A
talk by Dr Sarah Perkins to the Berkshire Mammal Group
9th
February 2017
Dr
Sarah Perkins is a wildlife biologist at Cardiff University, having
started her career as a conservation officer for the UK Wildlife
Trust. In an entire year of working as an Otter Conservation
Officer, Sarah only ever saw one otter – a road-killed one – and
became interested in quantifying the number of animals killed on the
roads each year. She worked abroad for several years, working on
wildlife diseases, before returning to the UK and taking a position
at Cardiff. There her interest in the number of animals killed,
which species are the most vulnerable, and whether there were
hotspots of roadkill that could be mitigated against, led her to
establish Project Splatter in 2013, as a collaborative citizen
science project – the subject of her talk to the Berkshire Mammal
Group.
Sarah
opened by acknowledging that road kill is a common sight and asking
generally how we engage with wildlife, and what the impact of roads
might be on animal mortality. She turned to the journal, Science,
which in December had published a paper on roadlessness. On screen
was a map plotting the incidence of roads in red, lined with 1 km
buffers into the surrounding habitat, and the road-free areas in
blue, in which roads would have no effect on wildlife. 80% of the
globe is still roadless, but much of this area is composed of the
Arctic regions, the Siberian tundra and deserts in north Africa and
Australia and other inhospitable environments. And the rest is
divided into 600,000 fragmented habitats, half of which are less than
1 km in extent and only 7% are of the largest size category). Only
9.3% are protected areas. So the clear conclusion was that roads
have the potential for a major impact on wildlife and its habitats.
The scale of road deaths
What
might be the scale of wildlife road deaths, she asked, pointing to
illustrative graphics: 100s, 10,000s, or 1,000,000s. Answering her
own question – after an uneasy pause – Sarah said we simply don’t
know, but can look at studies in other countries that have measured
the effects direct vehicle collisions. They propose some
dramatically varying estimates:
USA 80m birds killed on US roads per annum
Netherlands 0.2 – 2m birds
Belgium 4m
Denmark 8.3m
Spain 100,000
In the UK
a PTES survey was launched in 2001, which has since measured mammals
on roads for a period each summer. Usefully it has reflected the
decline of the hedgehog, and also picked up a fall in rabbit numbers.
But this survey is just in the summer, and just of mammals. Were
there any other figures? Well, yes, Deer Collisions
(www.deercollisions.co.uk) estimates 42,000 to 74,000 collision
deaths a year, information drawn from police and insurance reports.
The Mammal Society has produced estimates of 50,000 badger deaths a
year, and 100,000 fox deaths. For birds a BTO Road Deaths Enquiry in
1960, at a time when there was rather less traffic than now,
concluded a total of 2.9m avian road deaths. Sarah noted it took
until 1965 for the figures to be published.
Project Splatter
To draw
together contemporary data on all species, Sarah introduced Project
Splatter as a continuous, UK-wide survey, set up in January 2013.
She explained that it started out as a final year project, undertaken
with some reluctance at first by Sam Stafford, an undergraduate
reading Zoology at Cardiff. He devised a social media to capture
direct reporting by members of the public, and such was its early
success that he become highly motivated and earned the soubriquet,
“Splatter Sam”. This early success was cemented by the
involvement of the press, in particular the publication of a
two-page, full colour spread in the Independent, prompting
wider
media attention. It was, in Sarah’s words, “a fantastic start”.
The social media platform is designed to make the task of reporting
simple and accessible. Reports can be sent in by iPhone app, Android
app, Facebook, Twitter and by email or through the web. The scheme
accepts both occasional and regular reporting – there need be no
on-going commitment, though many of the 2,000 participants are
regular contributors – and on Monday the project offers feedback,
drawing attention to some of the quirkier reports.
The
project’s purpose is to quantify and map British roadkill,
determining which species are the most observed, and identifying
spatial and temporal hotspots: the ‘where’ and ‘when’. It
aims to raise awareness of the roadkill problem, and encourage
mitigation (such as green bridges). Ultimately it seeks to reduce
the negative impact of roads on wildlife.
Findings
To date,
Project Splatter has accumulated over 35,000 records. These include
33 mammal species, from shrews to wild boar, and these represent 62%
of the records.. Representing another 34% are the 74 bird species,
from blackcap to buzzard. There are very few reptiles and
amphibians. The five species most recorded as roadkill are:
15% Badgers
14% Rabbits
11% Foxes
7% Hedgehogs
7% Pigeons
And as
for distribution, the records come from throughout the country,
probably reflecting abundance. However, any analysis needs to
account for reporter bias; there are few reports from the Highlands
of Scotland, whereas Sussex generates more records than any other
county. (There, a paramedic has been involved from the start and is
a prolific provider of records.) Double counting is not considered a
problem at this stage; with 2,000 reporters and 8,000 reports a year,
there are simply not enough reports for duplicated to occur to any
degree.
Berkshire
A map of
the county indicated ribbons of reports along the M4, A34 and Vale of
the White Horse, with a cluster around Newbury and a broader blanket
of sightings to the west of the Thames around Abingdon.
In
Berkshire pheasants are the most prevalent casualties, at 39% of
reports compared with 23% nationally. (At 25% for badgers the local
and national tallies are in line, though other species tend to be
under represented.) But what do the figures suggest about pheasants’
behaviour. A graph of the monthly figures produce a peak in
September and October, when naïve young birds are released, and in
March, when feral pheasants escape into the countryside.
