Long‐term variation in reproductive traits of Bibron's agama, agama impalearis, in Western Morocco

Abstract

Female reproductive characteristics (clutch size [CS], egg volume [EV] and egg mass [EM]) of Agama impalearis and their annual variation were studied over a six‐year period (1993–1998) in the central Jbilet mountains, Western Morocco. Females produced one to two clutches per season and reproduced invariably from spring to late summer, irrespective of climatic conditions. Overall mean CS was 14 eggs per clutch (range: six to 23). CS was positively correlated with snout‐vent‐length (SVL), but not with relative laying date (RLD). There was no among year variation in CS within each age class with three‐year‐old females producing larger clutches over the studied period. Both SVL‐unadjusted and adjusted mean CSs varied significantly from year to year; the largest adjusted CS occurred in 1995 (14.6 + 0.6 eggs). A stepwise regression analysis using seasonal total precipitations and mean temperatures as independent variables indicated that clutch size is significantly related to spring precipitation, whereas it is not related to any other climatic variables tested, including all seasonal mean temperatures. Both EV and EM were not correlated with SVL, CS or RDL in any year, but they exhibit a significant annual variation with the smallest and lightest eggs produced in 1996 (1870.3 ± 372.4 mm³ and 1.05 ± 0.19 g, respectively) and the largest and heaviest ones in 1993 (2550.3 ± 647.7 mm³ and 1.16 ±0.27 g, respectively). Neither EV nor EM was related to precipitation or temperature. The results suggest that reproductive female A. impalearis are adapted to unpredictable proximate environmental factors, in particular spring precipitation which probably ensures sufficient resource levels for the long breeding season.