Road ecology impact on capybara species: Operational traffic events involving capybaras (Hydrochoerus hydrochaeris) on the western section of highway in Brazil

[Impacto da ecologia rodoviária nas espécies de capivaras: eventos operacionais de trânsito envolvendo capivaras (Hydrochoerus hydrochaeris) no trecho oeste de rodovia no Brasil]

ABSTRACT

Capybaras can cause serious traffic accidents, generally resulting in the death of the animal. The objective of this study was to verify the occurrence of accidents expressed as a heat map and propose mitigation measures. The data analyzed comprised a concessioned stretch of highway in the west zone of the state of São Paulo, between January 2019 and December 2020. The parametric data were analyzed using the One-Way ANOVA test and T test. Hotspot maps and Kernel density were done using QGIS 3.20 software. The 946 capybaras were involved in road accidents during this period and, of these, 623 were removed from the highway and 323 died in the accidents. Ten hot spots were found, all concentrated in points with human interference, pointing to the need for mitigating measures

Keywords:
wild animals; animal welfare; ecological effects; road fauna; environmental impact

RESUMO

Capivaras podem acarretar graves acidentes de trânsito, geralmente culminando com a morte do animal. O objetivo do estudo foi verificar a ocorrência dos acidentes expressos como mapa de calor e propor medidas de mitigação. Os dados analisados compreenderam um trecho concessionado de rodovia na zona oeste do estado de São Paulo, entre janeiro de 2019 e dezembro de 2020. Os dados paramétricos foram analisados por meio do teste One-Way ANOVA e do teste T. Mapas de Hotspots e densidade de Kernel foram feitos usando-se o software QGIS 3.20. Um total de 946 capivaras se envolveram em acidentes rodoviários nesse período; destas, 623 foram retiradas da rodovia e 323 morreram nos acidentes. Foram encontrados 10 focos de calor, todos concentrados em pontos com interferência humana, apontando para a necessidade de medidas mitigadoras.

Palavras-chaves:
animais selvagens; bem-estar animal; efeitos ecológicos; fauna rodoviária; impacto ambiental

INTRODUCTION

The capybara (Hydrochoerus hydrochaeris) is a member of the Caviidae Family, Rodentia order, a semiaquatic mammal and the largest herbivorous rodent in the world (Polegatto and Nascimento, 2019). As a native species of South America (Souza et al., 2020), it is found from Panama to the Uruguay River basin, in the north of Argentina (Alho et al., 1987). In Brazil, large populations of capybaras inhabit the Pantanal, the island of Marajó and the states of São Paulo and Rio Grande do Sul. Its habitat comprises bodies of water, fields or pastures with shrubby vegetation (Diretrizes…, 2008), and each portion of the habitat is used for a specific activity. Capybaras are herbivores, feeding mainly on grasses and aquatic plants. However, they can easily adapt to other food sources, such as corn, sugarcane, rice, beans and soybeans, contributing to their presence in anthropized areas (Ferraz et al., 2001). Clearance of native forests for pasture formation or tillage leads to the increase of capybara populations, which is aggravated by the absence of natural predators in pasture areas, their eating habits and reproductive potential (Vargas et al., 2007). Highway implementation and operation cause the fragmentation of natural environments and the disjunction of ecological relations between ecosystems; this is the leading cause of death of wild animals (Dias et al., 2021). According to Lima and Obara (2004), high occurrence of animal death on highways is mainly caused by two factors: first, the road shrinks habitats and directly interfere with the natural displacement of the species; second, there is food availability along the highway .Millions of wild animals are run over every year in Brazil, different taxonomic groups are affected, including amphibians, reptiles, birds and mammals (Ferreira et al., 2014). In the southeast region, mammals corresponded to 55% of the vertebrates involved in accidents, with capybaras being the main victims (Bueno et al., 2012). In fact, Curvo et al. (2020) have reported that capybaras are the most run over animal in Brazil. Due to its size and weight, this species can cause serious damage to vehicles and threaten the lives of highway users (Huijser et al., 2013). Another serious problem is the underestimation of trampling rates, when animals that do not die in the collision are able to move to adjacent vegetation, where they perish without being counted (Sássi et al., 2013). The ecology of roads is a subject that emerges timidly in the national scenario. As capybaras are large mammals, occurrences with it offers a high risk to highway users and directly influences local wildlife. The identification of stretches under high risk of accidents are an urgent matter, as well as local mitigation measures to reduce the number of occurrences involving capybaras (Valadão et al., 2018). The present study aimed to understand the occurrences involving capybaras in the sp-300 highway, to create a heat map with these data, to identify the hotspots (the most at-risk areas), and propose the implementation of mitigation measures, considering the safety of highway users and ecosystem reintegration.

