Research articleAn evaluation of odor repellent effectiveness in prevention of wildlife-vehicle collisions
Introduction
Wildlife-vehicle collisions (WVC) are a safety issue in many countries. Collisions with large mammals, ungulates in particular, result in traffic crashes with property damage, car passenger injuries and even fatalities. Several measures have been recommended to decrease the number of WVC. They can be divided into three elementary groups: measures affecting animal behavior, alert systems for drivers and systems protecting the infrastructure from animals entering. For a summary of the above-mentioned methods, we recommend works by Hedlund et al. (2004) and Huijser et al. (2007).
The best results in lowering WVC numbers (up to 83%) were achieved using fencing combined with over- and underpasses (Rytwinski et al., 2016). It is also apparent that the overall costs of these highly effective measures would be unacceptable specifically for the majority of secondary roads. Landscape connectivity and the securing of the possibility of wild animals crossing roads is another factor as to why fencing is only recommended for primary roads. Affordable countermeasures, such as repellents, which should both warn animals and allow them to cross roads are therefore suitable for secondary roads.
Repellents can be chemical, visual, acoustic or a combination (Mason, 1989). Taste repellents were used as useful tools in preventing damage to plants and odor repellents in reducing WVC (Hedlund et al., 2004). The majority of papers have been focused on taste repellents inducing a gastrointestinal malaise, whereas chemical repellents are tested only occasionally (e.g., Nolte and Wagner, 2000, Kinley et al., 2003).
We focused on chemical odor repellents as this is a financially affordable measure, especially when compared to fencing and other civil structures. Odor repellents, which are based on a foam carrier releasing an unpleasant scent, are popular in certain European countries where they are widely applied along roads as well as on crop fields or on young forests (Mason, 1998).
Chemical repellents seem to be a socially appealing alternative to reduce ungulates crossing the road where they are less visible to drivers (Reidinger and Miller, 2013). New products are continually becoming available, but their ability to repel wildlife is extremely variable, as they are based on various active substances (e.g., bittering agents, garlic, particulates, natural predator excretions, or putrescent egg). Odors associated with the mutual behavior of vertebrates consist of allelochemics (Whittaker, 1970), particularly important odors for interactions between organisms of different species. Allelochemics are thus odors in which the individuals of one species affect, among other things, the behavior of another species (see Whittaker and Feeny, 1971). Many of the odor repellents are based on the kairomones of different predators. Unfortunately, it has been shown that certain prey adapt themselves to the presence of kairomones in the environment (Brown et al., 1970). When the prey detects the presence of kairomones in the environment, it will change its behavior (e.g., Oriazola and Braňa, 2003). If odor repellents are used, additional contact with a potential predator is lacking (visual, acoustic) and therefore the prey should cross a road with higher caution. The animals, particularly ungulates, should be warned by the released scent with a predator or human odors that a danger exists (Clark and Avery, 2013). No behavior study was, to the best of our knowledge, conducted in this sense thus far.
There have not been many rigorous studies on odor repellent effectiveness in prevention of WVC. The effectiveness of odor repellent in moose-vehicle collisions has been reported by Andreassen et al. (2005). Elmeros et al. (2011) published a field study where they tested two odor repellents (Mota FL and Wolf Urine) and evaluated their effectiveness on roe deer (Capreolus capreolus) and red deer (Cervus elaphus). The authors concluded that both species tended to grow used to the scent and that both odor repellent types would also not work, as expected, in prevention of wildlife-vehicle collisions on roads. The ineffectiveness of the two odor repellent types was also demonstrated in a work conducted by Brown et al. (2000) in Alberta (Canada), as well as in a meta study conducted by Huijser et al. (2007, see page 113 and Table 11).
Information on odor repellent effectiveness often comes, however, from data provided by their producers (e.g., Putman, 1997). Producers claim that predator scent, which is continuously released from a foam installed along a road, will increase the vigilance of ungulates. Direct monitoring of ungulate behavior is usually impossible and therefore the repellent effectiveness is evaluated on the basis of carcasses found along roads or traffic crash data. Study designs concerning the effectiveness of repellents are often inappropriate, e.g., they do not contain control sections for elimination of confounding factors (e.g., Kušta et al., 2015) and therefore the decrease in the number of animal carcasses cannot be explicitly attributed to the effect of odor repellent.
Wildlife-vehicle collisions make up approximately 11% (data for 2016) of all registered crashes on roads in the police crash database in the Czech Republic. Roe deer were the majority of the species involved, followed by wild boar (Sus scrofa). The overall numbers of crashes with wildlife are on the rise. Between 2007 and 2016, the ratio of WVC to all registered traffic crashes rose from 4% to 11%. The ratio for domestic animals remains the same (approx. 1%) over the time interval. The rise in the overall number of individuals is the highest for wild boar which is becoming a Europe-wide problem (Massei et al., 2014). The problem of WVC is therefore urgent. Details about locations, dates of crashes and species can be seen at www.srazenazver.cz website (see Bíl et al., 2017) which is a web-map application gathering and analyzing data on WVC in the Czech Republic.
The aim of this study is to test the effectiveness of a particular preparation of odor repellents using a rigorously designed experiment as a Before-After-Control-Impact (BACI) study.
