Crocodilians Are Promiscuous But Not to the Benefit of Heterozygosity

Crocodilian mating systems are complex but molecular genetics is providing some of the tools necessary to begin their unravelling. The most significant unravelling has been the widespread occurrence of multiple paternity (more than one sire for a clutch of eggs) across the global crocodilian species. The advantages of this strategy are still being debated and may differ across the different species, being dependent on factors such as population density and habitat availability at the individual population level. This chapter reviews the available literature outlining the impact other complexities such as nest site selection, the potential for communal nesting and “alloprotection” (non-biological female exhibiting nest guarding of conspecific eggs) could have on defining the mating strategies of crocodilians. However, it is argued that any advantage of genetic gain, genetic variability or inbreeding avoidance that might achieved by multiple paternity is overcome by low embryo and offspring survival leading to low recruitment rates into the adult breeding population. The limitations of experimental design are also discussed which may be leading to upwardly biased estimates of hypothetical sire numbers.