Biodiversitat, Carretera nacional, Atropellament mortal, Amenaces, Vida silvestre
Data de recepció: 26/04/2021 | Data d'acceptció: 25/06/2021 | Data de publicació: 05/07/2021
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Wildlife roadkill in Odisha, India: the threat to biodiversity needs to be addressed
Wildlife roadkill in Odisha, India: the threat to biodiversity needs to be addressed
Over a 90–day period we assessed wildlife roadkill on National highway NH–16 in the state of Odisha, India. We recorded 123 vertebrate carcasses: 14 species of mammals, nine species of birds, and seven species of reptiles. Our findings reiterated NH–16 as a vulnerable site of roadkill of many native wild animals and birds. Further studies are required where linear infrastructure affects wildlife and appropriate management strategies are needed.
Key words: Biodiversity, National highway, Roadkill, Threats, Wildlife
Atropellos mortales de fauna silvestre en Odisha, India: una amenaza para la biodiversidad que es necesario abordar
Se evaluaron los atropellos mortales de fauna silvestre en la carretera nacional NH–16, en el estado de Odisha (India), durante un periodo de muestreo de 90 días. En total, la evaluación registró 123 cuerpos de vertebrados muertos pertenecientes a mamíferos (14 especies), aves (nueve especies) y reptiles (siete especies). Esta investigación sobre atropellos mortales confirma que la carretera nacional NH–16 es el punto más peligroso a este respecto para muchas especies de fauna silvestre nativa. Se requieren estudios adicionales para determinar cómo afectan las infraestructuras lineales a la fauna silvestre y establecer estrategias de gestión adecuadas.
Palabras clave: Biodiversidad, Carretera nacional, Atropello mortal, Amenazas, Vida silvestre
Atropellaments mortals de fauna silvestre a Odisha, Índia: una amenaça per a la biodiversitat que cal abordar
Es van avaluar els atropellaments mortals de fauna silvestre a la carretera nacional NH–16, a l’estat d’Odisha (Índia), durant un període de mostreig de 90 dies. En total, l’avaluació va registrar 123 cossos de vertebrats morts pertanyents a mamífers (14 espècies), ocells (nou espècies) i rèptils (set espècies). Aquesta recerca sobre atropellaments mortals confirma que la carretera nacional NH–16 és el punt més perillós pel que fa a atropellaments per a moltes espècies de fauna silvestre nadiua. Cal portar a terme estudis addicionals per determinar com afecten les infraestructures lineals la fauna silvestre i establir estratègies de gestió adequades.
Paraules clau: Biodiversitat, Carretera nacional, Atropellament mortal, Amenaces, Vida silvestre
The negative impact of roads on wildlife in protected areas was first reported in 1935 (Stoner, 1935). Collisions with vehicles are becoming a major cause of mortality for many species worldwide (Bager and Rosa, 2010). Road features such as length, width, state of the road surface, and the amount of traffic can influence the rate of collisions with animals (Smith–Patten and Patten, 2008). Roadkill has increased significantly in recent years, both in rural and urban areas (Laurance et al., 2014). The ecological effects of road construction include habitat loss or fragmentation of natural pathways and may affect the behaviour and biology of species. Collisions with speeding vehicles are especially high on national highways and motorways (Tejera et al., 2018). Road–related wildlife mortality caused by collision with moving vehicles affects healthy individuals as well as weak individuals in a population (Bujoczek et al., 2011) and may lead to local extinction of species (Clarke et al., 1998). Some animal groups, such as small or medium–size mammals, reptiles and birds, are more prone to vehicle collisions due to the changes in ecological behaviour. High speed roads and vehicular traffic affect wildlife by creating barriers to their movement across landscapes, particularly affecting long–ranging mammalian species such as tiger, elephant, leopard, dhole and wolf (Kerley et al., 2002; Blom et al., 2005). Furthermore, the roads may lead to fragmentation of their natural habitat and ultimately isolation of populations (Keller and Largiader, 2003).
Here we studied the intensity of roadkill in small segments of National highway 16 in Odisha (NH–16) and recommend management strategies to mitigate the vehicular collisions with of wildlife.
Material and methods
The study was carried out along a stretch of 11.7 kilometres on NH–16, from Ganja to the town of Chhatrapur in southern Odisha (Ganjam district), India, over 90–days. The NH–16 is 1,711 km long and it connects Kolkata and Chennai (fig. 1). As part of a routine biodiversity study by the Odisha Biodiversity Board in Southern Odisha, NH–16 is frequently used to travel to various biodiversity–rich destinations in this area. This activity provided researchers of the Board an opportunity to investigate roadkill of wild and domestic animals. The stretch of road studied does not pass through any protected forest areas, but it is not far from Reserved Forests (Kriamba RF and Lakhari Valley WL Sanctuary), a natural lake (Tampara Lake) and Rushikulya River. It thus forms part of an area inhabited by significant animal species. The most notable animal species found in this area are the striped hyena, jackal, domestic dog, Indian fox, Pallas’s gull, Brahminy kite, sea eagle, agamid lizard, and olive ridley (Tripathy et al., 2016). Moreover, the Rushikulya River mouth is an important mass nesting rookery for vulnerable olive ridley turtles (Lepidochelys olivacea).