METHODS

The study area comprised the stretch of the highway (SP-300), totaling 331.13km analyzed all accident occurrences involving capybaras during the period of January of 2019 to December of 2020. The road concessionary did the continuous monitoring of this stretch (24h, 7 days a week), with the aid of a support car and CCTV. Retrieved data contain, for each occurrence, the geographic coordinates and spindle, characteristics of the road and surroundings, numerical code of the occurrence, date, time, highway km, direction, popular and scientific name of the animal, quantity and final destination of the capybaras. Data was provided monthly to our research team, tabulated in spreadsheets in Excel format. For data analysis, we considered the overall number of occurrences, number of animals involved per occurrence, the surrounding area, the final destination of the animal (if buried beside the road or driven off the highway), the season of the year and the period of the day. Occurrences without geographic coordinates or wrong coordinates, or occurrences with incomplete data (date, time and final destination of the animal) were excluded from this study. Data were analyzed using the one-way ANOVA test and t-test, using GraphPad Prism 9® software. For Kernel Density and maps, we used the QGIS 3.20 software with the Geographic Coordinate System Datum SIRGAS 2000 and reference images of IBGE Cartographic Base (2019), Google Road© (2021) and Google Satellite© (2021). After the identification of hotspots, analysis of the surroundings was carried out to understand possible risk factors for the fauna, observing the existence of human interference in the points with higher density of occurrences.

RESULTS

During the study period, 414 occurrences were recorded, involving 946 capybaras, 47.89% (n = 453) reported in 2019 and 52.11% (n = 493) in 2020. Of this total, 623 were driven off the highway and 323 died and were buried beside the highway lane. Regarding the capybaras involved in the occurrences, 29.22% (n = 277) were solitary, 8.65% (n = 82) in pairs, 37.24% (n = 353) in groups of 3 to 9 individuals and 24.89% (n = 36) were families with more than 10 animals. Considering all capybaras involved in the occurrences, the rate of events was 0.04 capybaras/km/day, the mortality rate was 0.001 capybaras/km/day, thus for every 2.5 occurrences, one capybara died. Statistical analysis pointed to an effect of season and period of the day (p<0.05), with the spring of 2020 and the winter of 2019 registering the greatest number of occurrences (Fig. 1).

Considering all occurrences in the region, SP-300 highway represents 90.17% of all accidents, followed by the side roads SPA-486, SPA-561, SPA-615, SPA-568, SPA-553 and SPA-501 with event rates of 6.87%, 1.16%, 0.63%, 0.42%, 0.32% and 0.21%, respectively.

Figure 1
Number of capybaras involved in occurrences in each season of 2019 and 2020.

The late night and early morning periods, between 00:00 a.m. and 5:59 a.m., were the most accident-prone intervals in both years, with major peak of occurrences in the dawn hours of 2020, as shown in Fig. 2.

Figure 2
Number of capybaras involved in occurrences according to the period of the day: a) Morning (6-11:59 a.m.), Afternoon (12-5:59 p.m.), Night (6-11:59 p.m.) and Dawn (0-5:59 a.m.), in the years 2019 and 2020; b) summarized period in Day (6 a.m.-5h59 p.m.) and Night (6 p.m.-5:59 a.m.).

Using the Kernel Density map, the punctual intensity of the phenomena is plotted by interpolation methods. Points with the highest heat density were observed in the stretches between the cities (Fig. 3). The hotspots were identified, and the surroundings were observed for human interference. Fig. 4 shows the 08 concentration hotspots, noting that environment number 6 has two epicenters.

