Dogs And Photoperiodism

Do dogs have significant seasonal changes in behavior, especially in mood state, like people? I was asked this question recently, so I figured it was a good topic for a blog post. 

 

Photoperiodism is an animal's response to changes in the length of day and night. For example, there are known 24-hour hormonal cycles. The seasonal change in light exposure affects the somewhat timed expressions of melatonin and cortisol, so when the sun goes up or down these cycles are modified. In addition, the nervous system and bodily organs also have a coordinated circadian rhythm system that is affected by seasonal changes in light exposure. Disruptions to these systems can affect not only behavior but health and mortality. Female dogs go into heat based partly upon seasonal changes in light exposure, and when the females go into heat, they can display changes in mood state. Dogs and humans are affected by these changes in seasonal light exposure rhythms, both physical and behavioral, but the changes in dogs aren't going to be the same as they are for humans or other species. And every species needs to be seen as having unique responses to changes in seasons. There have been some studies on rodents showing increased aggression with varying light exposures in the laboratory. But we can't then assume that would happen in nature or in the same manner for the same biological reasons with other species. 

 

Sometimes there are defects in these systems. I have run across a handful of dogs that appeared to have a sort of "sundowner syndrome", also suspected by their veterinarians. One dog would dramatically change his behavior at night, not only was he more aggressive but there were other changes like symptoms of anxiety and restlessness. Could it be that there was another explanation for those changes? Sure. Maybe bad things had happened to him when the sun went down, and he became more suspicious. But, as I recall, there were other symptoms that looked medical. Those physical symptoms might have been a stress side effect. Unfortunately, most veterinarians do not have access to the experimental data, or the time or expertise to test dogs like this to give a definitive diagnosis.

 

I have heard it suggested that the reason there could be more reported dog bite and fight cases in the summer is because of these seasonal changes. Regarding seasonality of dog bite/ fight cases, we should also consider the influence of changes in human management of their dogs during the summer. Such changes could be that some dogs are more often placed in public competitive situations with other dogs in warm weather, whereas in the winter the dogs are more likely at home and less likely to encounter strange dogs. 

 

Intact female dogs will behave differently when in heat. They can be more irritable, restless, lethargic, and have changes in appetite. I've also seen female dogs act in ways that we would call "needy" with their human families and more "motherly" with their toys. Males that are near females in heat are also going to behave differently.

 

Photoperiodism effects on dog behavior haven't been thoroughly studied, but there are enough generalities to make some suggestions. Yes, if you look closely, you might see seasonal changes in your dogs, especially if they are intact or near intact dogs. They will also be affected by how we change how we manage them seasonally, and our mood states during those seasons. If you are stressed during seasonal holidays, for example, you can anticipate your dog might be influenced by your changes in attitude, schedule, resource provision, social interactions and management. On the other hand, most of this will run on automatic and there will be only a few things you might want to do differently if you are witnessing any noticeable changes in your dog. Thus, if your female is in heat, keep her away from intact male dogs; other female dogs in heat may make her cranky and trigger a fight; she isn't going to want male dogs messing with her if she isn't ready to breed; give her some fun time and play with her; and allow her to complete the cycle without hassling her. If your male dog is around females in heat, you'll need to more intensely supervise him since male dogs will do Olympian feats to get to those females; be more cautious of the potential for your dog to escape your home; and prevent fights between nearby intact male dogs. In summertime, you might want to be more selective where you take your dog, assuming that other dogs might not be as well managed, trained or socialized as your dog. 

 

I generally don't find these changes to be all that difficult to manage. I've had female dogs in heat in the home. It's not that big of a deal, except for the clean up being a bit if a nuisance. I've had friends who bred dogs, and for them, it was more of an effort since they had to take sometimes extraordinary steps to keep the males away from the females in heat, and to prevent or break up fights. This is all part of owning a dog. I'm not convinced that dogs suffer from seasonal affective disorder. My current opinion is that what owners are seeing is a reflection of themselves and how they are feeling and how that interpretation influences their dogs.

 

Seasonal changes are going to happen, and it is best to anticipate what might happen.

UPDATE: My opinion on this topic was quoted in this article: Can Dogs Get Seasonal Depression? Yes: Here’s How to Care for Them: “I’m not convinced that dogs suffer from seasonal affective disorder.” Sam Basso of Sam The Dog Trainer starts, “I am convinced, however, that dogs can mirror the feelings of their owners. So, assuming your dog is in good medical condition, and you observe your dog feeling low, master the concept of changing your dog’s mood state. In other words, what can you do to make your dog happy? It first starts with you.”