Roadkill

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For other uses, see Roadkill (disambiguation).
The battered remains of a roadkilled deer in South Carolina, US
Wide-ranging large carnivores like this bear are particularly vulnerable to becoming roadkill
A deer crossing and killed at night

Roadkill is an animal or animals that have been struck and killed by motor vehicles.[1]

History[edit]

During the early 20th century, roadkill or "flat meats" (or "Highway Pizza") became a common sight in all industrialized First World nations, as they adopted the internal combustion engine and the automobile. Roadkill can be eaten, and there are several recipe books dedicated to roadkill. One of the earliest observers of roadkill was the naturalist Joseph Grinnell, who noted in 1920: "This [roadkill] is a relatively new source of fatality; and if one were to estimate the entire mileage of such roads in the state [California], the mortality must mount into the hundreds and perhaps thousands every 24 hours."

In Australia, specific actions taken to protect against the variety of animals that can damage vehicles – such as bullbars (usually known in Australia as 'roo bars', in reference to kangaroos) – indicate the Australian experience has some unique features with road kill.[2] In North America, deer are the animal most likely to cause vehicle damage.

Distribution and abundance[edit]

Roadkilled kangaroo from South Morang in northern Melbourne, Australia
Wombat roadkill, Nerriga, New South Wales, Australia
Roadkilled deer just south of Richmond, Indiana, US. Animals may show little external damage, especially if tossed completely off the roadway.

The number of animals killed in the United States is estimated at a million per day.[3][4]

About 350,000 to 27 million birds are estimated to be killed on European roads each year.[5]

Species affected[edit]

Fauna mortality as result of roadkill can be very significant for species with small populations. Roadkill is estimated to be responsible for 50% of deaths of Florida panthers, and is the largest factor for European badger deaths in England. Roadkill is considered to significantly contribute to the population decline of many threatened species, including wolf, koala and eastern quoll.[6] In Tasmania, Australia the most common species affected by roadkill are brushtail possums and Tasmanian pademelons.[6]

A roadkill squirrel near a driveway

In 1993, 25 schools throughout New England, United States participated in a roadkill study involving 1,923 animal deaths. By category, the fatalities were: 81% mammals, 15% birds, 3% reptiles and amphibians, 1% indiscernible.[7] Extrapolating these data nationwide, Merritt Clifton (editor of Animal People Newspaper) estimated that the following animals are being killed by motor vehicles in the United States annually: 41 million squirrels, 26 million cats, 22 million rats, 19 million opossums, 15 million raccoons, 6 million dogs, 350,000 deer.[8] This study may not have considered differences in observability among taxa (e.g. dead raccoons are easier to see than dead frogs), and has not been published in peer-reviewed scientific literature.

Insects[edit]

A recent study showed that insects, too, are prone to a very high risk of roadkill incidence.[9] Research showed interesting patterns in insect/butterfly roadkills in relation to the vehicle density.

In 2003-2004, the Royal Society for the Protection of Birds investigated anecdotal reports of declining insect populations in the UK by asking drivers to affix a postcard-sized PVC rectangle, called a "splatometer," to the front of their cars.[10] Almost 40,000 drivers took part, and the results found one squashed insect for every 5 miles driven. This contrasts with 30 years ago when cars were covered more completely with insects, supporting the idea that insect numbers had waned.[11]

In 2011, Dutch biologist Arnold van Vliet coordinated a similar study of insect deaths on car license plates. He found two insects killed on the license-plate area for every 6.2 miles driven. This implies about 1.6 trillion insect deaths by cars per year in the Netherlands and about 32.5 trillion deaths in the United States if the figures are extrapolated there.[12]

Scavengers[edit]

One rarely considered positive aspect of roadkill is the regular availability of carrion it provides for scavenger species such as vultures, crows, foxes, Virginia opossums and a wide variety of carnivorous insects. Areas with robust scavenger populations tend to see roadkilled animal corpses being quickly carried off, sometimes within minutes of being struck. In particularly roadkill-prone areas, scavenging birds use roadkill for much of their daily nutritional requirements and can often be seen observing the roadway from perches on telephone poles and trees, waiting for small animals to be struck so they can swoop down and feed. Scavengers are at risk of becoming roadkill themselves, and are subject to evolutionary pressure to be alert to traffic hazards.

