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Dead animals at the roadside

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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.

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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).

This pigeon previously featured in the Tet Zoo ver 2 article ‘The detachable tails of pigeons’ (an article about terror-moulting).

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).

Fresh-ish shrews extracted from the stomach contents of the road-killed Barn owl.

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…

Giant roadside slug-monster. Photo © J. McGowan.

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.

Evidence for some pretty impressive scavenging on the side of the body... Photo © J. McGowan.

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.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com!

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The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Lou Jost 8:59 am 08/29/2011

    A great American writer, John McPhee, wrote one of my favorite nonfiction stories about roadkill, “Travels in Georgia”. He travels with a biologist who pays lots of attention to roadkills, not only for scientific reasons but for food. This biologist no longer buys meat, since it is there in abundance on the Georgia highways, free for the taking. Road pizzas.

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  2. 2. sterndavidi 9:08 am 08/29/2011

    Here (ACT/NSW) it is mostly kangaroos with the occasional wombat.

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  3. 3. Jerzy New 9:16 am 08/29/2011

    BTW, it is generally VERY bad idea to swerve to avoid hitting animal. Even at moderate speed, passenger car easily loses balance and then, you join the roadside carcasses. So if anything smaller than a Red Deer is on the road, brake correctly, but not swerve.

    I myself rather ignore it, and in rainy nights in Europe I regularily zigzag to avoid running over toads, which come in amazing numbers.

    BTW, I saw domestic cats which run straight in front of my car, and sprung out from between front and rear wheels of a running car (at least 60km/h), apparently unharmed.

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  4. 4. Jerzy New 9:22 am 08/29/2011

    I have a friend, wildlife photographer, who once started talking to me excitedly that he got dead roadkill raccoon dog from a friend. And he already got dead fox, marten and whole collection of other species. I asked, surprised, why a h*** he needs these things for? He answered that photographers bait raptors and carnivores with frozen chicken meat, but for perfect photo they want their buzzard, kite or whatever, to perch on some interesting carcass.

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  5. 5. John Harshman 9:31 am 08/29/2011

    You don’t mention the insects, so maybe you stopped only for relatively fresh carcasses, but you can get some very interesting beetles by turning over roadkill. I remember some very large and quite colorful silphids, for example. Sadly, my wife won’t let me touch so much as a feather when she’s around.

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  6. 6. DMA12 10:11 am 08/29/2011

    Their’s lots of roadkill around here. Most of it is deer, but occasionally you get an opossum or cat. I’m not sure about the U.K, but in America, deer numbers are soaring. They live everywhere, even in the suburbs.

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  7. 7. Alex Wild 10:33 am 08/29/2011

    We entomologists look for roadkill too, as carcasses attract interesting flies and beetles.

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  8. 8. ChasCPeterson 10:52 am 08/29/2011

    Friends who have bicycled extensively–like, across North America–tell me that turtles are by far the most common roadkill they see. There are also regional specialities–in the Mojave Desert, jackrabbits and sidewinders.

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  9. 9. vdinets 10:57 am 08/29/2011

    It is interesting to see how populations and behavior of carrion-eating species change in response to this new food source. Pairs of corvids learn to patrol miles of highways every morning looking for corpses accumulated during the night. Some vultures in the US now live further north than a hundred years ago, and many corvids have penetrated remote deserts following roads.
    The most roadkill I’ve ever seen was in outback Queensland. Even where traffic is very light, roads are sometimes lined with continuous mounds of kangaroo corpses for many miles. Someone joked on mammalwatching.com that the best way to see Australian mammals is from a glass-bottomed bus.

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  10. 10. BilBy 11:05 am 08/29/2011

    In Florida the roadkill is thick in some places. Armadillos, raccoons, lots and lots of deer, possums, cottontails. In some places it is mostly snakes and turtles – they seem to get channelled into certain crossing points and then they can have an almost zero escape chance (there are couple of papers on exactly that, I recall). With the roadkill also comes the scavengers. I have watched 50 black and turkey vultures gather round a fresh deer or feral pig and they seem to patiently wait while it bloats in the sun. Eventually one will move in, then another, then the carcass is just a pile of flapping black wings and stabbing heads. With luck a bald eagle or caracara will join in.

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  11. 11. Neil K. 11:13 am 08/29/2011

    I see six to seven road-killed barn owls, every time I make my thrice weekly 100 mile/160 km commute. U.S. residents may be interested in the California Roadkill Observation System where you can log sightings to contribute to a long-term crowd-sourced roadkill study. It is California-centric but they seem to accept records from other states.

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  12. 12. LeeB 1 7:10 pm 08/29/2011

    In New Zealand, as well as domestic animals introduced Australian possums and European hedgehogs are common roadkill.
    With respect to insects, they are not only attracted to roadkill but are also hit by cars themselves.
    As well as ending up on the windscreen some must be hit and thrown to the side of the road because it is common to see Myna birds and to a lesser extent Starlings patrolling the side of the road looking for them.

