By making the treacherous trek to a different pool to mate,salamanders can mix up their genes and keep healthy variation in each population. Unisexual salamanders may have less stamina because they don’t mate in the usual way. Instead of searching for the perfect partner, they steal sperm from nearby male salamanders of different species. The sperm kick-start egg production but rarely actually fertilize eggs; only occasionally does a male’s DNA sneak into a female’s offspring.
Ditching the guys can be efficient — every member of an all-female population can give birth, and that means more babies. But it seems that going it alone has drawbacks, too: These salamanders’ poorer endurance could be a disadvantage if environmental changes forced them to colonize new territory. Scientists tested salamanders’ endurance on a treadmill by gently prodding the amphibians and testing their fatigue every three minutes.R.D. Denton, K.R. Greenwald and H.L. Gibbs.