The effect of linear infrastructure on vertebrate fauna in Hluhluwe-iMfolozi Park and northeastern KwaZulu-Natal, South Africa.

Abstract

Global anthropogenic growth continues to increase, threatening not only wildlife but the health of the entire biosphere. The anthropogenic growth coincides with an increase in vehicle traffic, placing further stress on natural environments as the mortality rates of fauna from vehicle collisions rise, thereby increasing human-wildlife conflict. It is to avoid this human-wildlife conflict that protected areas are so beneficial. However, global studies have shown that public roads in protected areas cause large numbers of wildlife mortalities, threatening the stability of these wildlife refugia, and that increasing tourism rates add further ecosystem stress by increasing wildlife-vehicle collisions (WVCs). The conflict faced by wildlife is also disproportionate between taxa, with reptiles and large predators facing the highest threat levels. Therefore, effective measures must be taken to minimise the effect of anthropogenic structures on natural environments as vehicle traffic density increases globally, particularly in Africa, where little research has been conducted on the ecological impact of linear infrastructure. In light of the conservation challenges associated with linear infrastructures, this study had four aims. Firstly, to identify the species assemblage of vertebrate WVCs along the R618 road that bisects Hluhluwe-iMfolozi Park (HiP) and of the R22 road that passes through the northern border of iSimangaliso Wetland Park (ISWP). Secondly, to determine the demographics of reptiles present on paved roads in HiP, ISWP and an adjacent developing community on ISWP’s border. Thirdly, to determine the amount of road avoidance by lions (Panthera leo) and blue wildebeest (Connochaetes taurinus) in HiP. Finally, to determine the interaction with anthropogenic structures by cheetahs (Acinonyx jubatus) and African wild dogs (Lycaon pictus) in HiP. Roadkill and herpetofauna presence data were collected along R618 and R22 in HiP, ISWP, and the ISWP-adjacent Giba Rural Community (GRC) monthly from March 2021 to March 2023. Vertebrate mortality and reptile occupancy were determined by assessing species diversity and abundance, mapping hotspots of mortality and reptile occupancy and using a suite of ecological factors to identify drivers of vertebrate mortality and reptile occupancy. Spatial analysis programs and global positioning system (GPS) data collected from 11 lions and 21 wildebeest were used to determine the average distance to roads for the two species and to examine how this distance differed across road types. Additionally, GPS data collected from nine collared cheetahs and 17 collared African wild dogs were used to determine the average distance to anthropogenic structures and to compare these distances across structures. In addition, hotspot analyses were conducted to determine key areas of use near roads or anthropogenic structures and statistical analyses of the habitat features were performed to determine how they affected the distance kept from roads for lion and wildebeest and anthropogenic structures for cheetah and wild dogs across multiple wet and dry seasons from May 2019 to April 2022. A total of 1606 road mortalities were recorded, with small-bodied vertebrates (< 5 kg) comprising most of the identified species. Amphibians had the highest mortality rate (1066 individuals), while birds had the highest species diversity (31 identified species). High mortality levels were concentrated in areas with unsloped road surfaces and increased vehicle traffic within HiP, while the surrounding habitat had a larger influence on mortalities within ISWP. Reptile presence was significantly higher in protected areas. However, the majority (78.3%) were found as road mortalities, with a significant difference between the number of live and dead individuals observed between protected and unprotected land. Snakes comprised the majority (70.3%) of observed reptiles, with reptile observation frequencies varying according to habitat intactness and type, as well as vehicle traffic patterns and road design, with light conditions having a minor influence on reptile road occupancy. The majority of lion and wildebeest GPS fixes were within 1 km of roads in HiP, with hotspots of wildebeest activity near roads (within 400 m) occurring close to water sources, and hotspots of lion activity near roads occurring near areas frequently utilised by tourists or park staff. Where distance to dirt and paved roads, and to tourist locations, were key driving factors, significant differences were observed between lion and wildebeest males and females, with male lions and female wildebeest maintaining the smallest distances to roads. Finally, despite cheetah and wild dog heavily utilising over 20,000 ha (21%) of the total area protected by HiP, both species only had a significant presence in less than 3% (~2,880 ha) of HiP. Cheetahs also maintained greater distances from anthropogenic structures than wild dogs, with male cheetahs and female wild dogs maintaining the smallest distances for each species. Distances from anthropogenic structures were lowest near dirt roads and unfenced structures and highest from paved roads. The results showed that intervention is needed along portions of the two public roads in both protected areas and the ISWP adjacent GRC, particularly during the wet season, with mortality rates as high as 13 carcasses per km. Mitigation measures should be implemented to reduce wildlife mortality along roads in both locations, with specific measures targeting small vertebrates. All planned mitigation measures should focus on the sections identified as high mortality zones. Further studies are needed, as roads in HiP clearly negatively affect lions and blue wildebeest, with both species avoiding them. As hotspots of lion, blue wildebeest, cheetah, and African wild dog activity were centred around areas with typically high rates of human visitation, this increases the risk of human-wildlife conflict and the influence of human activity on movement patterns in both lions and blue wildebeest. This is of concern as lions, cheetahs, and African wild dogs are species whose persistence is threatened in HiP. Therefore, this study's results provide key insights into conservation concerns and further indicate the need for more effective species management to reduce human-wildlife conflicts in the rural communities surrounding HiP and ISWP.