New Zealand copperhead
Besides Ireland, New Zealand is notable for being the only large, non-Arctic region without snakes. 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 Urewera Mountains. 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, no doubt, many prospectors in the area would disagree.
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, they would likely survive if introduced. If any copperhead snakes do live in New Zealand, they may pose a threat to indigenous wildlife.
Almost every snake sighting in New Zealand resembles Australian copperheads (Austrelaps), implying that, if they exist, they’re likely not a native species. Some theorize the copperheads could have been introduced accidentally by gold miner’s ships, as they often came from South Australia. British Cryptozoologist Karl Shuker speculates these copperheads may have arrived in New Zealand naturally, by being marooned on a piece of vegetation, a phenomenon called "oceanic dispersal."