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(Fred Lum/The Globe and Mail)
(Fred Lum/The Globe and Mail)

COLLECTED WISDOM

Why black dominates the squirrel world Add to ...

Collected Wisdom heads out into the woods this week to discover why so many grey squirrels are actually black.

THE QUESTION

If black and grey squirrels are of the same species, asks Robert Findlay of Toronto, why aren't their numbers approximately the same? The black squirrels always seem to be in the majority.

THE ANSWER

To get to the bottom of this, you have to look at the typical squirrel family – Ma Squirrel, Pa Squirrel and all the kids.

“The way coat colour is inherited in the grey squirrel (Sciurus carolinensis) explains why there are often more black than grey squirrels in a family,” writes

Alison Thomas, senior lecturer in genetics in the Department of Life Sciences at Anglia Ruskin University in Cambridge, Britain.

“Black hairs result from an imbalance in the pigmentation process,” she writes. “The hairs of squirrels, as indeed of all mammals, appear coloured as the result of melanin pigments deposited in them during their development. There are two main forms of the melanin: a dark eumelanin and a paler pheomelanin, and the normal ‘grey' coat colour of squirrels results from carefully controlled amounts of light and dark pigment during the development of the hairs.”

Squirrels develop black coats when control systems break down – when the hair-forming cells receive the genetic message to produce only black pigment.

“In the molecular ecology research laboratory at Anglia Ruskin University in Cambridge, we have identified the culprit gene that is mutated and which locks the hair cells into forming only the black pigment,” Dr. Thomas writes. “More black than grey squirrels appear in families because this genetic change is dominant.”

The way genetic inheritance works, she says, is for an individual to receive one copy of each gene from each parent. Because the black-coat gene is dominant, a squirrel will be black if one or both of its pigment-forming genes is the black version. Grey squirrels result only if both copies are the “recessive” normal-pigment gene. “Thus, if two black squirrels mate, most pups will have one or two black-pigment genes, so black squirrels will be in the majority in a family.”

THE QUESTION

Everyone knows that Sir John A. Macdonald was a drinker, writes Maxwell Yalden of Ottawa, but what did he drink? Beer, wine, whisky? All three?

THE ANSWER

The short answer is all three, says Peter Gorman of Toronto, and he cites the following passages from Patricia Phenix's book Private Demons: The Tragic Personal Life of John A. Macdonald.

  • “Thomas Ramsay ran three or four shops in town, including a grocery store, and he shared John A.'s love of books, beer and women.”
  • “Family friend James Porter recalled that John A. was as fond of whisky as was his father, Hugh.”
  • Re: his 1850 trip to England: “Now he travelled first class, enjoying the finest in whisky, clarets, and sherry.”
  • HELP WANTED

  • Possibly thinking of Sir John A., Ron Baylis of Cobourg, Ont., asks: Why do we clink glasses before having a drink?
  • “Why are dishwasher cycles so long?” asks Sam Barnes of Mississauga. “My machine takes around 60 minutes. I realize some of this is drying time, but could we not get clean dishes with three five-minute washes and three three-minute rinses? The savings in energy and water should be considerable.”
  • “We drive on the right, and when we're walking, we almost always keep to the right in order to pass,” writes Brian P.H. Green of Thunder Bay. “In Britain, where they drive on the left, do pedestrians pass on the left?”

Let's hear from you: If you have the answer to one of these questions (or want to pose a question yourself) send an e-mail to wisdom@globeandmail.com. Please include your name, location and a daytime phone number.

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