A Little Bit More
Since hair is a non-living material, it becomes worn over time and must be replaced periodically. During periodic molts, usually once or twice a year, old hairs are lost and new ones replace them. In many northern species, the molts are in the spring and fall. As you might expect, the summer covering of hair is generally shorter, with less insulating ability than the winter one. The difference in appearance between a “summer horse” and a “winter horse” is quite striking and easy to see; all because of the difference in hair.
Mink have their best prime coat in late fall, just after their molt; after that there is a progressive decline in the quality of their fur and the price it will bring. The seasonal color change of some weasels and rabbits is caused by molting and new hair growth, not by hair color change. Length of daylight, called photoperiod, appears to be an important factor in initiating this color change.
Although all mammals have hair, some may appear to lack it at first. Whales and porpoises have only a few scattered bristles about their lips, or hair may be present only in the young. “Hairless” mammals don’t require hair for insulation, but rely instead on thick layers of blubber under the skin to retain body heat or they live in an environment that is warm enough for survival.
Humans have little hair and are unable to live in many regions of the world without some kind of artificial insulation. In the distant past, humans used their intelligence to fashion their own “insulation” by removing the skins of furry mammals and wrapping in these for warmth. Without this creative insulation, humans couldn’t have spread to so many places throughout the world.
Definitions
uniquely: having no equal, only one of its kind
Activities
Warm Coat?
Objectives: Experience how insulation works
Materials: 2 similar winter coats, coat hanger, 3 thermometers (1 can be used in multiple settings), and 2 volunteers.
How often have we heard the admonition to “be sure you wear your warm coat or you’ll get cold”? A coat, hair, any insulating property, does not in itself make us warm, we make ourselves warm! However, unless we’ve thought this concept through, many people may have the strong notion and believe that a coat actually MAKES them warm!
Here’s a simple, rather straightforward exercise that may help students more clearly understand how an insulating property helps to keep us warm or cool.
1. Place each of three identical thermometers on a small cardboard backing that can be hooked onto a pocket or blouse collar
2. Place all 3 thermometers together for a few minutes to be sure they all read the same (you’ll need to take note of any variation)
3. Establish the “room” temperature (temp of where you’re doing this)
4. Now arrange 3 different units that can be monitored with the thermometer.
a. Hang a winter coat on a hangar and place at chair height in the room. Hook the thermometer inside the coat
b. Place a second winter coat (preferably one that is identical or very similar to the first one) on a volunteer and have them seated next to the first coat/hangar. Hook the second thermometer on a shirt pocket or collar under the coat
c. Have the second volunteer, with no coat, sit next to the volunteer in the coat. Hook the third thermometer on a shirt pocket or collar against the subject in plain view.
5. Allow approximately 15 minutes for temperatures to stabilize (you can shorten this if the coated subject gets too warm).
6. Now note and write down the temperature of the thermometer under the “empty” coat, the temperature under the coat that is being worm, and the temperature on the collar/pocket of the subject not wearing a coat.
There are some variables that can take place that may affect your results but, in general, you should see the following results:
1. The temp under the coat on the hangar should be the same as the room temp
2. The temp under the coat on the subject should read higher than the room temp
3. The temperature on the coatless subject may read the same or just a little bit higher than the room temp.
Now have your students think about and explain why these temperatures differ. If they’re not sure, have them look over the poster again to refresh their memory.
Key Concepts
Structures and Functions, Adaptations and Diversity
Questions
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Posted by Christine Sopczak on April 09, 2006 at 12:14 AM
Q: Do hares or rabbits change their fur colour according to the season? Is the colour change affected by the snow or does the change occur for another reason?
Thank you
A: Yes, some do. Those species that change color seasonally are the Snowshoe Hare, White-tailed Jackrabbit (only in northern parts of range), Arctic Hare, and Alaskan Hare. The temperature is not what initiates these changes but changes in daylight length. In the fall, as days become shorter, the animals register this change and their fur coats respond by changing into white. In the spring, the reverse is true and they become brown or gray. Good question - thanks for asking.
Posted by gretchen Sankovitz on February 20, 2006 at 01:22 PM
Q: When comparing hair insulating factors(fusi) and structures of the rabbit, caribou, whitetail deer, bear, and moose, which is the best? Thank you, Gretchen
A: Boy, now this is difficult one! I did some research but wasn't able to find much about insulation values at all among these animals. The main function of animals' fur is to trap air that will provide insulation from the cold. I was able to determine that the Snowshoe Hare has especially good insulation but exactly how well it relates to the other larger mammals, I'm not sure. I do know, however, that smaller animals have a greater surface area in proportion to their body mass and therefore lose heat more quickly than larger animals. If we look at hares, with this in mind, I would "assume" (this is where we might get into trouble)that the Snowshoe's fur is especially effective insulation since it will lose heat more quickly than a moose, for example, if all else is equal. Hope this makes sense and that it helps a wee bit.
Posted by S.M.B on March 03, 2005 at 12:37 PM
Q: Why do we have hair??????
A: Hair's main value is to help insulate mammals -keep them warm. Hair can also have an important role in some species in the identification of males from females - human males have lots of facial hair, females do not.
Posted by MATTHEW DUESER on February 22, 2004 at 09:05 PM
Q: HOW DOES HUMAN HAIR INSULATE THE BODY? IS IT A GOOD FORM OF INSULATION?
A: Humans have so little hair on their bodies that it doesn't do much, if any, good. Humans do have enough on their head, however, that this does help. We lose lots of heat from our heads and the hair there does make a difference. Anyone who has had their head shaved in the winter knows all too quickly how much cooler they feel.