Title
Reproductive characteristics of the order Crocodylia
Author(s)
Thorbjarnarson, JB
Published
1996
Publisher
Herpetologica
Abstract
Information on crocodilian egg and clutch characteristics is reviewed. The relationships between female size and egg mass, clutch size, and clutch mass are quantified, and the effects of nest mode, relative snout width, and family are examined. At the interspecific level, egg mass, clutch size, and clutch mass are strongly correlated with female size. However, larger species produce relatively smaller clutches and eggs. In most cases, similar relationships were found at the intraspecific level as well. Crocodylids are more variable in terms of nesting mode (hole and mound nesters) than alligatorids (all mound nesters). After correcting for differences in female length, no trade-off between clutch size and egg size was found at the interspecific level. The effects of family, snout width, and nest mode were also examined independent of female size. Clutch size and clutch mass were greater in the Alligatoridae than in the Crocodylidae and the Gavialidae. However, data on reproductive frequency suggest that crocodylids nest more frequently than alligatorids, and no significant difference in mean annual clutch mass was found between these two major phylogenetic groups. Narrow-snouted species lay significantly smaller clutches than other crocodilians. Consistent patterns of relative egg mass/clutch size variation were found within genera in the Alligatoridae. Alligator produces large clutches of small eggs. Tropical alligatorids have large relative clutch masses due to the production of relatively large eggs (Melanosuchus and Paleosuchus) or relatively large clutches (Caiman). Within the genus Crocodylus, the four species that inhabit strongly seasonal riverine or lacustrine environments are all hole nesters that invest relatively little in each reproductive bout (C. intermedius, C. palustris, and C. johnsoni) but may compensate with high reproductive frequencies. Gavialis may also follow this general pattern. Among the true crocodiles, two species have notably large clutch masses (C. niloticus and C. porosus). In terms of reproductive characteristics, C. cataphractus is the most unusual species, laying very small numbers of very large eggs.
Keywords
CROCODILIAN NESTING HABITS; LIFE-HISTORY TRAITS; OPTIMAL EGG SIZE; CLUTCH SIZE; BODY SIZE; ALLIGATOR; EVOLUTION; COVARIATION; ENVIRONMENT; INCUBATION
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PUB11764