A Gordon Tullock-esque insight about the law of demand and why bats hunt at night, on p. 30 of Richard Dawkins’ The Blind Watchmaker (thanks to Don Boudreaux for the recommendation):
Bats have a problem: how to find their way around in the dark. … But the daytime economy is already heavily exploited by other creatures such as birds. Given that there is a living to be made at night, natural selection has favored bats that make a go of the night-hunting trade.
In other words, animals are careful shoppers. Bats, or their ancestors, moved from higher-priced daytime hunting to lower-priced night-time hunting. Prices, in this case, being not money, but effort, food availability, and amount of competition. Had night and day’s hunting “prices” been the same, bats’ nocturnalism, and related traits such as sonar, would likely not have evolved.
Economics is everywhere, day and night.
Inertia Wins! 