Rondinini et al (2002) hedgehog roads bar movements
Title: Roads as barriers to movement for hedgehogs, Functional Ecology 16; 504-509. 2002
Authors: C. Rondinini & C.P. Doncaster
Background to study
Hedgehogs are among the most commonly encountered victims of road traffic and road deaths occur at an overall annual rate of approximately 1-2 per kilometre of road in Western Europe. This study investigates whether hedgehogs avoid crossing roads whilst foraging and thus aims to determine whether roads act as barriers to hedgehog movements.
- Hedgehog foraging behaviour was monitored during autumn (September-October) using radiotelemetry in two sites (Thornden and Redbridge) in Southampton where hedgehog abundance was high and where each site was composed of a large school playground and an abutting motorway and surrounded by residential properties.
- At each site, four male and four female adult hedghogs were located by torchlight and tagged with a Biotrak 7g radio-transmitter. The location of each individual was determined an average of 11.1 times for an average of 3 hours within five replicated sessions per individual, over a period of 6-13 days.
- For each observed trajectory, 100 random walks from the same start point were simulted. Each simulation had the same number of locations and the same frequency distribution of distances between consecutive points as the observed trajectory of the focal individual and were constrained to finish at the start point of the last observed location.
- The rate of road crossings, considering type of road (categorised as small = <4m wide, large= >4-m wide, motorways) was compared between the observed trajectories of each tagged individual and those simulated to be random to determine whether hedgehog movement differed from that considered as random (simulated dataset).
- The proportion of observed locations by habitat type (road verge, urban, gardens, amenity grass and woodland) were compared between the observed habitat use and that expected from a random walk to determine habitat preferences.
- Hedgehogs moved a mean of 380 m per trajectory and their average range use covered an area of 5.0 ha which did not vary significantly between sites or between sexes.
- Over 75% of observed trajectories did not cross any type of road, resulting in a median crossing rate of 0.0 crossings per km and below the rate observed from the simulated trajectories (0.36 crossings per km)
- None of the observed trajectories of the tagged hedghogs crossed motorways or large roads compared to an expected rate of 0.22 and 0.44 per km for simulated trajectories.
- More than half of the individuals were never observed crossing small residential roads at one of the sites.
- There was a trend of decreasing probabilities of road crossing rates with increasing size of roads.
- Road verges were the least perferred habitat type used by tagged individuals and significantly avoided when compared with amenity grassland and garden habitat types.
- Where road verges were used, they were mainly used as daytime rest sites where thick scrub was present.
Key messages to landowners and managers derived from these results
- Roads, in particular larger A-roads and motorways, act as barriers to hedgehog movement and the provision of structures that may encourage movement across roads, by hedgehogs, are an important consideration for both new and existing road networks.
- Research into the types of structure that would facilitate hedgehog movement is recommended.
- Thick scrub along road verges are utilised by hedgehogs, particular if other favourable habitat is locally unavailable, therefore sensitive management of scrubby vegetation along road verges is recommended.
- Research into what road attributes (surface, lighting, traffic flow) influence hedgehog movement would be beneficial for determining what influences the perception of hedgehogs to avoid or cross roads.