Reproductive Aspects of one of the Southernmost Tortoise Population in the World

KUBISCH, ERIKA; ECHAVE, MARIA EUGENIA; CARBAJAL, MIRTA

Charleston

Simposio; 21th Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles; 2023

The vulnerable Chaco tortoise (Chelonoidis chilensis), inhabits the Monte and Chaco regions of Argentina, Paraguay and southern Bolivia, having the southernmost populations of continental tortoises in the world. Little is known about the life history and reproduction of this species. The aim of this work is to describe observations of the reproductive aspects of one of the southernmost population of tortoises in the World, in San Antonio Oeste Argentina. Where the average monthly temperatures rang from 1 to 30°C with minimum extremes of -11.5°C in winter and maximum extremes of 44.6°C in summer.Between 2018 and 2023 we have been monitoring a wild population and some individuals in semi-captivity, we have placed temperature sensors with data loggers in 3 nests, and we have recorded incubation periods in 6 nests. Mating was observed from October (spring) to February (summer), with a peak in December (N= 23). They lay up to 4 clutches per season from late December (summer) to April (autumn) with a peak in February (N= 6). Cluch size was from 1 to 5 (mean= 3.4) hard-shelled and nearly spherical eggs. Hatchlings emerged from 374 to 615 days later (average of 426 days), turning out to be the longest incubation period for a tortoise. The embryos of this Patagonian population experience nest temperatures ranging from 1.1°C minimum to 44°C maximum. It will be necessary to promote studies of temperature dependent sex determination and whether climate change will influence the distribution of this species. Since the production of both sexes is a limiting factor for the expansion of the distribution of the species.Likewise, the long incubation period makes the nests more likely to be trampled by cattle or to be preyed on by small mammals such as armadillos, skunks or foxes, and especially by wild boars, which are widely dispersed throughout the area, generating with this situation fewer chances. of survival for this species that already has great threats.