Wildlife crossings are structures that allow animals to cross human-made barriers safely. They may include: underpass tunnels, viaducts, and overpasses (mainly for large or herd-type animals), fish ladders and green roofs (for butterflies and birds). Wildlife crossings are a practice in habitat conservation, allowing connections or re-connections between habitats, combating habitat fragmentation. They also assist in avoiding collisions between vehicles and animals, which in addition to killing or injuring wildlife may cause injury to humans and property damage.
Wildlife Overpass, Banff National Park, Alberta, Canada. (Image source)