Movement characterization of the vulnerable tortoise Chelonoidis chilensis

KAZIMIERSKI, LAILA; KUBISCH, ERIKA L.; JOSEPH, JULIEN; ECHAVE, MARIA EUGENIA; CATALANO, NICOLAS; ABRAMSONI, GUILLERMO; LANERI, KARINA

Tucson

Simposio; 20th Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles; 2022

TSA (Turtle Survival Alliance) y la IUCN Tortoise and Freshwater Turtle Specialist Group

The Chaco tortoise (Chelonoidis chilensis) is the southernmost species of land tortoise in the globe. It is currently in a vulnerable state not only because of the reduction and destruction of its habitat, but also due to its value in the illegal pet market. As a grazer and as a seed disperser, it is also a key species in the dry ecosystem where it lives. Despite all of this, there are no reported information about C. chilensis’s movement so far. In this work, we investigate this species by complementing three monitoring techniques, including a device designed and developed by our team. We studied the movement of several individuals in the southernmost distribution in Patagonia using different and complementary tracking techniques: spool-and-line, radiotelemetry and GPS-based. We obtained trajectories that we could characterize on a micro and macro scale depending on the technique used in each case. We estimated the Daily Home Range (DHR) and the speed of movement. We also measured the tortuosity of the walk and characterized the mean square displacement. We found that C. chilensis remains within a DHR of 860 ±15 m2 (spring-season) and 769 ±12 m2 (summer-season). We also found that the most probable value of their velocity is 0.4 ±0.1 m/min, with a median value of 0.6 ±0.1 m/min, and that its displacement is characterized by a subdiffusive mean square displacement. Particularly, we observed that C. chilensis can travel as much as 300 meters in one day. The complementarity of our monitoring techniques allows to study and characterize the movement of this species on different scales: with the high spatial resolution of the spool-and-line we can describe tortuosity, while with GPS-based and radiotelemetry techniques we can describe trajectories with temporal resolution.