DISCUSSION

Capybaras are a generalist species with great displacement capacity and are very attracted by favorable environmental resources or characteristics (Deffaci et al., 2016). The rate of occurrences found in this study is high when compared to Bueno et al. (2013), which observed 51 run over capybaras in four years, in a 180.4km stretch between Rio de Janeiro and Juiz de Fora. Huijser et al. (2013) and Freitas and Barszcz (2015) observed in their studies that among the accidents involving animals, the highest rate of driver's death occurs in collisions involving capybaras, attributing the severity of the accidents to their size and weight, and to the fact that this species lives in flocks. This was also observed in our results, in which 62,13% of the animals were in groups with more than three individuals. The number of capybaras driven off the highway was higher than the ones that died in the accident and were buried beside the road. This record may be underestimated, as a portion of the run over animals may have died later as a direct consequence of the hit, however outside the monitoring area (Sássi et al., 2013). As for the season of the year, Huijser et al. (2013) observed that the highest rate of dead capybaras occurred in summer, between November and May. However, we observed the highest occurrence in winter, between June and August, followed by spring, between September and November, similar to the results found by Turci and Bernarde (2009), who associated the fact to the dry seasons, suggesting that, during this period, there is increased migration for foraging, in search of water and food.

Figure 3
Kernel density map of the global number of capybaras involved in occurrences (2019-2020).

Figure 4
Hotspot area, highway coordinates of central points (attitude and longitude);1) -49,839037, -21,631727; 2) -50,082647, -21,442313; 3) -50,237290, -21,393035; 4) -50,407624, -21,265564; 5) -50,430158, -21,245596; 6) -50,56655, -21.19976, 6) -50,56655, -21.19976;7) 7) -50,647303, -21,207355; 8) -50,695396, -21,214723.

In our study, most of the events occurred in the evening, similarly to Nievas (2019), who observed that anthropic areas had a low activity of capybaras during the day, when temperatures are high, and higher movement activity in the dusk and at night, linking greater activity with cooler periods of the day. Moreover, these periods have less light, making it harder for drivers to spot animals on the highways (Jardim et al., 2017). A report from the Institute of Environment and Water Resources from Federal District (Brasil, 2013) shows that the paved, duplicated and long extension lanes result in an increased speed average for vehicles, which could explain the higher concentration of occurrences in the SP-300 highway, when compared to the smaller side roads. In all hotspots identified through Kernel density there were anthropization signs in the surrounding areas, mainly fragments of forests with rivers or lakes in the proximity. Curvo et al. (2020) reported similar findings, correlating such areas to the semiaquatic habitats of capybaras. Studies are necessary to devise mitigation strategies to preserve the fauna and also increase highway safety for drivers. According to Abra (2012), an observed decrease in the number of accidents involving capybaras, from 33% in 2009 to 25.3% in 2010, in the SP-225 highway, was the result of the installation of wildlife passages in this stretch. Huijser et al. (2013) also emphasize that the creation of wildlife passages must be associated with a perimetral fence for a more efficient measure. Lozano and Patiño-Siro (2020) suggest a combination of multidisciplinary efforts to reduce wildlife runovers and highway accidents. Combining strategies, like the vertical signs and surfaces that inform the drivers of the need to slow down before a curve and the construction of curves with greater radius, providing more room for vehicle maneuvering, as well as multi-species wildlife crossings, road barriers for animals and information for the drivers, is likely to result in significant reduction in accidents involving animals. Jötten and Camara (2017) reported on the relevance of the relationship between design and environmental education, and the importance of "social design" (or socially responsible), agreeing with this idea, we developed an educational pamphlet, to raise awareness about careful and responsible driving. This pamphlet contains useful guidance on how the driver should proceed in the event of an accident or sighting of an animal on the highway. Overall, capybaras correspond to more than one third of all accidents involving animals in Brazil (Abra et al., 2021), emphasizing the urgency of management actions that limit the access of these animals to the highway. Our study points to the presence of areas with environmental degradation and anthropization around the observed hotspots, clearly indicating the need for environmental policies aimed at environmental protection as well as driver safety. All databases that served as sources for the development of this research are preserved by a confidentiality agreement. Moreover, all the data compiled and analyzed, as well as the conclusions are of sole and exclusive responsibility of the authors, without conflict of interest.

CONCLUSION

In this work, we identified accident hotspots and characterized the surrounding areas, considering the natural behavior of capybaras. We showed the need for mitigation measures and development of wildlife passages associated with fences and highway signaling. It is also clear that continued education, awareness of drivers and the creation of public policies are necessary for habitat and fauna preservation.

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Publication Dates

• Publication in this collection
  21 Feb 2025
• Date of issue
  Mar-Apr 2025

History

• Received
  16 May 2024
• Accepted
  11 Sept 2024