New Zealand is notable for being the only non-Arctic region without snakes besides Ireland. Despite this, various accounts of presumably introduced snakes, often resembling Australian copperheads, have been reported. Many of the reports are from the 19th century. 

For instance, an 1869 newspaper mentioned a snake found in the upper Waikato River. In 1875, a group of loggers claimed to have found a three-foot-long snake in the UreweraMountains. Unfortunately, they killed it and chopped it up before it could be studied. In 1886, a snake was found at a racecourse near Auckland. 

Many of the more recent reports come from the West Coast region, which takes up almost 10% of the land, but 0.75% of the population. One of the more widely reported sightings was in 1990, when a gold prospector encountered a snake 50 kilometres east of Greymouth. As he started getting tired from working, he rested on the top of a bank. Suddenly, a 2.5 foot copperhead snake coiled itself on his arm. Alarmed, he quickly flailed his arm around and the snake fell off. His sighting was considered intriguing enough that the New Zealand Ministry for Primary Industries (MPI) did an investigation. They were unsuccessful in finding any snakes, and concluded they likely didn’t exist, though many prospectors in the area assuredly disagree.

Almost every sighting of snakes in New Zealand resemble Australian copperheads (Austrelaps), implying they were if they exist, they’re likely introduced, not native. Some theorize the copperheads could have been introduced accidentally by gold miner’s ships, as they often came from South Australia. A herpetologist from the MPI speculated that copperheads could remain undetected, since they are quite elusive and tend to avoid humans. Similarly, since copperheads live in Tasmania, which is very ecologically similar to New Zealand, its likely they would survive if introduced. If any copperhead snakes do live in New Zealand, they may pose a threat to indigenous wildlife.