Nest Defense in Horned Lizards…and Beyond?

Sherbrooke, Wade C.

Southwestern Research Station

American Museum of Natural History

Central Park West & 79th St.

New York, NY

Various forms of parental care are spread throughout the evolutionary diversity of organisms to enhance offspring survival. Among lizards, parental behaviors are almost unreported in the speciose lineage Iguania. The genus Phrynosoma includes oviparous and viviparous species in various clades. I will review findings illustrating that immediately post-nesting females of three species remain at their nest site and physically attack, with buts and bits, an egg-eating predatory snake (Salvadora hexalepis) when it approaches their nest. Females similarly approached pre-nesting and immediately after having departed their nest site failed to exhibit similar attack behaviors. Preliminary data suggest that recently birthing females of one species do not protect their offspring by attacking the same snake species, also known to eat juvenile lizards. Observations of such behaviors require: 1) being at the nest site for several days immediately following egg-laying and nest-covering, and 2) observing reactions of females at their nests to approaches by egg-eating predators. I suggest that lizard biologists pursue such observations with other groups in the hope of expanding our understanding of the evolution of parental care in iguanian lizards.