One recent study approached grass eating in dogs with the hypothesis that grass alleviates digestive distress (McKenzie et al. 2010. Reduction in grass eating behaviours in the domestic dog, Canis familiaris, in response to mild gastrointestinal disturbance. Applied Animal Behaviour Science 123: 51-55).

In that study, the authors fed dogs a diet that produced loose, watery stools, to mimic a condition of a mild digestive upset. They also fed the dogs a standard diet that produced normal stools, and gave the dogs two types of grasses to eat during each experimental condition.

The results were that the dogs ate more grass when they were fed a standard diet than when they ate the diet that caused the digestive upset. So much for that hypothesis.

Then there's vomiting.

I found a study that looked at whether dogs vomit more when they eat grass (Sueda et al. 2008. Characterisation of plant eating in dogs. Applied Animal Behaviour Science 111: 120-132),

In that study, the authors surveyed 1571 dog owners on the internet and found that 79 percent of the dogs ate grass, and of these, only 9 percent were sick before they ate the grass, and 22 percent vomited after eating the grass.

These results show that the vomiting hypothesis doesn't seem to hold any water either.

So why do dogs eat grass?

Ask yourself that question the next time you eat a luscious salad.

My guess is......because it tastes good.

--Con Slobodchikoff

Puppies Get Socialized By Watching TV

My Standard Poodle Raja has no interest in watching TV. Dogs could be cavorting and barking across the screen, and he could care less. Even closeups of dog faces produce no results. If I try to call his attention to something that I think might interest him, he will sleepily open an eye out of politeness and then promptly go back to sleep on the couch in front of the tube.

I have always assumed that this is because dogs see TV screens differently from us. The typical screen flickers at 50-60 cycles per second (Hertz for the technically-minded), which is adequate for our eye to fuse it into a solid picture (again, for the technically-minded, the flicker-fusion-frequency). Dogs, on the other hand, fuse flickers into solid pictures at around 70-80 cycles per second, far above the flicker of the TV screen. Instead of a solid picture, they must see a whole bunch of flickers.

However, a recent study has found that puppies that are 3 to 5 weeks old can see a TV screen and respond to the objects that they are seeing on the TV (Pluijmakers et al. 2010. Exposure to video images between 3 to 5 weeks of age decreases neophobia in domestic dogs. Applied Animal Behaviour Science 126: 51-58). The study played back both sounds and sights of people, dogs, traffic, and objects such as vacuum cleaners, in an 8 minute video clip that was played to the puppies each day for 2 weeks from the time the puppies were 3 weeks old until they were 5 weeks old.

The study found that puppies who were exposed to different images and objects on the TV screen at that early age were much less fearful of strange situations by the time they were 8 weeks old. This is a critical time for puppies, when they are learning about the world around them, and what they learn during this time stays with them for the rest of their lives.

And fearfulness can affect a dog's lifespan. Another recent study found that fearful dogs had a significantly shorter lifespan than more confident dogs, probably as a result of constant stress (Dreschel, N. A. 2010. The effects of fear and anxiety on health and lifespan in pet dogs. Applied Animal Behaviour Science 125: 157-162).

So why is my Raja so uninterested in watching the TV, if 3 week-old puppies can see what is happening on the screen? The short answer is, I don't know. But a longer answer might be that he probably was never exposed to the TV as a puppy, and never got used to watching. He came to us as an adult rescue dog, and I have no idea what his early background was.

Chances are, by the time he saw a TV screen, it was already too late for him to make any sense out of it.

Sometimes, I think he has a point.

--Con Slobodchikoff

Dreaming of Dogs

I’ve always been a dreamer. I don’t mean that in the idealistic sense of believing deep down that anything is possible, but rather in the literal sense of having lots of dreams each night. They are always vivid, in full color, and I remember several each night. Even though my school French has always been poor, the language would show up in my dreams when I was studying it, though that’s supposed to be the sign of really knowing the language. (I do deserve to dream in Spanish, which I speak reasonably well, and in fact I do dream in that language regularly.)

With dreams showing up each night like free movies designed by me for me, naturally I dream about dogs a lot. Just in the last week or so, I’ve had three such dreams.

The first dream was about a dog trying to block the waves from ruining a little kid’s sandcastle before the judging of a contest.  The dog ran in between the sand castle and a big wave and blocked the full force of it from destroying the castle. The child who had built this particular castle had been bullied and teased by some other competitors, but ending up winning an award from the judges, thanks in part to the dog’s quick move. In my dream, I was very excited about what the dog’s actions might mean about dog’s cognitive abilities since he acted to prevent a future problem and chose the child who most needed the help.

