The effects of roadkills are “much more shocking” than previously thought, researchers warn based on an analysis of animal populations worldwide.
Collisions with vehicles on the road were the leading cause of death for almost a third (28%) of all 150 animal populations studied – ahead of disease, hunting and robbery.
The researchers said their findings, recently published in the journal Biological Reviews, suggest some mammalian populations may be reaching a “tipping point” as a result — a critical threshold that, if crossed, could become irreversible.
Lead researcher Lauren Moore, from the University of Nottingham Trent’s School of Animal, Rural and Environmental Sciences, said: “The scale of road fatalities is far more shocking than we had previously imagined and it is clear that for some it is a possible one Turning point introduces wild populations.
“While sometimes the sheer number of animals killed may seem relatively low, road killing can directly and indirectly contribute to mortality rates outnumbering reproduction rates, leaving populations vulnerable.”
Ms Moore and her colleagues reviewed 83 studies examining mammalian deaths in 69 species.
Of the 83 studies that focused on the UK, two found that 29% of polecat deaths and 25% of hedgehog deaths were due to roads, while 9% of the hedgehog population were killed on roads.
Ms Moore said the polecat research showed that the time, money and effort expended in rehabilitating injured or ill creatures “were negated by roads” and that “roads made efforts to strengthen or reintroduce endangered species.” be limited”.
The top species killed on roads worldwide included Tasmanian devils (native to Australia), Virginia possums, San Clemente Island foxes (native to California), African wild dogs (native to sub-Saharan Africa), and fox squirrels (native to North America).
The team also found that for some animal populations, up to 80% of all known deaths were due to vehicle collisions.
More than half (58%) of all fox squirrel deaths in the population were attributed to vehicles, along with nearly half (46%) of Virginia opossum deaths, the study showed.
In the Iberian lynx in Spain – classified as “Vulnerable” by the International Union for Conservation of Nature (IUCN) – vehicle collisions accounted for 59% and 80% of total deaths in two populations, respectively.
Meanwhile, 38% of San Clemente Island’s “Vulnerable” African wild dogs and 48% of its “Near Threatened” fox populations have been killed on roads.
Of 50 Tasmanian devils classified as “Vulnerable” released into the wild from captive breeding programs, the researchers found that 38% were killed on roads.
The team also said that the growth rate of Brazil’s “vulnerable” giant anteater populations has been halved due to vehicle collisions, and if this continues, the populations are likely to become extinct in about 10 years.
Other species also likely to have been killed on roads were genets, western quolls, wallaroos, gray wolves, gray foxes, American black bears and cougars.
dr Silviu Petrovan, co-author of the study and senior researcher at the University of Cambridge, said: “We all see roadkills from driving, but as this study shows, this mortality can have very different effects across different species.”
Ms Moore added: “The impact of roads on wildlife populations is one of the most pressing conservation issues of our time and with the proliferation of road networks around the world, we urgently need to address it.
“Quantifying the impact of roadkills in this way is important to inform management and road planning decisions, as well as future mitigation work.”