In contrast, areas where scavengers have been driven out (such as many urban areas) often see roadkill rotting in place indefinitely on the roadways and being further macerated by traffic. The remains must be manually removed by dedicated disposal personnel and disposed of via sanitary cremation; this greatly increases the public nuisance inherent to roadkill, unnecessarily complicates its disposal, and consumes additional public money, time and fuel that could be spent on other roadway maintenance projects.

Research[edit]

US state wildlife roadkill observation systems[edit]

Recently (since 2009), statewide roadkill observation systems have sprung up, enrolling hundreds of observers in reporting roadkill on a website. The observers, who are usually naturalists or professional scientists, provide identification, location, and other information about the observations. The data are then displayed on a website for easy visualization and made available for studies of proximate causes of roadkill, actual wildlife distributions, wildlife movement, and other studies. Roadkill observation system websites are available for the US states of California,[13] Maine,[14] and Idaho.[15] In each case, index roads are used to help quantify total impact of vehicle collisions on specific vertebrate taxa.

State wildlife roadkill identification guide[edit]

The first wildlife roadkill identification guide produced by a state agency in North America was published by the British Columbia Ministry of Transportation (BCMoT) in Canada in 2008.[16] BCMoT’s "Wildlife Roadkill Identification Guide" focused on the most common large carnivores and ungulates found in British Columbia. The guide was developed to assist BCMoT's maintenance contractors in identifying wildlife carcasses found on provincial highways as part of their responsibilities for BCMoT’s Wildlife Accident Reporting System (WARS).[17]

Prevention[edit]

Mountain goats used to cross US Route 2 to reach a salt lick on the other side of the canyon. Now they can get there via rocky passageways underneath these bridges, shielded from view by tree cover and the steep hillside.
Traffic signs are often used to warn of areas with increased animal activity. These signs are not always successful, as shown by the dead emu in the far distance to the right of the sign.

Collisions with animals can have many negative consequences:

  • Death and suffering of animals struck by vehicles
  • Injury to, or death of, vehicle occupants
  • Loss of valuable livestock or pets
  • Harm to endangered species
  • Vehicle damage
  • Economic losses (cleanup, repairs to vehicles, etc.)
  • Roadkill is a distasteful sight, particularly costly to locations economically reliant on tourism.[6]

Regardless of the spatial scale at which the mitigation measure is applied, there are two main types of roadkill mitigation measures: changing driver behavior and changing wildlife behavior.[18]

There are three potential ways to change driver behavior. Primary methods focus on changing driver attitude by increasing public awareness and helping people understand that preventing roadkill will benefit their community. The second potential way is to make people aware of specific hazardous areas by use of signage, rumble strips or lighting. The third potential way is to slow traffic physically or psychologically, using chicanes or speed bumps.

There are three categories of altering wildlife behavior. Primary methods discourage wildlife from loitering on roadsides by reducing food and water resources, or by making the road surfaces lighter in color which may make wildlife feel more exposed on the roadway. Second are methods of discouraging wildlife from crossing roads, at least when cars are present, using equipment such as ultrasonic whistles, reflectors, and fencing. Third are mechanisms to provide safe crossing like overpasses, underpasses and escape routes.

Large animals[edit]

Collisions with large animals with antlers (such as deer) are particularly dangerous, as the animal's head has a tendency to separate and come through the windshield[citation needed], but any large, long-legged animal (e.g. horses, larger cattle, camels) can pose a similar cabin incursion hazard. Injury to humans due to driver failure to maintain control of a vehicle either while avoiding, or during and immediately after an animal impact, is also common.

