Control of the Effect of Human Activities as a Confounding Variable in a Study Conducted within the Influence Zone of Highway 40d in Mexico
Roads cause disturbances to wildlife from the beginning of their construction and once the road is in operation, people usually make use of the habitats, reducing the quality of these. Added to this are the effects caused by light and noise from vehicles. These propagate through the land adjacent to the road causing changes in the use that fauna make of the habitat. This led us to ask ourselves what attributes inherent to the road and the terrain influence the vertebrate fauna and what factors associated with human activities can be considered as confounding variables for the interpretation of the results? The study was conducted in the proximity of the Durango - Mazatlan (40D) highway in Mexico. Three paired areas were selected where signs of wildlife presence were recorded during spring and fall from 2018 to 2020 and these data were used as response variable. We used as explanatory variables the inherent characteristics of the natural terrain and the road, as well as those related to human presence in the habitat. GLM's were adjusted to determine the influence of these on our response variable. We found that the inherent variables of the road and terrain have a significant influence on the number of faunal traces found. The method used allowed us to identify and distinguish the influence that human activities exert on the fauna within the road's influence zone. The differential way in which organisms respond to human presence and activity makes it difficult to isolate this effect from the one we wish to evaluate, such as that of the road. Therefore, it is suggested that the variables used in this study be used as a control measure of this effect in the work carried out in the proximity of roads.