Captive rearing affects growth but not survival in translocated juvenile tuatara

Abstract

Translocations are increasingly used in species conservation, but success rates can be low. Experimental approaches are needed to compare the outcomes of translocation strategies, including those involving head-starting (the rearing of juveniles in captivity before release). Here, we studied the reintroduction of head-started and wild-caught juveniles of a distinctive reptile, the tuatara Sphenodon punctatus, on the South Island of New Zealand. We compared morphometric, ecophysiological, behavioural and spatial aspects for juveniles from three groups (wild-caught from a warmer climate, head-started from a warmer climate and head-started from the local climate), focusing on the first 5months of summer following release. Group did not affect body condition at recapture, but wild-caught juveniles, despite being the only animals with ticks at release, grew faster and had higher inferred body temperatures than individuals head-started in a warmer climate. Wild-caught juveniles were less frequently seen emerged than juveniles head-started at the release site, and no animals had ticks at the summer's end. Mean dispersal distance and home-range size did not differ significantly between groups, and all groups had high survival (96.4-100% over first summer; at least 66.7-73.3% after the first winter following release). We conclude that, for most metrics, post-release performance of head-started and wild-caught juvenile tuatara was similar, and that head-started groups can differ between each other as much as between captive and wild. Our results emphasize the species-specific nature of translocation outcomes.