Acoustic warning deer horns can be mounted on vehicles to warn deer of approaching automobiles, though their effectiveness is disputed.[19] Ultrasonic wind-driven whistles are often promoted as a cheap, simple way to reduce the chance of wildlife-vehicle collisions. In one study, the sound pressure level of the whistle was 3 dB above the sound pressure level of the test vehicle, but caused no observable difference in behavior of animals when the whistles were activated and not activated, casting doubt on their effectiveness.[18]

Small animals[edit]

In regions where squirrels, rabbits, birds, or other small animals are plentiful, a tire-flattened one is a common sight on roadways. Motorists have caused serious accidents by trying to swerve or stop to avoid a squirrel in the road.[20][21][22] Such evasive maneuvers are pointless, since small rodents and birds are much more agile and have much quicker reaction times than motorists in heavy vehicles. There is very little a driver can do to avoid an unpredictably darting squirrel or rabbit, or even to intentionally hit one. A humane and prudent course of action is to continue driving in a predictable, safe manner, and let the small animal decide on the spur of the moment which way to run or fly; the majority of vehicular encounters end with no harm to either party.[23]

On the other hand, slow-moving reptiles such as turtles and snakes are easily steered around, if speed and traffic conditions permit such evasive maneuvers. Medium-sized slow-moving mammals such as opossum, beaver, or skunk should be avoided if possible.

Night driving[edit]

Although strikes can happen at any time of day, deer tend to move at dawn and dusk, and are particularly active during the October–December mating season. Driving at night presents its own challenges: nocturnal species are on the move, and visibility, particularly side visibility, is reduced. When headlights approach a nocturnal animal, this makes it hard for the creature to see the approaching car (nocturnal animals see better in low than in bright light). Furthermore, the glare of vehicle headlights can dazzle some species, such as rabbits; they will freeze in the road rather than flee. The simple tactics of reducing speed and scanning both sides of the road for foraging deer can improve driver safety at night. Drivers may see the retro-reflection of an animal's eyes before seeing the animal itself.

Wildlife crossings[edit]

Wildlife crossings allow animals to travel over or underneath roads. They are most widely used in Europe, but have also been installed in a few US locations and in parts of Western Canada. As new highways cause habitats to become increasingly fragmented, these crossings could play a crucial role in protecting endangered species.

In the United States, sections of road known to have heavy deer cross-traffic will usually have a warning sign depicting a bounding deer. Similar signs exist for moose, elk and other species.

In the American West, roads may pass through large areas designated as "open range", meaning no fences separate drivers from large animals such as cattle or bison. A driver may round a bend to find a small herd standing in the road. Open range areas are generally marked with signage and protected by a cattle guard.

In an attempt to mitigate $1.2 billion in animal-related vehicular damage, a few states now have sophisticated systems to protect motorists from large animals.[24] One of these systems is called the Roadway Animal Detection System (RADS).[25][26] A solar powered sensor can detect large animals such as deer, bear, elk, and moose near the roadway, and thereafter flash a light to alert oncoming drivers. The sensor's detection distance ranges from 650 feet to unlimited, depending on the terrain.

Canopy crossings[edit]

The removal of trees associated with road construction produces a gap in the forest canopy that forces arboreal (tree dwelling) species to come to the ground to travel across the gap. Canopy crossings have been constructed for red squirrels in Great Britain, colobus monkeys in Kenya, and ringtail possums in Far North Queensland, Australia.[27] The crossings have two purposes: to ensure that roads do not restrict movement of animals and also to reduce roadkill. Installation of the canopy crossings may be relatively quick and cheap.

Escape routes[edit]

Banks, cuttings and fences that trap animals on the road are associated with roadkill.[28] In order to increase the likelihood of escape from a main roadway, escape routes have been constructed on the access roads. Escape routes may be considered as one of the most useful measures, especially when new roads are being built or roads are being upgraded, widened or sealed. Research may be undertaken into the efficacy of escape routes by observations of animals’ response to vehicles in places with natural escape routes and barriers, rather than trialing purpose-built escape routes.

