QotW: How do huskies stay cool?
Alex asks: I have several friends with huskies, who claim that the thick fur of the dog protects them not only from the cold, but also from a hot summer’s day as well. Can this possibly be true?
Matthew Hall sweated over this question with Christof Schwiening from Cambridge University...
Matt - Let’s help out our animal lovers and get to the bottom of this hot topic. On the forum, we got a response from Evan who thinks "dogs often shed their hair when the seasons change, adopting a thicker, more insulating winter coat. That allows them to 'insulate themselves from the cold of winter and from the heat of a hot summer's day', but not in the same season. To turn up the heat on finding an answer, I combed through some professionals in insulation, and found Christof Schwiening from Cambridge University.
Christof - Your friends are right, Alex, but there is nothing very special about huskies. Insulation, and fur is a relatively good insulator, has the property of reducing energy transfer across the insulating material in either direction, whether the temperature on one side is colder or hotter than the other.
For example, insulation in the roof of a house will keep it warmer in winter, and cooler in summer. Equally, insulation within a flask will help maintain the temperature of cold or hot liquids put into it. So, by extension, an animal with a furry coat should lose less heat in cold conditions and gain less heat in a hot environment. That is, insulation helps to isolate the animal's own body temperature from the external environmental temperature.
Matt - Well, the problem here is that it conflicts with our own experience, and simply extrapolating our physiology to other animals can be problematic. If you put on a thick winter jacket in the summer you will rapidly overheat - especially if you also do some exercise whilst wearing it.
Christof - What is missing here is the difference between how dogs and humans regulate their body temperatures in hot environments. Our main way of losing heat in warm conditions is through the evaporation of sweat from our skin. Putting insulation over the skin, or indeed just preventing air flowing over it, stops our ability to lose heat and so we rapidly become too hot.
In hot environments, dogs don’t lose much heat by sweating. Like us, they do still lose heat by evaporating water, but that water comes from panting, and fur does not prevent that process . Dogs can also lose heat by lying down on a cold surface, and fur does not prevent that either: the animal’s fur gets squashed flat and loses its insulation properties as the trapped air is pushed out of it.
So, in most mammals fur does not interfere with active heat regulation. Instead, it helps isolate body temperature from a potentially changing external environment and in this case humans are the odd ones out, because we rely mainly on sweating to keep us cool.
Matt - It’s a good thing here the naked scientists don't have to worry about our sweat getting disturbed by clothes. Get excited though, because our next question of the week - from Monique - is pretty sun-sational.
Monique - Can you tell from a painting or a photo, if it’s sunrise or sunset?