Roads and their associated users as a threat to wildlife: an approach to assessing amphibian roadkill in the Vhembe Biopshere Reserve (Western Soutpansberg), Limpopo Province, South Africa

Abstract

Transportation networks are associated with a number of threats that degrade the integrity of wildlife. These threats have been understudied in the Soutpansberg Protected Area (SPA), one of the core areas of the Vhembe Biosphere Reserve (VBR). As part of the Makhado-Musina Special Economic Zone (MMSEZ) plan, road infrastructure upgrades to support the expanding economic activities are proposed within the VBR. This includes the expansion of road lane from single to dual lanes by 2050, which has the potential to accelerate threats to wildlife by creating barriers and cause potential increases in wildlife roadkill for multiple taxonomic groups. One of the most understudied but likely most impacted groups is amphibians. Globally, many amphibian populations are declining at a rapid rate due to growing anthropogenic threats (for example, habitat loss and degradation, as well as climate change). Road upgrades in the VBR will potentially further increase negative impacts on smaller vertebrates, such as amphibians and reptiles, as they easily cross the barriers (that is, fencing) surrounding protected areas and other properties. Amphibian mortality due to direct roadkill incidents has gradually become one of the contributing factors that affects the persistence of amphibians, thus influencing their population decline. However, the ecological impacts of roads on African amphibians during seasonal migrations are poorly studied. Therefore, using driven surveys at a speed of 20 to 30 km/h, this study recorded amphibian roadkill on regional road networks that surround the western Soutpansberg mountain range. South African folklore regarding amphibians can cause people to disregard their value in the ecosystem, which may influence human persecution, consequently contributing to their further decline. To examine this belief, a questionnaire-photo survey was administered to 246 households in Ha-Kutama village, in the SPA. This was to determine whether attitudes, knowledge and cultural beliefs have an influence on the participation of local members of the public in citizen science campaigns to raise awareness, encourage them to report roadkill sightings, which could ultimately provide valuable data. These data would identify which amphibian species are most at risk in which areas (hotspots), resulting in mitigation measures being proposed and adopted, and consequently, assisting in the conservation of amphibian species, particularly from roadkill. The outcomes of the study established a baseline amphibian roadkill inventory comprising a total of 248 individuals belonging to eight known species. The average amphibian roadkill rate for the monitored roads was 0.09 roadkillkm-1day-1. The distribution of amphibian roadkill along the xi monitored roads was non-random, which demonstrated that amphibian roadkill in the study area was spatially clustered at specific road locations (hotspots). Amphibian roadkill was significantly influenced by roadside habitat characteristics (x2 = 17.091; df = 5; N = 248; p < 0.05). Road sections that were adjacent to open savannah bushland had a higher incidence of roadkill (Jacob’s Index of 0.17) than road sections closer to waterbodies (Jacob’s index of 0.08). This was despite amphibian breeding being associated with wet habitats. The study findings provide baseline data that confirm the potential threat of roads and their users on the survival of amphibians in South Africa. Although the study indicates positive attitudes towards amphibians in the studied village, negative cultural beliefs, attitudes and a lack of knowledge about amphibians may reduce the effectiveness of developing and implementing citizen science campaigns (amongst specific demographic groups) to obtain amphibian roadkill data in the future. Consequently, more awareness around the value and importance of amphibians, including as an indicator of ecosystem health, is required.