In the second dream, I was running slow motion through a field of daisies with many dogs, most of whom belonged to clients. For years, I’ve said that people probably picture the daily life of anyone who works with dogs to be like this scene in my dream. The reality, though still wonderful, involves a lot of hard work, a lot of cleaning up, and the use of highly developed skills, experience, and education to prevent aggressive dogs from causing injury.

I was running a race in the third dream. A dog joined me after a couple of miles and ran with me the rest of the way, keeping me going over the last few miles when I was struggling and wanted to stop. As I crossed the finish line, I turned to give this dog some water, but he was gone. I looked all around, but couldn’t find him. Then I learned from some other people that every tired runner finishing the race mentioned having this dog as company, but that he always disappeared at the finish line.

Do you dream of dogs? What canine thoughts dance in your head as you sleep?

--Karen London

Is Dominance A Useful Concept In Dog Behavior?

Is dominance a useful concept in dog behavior?  In the past, much of our thoughts about dominance in dogs came from captive wolf populations where there was a linear dominance hierarchy, with an alpha wolf who was most dominant, then a beta wolf who was dominant over everyone except the alpha, and so on down the line, until we got to the omega wolf who was dominant over no one.

When wild wolves were studied, the concept of dominance in wolves became much looser, because wild wolf social groups are either family units or extended family units (parents, young, and siblings of parents), and adult wolves tend to assume more dominant positions over the younger wolves, but otherwise the situation is fairly fluid. (See the March 19, 2010 post on this blog by Dr. Suzanne Hetts on dominance myths, and the YouTube video by Dr. L. David Mech on wolf dominance at: http://www.youtube.com/watch?v=tNtFgdwTsbU).

But our training methods of dogs go back to the concepts of dominance derived from captive wolf groups.

 Some of our training methods assume that we have to be physically dominant over our dogs. This involves in extreme cases the alpha roll, or rolling the dog over on his back and standing over him (something that I personally do not recommend, as it is a way to get bitten and possibly traumatize everyone concerned, including the dog).  Other methods involve pushing the dog down for a "sit" or a "down" command, and yanking a dog around on a leash.

Non-physical methods include giving dogs less priority of access to resources such as food or space.  For example, a dog might be required to wait before getting food, or might be expected to tolerate having her food bowl taken away by her people half-way through her dinner without her showing any signs of aggression.

But dogs are not wolves, even though genetically they share more than 99 percent of their genes with wolves.

And because dogs have been domesticated for a long time, it is hard to get humans out of the equation and find out what is normal for social groups of dogs when they are not interacting with people.

Surprisingly few studies have looked at the social interactions within dog packs that have not been associated with people.

A recent study looked at dominance interactions in a free-ranging social group of dogs that had relatively little contact with humans in the suburbs of Rome, Italy (Cafazzo, S. et al. 2010. Dominance in relation to age, sex, and competitive contexts in a group of domestic dogs. Behavioral Ecology 21: 443-455).

The dog social group had 27-40 dogs, and was observed for a total of 15 months. During that time, the composition of the group changed by some dogs leaving, others joining the social group, some dogs dying, and some pups being born to females.   The authors of the study present their results based on observations of 6 adult males, 5 adult females, 1 subadult female, 4 subadult males, 5 juvenile females and 6 juvenile males, or 27 dogs in all.

The authors characterized dominance interactions as two kinds: agonistic dominance, and formal dominance. They defined agonistic dominance as situations where one dog acts aggressively and the other dog acts submissively. They defined formal dominance as situations where one dog gives another dog a submissive signal without the first dog showing any aggression.  They studied dominance interactions under the following conditions:  1) when there were no resources for the dogs to compete; 2) when the dogs had to compete over food; 2) when the male dogs had to compete over receptive females.

The bottom line in this study is that dominant status did not always correlate well with aggression.  The aggressive dogs were not necessarily the most dominant in terms of submission of other dogs when there was no competition for food or females. 

Dominant status did correlate well with the formal dominance described by the authors, where one dog produced signals that another dog responded to with submission.  Such formal dominance gave dogs priority of access to food when they were competing, and gave some males priority of access to receptive females.

So what does this study mean for us?

One take-home message is that you don't need to be aggressive with your dog for her to acknowledge that you are more dominant (or at least, for you to have higher status than your dog).  All you need to do is have the right kind of signals that your dog understands. In other words you have to learn to communicate with your dog rather than beat her into submission.

Another take-home message is that despite our long association with dogs, we still don't really know how they think.  We know what dominance means to us, but we are still struggling to find out what it means to dogs, and whether our idea of dominance is even a meaningful concept for our furry friends.

--Con Slobodchikoff