REPRODUCTION BY A SMALL AGAMID LIZARD, CTENOPHORUS PICTUS, DURING CONTRASTING SEASONS

Abstract

Reproduction in a population of painted dragons, Ctenophorus pictus (Agamidae), in semi-arid South Australia was studied over two years with distinctly contrasting climatic conditions. Data were collected from wild lizards to assess the influence of inter- and intra-seasonal conditions on reproductive characters of the small, short-lived lizard during a very wet year and a season with average rainfall. Females began to develop ova at the end of winter (August) and laid eggs during the spring and early summer, coinciding with the period of testicular enlargement in males. Potentially four, or possibly more, clutches of 2 to 4 eggs (mean 2.6) were produced by females each year. Egg moisture content varied considerably and ranged between 45 and 79% (mean 66%) of total egg mass. Eggs contained less moisture in the wet year (1992–93). Females containing oviducal eggs were marginally larger in the wet year of 1992–93 than in 1991–92. Eggs collected late in the reproductive season were significantly larger than those collected earlier. A ‘parental investment’ model can be used to explain this intra-seasonal shift in egg size. When adjustments for female size were made, reproductive investment was consistent between the two years of the study, with no difference in egg mass, clutch mass or clutch size detected. The reproductive strategy of C. pictus remained remarkably invariant considering the dramatic difference in climatic conditions between the two years of the study.