Section snippets
Data
WVC occur in a spatial pattern along roads (Gunson et al., 2010, Bíl et al., 2016). Places where WVC (and any other crashes) concentrate are called clusters (Elvik, 2008, Erdogan et al., 2008, Bíl et al., 2013). We computed the clusters from existing WVC data between 2009 and 2012 in order to identify suitable locations for odor repellent installation. These clusters (WVC hotspots) were used as the main sections. Certain methodological issues concerning the evaluation of safety measures along
Odor specification
We tested “Pacholek” odor repellent from Ekoplant Company (Praha, Czech Republic) which is based on isovaleric acid, i.e., naturally existing fatty acid which occurs as part of essential oils. It is a transparent liquid dissolved in the majority of organic dissolvents. The repellents were applied 80 cm above the ground as foam to wooden poles. Based on the instructions from the producer, the poles were placed at intervals of 10 m and the foam (scent carrier) was regularly rejuvenated by
Results
Data were analyzed as the three data sets (Carcass data and WVC crash data from 8 to 10 roads) separately and then all together (see Fig. 2 for explanation).
Discussion
WVC pose a problem in traffic safety, especially when large animals are involved. Ungulates negatively impact grain crops, vegetables, fruit trees or occur on or near roads and along airports creating risk of wildlife-vehicle collision both for themselves and for humans (Craven and Hygnstrom, 1994, Conover, 1997). A number of studies have shown that the most effective method for impeding ungulate movement is fencing. Fencing is rather expensive, however, to install and maintain (Romin and
Conclusions
We evaluated the effectiveness of an odor repellent (specifically the product “Pacholek” of the Ekoplant Company) on the basis of a Before-After-Control-Impact study design. Up to 43% of WVC reduction can be expected when this kind of odor repellent is properly applied along roads. This requires, however, maintaining of all of the standards involving odor installation and regular scent rejuvenation. This conclusion, on odor effectiveness, was based on an analysis of 201 WVC records (ungulates)
Acknowledgments
This work was supported by the Ministry of Education, Youth and Sports within the National Sustainability Programme I, project of Transport R&D Centre (LO1610), on the research infrastructure acquired from the Operation Programme Research and Development for Innovations (CZ.1.05/2.1.00/03.0064).
References (35)
- et al.
Srazenazver.cz: a system for evidence of animal-vehicle collisions along transportation networks
Biol. Conservat.
(2017) - et al.
Identification of hazardous road locations of traffic accidents by means of kernel density estimation and cluster significance evaluation
Accid. Anal. Prev.
(2013) A survey of operational definitions of hazardous road locations in some European countries
Accid. Anal. Prev.
(2008)- et al.
Geographical information systems aided traffic accident analysis system case study: city of Afyonkarahisar
Accid. Anal. Prev.
(2008) - et al.
Effectiveness and costs of odor repellents in wildlife-vehicle collisions: a case study in Central Bohemia, Czech Republic
Trans. Res. D
(2015) Biochemical ecology of higher plants
- et al.
How (not) to work with small probabilities: evaluating the individual risk of railway transport
- et al.
The effect of scent-marking, forest clearing, and supplemental feeding on moose–train collisions
J. Wildl. Manag.
(2005) - et al.
The KDE+ software: a tool for effective identification and ranking of animal-vehicle collision hotspots along networks
Landsc. Ecol.
(2016) - et al.
Allomones and kairomones: transspecific chemical messengers
Bioscience
(1970)
Repellency of three compounds to caribou
Wildl. Soc. Bull.
Effectiveness of chemical repellents in managing birds at airports
Monetary and intangible valuation of deer in the United States
Wildl. Soc. Bull.
Deer
Effectiveness of odour repellents on red deer (Cervus elaphus) and roe deer (Capreolus capreolus): a field test
Eur. J. Wildl. Res.
A Guide to Developing Quality Crash Modification Factors
Spatial wildlife-vehicle collision models: a review of current work and its application to transportation mitigation projects
J. Environ. Manag.
Cited by (13)
A descriptive analysis of Deer-vehicle collisions along Missouri interstate highways
2023, Trees, Forests and PeopleSpatial analysis of wildlife-train collisions on the Czech rail network
2020, Applied GeographyCitation Excerpt :Despite this fact, train collisions with amphibians (Budzik & Budzik, 2014; Dornas et al., 2019) or hares (Reck & Schmüser, 2019) have also been studied. Various mitigation measures, such as fences (Barrientos et al., 2019; Carvalho et al., 2017; van der Grift, 1999), various crossing structures (McCollister & van Manen, 2010; Simpson et al., 2016), sound signals (Babińska-Werka et al., 2015; Backs et al., 2017) or odor repellents (Andreassen et al., 2005; Bíl et al., 2018; Kušta et al., 2015) were tested to avoid collisions with wildlife along the transport infrastructure. Methods to monitor and mitigate wildlife mortality on railways have been discussed in detail by Carvalho et al. (2017).
Benefits and challenges of collaborating with volunteers: Examples from National Wildlife Roadkill Reporting Systems in Europe
2020, Journal for Nature ConservationCitation Excerpt :The system is well used by members of the Czech hunting association to provide evidence of game species. An app also includes collection of roadkill data from time-limited campaigns, such as a four-year test of the efficacy of odor repellents to repel wildlife on multiple roads across Czechia (Bíl, Andrášik, Bartonička, Křivánková, & Sedoník, 2018). Data are used by students from many Czech universities for their final thesis as well as by practitioners, for example the National Road Administrator, as a basis for AVC mitigation plans.
On reliable identification of factors influencing wildlife-vehicle collisions along roads
2019, Journal of Environmental ManagementCitation Excerpt :Wildlife-vehicle collisions (WVCs) are a global issue as many animals are killed on a daily basis on both roads and railways (e.g., Bissonette and Kassar, 2008; Rowden et al., 2008; Benítez-López et al., 2010; Sullivan, 2011; Niemi et al., 2017; Santos et al., 2017). Identification of the factors which influence the emergence of WVCs is important for application of suitable preventive measures (e.g., Huijser et al., 2007; Bíl et al., 2018). WVC numbers are rising in a number of countries (Sullivan, 2011; Morelle et al., 2013; Bartonička et al., 2018).