No Males Found: Lizards and Foals at a Desert Refuge

Spring Survey at Mesquite Flats

1Every April, the crew at Mesquite Flats Wildlife Refuge in southern New Mexico counts the animals that live among its sand hills and creosote bushes. This year, sixth grader Tobias Lindqvist joined the survey as a volunteer with refuge biologist Dr. Hiroshi Tanabe. The crew set out buckets sunk level with the ground. Each morning, Dr. Tanabe lifted out any lizards that had fallen in overnight, checked whether each one was male or female, photographed its back and let it go. Tobias recorded the data.

2Two kinds of whiptail lizards turned up most often. Western whiptails reproduce the way most lizards do: a male and a female mate, and the female lays fertilized eggs. New Mexico whiptails are unusual. Surveys almost never find a male of this species. A female lays eggs that develop without being fertilized, and each hatchling gets all of its genetic information from its mother. Two summers ago, the refuge raised one young New Mexico whiptail alone in an indoor enclosure until it was grown. That lizard laid three eggs, and all three hatched.

3The refuge is also home to a small herd of free-roaming horses, and the crew records the coat color of every new foal. In these horses, one gene with two alleles decides whether a horse is chestnut. Allele E is dominant and gives a dark coat, such as black or bay (brown with a black mane and tail). Allele e is recessive. A horse with two e alleles (ee) has a chestnut coat, which is reddish brown with no black hair. The refuge vet has tested hair samples from many of the horses to learn their genotypes.

4Last spring, a dark mare and a dark stallion, both tested as Ee, had a chestnut foal. The crew named him Rusty.