This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
It’s a sad fact of modern life that thousands of animals of all different kinds get killed on roads every year following collisions with motor vehicles.
Here in southern England there’s a list of creatures you see dead at the roadside all the time. In some cases, these animals have to cross roads because that’s the only way they can get from A to B (in the case of amphibians, say, to their breeding areas); in other cases it’s because animals are reckless and/or poor to useless at avoiding traffic. I’ve seen rabbits and foxes run out in front of traffic during moments of abandon, while low-flying birds like thrushes (Blackbirds Turdus merula especially) frequently fly across roads just a metre or so above the ground. Woodpigeons Columba palumbus seem to deliberately swoop low right in front of cars during their display flights. However, speedy, smart animals get killed on roads a lot as well – in the tropics, non-human primates, for example, fare poorly as road casualties, and populations of some big carnivoran species have been severely affected by mortality on roads. Between 10 and 20% of all the Florida panthers Puma concolor alive, for example, get killed on the roads each year (Land & Lotz 1996).
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So, combine an extensive road network with large amounts of traffic (the situation you have here in the UK)…. the result: lots and lots of roadkill. Things aren’t helped by the fact that some people seem to actually enjoy running animals over with their cars. Rabbits, pigeons, squirrels, foxes and pheasants make up the majority of dead animals you get to see (rabbits alone make up about 60%), but badgers, hedgehogs and deer are abundant casualties too. To give you some idea of the numbers involved, annual road-killed estimates for hedgehogs range from anywhere between 20,000 and 100,000 (Harris et al. 1995). Higher numbers have been estimated for other European countries. A 1998 estimate put the number of road-killed hedgehogs in The Netherlands at between 113,000 and 340,000 (Huijser & Bergers 1998), while a 1999 estimate for Belgium put the number for that country between 230,000 and 350,000 (Holsbeek et al. 1999). About 50,000 badgers are probably killed each year on Britain’s roads (Harris et al. 1995). These numbers are almost certainly significant enough to pose a threat to the health of the overall population.
I’ve spent a lot of time on the road with Jonathan McGowan. Jon is a professional taxidermist [website here] with a more than usual interest in examining and collecting dead animals (cough cough cough). He’s not only really good at spotting and identifying things from the car, he’s also inclined to stop and pick things up, or at least examine them at close range. Here are a few stories about recent adventures with Jon.
Here’s a poor Barn owl Tyto alba collected close to Honiton in Devon. As usual, picking up a dead one gives you a good chance to examine various of its owly peculiarities, like its specialised, ‘fringed’ feathers, facial disk and semi-zygodactyl feet (where digit IV can point forward, or be rotated to point backwards). I’ve seen dead owls at the roadside on six or seven occasions. I have a skeletonised Tawny owl Strix aluco collected as roadkill, and deep-frozen, road-killed Barn owl and Long-eared owl Asio otus (found in Spain). The usual thinking behind these deaths is that the owls have swooped low across the road while hunting and have then collided with a passing vehicle.
The number of owls killed on roads is, again, pretty high. Of the Barn owl alone, Shawyer (1987) said that it was about 5000 per annum, and I can’t believe it’s decreased since he was writing. Estimates from the recovery of ringed birds suggest that as many as 49% of all the Barn owls that die every year in the UK die as a result of vehicle collisions, but this doesn’t represent a true proportion of mortality across the population since owls that die on roads are obviously more likely to be seen and/or collected than those that die elsewhere, by other means. Furthermore, “[I]t remains debatable whether or not this unnatural cause of mortality is contributing to any major increase in death rate or is simply replacing some other more natural cause” (Shawyer 1987, p. 56).
Jon later skinned and dissected the Barn owl we’d picked up. It was already evident from the excellent condition it was in that it was a very fresh corpse – only a few hours old. Further evidence for this came from its intact, well preserved stomach contents. Four shrews (at least three were Common shrew Sorex araneus) could be pulled out of its stomach, three of them without much visible evidence of digestion (the fourth, however, was partly digested). Given the speed at which birds digest their prey, the owl had obviously been killed very soon after consuming these prey. As is typical for owls, the individual had obviously swallowed these prey whole. We looked at how owls catch and kill their prey just a few months ago.