Fencing[edit]

In the New Forest, in southern England, there is a proposal[citation needed] to fence roads to protect the New Forest pony. However, this proposal is controversial.[29]

HAYTAP's "Brake for Animals!" campaign

Attractive nuisances[edit]

On roadways where rumble strips are installed along road shoulders, they may accumulate road salt in regions where it is used. The excess salt constitutes an attractive nuisance because it may attract both small and large wildlife in search of salt licks; these animals are at great risk of becoming roadkill or causing accidents.[30][31][32]

Eating roadkill[edit]

Main article: Roadkill cuisine

Cultural aspects[edit]

  • The fact that most people's encounters with roadkill occur long enough after the time of death for the carcass to be further macerated by traffic, or begin to decompose, has contributed to strong negative or ironic cultural associations and taboos. For example, when the Tennessee legislature attempted to legalize the use of accidentally killed animals, they became the subject of stereotyping and derisive humor.[33] Songwriter and performer Loudon Wainwright III released his deadpan humorous song "Dead Skunk (in the Middle of the Road)" in 1972, and it peaked at number 16 on the Billboard Hot 100 rankings.[34]
  • Roadkill is sometimes used as an art form. Several artists use traditional taxidermy preparation in their works whilst others explore different artforms. International artist Claudia Terstappen photographs roadkill[35] and produces enormous prints which see the animals floating eerily in a void.[36] Roadkill as art is not new, American artist Stephen Paternite has been exhibiting roadkill pieces since the 1970s.[37]

Intentional collisions[edit]

Research conducted in Ontario, Canada in 1996 found a high number of reptiles killed on not normally travelled portions of the road, which led to the presumption that some drivers intentionally run over reptiles. To verify this hypothesis, an experimental research was conducted in 2007, which found that 2.7% of motorists intentionally hit reptiles such as snakes and turtles. The rate of intentional hits was five times higher for male drivers.[38]

See also[edit]

Further reading[edit]

  • Roger M. Knutson: Common Animals of Roads, Street, and Highway: A Field Guide To Flattened Fauna.[39]

References[edit]

