Sunday, February 24, 2008
Strangers in the night
Action on the skunk singles scene is picking up.
These photos from two cameras were taken an hour and 35 minutes apart on a rainy night. I suspect they are the same two animals, a pair, and that this is not business as usual. As flawed as they are, the pictures tell us that the striped skunk breeding season is underway.
In the eastern US and upper midwest skunks den together in winter. (I am not sure it's the same in mild parts of California.) Researchers most commonly encounter female slumber parties, but single males often join the group (and all male sleeping groups are found more rarely). This is a good arrangement from the standpoint of energy conservation, but not for orgies.
While the sleeping arrangement looks suspiciously like a seraglio, it is not. The male has no command over the ladies, and there is no evidence of the dormitory effect or synchronized estrous cycles in skunks.
When the temperature rises and the wind lets up bedmates forage independently, and as in many other solitary mammals, males pursue carnal knowledge one female at a time.
I have a hunch that these strangers in the night are a'courtin'. If true, he's following her because she is in the proceptive phase of her estrous cycle. This is the short period before estrus when a female's pheromones have a potent come-hither-come-yon effect on males, though they reject amorous advances. It's a common pattern in carnivores.
Several males may be attracted to such females, and a honcho emerges from the competition. The winner takes all when the female comes into heat a short time later, or at least he has the first shot at siring the litter.
The all-too-common indicator of the breeding season are dead skunks in the middle of the road. I used to keep count of dead skunks on route 66 when I drove from Front Royal, Virginia to Washington D.C. for weekly meetings, and a bell-shaped curve tracked the frequency over time rather nicely. Male activity usually picks up in the second week of February, even when the temperature is 10 degrees C, but over the years I often saw dead skunks in January. A second spate of flattened skunks would apppear later in the spring and early summer when youngsters were up and about.
The uniqueness of this American road experience moved Loudon Wainwright to compose "Dead Skunk" in 1972, and for six weeks it was #1 on the charts in Little Rock, Arkansas, where apparently it stirred strong emotions.
A number of my colleagues were quite taken with the song, but I always felt that the lyrics could have encompassed other eternal themes like the rake and rambling boy "looking for love in all the wrong places".
The erotic wanderlust of male skunks has not been adequately investigated. In fact the only paper on the subject was written by herpetologist Carl Ernst whose 10-month-old pet male skunk developed disturbing rutting habits for a period of five weeks. The previously docile animal "nervously prowled about and examined every possible hiding place, sniffing loudly..." Its appetite doubled and it peed a pungent urine indiscriminately, which it also lapped and rolled in.
Rutting behavior is a hypersexual phase in the reproductive cycle of polygynous male ungulates and manifests itself in anorexia, aggressive behavior, frequent urination and scent marking, wallowing and increased activity.
Why it occurs in the striped skunk is another question. Maybe it is related to the observation that litter size and weaning success of captive skunks is greatest in females that breed earlier in the season. Timing of birth is often critical, and early-born skunks have more time to grow under favorable conditions.
If so, Ready-Freddies who play the field early in the season would have a reproductive advantage.
Ernst, C.H. 1965. Rutting activities in a captive skunk. Journal of Mammalogy, 46(4):702-703.
Wade-Smith, J. and B. J. Verts. 1982. Mephitus mephitus. Mammalian Species, No. 173, pp. 1-7
Wade-Smith, J. 1978. Reproduction in captive striped skunks, Mephitus mephitus. American Midland Naturalist, 100:452-455.
Sunquist, M.E. Winter activity of striped skunks (Mephitus mephitus) in east-central Minnesota. American Midland Naturalist, 92:434-446.