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Categorized | Featured, Outdoors

Squirrel Colors

Ranger Steve’s Nature Niche

Ranger Steve Mueller

By Ranger Steve Mueller

Does your family have specific recognizable gene characteristics? I have two dimples that my brothers and dad also possess. One is on my cheek and the other is on the side of my stomach. My dad and brothers have those dimples but they are on the opposite side of their bodies. Their hair parts on the left side of the head like it does for most men. My hair naturally parts on the right side. These are genetically inherited characteristics. 

Jackie Gage said that this cute little red “dwarf” squirrel has been coming to her home in Cedar Springs for at least a couple months. She said it was hard to get a picture of him because he was so fast and flighty but her granddaughter Brenda Reed finally got a photo. Jackie doesn’t think he’s a baby squirrel because he’s never gotten any bigger than the 6 inches or so he is now. “He chases the big squirrels up trees and across the yard and is quite aggressive,” she said. “I’ve named him Brat because he is one!” Photo by Brenda Reed.

I figure the two characters of dimples and hair part must be encoded on a chromosome that experienced a form of genetic inversion or possible crossover. Understanding of genetics has advanced remarkably since I took genetics in college. Now my focus is on butterfly genetics where genome sequencing is used to study similarities, differences, and development of new species in progress. I listen to scientists explain their research at conferences to demonstrate how genetic drift occurs in wild populations. I can best address squirrel genetics by attempting to overview gene inheritance for butterflies where my understanding is more complete.

Gene Drift character is more evident for some species than others. A plant group known as wild buckwheat is experiencing active speciation among individuals that look virtually identical. They have become genetically and reproductively isolated into different species even though they look the same. There is a group of blue butterflies that require buckwheat plants for larval food plants and the butterfly populations have separated into new genetically isolated species that look nearly identical. They do not interbreed with each other and each requires its own specific new species of buckwheat. This new species development in progress is being tested.

For field biologists like me to determine the species of blue buckwheat butterfly, it is necessary to determine the species of buckwheat plant the caterpillar requires. Another way is for scientists to examine gene sequencing of mitochondrial DNA and RNA. It is necessary to end this crash course in genetics without adding pages of detail. I expect readers have heard of the Human Genome Project and if not Google it for a brief paragraph introduction. To address squirrel color inheritance we will leave genetic species development. 

Kathy Bremmer, of Cedar Springs, said this two-toned squirrel has been visiting their feeders for a week or so. She said she did some research on the Internet but couldn’t find another one just like it. Ranger Steve says in the article here it could be an albinism mutation.

Frequently squirrels express genetic variation within their own species much like people do. Three common squirrel species in our area are the red, gray, and fox squirrels. Red squirrels are small with red fur and white bellies. The fox squirrels have rusty red fox-colored fur and tails with reddish bellies but some have red tinted black fur. The gray squirrels have gray fur and tails, with white bellies. They also have genetically distinct black individuals. The squirrel color phases are not significantly different from hair color variations in people.

The black-haired squirrel color is the result of a recessive gene that it must receive from both parent donors. If the squirrel gets a fox-colored hair gene and black-hair gene, the offspring will have fox-colored fur. Two fox-colored genes result in fox-colored individuals. Two black-hair genes create a squirrel having a black color.

Pictures of the color variant and “dwarf” squirrel sent to the paper are due to genetics that I cannot adequately identify. There are multiple possibilities to explain what has occurred. Dwarfism can occur in other species much like it does in people but they should have short limbs. The two small squirrels that have not become normal sized over a period of months could indicate a dwarf gene mutation. There are two half-sized red squirrels that are not dwarfs in our yard. They will grow. Squirrels commonly bear young in late fall or winter. 

The odd white and reddish-brown squirrel is more difficult to explain. It is not an albino. Albinos are individuals that do not inherit a gene for color pigment. Perhaps an albinism mutation occurred during early embryo development. Albinism is surprisingly frequent in squirrels. I have a picture on our wall of an albino red squirrel photographed at the Howard Christensen Nature Center. My in-laws had one in their Minnesota yard and I have heard of many others. Albinos lack eye pigment and have pink eyes. 

The two-toned squirrel pictured is caused by genetic variation caused in a manner I cannot readily explain but I could elaborate with detailed possibilities. Many nature niche mysteries continue to intrigue us so simply enjoy.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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