When we think of evolution, we usually think of slow, gradual changes that occur over thousands or millions of years. However, this isn’t always the case: sometimes evolution can produce fast results! Take the coat color of the gray squirrel, who resides mostly in the eastern U.S., for example–nowadays, most are gray in color, but even just two centuries ago, most were black! What has prompted this change in color, and how did it happen so quickly?
All that separates gray and black squirrels is one tiny genetic difference: a piece of DNA that controls how much pigment is added to their fur. So how would natural selection favor the gray squirrels, which contain two complete copies of the “pigment” gene? One theory is that most of the forests in North America used to be “old growth,” with several layers of tree cover, which created dark shadows on the forest floor. This favored darker squirrels, because they could hide from predators. However, modern North American forests have been thinned by the lumber industry, and “new growth,” with more spindly tree trunks, create less shade, so perhaps black-furred squirrels stand out more than gray. Black squirrels actually tend to be more proliferous in urban environments, where building shadows mimic sort of an “old growth” forest landscape.
What SquirrelMapper aims to do is get citizen scientists involved in gathering and submitting data on where they are sighting squirrels of different coats. The process for adding your data is very simple:
- Register with SquirrelMapper.
- Print off this handy identification guide to take with you into the field:
- Search for squirrels in your neighborhood, or just keep the recording sheet in your car or another easily-accessible spot, so you can jot down notes when you run across a little critter during your everyday activities.
- Record the results online on the “Add Records” page.
Easy as that! If you don’t have internet access, you can also mail your records to:
Syracuse, NY 13210
You can also contribute by measuring whether the squirrels’ camouflage actually provides them with a selective advantage in different visual environments in the project’s “squirrel hunt” exercise.
You can view an interactive map of all of the submitted squirrel sightings here, including some cool pie charts of what kinds of squirrels have been sighted in different regions of the country–I couldn’t believe the difference between the east and west coast! However, the more data that is included in the project, the more accurate the results, so get involved and share your own observations!
Photo Credit: Wikipedia