A Slow and Underappreciated Forest Megafauna: Food Habits, Movements, and Multiscale Habitat Preferences of Critically Endangered Sundaic Giant Tortoises (Manouria emys emys).

Abstract

Sundaic giant tortoises (Manouria emys emys) are the largest chelonians in Asia. Classified as critically endangered, they are extremely rare throughout their range. The limited knowledge of their behavior and ecology hampers effective conservation initiatives. We integrated GPS tracking, behavioral observations, local ecological knowledge, resource selection functions, spatial distribution modeling, and landscape functional connectivity to assess key aspects of their food habits, movement patterns, and habitat relationships at local and broad scale in Sumatra, Indonesia. Sundaic giant tortoises were predominantly diurnal (93% of activities) and had a mean home range of 27.5 ha (±28.8 SD; N = 3 individuals, autocorrelated kernel density estimate). We identified 40 plant species from 20 families, including ferns, monocots, and dicots, consumed by the tortoises. They consumed the fruits of 30 of these plants, swallowing seeds as large as those of Durio and Artocarpus (>2 × 4 cm), indicating potential seed dispersal over distances exceeding 1 km. Habitat preference analysis at both local and island-wide scales showed a consistent preference for primary rainforests with steep slopes at moderate altitudes, and near rivers, mostly on the western side of the island. We identified 15 "priority areas," that is, those with high habitat suitability but lacking formal protection. Among these, only one, Gunung Talang, lacked connectivity with other forest areas, prompting us to propose a wildlife corridor connecting it to Kerinci Seblat National Park. In addition, we argue that Sundaic giant tortoises hold potential for rewilding operations in Sumatra and other parts of their range, emphasizing the need for targeted conservation efforts.