Elsevier

Journal of Environmental Management

Volume 205, 1 January 2018, Pages 209-214
Journal of Environmental Management

Research article
An evaluation of odor repellent effectiveness in prevention of wildlife-vehicle collisions

https://doi.org/10.1016/j.jenvman.2017.09.081Get rights and content

Highlights

  • We tested the effectiveness of odor repellent preparation in prevention of WVC.

  • 201 killed mammals (roe deer and wild boars) were identified in total over 47 months.

  • A WVC decrease between 26 – 43% can be expected on the treated road sections.

Abstract

Wildlife-vehicle collisions (WVC) amount to 11% of all registered traffic crashes in the Czech Republic causing, apart from numerous deaths and serious injuries to animals, property damage and injuries to car passengers. Odor repellents have the potential to lower the overall number of WVC and allow animals to cross roads at the same time.

We tested the effectiveness of odor repellent preparation in prevention of WVC. 18 places were selected on the Czech road network where WVC were concentrated on the basis of traffic crash data. Control sections on the same road segments were also delimited in order to keep the traffic intensities constant.

We applied a Before-After-Control-Impact (BACI) study design to control not only the effect of the measures but also the expected natural variations in wildlife populations over time. Data were compared before and after odor repellent installations. Wildlife carcass gathering was carried out during the spring and autumn. We also used the police crash database to supplement carcass data when no field works were carried out. 201 killed mammals (roe deer and wild boars) were identified in total over 47 months.

We applied a Bayesian approach as only a limited numbers of WVC were available. A WVC decrease between 26 – 43% can be expected on the treated road sections. These numbers are, however, up to three-times lower than those claimed by producers of odor preparations.

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).

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