By Rachel Stockwell, Research Assistant, Project Splatter
There are approximately 365,000km of roads, (Richardson et al. 1997), and 34.5 million vehicles in the UK; figures which increase every year. Both roads and traffic are known to have detrimental effects on local wildlife, including habitat destruction and fragmentation, as well as causing environmental disturbance (Vercayie and Herremans 2015). The ultimate effect of roads on wildlife is that they can cause mortality and unfortunately, wildlife roadkill is not an uncommon sight in many countries.
The question is however, across the UK, which species are being lost as roadkill, and when and where is this happening? To address these questions, the People’s Trust for Endangered Species (PTES) have run a nationwide ‘Mammals on Roads’ survey for the past 14 years. This citizen science survey recruits members of the public to drive a standardised section of a single carriage road in the summer, recording all mammal sightings; – dead or alive.
This work demonstrates the value of collecting roadkill data over many years, with the data having picked up long-term declines in the hedgehogs across the UK (Roos et al. 2012). Despite the long term data collected by ‘Mammals on Roads’, there still remains a need to know where and when all of our species are seen as roadkill in the UK. To address this question ‘Project Splatter’ was initiated.
Project Splatter – ‘Social media PLATform for Estimating Roadkill’ – is a citizen science research project which collates wildlife roadkill reports sent in by members of the public via social media. Feedback is provided to our followers on social media via a weekly ‘Splatter report’ alongside graphs and maps of our latest findings. Initiated in January 2013, to date we have received over 18,000 reports of 162 different species across the UK from the Channel Islands to the Highlands and Islands. Indeed, our latest map showing reports across the UK demonstrates the extent of reporting (Figure 1).
The majority of wildlife reported to the project are mammals (62%), with 34% birds and the remaining 4% consisting of a small number of amphibians and reptiles. Our iconic UK species, the badger, is the most frequently reported, followed closely by rabbits and foxes (Figure 2).
As well as reports of common species we also get reports of species that you may not know exist in the UK. The wild boar, for example, was driven to extinction at the end of the 13th century (Wilson 2013) but with numerous escapees from captive boar farms, they became established again in the late 90’s (Goulding et al. 2003), with stable populations in Kent/Sussex and the Forest of Dean. We have received 5 roadkill reports of wild boar, 2 of which are from the Forest of Dean area, and the other 3 from Avon and Hampshire, showing possible spread of this re-established species.
Concerned about the diversity and number of animals that were being reported to us via Project Splatter, in 2015 we ran a survey to determine if members of the public were engaging with common UK wildlife species by seeing them alive in their natural habitat or, sadly, only dead on roads. Hence, the survey ‘Dead or Alive’ was borne via social media. Over 1,400 people responded and of the 21 species listed in the survey, unsurprisingly the top 5 species that were seen dead reflected the top 5 species reported to us as roadkill (Figure 3). Badgers were the least commonly observed alive out of the top five with only 5% of people having observed a live animal.
In terms of where wildlife roadkill is being observed the majority are on A-roads (Figure 4). These roads have a higher traffic volume and speed than minor roads, but why do we not see more casualties on motorways where traffic volume and speed is at its highest? The answer is most likely due to the extent of A-roads in the UK; there are 29.1 thousand miles of A-roads in the UK, but only 2.3 thousand miles of motorway (Department of Transport).
Figure 4: Wildlife roadkill reports submitted to Project Splatter, by road type in the UK January 2013 – March 2016.
Refining further the question of where wildlife roadkill are observed, we carried out a study, aiming to identify hotspots in the UK, using Project Splatter data collated from 7th January – 7th October 2013. Statistical spatial modelling revealed several potential wildlife roadkill hotspots across the UK. Nine mammal hotspots were identified, including a badger hotspot in the South-West of England, and a rabbit and hare hotspot in the South-West of Scotland. For birds, seven hotspots were identified, including a pigeon hotspot in the centre of West Sussex and a pheasant hotspot located in the counties of Northamptonshire, Oxfordshire, Buckinghamshire and Warwickshire. The question is, what mechanisms might contribute to wildlife roadkill in these specific locations? One factor that is known to be highly prevalent on our motorways and A-roads which alters animal behaviour is artificial lighting. Lighting from street lamps can cause disorientation for animals (Mathews et al. 2015; Rodríguez et al. 2015). Nocturnal animals are especially vulnerable to artificial lighting due to their rod-rich retinas, meaning they have highly sensitive eyes but with relatively low visual acuity, which can cause them to become temporarily blinded when exposed to bright light (Rich and Longcore 2006). This temporary blindness could make animals more likely to suffer mortality on roads through wildlife vehicle collisions (WVCs) (Gaston and Bennie 2014). As such, species specific traits (e.g. nocturnal versus diurnal) may render certain species more vulnerable to mortality on roads than others. We are currently using data submitted by citizen scientists to determine the relationship between artificial lighting, road type and spatial variation in landscape features, in order to explore their association with WVCs.
To continue our future research we need your continued help to estimate the impact of roads on our wildlife! Please join us in our research and next time you go on a journey, why not pass the time by looking out for roadkill and let us know when, where and what you spot! You can report to the project by:
1) Twitter (@projectsplatter) and Facebook (https://www.facebook.com/SplatterProject13)
2) Website (www.projectsplatter.co.uk) through an online form
3) Email (firstname.lastname@example.org)
4) Android app, available from the Google Play Store.
Gaston, K. J. and Bennie, J. (2014). Demographic effects of artificial nighttime lighting on animal populations. Environmental Reviews 22:323-330.
Goulding, M. J., Roper, T. J., Smith, G. C. and Baker, S. J. (2003). Presence of free-living wild boar Sus scrofa in southern England. Wildlife Biology 9:15-20.
Mathews, F., Roche, N., Aughney, T., Jones, N., Day, J., Baker, J. and Langton, S. (2015). Barriers and benefits: implications of artificial night-lighting for the distribution of common bats in Britain and Ireland. Philosophical Transactions of the Royal Society B-Biological Sciences 370.
Rich, C. and Longcore, T. (2006). Ecological consequences of artificial night lighting. Washington, DC: Island Press, pp. xx, 458 p.
Richardson, J. H., Shore, R. F., Treweek, J. R. and Larkin, S. B. C. (1997). Are major roads a barrier to small mammals? Journal of Zoology 243:840-846.
Rodríguez, A., García, D., Rodríguez, B., Cardona, E., Parpal, L. and Pons, P. (2015). Artificial lights and seabirds: is light pollution a threat for the threatened Balearic petrels? Journal of Ornithology 156:893-902.
Vercayie, D. and Herremans, M. (2015). Citizen science and smartphones take roadkill monitoring to the next level. Nature Conservation-Bulgaria 29-40.
Wilson, C. J. (2013). The Establishment and Distribution of Feral Wild Boar (Sus scrofa L.) in England. Wildlife Biology in Practice 10:1-6.