  1. ^ Case, R. M. 1978. Interstate highway road-kill animals: a data source for biologists. Wildlife Society Bulleting 6:8-13.
  2. ^ "Report shows high animal road kill toll in Tasmania". Abc.net.au. 2005-11-24. Retrieved 2013-02-20. 
  3. ^ Wollan, Malia (12 September 2010). "Mapping Traffic’s Toll on Wildlife". The New York Times. Archived from the original on 5 November 2011. Retrieved 14 August 2013. 
  4. ^ Seiler, Andreas; Helldin, J-O (2006). "Mortality In Wildlife Due To Transportation". In Davenport, John; Davenport, Julia L. The Ecology of Transportation: Managing Mobility for the Environment (Springer). pp. 166–8. ISBN 1-4020-4503-4. Retrieved 14 August 2013.  Google Books
  5. ^ Erritzoe J., Mazgajski T. D., Rejt Ł. 2003. Bird casualties on European roads — a review. Acta Ornithol. 38: 77–93.
  6. ^ a b c Alistair J. Hobday and Melinda L. Minstrell: "Distribution and abundance of roadkill on Tasmanian highways: human management options", in Wildlife Research, nr. 35 1998
  7. ^ "Roadkill 2007 – Summary of Past Data". Roadkill.edutel.com. Retrieved 2013-02-20. 
  8. ^ "Animal People Newspaper". Animalpeoplenews.org. Retrieved 2013-02-20. 
  9. ^ Rao, R. Shyama Prasad; Girish, M. K. Saptha (2007). "Road kills: Assessing insect casualties using flagship taxon" (PDF). Current Science (Current Science Association) 92 (6): 830–837. Retrieved 25 June 2013. 
  10. ^ "'Splatometer' to count bug life". BBC News. 30 June 2003. Retrieved 4 June 2014. 
  11. ^ McCarthy, Michael (2 Sep 2004). "40,000 'splatometers' can't be wrong: insect population is in decline". The Independent. Retrieved 4 June 2014. 
  12. ^ Messenger, Stephen (10 Jul 2011). "Trillions of Insects Killed by Cars Every Year, Says Study". TreeHugger. Retrieved 22 June 2014. 
  13. ^ "wildlifecrossing.net/california". Wildlifecrossing.net. Retrieved 2013-02-20. 
  14. ^ "wildlifecrossing.net/maine". Wildlifecrossing.net. Retrieved 2013-02-20. 
  15. ^ "Roadkill — Wildlife Collision Mortalities | IFWIS". Fishandgame.idaho.gov. Retrieved 2013-02-20. 
  16. ^ "th.gov.bc.ca". th.gov.bc.ca. Retrieved 2013-02-20. 
  17. ^ "th.gov.bc.ca". th.gov.bc.ca. Retrieved 2013-02-20. 
  18. ^ a b Magnus, Z., L.K. Kriwoken, N.J. Mooney, and M. E. Jones. 2004. Reducing the incidence of wildlife roadkill: improving the visitor experience in Tasmania.
  19. ^ Palmer, Janice. "Deer-Whistles Ineffective, Says Bioacoustics Researcher." November 2002. 21 November 2008
  20. ^ Marshall, Edward (March 31, 2008). "Squirrel blamed for accident: Couple struck head-on after woman swerves to avoid animal". The Journal (Martinsburg, WV). Retrieved 6 May 2012. 
  21. ^ "Driver says squirrels made him crash into garage". Chicago Sun-Times. October 3, 2011. Retrieved 19 April 2012. 
  22. ^ "Confused squirrel causes three-car accident". South Whidbey Record. Sound Publishing Inc. 25 Jun 2008. Retrieved 19 April 2012. 
  23. ^ "Swerving can be worse than hitting animal on road". USA Today. 11 Jan 2012. Retrieved 6 May 2012. 
  24. ^ ""Animal Vehicle Crash Mitigation," Oregon Department of Transportation" (PDF). Retrieved 2013-11-16. 
  25. ^ "Roadway Animal Detection System, Sensor Technologies & Systems, Inc." (PDF). Retrieved 2013-11-16. 
  26. ^ "Animal Detection System, Safeguards Technology, LLC" (PDF). Retrieved 2013-11-16. 
  27. ^ Norwood, C. (1999). Book Review: Linkages in the landscape: The role of corridors and connectivity in wildlife conservation. Pacific Conservation Biology 5: 158.
  28. ^ Shaw, R. A., Jones, M. E. and Richardson, A.M.M. (2003). Predicting the location of wildlife road-kill in Tasmania (In-prep).
  29. ^ "Fencing to protect ponies". BBC News. 2009-01-21. Retrieved 2010-04-10. 
  30. ^ "Wildlife-Vehicle Collision and Crossing Mitigation Measures: A Toolbox for the Montana Dept of Transportation, May 2007". Mdt.mt.gov. 2013-04-19. Retrieved 2013-11-16. 
  31. ^ "Reducing Moose–Vehicle Collisions through Salt Pool Removal and Displacement: an Agent-Based Modeling Approach, Ecology and Society, 2009". Ecologyandsociety.org. Retrieved 2013-11-16. 
  32. ^ "U.S. FHWA, Public Roads, Of Moose and Mud, Sept/Oct 2005". Tfhrc.gov. Retrieved 2013-11-16. 
  33. ^ Firestone, David (1999-03-14). "Statehouse Journal; A Road-Kill Proposal Is Food for Jokesters". The New York Times. Retrieved 2010-04-10. 
  34. ^ Dead Skunk Songfacts.
  35. ^ http://www.claudiaterstappen.com/roadkill
  36. ^ "After Life". 
  37. ^ "Roadkill artist speaks of controversial work". Stroud News & Journal. Retrieved 2007-10-16. 
  38. ^ E. Paul Ashley et al. "Incidence of Intentional Vehicle–Reptile Collisions", in Human Dimensions of Wildlife, nr.12, 2007
  39. ^ "Roger M. Knutson". Biology.luther.edu. 2013-02-15. Retrieved 2013-02-20. 

External links[edit]