Assessing the effects of multiple off-road vehicle (ORVs) tyre ruts on seaward orientation of hatchling sea turtles: implications for conservation

Abstract

The time it takes a hatchling sea turtle to cross a beach and reach the sea after emergence considerably affects its ability to avoid predators and survive this first journey. Impediments, such as tyre ruts across a hatchling’s route, may increase the travel time and, consequently, reduce the probability of survival. To assess the effects of multiple tyre ruts on the seaward orientation of hatchling loggerhead sea turtles, we performed a census of tracks on several beaches on Boa Vista Island, Cape Verde. Through this census, we were able to calculate the average number of tyre ruts a hatchling is likely to encounter on its way to the sea; we also determined the depth and width of those ruts and the distance between tracks. Based on these results, we designed and carried out a field test to analyse five different experimental treatments along a 15-m test path length. The experimental treatments included minor, moderate, and severe tyre rut scenarios, as well as a management scenario and a control. The length of time it took hatchlings (n = 162) to traverse each treatment was recorded. We found that each treatment significantly affected the time it took the hatchlings to reach the sea, and our generalized linear models (GLMs) indicated that it took the turtles longer to cross the areas with a greater number of tracks and with deeper tracks. Our results show that vehicle use on beaches has an effect on loggerhead hatchling dispersal. These findings highlight the importance of beach management and the promotion of a sustainable development plan to increase hatchling recruitment.