Habitat quality in farmland influences the activity patterns of giant Galapagos tortoises

Abstract

Many Galapagos giant tortoises make seasonal migrations from arid lowlands in the wet season, to humid highlands in the dry season. However, for critically endangered Western Santa Cruz giant tortoises (Chelonoidis porteri), at least 88% of the habitat in the highlands is now used for agriculture. To understand the impact of agricultural land use on tortoise behavior, we conducted 242 30-minute observations of tortoises on farms. We (1) recorded the time tortoises spent eating, walking, and resting in three different land-use types, (2) measured their temperature, and (3) quantified their selection of fine-scale vegetation characteristics. We found that tortoises rest for significantly longer periods when they are in abandoned land, compared to livestock, grazing, and touristic land. Generally, tortoises rested for longer when they were cooler. Time spent eating was increased by the density and proportion of ground vegetation, while time spent walking was reduced by tall vegetation. These findings suggest that the distribution of land-use types and the fine-scale composition of thermoregulatory and grazing resources within farmland have important implications for the behavior of tortoises while in human-modified land. Wildlife managers and landowners wishing to support tortoises on farms should focus on rehabilitating abandoned land and encouraging a heterogenous mix of sun and shade, and short ground vegetation across land-use types.