Life history, demography, diet and habitat associations in the southwestern earless lizard, Cophosaurus texanus scitulus from northern and southern limits of its geographical range

Abstract

I studied life history traits, demography, diet composition and habitat associations in the southwestern earless lizard, Cophosaurus texanus scitulus. Individuals from various age classes were sampled from populations at the northern (FCM) and southern (CAS) boundaries of its geographic range (FCM, foothills of Chinati Mts., Texas, USA; CAS, Castonos, Coahuila, Mexico). Males had higher growth rates as compared to females between the juvenile-to-yearling stages at both sites. Significant differences were also found for yearlings, and between yearling-to-adult stages. Growth rates decreased as a function of increasing age and were lowest in adults, and highest during the juvenile-to-yearling and yearling age classes. Earliest date on which a female was found to contain oviductal eggs was 19 May and 10 June, for the CAS and FCM sites, respectively. No females with oviductal eggs were found between 01 March and mid-May. Most females in reproductive condition had a SVL of 53-61 mm, and 57-64 mm, at the CAS and FCM sites, respectively, indicating that most females attain maturity at an age of 10-11 months. Clutch sizes were significantly smaller for females from the FCM site. Sex ratio was significantly biased toward females Survivorship was highest between yearling and adult age classes. Most lizards were found in areas with creosote and mesquite. These lizards are generalist predators that feed on a wide variety of arthropods. © 2007 Brill Academic Publishers.