Saturday, February 23, 2008

Eastern Gray Squirrel Copulation

Yes, it's that time of year. There are two seasons for Gray Squirrel copulation, December through February and May through June.
I'd noticed that suddenly even though it's extremely cold, that there were nine squirrels this morning in the feeding area. Over the last few days the squirrel group had expanded daily and now I know why.
Male squirrels start following a female 5 days before she goes into estrus even though her vagina is still closed. The guys were out in force. Some may have come from as far away as 500 meters.
Male squirrels compete with each other for the chance to mate with a female. The visible cue of a female in estrus is an enlarged pink vulva. This is usually a condition which lasts less than 8 hours. (Looking at all the males around here, I’m assuming she’d get very tired if the condition lasted much longer than that.)

The Gray Squirrel is considered polygynandrous. Another way of saying that they are promiscuous and a female may mate with several males. Actually, it’s unclear to me if she has that much choice in the matter or if those males who may follow the first have any chance at fertilization. After the less than 30 second copulation and ejaculation, a gelatinous white vaginal plug forms, preventing further sperm entry. It looks like the joke is on everybody but Number One.

Though unlike what occurs with some species of bird, I don’t see the other male squirrels running over to interrupt the copulation.
And not only does the female go into estrus twice a year but male squirrels cycle through testicular recrudescence and regression twice a year as well. That way one assumes the problem of raking their protruding testicles across rough bark doesn’t have to occur year round. Besides all that friction could really cut down on their speed.
Now after all that talk about Squirrel sex, how about something completely different?
We haven't visited taxonomic classification in awhile, here is that of the Eastern Gray Squirrel

Kingdom: Animala
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Order: Rodentia
Suborder: Sciuromorpha
Family: Sciuridae
Subfamily: Sciurinae
Genus: Sciurus
Species: Sciurus carolinensis
Donegal Browne
P.S. Sorry about no Bald Eagles along the Mississippi today, I'm down with a virus. Besides we'd have missed all that squirrel sex if I'd left home.

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