Long-term wildlife road-kill counts in New Zealand

We compare the number of medium-sized animals (between rat and dog-size) killed on repeated counts along the same 1660 km of North Island highways in 1984, 1994 and 2005 with other counts going back to 1949. Eleven mammal and 14 bird species were recorded, but Australian possums (Trichosurus vulpecula), hedgehogs (Erinaceus europaeus) and rabbits (Oryctolagus cuniculus) predominated, and pukekos (Porphyrio porphyrio), mynas (Acridotheres tristis), and Australian magpies (Gymnorhina tibicen) were the most common birds. Counts of possums, hedgehogs and rabbits ranged between 0.7 and 89 corpses/100 km, and changed dramatically over six decades. The possum count rose 80% between 1984 and 1994, but declined 60% by 2005. A possible irruption of hedgehogs is reported in 1988-89, followed by an 82% decline in their numbers between 1994 and 2005. Although rabbit hemorrhagic disease was introduced to New Zealand in 1997, rabbit road-kill increased 59% between 1994 and 2005. The relationship between road-kill and traffic volume indicates that roads carrying more than 3000 vehicles per day act as barriers to larger mammals, while vehicles on less busy roads are more dangerous for crossing animals. We suggest that regular counts taken at annual intervals over the same roads is a useful method for gathering information about the changing distribution and relative abundance of certain animals on a provincial or national scale and over long periods of time. Regular counts at seasonal, monthly or weekly intervals are also a rich source of information.