Navigating agricultural landscapes: Responses of critically endangered giant tortoises to farmland vegetation and infrastructure

Context: Interactions between wildlife and anthropogenic infrastructure, such as roads, fences, and dams, can influence wildlife movement, and potentially cause human-wildlife conflict. In the Galapagos archipelago, two species of critically endangered giant tortoise encounter infrastructure and human-modified vegetation in farms, which could influence movement choices.

Objectives: We investigated factors influencing tortoise movement and habitat selection in the agricultural landscape of Santa Cruz Island, Galapagos.

Methods: We examined the movement of 27 tortoises collected using GPS tracking between 2014 and 2020, in relation to the location of vegetation, ponds, fences, and roads.

Results: We found that tortoises preferred pasture over native vegetation, but there was little difference among their preferences for native vegetation, crops, or invasive vegetation. Tortoises also travelled slower in pasture, and faster in invasive vegetation, compared to crops and native vegetation. Tortoises were more likely to be found closer to ponds than predicted by chance. Our results indicated that most fences were porous to tortoises, with limited impact on their movement. Tortoises were more likely to use areas near roads with low-traffic.

Conclusions: Pastures and ponds are important habitats for tortoises in farms and are likely to be used preferentially by tortoises. Overall, fences and roads did not strongly obstruct tortoise movements, however, this may lead to potential injury to tortoises on roads and property damage for farmers. To best identify priority areas for managing wildlife on farms, we recommend evaluating the combined effects of multiple anthropogenic landscape features on wildlife movements.