As they age and hear the incessant ticking of their biological clocks, unmated female speckled wood butterflies ramp up the amount of time they spend flying to catch the attention of males, European scientists have found. Older, unmated females are on the wing for more than half the day, an increase of some 35% from the behavior of young virgin or older mated females.
The patrolling behavior of male speckled woods has been well studied. Like many North American nymphalids, pugnacious territorial males stake out perches where they were presumed to lay in wait for females and ambush them in fiercely guarded “sunspots” — sunny openings on the forest floor.
The research, reported recently in the January 2011 issue of Animal Behaviour, suggests that unmated older females increasingly are on the prowl for sex as they age, but they don’t seem to have a local “cougar bar” to hang out in — apparently they just stay on the wing a lot and hope that they’re spotted. One reason males guard their sunspots so jealously, the authors believe, is that they are thought to provide vantage points where male butterflies have the best chance of seeing unmated females in flight, not because the sunspots attract females. With this increased visual detection, and more time spent in flight by females, males are able to pursue females with minimal effort and a high chance of mating success, according to the news account at BBC Earth News.