Tuatara have more of a taste for seabird chicks and eggs than we thought, according to a new study. The key to figuring that out? Toenail clippings. Sarah Lamar from Victoria University of Wellington analysed chemical signatures in clippings from Takapourewa/Stephens Island tuatara, finding that fairy prions made up a disproportionate chunk—up to 40 per cent—of the diet of large males.
Tuatara are “gape-limited predators”, which means “they don’t really take little bites… If they can put it in their mouth, they eat it,” says Lamar. A seabird chick’s head is the perfect size for a tuatara snack, and it’s common to see headless seabird carcasses on Stephens Island, at the northernmost tip of the Marlborough Sounds. “But we didn’t know the extent to which they were eating seabirds, or whether it was kind of rare,” Lamar says. She speculates that tuatara target the head because the brain tissue is rich in fatty acids and other nutrients.
The study raises questions about reintroductions of the iconic reptile to the mainland, where seabirds have been all but wiped out. Without thriving seabird colonies living alongside them, how will the tuatara fare? “Think of how fish oil is good for us—we suspect that seabirds function the same way for tuatara. Maybe they can exist without it, but it’s an extra vitamin boon,” says Lamar. Future research will aim to unravel the role of seabird nutrients in tuatara fitness, but in the meantime, she says, “this really emphasises the need for holistic approaches to conservation”.