Sex ratio of black caiman (Melanosuchus niger) hatchlings in a sample of the wild managed population from the Mamirauá Reserve, Central Amazon

Razão sexual de filhotes de jacaré-açu (Melanosuchus niger) recém eclodidos em uma amostra da população silvestre manejada da Reserva Mamirauá, Amazônia Central

Sex determination in crocodilians is dependent on environmental temperature, in which extreme temperatures favor the development of females, while intermediate temperatures favor males. Understanding such temperature dependence in light of current climate change is urgent, as males are the main targets in species’ sustainable management. Here we analyze the sex ratio of newly-hatched Black caiman (Melanosuchus niger) hatchlings from a wild managed population in Central Amazonia. We captured 86 newly-hatched hatchlings and determined their sex through histological analysis of the gonads. We identified 58% males and 42% females among the 86 hatchlings analyzed (male-to-female ratio of 25:18) We identified 58% males and 42% females among the 86 hatchlings analyzed (male-to-female ratio of 25:18) suggesting that the sex ratio of Black caiman hatchlings in 2023 in the area was relatively balanced. This balance contrasts with expectations of a female bias under recent warming conditions and indicates the potential recruitment of males into the population, which is essential to ensure population equilibrium and the long-term viability of harvest quotas.

KEYWORDS:
crocodilians; sustainable management; nesting