Another animal often seen at the roadside in parts of the UK is the European polecat Mustela putorius. Polecats mostly died out in England by about the time of the First World War, but in recent decades they’ve recolonised large tracts of their former range and now occur across much of southern England. Funny story. While driving through the Dorset countryside recently (with Jon and our mutual friend Mark North), my journey was made temporarily unpleasant by an unbearable smell that had very strong, shall we say, lavatorial overtones. I assumed it was coming from slurry or manure that had been used as fertiliser on a field, and I longed to be out of its range. Jon then brought to our attention the fact that he’d just seen a dead, very intact polecat at the side of the road – we’d driven past it and he was now going to turn the car around, return to the spot and collect it. So that’s what we did. We pulled up alongside the seemingly fresh carcass and I opened the car door to step out. The source of the smell was revealed. It seemed amazing that just one small dead mustelid could have such an impact on the countryside for what seemed like miles around. Needless to say, we didn’t collect it.
Then there’s weird stuff. Check this out…
This rather peculiar organic object – encountered by Jon at the side of the road in Dorset – was first assumed to be a sandbag (this photos and those below ©, courtesy of J. McGowan of The Natural Stuff, used with permission). Slender, flattened and vaguely cylindrical, it’s pale grey and with a smooth surface. You should get a rough idea from the grass how big it was - about 90 cm long. But it ain’t no sandbag. As demonstrated by its head, forelimb anatomy and overall shape, it’s a Badger Meles meles. Apparently, a partially decomposed, misshapen badger, with chunks taken out of its body, folded-over ears and mangled, partially destroyed limbs.
It’s very weird appearance just seems to be due to its decomposition. But why is it hairless? As you’ll know if you’ve read those Montauk monster and Cerro Azul monster articles, mammal carcasses lose their hair if left to decompose in water. We don’t know anything about the taphonomic history of the dead badger shown here, but it wasn’t found anywhere close to water, nor is there any indication that it had spent any time decomposing in water. There is, of course, always the outside possibility that it had been moved by a person for some reason… dead animals – badgers in particular – are sometimes dumped at the roadside after being killed in underhanded fashion. But it looks most likely that this was a hairless freak. It must have been a very odd-looking badger if that really was the case.
Even in a country where the most exotic animals you might encounter on the roads are owls, hedgehogs and mustelids, I still think there are lots of interesting things to say about British roadkill. And I really had to resist the urge to start talking about the data from tropical countries; the ones where armadillos, anteaters, monkeys, snakes, lizards and alligators end up dead on the roads. Those of us interested in dead animals appreciate roadkill as a source of specimens. However, the impact that death on the roads has on many animal populations remains depressing, downright worrying, and something that we should try to reduce, at least as goes animals with declining populations. How, I don’t know.
For previous Tet Zoo articles on (or mentioning) roadkill and/or weird carcasses, see...
Refs - -
Harris, S., Morris, P., Wray., S. & Yalden, D. 1995. A Review of British Mammals: Population Estimates and Conservation Status of British Mammals other than Cetaceans. Joint Nature Conservation Committee, Peterborough.
Holsbeek, L., Rodts, J. & Muyldermans, S. 1999. Hedgehogs and other animal traffic victims in Belgium: results of a countrywide survey. Lutra 42, 111-119.
Huijser, M. P., Bergers, P. (2000). The effect of roads and traffic on hedgehog (Erinaceus europaeus) populations. Biological Conservation, 95, 111-116
Land, D., and M. Lotz. 1996. Wildlife crossing designs and use by Florida panthers and other wildlife in southwest Florida. In Evink, G. L., Garrett, P., Zeigler, D. & Berry, J. (eds). Proceedings of the 1996 International Conference on Wildlife Ecology and Transportation. Available online.
Shawyer, C. R. 1987. The Barn Owl in the British Isles: Its Past, Present and Future. The Hawk Trust, London.