Road-kills in New Zealand: long-term effects track population changes and reveal colour blindness

Abstract

Road-kills were recorded at random throughout New Zealand, on 96359 km of roads, avoiding towns and busy motorways, from 1963-2018. Traffic increase from 1.04 m to 4.33 million vehicles during the study had little effect on mortality, even at the greater traffic density in the North Island. Seasonal changes measured on 8435 km (151 trips) between Lower Hutt and Otaki from 1985-2015 showed lowest mortality in winter. Major differences in species identification between two independent observers on the same route, from 2009-2014, resulted from one being red/green colourblind. Possum (Trichosurus vulpecula) numbers dipped briefly in the 1970s, peaked in the 1990s, and have declined since then where there has been widespread poisoning to protect trees, birds, and limit bovine TB. Rabbits (Oryctolagus cuniculus) increased steadily after control was lifted in the 1980s and now dominate the road-kills; the effect of RHD, introduced in 1997, does not register, probably because it causes short-term local oscillations. Hedgehog (Erinaceus europaeus) numbers show no clear trend and, unlike the other species, North and South Island patterns differ; the lower numbers in the South may reflect the cooler climate. Brown hares (Lepus europaeus) remain relatively stable, with a doubling in numbers since the 1980s in parallel with rabbits. The predators, cats (Felis catus) and mustelids (Mustela furo, M.erminea, M. nivalis), followed their prey increase until the 1990s when extensive predator control began; they then declined, although rabbit and rat (Rattus rattus, R. norvegicus) numbers continued to rise. In the 1950-60s, far more live mammals were being seen on and from roads, and adaptations to traffic have evolved. These historical records may be useful to assess future changes in road-kill following the adoption of silent electric cars, driverless vehicles, and public transport.

Road mortality in the blue‐black grassquit (Volatinia jacarina) is seasonally driven and sex‐biased

“…Millions of animals are killed on roads every year (Grilo et al, 2020; Loss et al, 2014). Among vertebrates, avian species are one of the most affected taxa (Pinto et al, 2020) with thousands of individuals being killed every year in Europe (Grilo et al, 2020), North America (Bishop & Brogan, 2013; Loss et al, 2014), Africa (Grilo et al, 2021), Asia (Silva et al, 2020), Oceania (Flux et al, 2022) and South America (Bager et al, 2015).…”

Better Safe than Sorry – Understanding the Attitude and Habits of Drivers Can Help Mitigating Animal-Vehicle Collisions

“…For example, the number of reported accidents with largebodied ungulates has increased by 36% between 2003 and 2015 in Sweden (Gren and Jägerbrand, 2019), became almost tenfold larger in Lithuania between 2002 and 2017 (Kučas and Balčiauskas, 2020), and doubled in Poland between 2001(Borowik et al, 2021. Although it should be mentioned that these numbers could be influenced by the methodology of the survey (Flux et al, 2022). As collisions with large-bodied mammals pose remarkable traffic safety risks, there is far more accurate information on these incidents compared to AVC involving smaller-bodied animals (Marcoux and Riley, 2010).…”