Induction of oviposition produces smaller eggs in tuatara (Sphenodon punctatus)

Induction of oviposition by injection of hormones has been used successfully to collect eggs from at least three orders of reptiles. Eggs of tuatara (Sphenodon spp.) have been collected by induction since 1985. We investigate whether inducing egg laying affects clutch size, egg mass, hatching success, or hatchling size, and describe considerations necessary when deciding whether to induce egg laying or collect eggs from nests. Altogether, 320 tuatara (S. punctatus) eggs were collected for incubation from Stephens Island in November 1998: 166 by induction and 154 from nests. Induced eggs (mean = 4.498 +/- 0.060 SE) were significantly smaller than naturally laid eggs collected within a few days of oviposition (mean = 5.375 +/- 0.070 SE). Induced eggs resulted in significantly smaller hatchlings following incubation in captivity, and the difference was still significant when hatchlings were 10 months old. Reduced size of hatchlings has consequences for long-term fitness.