Individual variability shapes interaction rewiring and fosters ecosystem restoration by reintroduced giant tortoises in the Seychelles

Abstract Introduction Giant tortoises are critical for restoring lost ecological interactions on islands. Following their extinction in Seychelles centuries ago, key ecosystem processes like seed dispersal, browsing, and nutrient cycling were disrupted. While their role as keystone species is clear, we lack understanding of how differences between individual tortoises influence the rewiring of these distinct ecological processes. Methods We sampled ecological interactions of reintroduced Aldabra giant tortoises on Aride Island using a multi‐method approach: focal observations, fecal examination, and DNA metabarcoding to quantify their roles in detritivory, browsing‐grazing, and seed dispersal. We measured individual performance by the number of interactions with plant species and the proportion of native versus exotic plants consumed. We assessed differences in individual ecological roles using their topological and structural positions in individual‐based networks as a proxy for their contribution to each ecological process. Results Tortoises dispersed more than 10,000 native seeds in 2 months, with only three individuals accounting for more than 80% seeds dispersed. Individuals exhibited significant differences in their performance as seed dispersers of native flora, browsers–grazers of exotic flora, and detritivores. Individuals did not show congruence in their topological roles across individual‐based networks. Conclusions Our study shows the rapid establishment of ecological interactions post‐reintroduction, while highlighting the importance of studying individual‐scale variability in restoration programs aimed at rewiring ecological interactions. We argue that critical ecosystem functions in small islands such as Aride may depend substantially on a small number of individuals with diverse and contrasting ecological roles.