Some species of these small southwestern lizards are all-female. They appear to be the result of cross-breeding between two other lizard species, which left them with twice the usual number of chromosomes. That fluke makes them well-suited to producing offspring all on their own, without needing a complementary male set of chromosomes to complete the picture.
The whiptails haven’t forgotten about sex totally, though. These all-lady lizards engage in pseudosexual behavior—like mounting each other—before laying their eggs. Even among go-it-alone breeders, old habits die hard.
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