The obvious and intelligent option is to take up trail cameras and hide it in the place where the animal frequently visits. The camera should be hidden properly so that the animal won’t see it or damage it. If the trail cameras are properly camouflaged and placed the only way the animal can find the camera is through smell or scent around to camera. So try to avoid this as well.
Digital rangefinder cameras can also be used equally like trail cameras but range finder cameras are losing its shine to single lens reflex cameras. The digital rangefinder cameras were popular in 1930s to 1970 but now there are modern cameras with advanced technologies which have over taken the digital rangefinder cameras.
As trail cameras and digital rangefinders are for hunting we need to have predator calls also to complete the hunting baggage packing. There are different types of predator calls. Some even allows the users to add different sound to the instruments. In some cases there might be some limitations on the number of sound added based on the money that you have paid. These are called pre programmed predator calls. Based on your need you can choose your predator calls.