Reproductive cycle of male and female spiny lizards, Scelophorus melanorhinus in a tropical dry forest.

Male and female reproductive cycles are described for Sceloporus melanorhinus in Chamela, Jalisco, Mexico. Both males and females reached sexual maturity at 62 mm snoutvent length. Testes mass of adult males began to increase in March, reached maximum size in July, and began to decrease in August and September, reaching minimum size in October and November. Testes size was associated with increasing photoperiod, but not with temperature or precipitation. Enlarged vitellogenic follicles first appeared in May, and oviductal eggs were found from June to September. Vitellogenesis, follicular growth, and egg production were correlated with increasing photoperiod, temperature, and precipitation. Females produced a single clutch during the reproductive season. Mean clutch size based on oviductal eggs was 7.7 (range = 5 to 9). Clutch size was not correlated with female snoutvent length.