Reproduction, growth, survivorship and activity patterns in the southwestern earless lizard (Cophosaurus texanus scitulus) (Phrynosomatidae) from theBig Bend Region of Texas

This study reports on various aspects of reproduction, growth and survivors hip in a population of the southwestern earless Lizard, Cophosaurus texanus scitulus, from Big Bend Ranch State Park in west Texas (U.S.A.) over a two year period. Testis enlargement began in mid-April. For females, the earli est presence of oviductal eggs was the first week of June. No females with oviductal eggs were found after 27 August. Yolked follicles were first obse rved in females collected on 10 April 1998 and 4 April 1999. Egg weight ran ged from 13 - 35% of the total weight of a female with oviductal eggs. Mean clutch sizes ranged from 2.77 - 4.67 over the two year period. Females col lected earlier in the season had larger fat bodies and higher levels of sto rage lipids. Males had higher growth rates than females in the juvenile-to- yearling age class and in the growth period between yearling and adult. Adu lt males were significantly larger than females. No bias in the sex ratio w as found for any agr: class in 1998. In 1999, the sex ratio was skewed in f avor of yearling males. Survivorship was low for males (juveniles, 12%; yea rlings, 29%; adults, 24%) and females (14, 37 and 16%, respectively). Peak periods of activity were between 1000 - 1159 hr CST.