    And that says a lot about modern New Zealand, the commonly seen creatures near the roads are mainly introduced (although Pukeko and Reef herons are seen as well).

    LeeB.

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  13. 13. David Marjanović 5:31 am 08/30/2011

    With respect to insects, they are not only attracted to roadkill but are also hit by cars themselves.

    Oh yeah. That’s how I recently saw my first nematomorph. :-)

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  14. 14. Chelydra 9:16 am 08/30/2011

    In my experience turtles are definitely the most numerous conspicuous roadkill in the eastern US. I’m actually about to hatch out my first turtle eggs salvaged from a fresh roadkill (in this case a western painted turtle, Chrysemys picta bellii).

    Anyone know of any papers similar to this one regarding other taxa? If I recall correctly about 3% of drivers purposely collided with turtles and snakes, even off the road on the shoulder.

    Incidence of intentional vehicle-reptile collisions.
    Ashley, E. Paul; Kosloski, Amanda; Petrie, Scott A.
    Human Dimensions of Wildlife, Vol 12(3), May-Jun 2007, 137-143.

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  15. 15. andrewwright73 10:01 am 08/30/2011

    In Bangkok it seems to depend on district but the main ones I’ve seen in 10+ years here are Common Asian Toads (especially wet areas), rats (and dogs and cats), young Water Monitors, baby Reticulated Pythons (approx 1m), Tokay Gekkoes, Calotes agamids, and, in leafy areas, Golden/Ornate Flying Tree Snakes. Senseless waste! :-(

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  16. 16. Hai~Ren 10:59 am 08/30/2011

    Here in Singapore, where much of our native wildlife is nocturnal and extremely shy, roadkill provides an invaluable way of providing physical evidence – leopard cats and pangolins are very rarely encountered in the wild, but the occasional roadkill victim indicates that they are still present in our forests.

    And several years back, a taxi collided with a sambar deer – deer were supposedly wiped out many decades ago, but appear to have re-established a small population from zoo escapees.

    I also once found an American bullfrog sitting on the road just outside a farm that raises these amphibians for human consumption. The bullfrog tried to cross the road, with tragic messy results.

    Besides roadkill, I wonder if anyone else has taken a look at the animals killed by trains; over several days, I explored a stretch of railway track, and found
    numerous carcasses of various species, ranging from rats, domestic dogs and cats, to snakes, lizards, turtles, birds, and even a pangolin!

    Oh, and I happen to have an entire blog dedicated to animal carcasses I stumble upon in Singapore.

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  17. 17. Hai~Ren 11:00 am 08/30/2011

    Silly me, forgot to link to Monday Morgue, my blog dedicated to animal carcasses: http://mondaymorgue.posterous.com/

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  18. 18. Dartian 11:02 am 08/30/2011

    Chelydra: “Anyone know of any papers similar to this one regarding other taxa?

    Not really, but the issue is brought up by Drews (1995); while that paper is about animal road mortality in general, the author did witness a couple of times how people tried to hit baboons with their cars (baboons are considered vermin in Tanzania). Drews also suspected that some people might use their cars for opportunistic meat poaching, by intentionally colliding with antelopes and other game animals.

    Reference:
    Drews, C. 1995. Road kills of animals by public traffic in Mikumi National Park, Tanzania, with notes on baboon mortality. African Journal of Ecology 33, 89-100.

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  19. 19. naishd 11:28 am 08/30/2011

    Thanks loads for great comments (let me say again that it’s especially appreciated these days, what with the logging-in and all that).

    A particularly good set of articles on North American roadkill data – covering such groups as large carnivorans, deer, owls, turtles and amphibians, and also looking at management strategies and collisions on railways – was published in 1996 in the Proceedings of the International Conference on Wildlife Ecology & Transportation. All the papers are available, for free, here.

    Darren

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  20. 20. KarMannJRO 5:42 pm 08/30/2011

    Oh, I shouldn’t let it go without mentioning that here in Arizona, along the famous old Route 66, we have a place called the Roadkill Cafe, with menu item names in keeping with the theme.

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  21. 21. ChasCPeterson 5:47 pm 08/30/2011

    The Savannah River Ecology lab has published a series of papers on road hazards to reptiles and amphibians.
    quick list

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  22. 22. jwmorenob 2:54 am 09/7/2011

    Here in Panama roadkill is a common view. I have seen snakes, domestic cats, opossums, tamanduas and mostly lots of agoutis crahed by cars. needless to say I have collected one or two of those.

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  23. 23. MJ Simpson 7:38 am 09/7/2011

    You would think that natural selection would come into play with birds, favouring those individuals who tend to fly higher.

    Link to this

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