An observer drove along the 11.7 km road stretch every three to four days at a speed of 30 to 40 km/hr to locate road killed animals and recorded the species, location, and date of dead animals found. We performed a total of 90 days of cumulative surveys and covered a total distance of 1,053 km. We excluded carcasses of animals that we were unable to identify. All road–killed fauna were removed after data were recorded to avoid repetition. We calculated the percentage of species killed by vehicles during the study period by estimating species–wise roadkill from total observations (Behera and Borah, 2010). Based on the observation of roadkill, we also estimated roadkill per year by extrapolating the observed roadkill data using the equation:
(Number of carcasses of each species / Number of sampling days) x 365 days
We also estimated the rate of roadkill per day per kilometre by dividing the number of observed carcasses of each species by the total number of days found within the study period (03/02/2018 to 26/10/2018) and adding another 10 days (assuming that carcasses killed at the most 10 days prior to beginning of the study and again dividing 11.7 km to get the rate of roadkill per km in this vulnerable site).
A total of 123 individual fauna were found killed by vehicles on the NH–16 during the 90 days of the survey. Roadkill consisted of 14 species of mammals, nine species of birds, and seven species of reptiles. Table 1 lists the species and numbers of animals found. Roadkill occurrence was highest for the golden jackal and lowest for the striped hyena, grey mongoose, Indian hare, Indian robin, white bellied drongo, greater coucal, collard dove and green keelback. The rate of roadkill/day/km was estimated to be low or less than one at any given sampling site. However, the estimated roadkill per year for golden jackal was higher. The present observation of the total number of carcasses of each species was significantly different from the estimated value of carcasses per year (F = 9.2, p < 0.004) (fig. 2). The species most frequently found was golden jackal (Canis aureus) (n = 27), followed by garden lizard (Calotes versicolor) (n = 17). Figure 3 shows images of several species of roadkill found on the NH–16.
It is evident from the present study that small to medium–sized animals and nocturnal animals were the prime victims of vehicles. Various species of birds, such as the Jungle babbler, Spotted dove, Eurasian collared dove, magpie robin, and red–vented bulbul commonly roam on the road to feed on grains and seeds that drop from food transport vehicles. Furthermore, insects, including many butterflies, are attracted to roads during the monsoon season to obtain salts, minerals and moisture, which many insectivorous birds feed on (Behera and Jena, 2010). Some portions of the stretch are within the municipal dumping yard site, and scavenging species such as jackal, often get killed by speeding vehicles when crossing the road. Other scavengers are often killed scavenging these remains. Carcasses of domestic dog (Canis familiaris) are often found on the road but these data were not included in the current investigation.
Roadkill counts have been used to determine mortality caused by vehicles on wildlife populations (Newmark et al., 1996, Romin and Bissonette, 1996) and as an index of abundance of mammals across seasons (Davies et al., 1987) and years (Hicks, 1993). Reports of roadkill of free–ranging vertebrates caused by vehicular traffic in India are increasing (Sharma, 1988; Dhindsa et al.,1988; Gokula, 1997; Kumara et al., 2000; Rajvanshi et al., 2001; Vijayakumar et al., 2001; Behera and Borah, 2010). Our results support previous findings reporting high speed roads and vehicular traffic as an important cause of mortality of wild animals. Studies have shown that roads act as barriers for movement of animals and affect the animal populations through which they pass (Forman and Alexander, 1998), with the most conspicuous effect of roads on wildlife being collisions with motor vehicles (Malo et al., 2004). Although collisions between vehicles, birds and animals are common, data on the avian taxa killed in road accidents and the frequency of roadkill is scarce despite the occasional surveys carried out (Kumara et al., 2000; Chhangani, 2004; Behera and Jena, 2010). In this present study we documented nine species of bird carcasses and a total of 19 dead birds were found on the road. For the present study, conducted using random sampling and 90 days in the field, we documented 123 carcasses in a determined stretch of the NH–16, and when these data were extrapolated per day per km they gave a minimal number of roadkills. However, while the rate of roadkill was estimated for a year based on the observed data, it found a substantial number of roadkill, and this is clearly a matter of concern (fig. 2).
The actual number of roadkill might be higher than that observed where simple counting methods were used as our study was conducted randomly rather than by daily observation. This approach can be affected by animal size, skill of field observers, weather conditions, and traffic volume (Guinard et al., 2012). Furthermore, observations by local people working in local hotels and small shops, and also vendors might also be included citizen science, that is, the collection and analysis of scientific data by the general public has been successful in documenting natural observations (Chandler et al., 2017). Though the study site was not near a protected area, our findings show many important wild fauna species can be found outside protected areas in this part of the state.
Our results reinforce the dangers of national highways for many native wild animals and birds. As the average width of a four–lane national highway in India is 23 meters, it is difficult for wild animals to cross quickly and their chances of being hit are high. In view of these circumstances, several protective measures are proposed for policy makers to take into account: (1) In areas with frequent animal crossings, the speed limit should be limited to a safe level by means of speed breakers or barricades. (2) Awareness of wildlife should be promoted, especially among drivers of vehicles transporting goods. Drivers need to be encouraged to develop compassion for wild animals and birds and need to be trained to follow proper driving protocol. To allow animals to cross roads they should drive more slowly and more carefully, looking ahead, and avoiding sudden braking and swerving. (3) Fluorescent sign boards of adequate size should be suitably positioned to indicate animal corridors, and (4) Specific plant species with less canopy cover, such as Streblus asper, Mimusops elengi, and Ficus microcarpa, should be planted along the road dividers so that animals standing on the dividers can be seen by drivers before they cross the road. Furthermore, road dividers (which are generally placed in the middle of the highway to separate lanes) also need to be barricaded on both sides to stop wild animals suddenly crossing.
Finally, more precise studies are required to enumerate the exact volume of roadkill on this and other highways where wildlife is endangered so as to develop optimal management and prevention strategies.
We thank the Chairman and Member Secretary, Odisha Biodiversity Board, Bhubaneswar, India for allowing us to carry out such work during our field tour.