In a case like this, the best thing to do is get the address of where the animal in question is, then find out which animal welfare/rights/rescue organisations cover that area, by searching on a search engine (preferably a charity search engine). IF THERE IS NO DANGER POSED TO YOU by taking photographs / video as evidence, also do this. Contact the local animal charity or organisation covering the area, with the information you have. Keep contacting them for updates, and to make sure they have been out to see the animal. If you can, keep an eye on the animal yourself, to check their health is not deteriorating. If you feel the organisation you contacted is not interested, contact animal rights organisations in your area.