Using
SaTScan models, the Project has identified nine county clusters for
mammals, some comprising single species and some of multiple species.
There are obvious clusters, such as for badgers in Somerset, where
they are presumed to relate to animal abundance, while others are as
yet unexplained, such as the concentration of rats in northern
England.
For birds
there are seven such clusters. An analysis of these suggests some
behaviours tends to endanger certain species. Blackbirds, for
instance, have a tendency to last-minute flight from possible
predators, and a low, undulating flight pattern, and so are innately
vulnerable to vehicles. In discussion afterwards it was noted that,
conversely, crows have an enhanced ability to judge the paths of
approaching danger, and avoid on-coming vehicles.
Sarah
asked which roads were the most deadly: Motorways, A roads or B
roads. The answer was A roads. Is this the effect of lighting, she
wondered, increasing visibility and causing animal avoidance?
Hedgehogs were cited as an example of a vulnerable species, falling
from 30m in 1950, when there were far fewer motorways and major
roads, to 1.5m in 1995. 20-40,00 are killed on roads per annum –
far too high a figure.
Peak
reporting is in September, July and April, with winter the lowest.
Perhaps unsurprisingly the peaks coincide with seasonal breeding and
dispersal activity, while many creatures hibernate during the winter.
Yet this varies from year to year, according, in part to temperature
and the weather, which affects activity and therefore vulnerability
to vehicles.
Disappearance of carcasses
It is
accepted that scavengers clear carcases and therefore evidence, so
establishing the rate of disappearance would give a useful correction
factor when analysing the figures. One early study was by Fred
Slater, who set out chicken carcasses and measured the tracks of
scavengers left in a surrounding sand pit. He established the rate
of disappearance was rapid, suggesting that reporting was
underestimated 12-16 fold.
To extend
this research for the project’s own purposes the University of
Cardiff undertook to study the rate of disappearance. Chicken heads
were distributed by student Harry Williams at twelve locations around
the city, with camera traps set up: some in parks, some in streets.
As an amusing aside, Sarah recounted how some of the cameras
disappeared, then reappeared, many with footage of puzzled residents
investigating the device, and then, having realised what it was,
putting it back! The survey was carried out both day and night, and
recorded 120 sessions.
Six
principal species of scavenger were identified: corvids, foxes, dogs,
cats and gulls. How long it took for the carcasses to be taken varied
according to the time of day: in the daytime it was very quick, but
at night it tended to lie untouched until at dawn, when scavenging
was dominated by foxes and domestic cats. Quantifying that, it was
established there was a 75.8% chance of removal within 12 hours. On
average it took 2 hrs, 13 mins in the day; 8 hrs and 47 mins at
night.
To
illustrate which scavengers eat carcasses, Sarah showed a short video
made up of day and night-time footage from the camera trips. During
the day there were plenty of corvids (crows and magpies), cats and
dogs; at night, there were rats, foxes, gulls, magpies and –
surprisingly – wood mice (visible mainly by their large reflective
eyes). Urban foxes were brazen, while rural foxes markedly more
timid.
Associated Research
Project
Splatter’s records are considered open source and available to
share, and so feed into several other studies. Among these are the
records of polecats, which are sent to the Vincent Wildlife Trust to
help monitor the expansion of this species out from central Wales.
Records have been used to help with mapping invasive species, eg
Wallaby in Surrey; Wild Boar in Bristol. But perhaps the most
systematic is the 20-year-old otter project run by Liz Chadwick, also
at Cardiff University.
Cardiff University Otter Project
In this
project otter carcasses are taken to Cardiff for post mortem
examination, where the livers and kidneys are checked for
contaminants in habitat, parasites are identified, signs of fecundity
noted. Rather sadly, Sarah noted the discovery of four nearly
full-term foetuses that had died when their mother had been hit. The
results of post mortems contribute to various study programmes, the
decline of eels and the presence of Toxoplasma gondii, for
instance. The otter is a sentinel for watercourse purity and so much
can be gained by their examination.
Dead or Alive
A
spin-off project, entitled ‘Dead or Alive’, was set up to
quantify popular interaction with wildlife; do most people see
wildlife alive, or just as roadkill? The project conducted a
four-week survey, eliciting 1,400 responses! To take one of the top
five roadkill species, the badger, it was possible to establish that
7% of respondents had never seen one, but 88% had seen one dead. As
few as 5% had only ever seen live badgers.
Only seen alive Ever seen dead
5% Badger 88%
Respondents
were invited to leave comments too, and the responses indicated a
high level of concern about the spread of invasive species.
Roadkill Sub-culture
Touching
on an interaction of a more unusual nature, Sarah spent a few minutes
describing some aspects of roadkill’s place in art, design,
clothing and food. She pointed to the activity of ‘freegans’,
those who eat roadkill, and the existence of roadkill chefs and
‘badger balti’. She illustrated some of the work of Adam
Morrigan, the roadkill artist, and of Jez East/ton Design
Conclusions
Returning
to Project Splatter, Sarah drew together the various threads of her
talk, summarising the role of roadkill research as a contributor to:
- Conservation
- Understanding populations and behaviours
- Academic research, eg. the otter project
- Identifying habitat contamination
- Mapping invasive species
- Public engagement
She ended
by urging the audience to get involved, and supporting imminent moves
for new legislation being led by Wendy Morton MP: the Local Authority
Roads (Wildlife Protection) Bill.
No comments:
Post a Comment