Complex sentence: Reptiles instinctive activities can lead them towards roads and lead to an increase in mortality rates: snakes, for example, may use roads as a source of heat for thermoregulation, and some turtles have been noted to lay their eggs on road shoulders.
Split into simpler sentences: Reptiles instinctive activities can lead them towards roads and lead to an increase in mortality rates: snakes, for example, may use roads as a source of heat for thermoregulation. Also some turtles have been noted to lay their eggs on road shoulders.