Road kill counts in nature studies

ROSS GIBLIN/The Dominion Post

JUST ANOTHER STATISTIC: Possums still top the list of creatures found dead on the roads, even though hundreds more of them were being killed a decade earlier.

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Two scientists have been flat out on a road trip with a macabre twist - logging road kill victims.

The 1660-kilometre squashed-critter rally gave a valuable insight into animal population trends, uncovering a mysterious drop in the numbers of squashed hedgehogs and possums.

"We wanted to show that road counts are a useful and relatively cheap way of measuring changes in the abundance of some animals," scientist Bob Brockie said.

He and colleague Richard Sadleir completed road kill missions in 1984, 1994 and 2005, driving 1660 kilometres from Lower Hutt to Northland and back.

The results of their 2005 study have been published in the latest New Zealand Journal of Zoology.

"One of us drove while one recorded our combined observations in a notebook. Most animals were readily identifiable, but we turned back occasionally to examine puzzling remains."

Analysis by Wayne Linklater of Victoria University showed roads carrying more than 3000 vehicles a day were a barrier to mammals, with less busy roads proving to be actually more dangerous.

The 2005 results were compared with similar surveys dating back to 1949. They showed a recent drop in hedgehog numbers, with just 21 found compared with 112 in 1984.

"The hedgehog population has nose-dived since the 1950s. They used to be 40 times more abundant here than any other place in the world. Now they're about as abundant as the United Kingdom."

The reason for the fall in hedgehog numbers was unknown, but mirrored a similar drop in Britain. Possum numbers fell from 602 in 1994 to 243 in 2005.

Their numbers had fluctuated over time, with the population slowly moving north. "We got evidence of possums spreading into the last corner of the North Island up near Kaitaia."

The fall could be a result of more money being spent on possum control, the study said. The most common squashed mammals were possums, hedgehogs and rabbits, with fewer cats, hares, ferrets and stoats.

Fewer birds were recorded, and only harrier hawks, pukekos and magpies were spotted regularly.

One of the more unusual finds was an adventurous eel whose wandering had proved fatal.

OUT FOR THE COUNT

The five most common North Island roadkill* victims in 2005

Possum 243
Rabbit 123
Hedgehog 21
Magpie 9
Cat, Hare, Pukeko 5

*Roadkill over a distance of 1660 kilometres on North Island roads.

- © Fairfax NZ News

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