Install acoustic wildlife warnings along roads
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
Collisions with vehicles can be a major cause of mortality for wild mammals and, especially where larger mammal species are involved, a cause of injury, death and economic loss for motorists (Conover et al. 1995). A range of interventions may be employed to deter mammals for accessing roads. This can include use of acoustic warnings which can either be devices that emit sounds or modifications to the road surface that produce noise when vehicle tyres pass over them.
See also: Fit vehicles with ultrasonic warning devices.
Conover M.R., Pitt W.C., Kessler K.K., DuBow T.J. & Sanborn W.A. (1995) Review of human injuries, illnesses, and economic losses caused by wildlife in the United States. Wildlife Society Bulletin, 23, 407–414.
Supporting evidence from individual studies
A before-and-after study in 1997 in a mixed hardwood forest in Zealand, Denmark (Ujvári et al. 2004) found that acoustic road markings did not alter the behaviour of fallow deer Dama dama. Behavioural responses varied among nights, but deer showed increasing indifference to sounds from road markings over 11 nights (i.e. deer appeared to become habituated). Behaviour differed before (flight: 2%, no reaction: 96–99%) and during playbacks, but deer reactions declined over 10 nights of playbacks (night 1: flight 13%; nights 8–10: flight 3–0%, no reaction 88–99%). An area of forest next to an unpaved road closed to vehicles was selected where a herd of 6–12 fallow deer were fed (maize). Recordings of a car passing two types of acoustic road markings which produced sounds when a vehicle’s tyres passed over (low frequency longflex; higher spossflex), multiplied to 70 sequences (each 0.11–0.16 s) were made. Behavioural responses of deer to play-back sounds (58 decibels) at predetermined time intervals (exposure for: 5, 2, 7, 3, 1 and 2 minutes) were monitored over 11 nights in February–March 1997. Behaviour was also recorded every 15 minutes during the two nights before sound trials commenced.Study and other actions tested
A controlled study in 2005 in a grass enclosure in Western Australia, Australia (Muirhead et al. 2006) found that Roo-Guard® sound emitters did not deter tammar wallabies Macropus eugenii from food and so were not considered suitable for keeping them off roads. There was no significant difference between the use of the enclosure or food sources when the Roo-Guards were switched on or off. This was the case even when there was an alternative source of food available away from Roo-Guards. The device did not result in any obvious behavioural responses such as flight or distress. Nine tammars were kept in an enclosure (60 × 30 m), with a test area (60 × 20 m) divided into 12 squares. The remainder of the enclosure was covered in trees and bushes. Roo-Guard® Mk II high-frequency sound emitters were installed on the edge of the test area, 0.5 m off the ground. Animals were observed though a night-vision scope on three nights (18:00–21:00 h) with the Roo-Guard turned on and three with it turned off, for each of four treatments: food 20 m from Roo-Guard, or food 20 and 60 m from Roo-Guard, and the same two treatments but with the sides with food and Roo-Guards swapped over.Study and other actions tested