It wouldn’t take much to wipe out New Zealand’s rarest insect.
In fact, the Canterbury knobbled weevil (Hadramphus tuberculatus) has already had a few brushes with extinction. The 15mm-long insect was actually thought to be extinct for many decades after all of its known habitats were converted to farmland. It was rediscovered in 2004 on a 10.5-hectare reserve located outside of Canterbury, on New Zealand’s South Island, where it depends on a very specific plant called golden speargrass (Aciphylla aurea) for its food and shelter.
That habitat itself faces quite a few threats, including invasive plants and predators. In 2005—just one year after the weevil was rediscovered—a good portion of the reserve burned down after a passing bus dropped a spark into dry grasses.
Today the weevils are protected but they aren’t exactly thriving. The population is estimated at fewer than 100 individuals.
Boosting that number presents more than a few challenges. For one thing, there’s nowhere left for the weevil to expand its range. All of the other nearby habitats that have the same qualities as the reserve—altitude, temperature and rainfall—have been converted into inhospitable farms or grassland.
For another thing, scientists know very little about how the weevils breed, eat or use their habitat. In part that’s because no one knew they existed for so long, but even following their rediscovery the insects remain difficult to study in the wild. They spend a lot of time underground and the needle-like speargrass leaves offer protection not just from predators but from scientists’ prying eyes and fingers.
Keeping the species safe in the long run requires learning a lot more about the weevil’s live cycle, and a new paper published this month in New Zealand Entomologist takes the first big step toward accomplishing that. Researchers from the University of Wisconsin-Madison and Canterbury’s Lincoln University collected four adult weevils from the reserve, took them back, and, after a few months of careful work, got them to breed in captivity. As detailed in the paper, they produced two new adult weevils and two larvae. They also gained a better understanding of how to accomplish even more successful captive breeding in the future if it ever becomes necessary to ensure the species’ survival.
Lead researcher Emily Fountain, a postdoctoral research at the University of Wisconsin-Madison, said she never expected to work with the species when she first came to New Zealand in 2009. “My plans were to work on birds for my PhD, but I got hooked on weevils and a three-month project turned into a several year PhD,” she says. “When I first started working on the weevil, it was still listed as extinct on the IUCN Red List, so it was kind of like working with the living dead. I became really passionate about what some may consider a drab looking weevil and I wanted to fill in all the missing knowledge on its genetics, evolution and ecology.”
Fountain, now back in the States, is still working with the weevil by assisting the Endangered Species Foundation of New Zealand—which last month named the insects one of New Zealand’s ten rarest species—with the development of a conservation plan. “They are considering options like captive rearing and also continued monitoring of the current population, as well as pest and weed control,” she says. “Some pest trapping and weed removal has been done but unfortunately due to a lack of resources we have not been able to implement the kind of pest control program that is needed at the reserve.” Fountain’s previous research found invasive hedgehogs, ferrets, feral cats and stoats at the reserve. None appeared to be eating the endangered weevils, but they were shown to be eating other nearby invertebrates. Meanwhile invasive rats and rabbits, as well as non-native wallabies, consumed the vegetation, which could have an impact on the weevil’s habitat.
Last month’s “ten most endangered list” has already brought a lot of attention to this little-seen weevil. “There has been more interest to this work than I was expecting,” Fountain says. “I think a key part in conservation success is having the community involved and interested in the conservation of a species and the ESFNZ has done an amazing job in getting the public's attention.”
The Canterbury knobbled weevil isn’t quite a conservation success yet, but Fountain’s work has set the stage for the future. For a species that once disappeared for decades, having any future at all is good enough news for now.
Photo: Endangered Species Foundation of New Zealand