My information is gathered from Personal experience as I worked with them for 4 years and from :Nowell, K., and P. Jackson. 1996. Wild cats—status survey and conservation action plan. IUCN/SSC Cat Specialist Group, Gland, Switzerland. (International Union for Conservation of Nature). The IUCN is the world expert on mammals and is a group that decides wether species are red listed or not .In southern California, on average, an adult killed about 48 large and 58 small mammals per year and fed for an average of 2.9 days on a single large mammal (Beier et al. 1995) taken from BC Species and Ecosystems Explorer. Also some info taken from Sunquist, Mel., Sunquist, Fiona., Wild Cats of the World, University Of Chicago Press; 1 edition (Aug 15 2002). That is an outdated report from 1994, and also keep in mind that is how much they "need", and not an actual detailed study of how much each animal kills. Also like I mentioned before "On average a cougar will kill a deer every 8-16 days and 80% of their diet consists of deer (dependant on area, some areas have a 80% kill of elk or moose etc)".Cougars can and have been known for killing 50 deer a year, that does not mean they "feast" on or "need" that many.Cougars are known for being easily spooked and leaving fresh kills when approached by coyotes, wolves and even bear.