Great question, often asked, and I will answer shortly. But first this is not a Bigfoot thread, but I did need to answer your inquiry. So I will make it Cop Corner related. Over the years, especially since 2008 when I went looking for answers to my sighting in Michigan in 1975, and that god awful scream that came from my best friends backyard ( 10 acres, mostly wooded, in Mt. Hayley Township of Midland County, Michigan, Sept 1st 1996 at appx 3 am, that shook his house, and even though he had several loaded guns, we both agreed no way in hell did we want to go outside and possibly deal with whatever could do this. I have read and heard interviews of over 10,000 witnesses. Dozens, maybe hundreds, have been from Law Enforcement officers and game wardens, and forest service personnel, and even more from ex military. One of the earlier ones was the famous case by police officers in Whitehall, NY in 1976, I believe that went national. Wes Germer, who runs my favorite site called Sasquatch Chronicles, of which I am a member, does interviews and has now logged over 700 episodes and interviewed well over a thousand witnesses. A fair number of these are law enforcement. However Wes states that he is contacted by a good many law enforcement officers with their experiences, but the majority do not want to go on air for fear of possible retribution or being labeled a kook and have vested pensions to worry about. Very much like what happened in the military and commercial aviation with UFOs. These guys and gals could be grounded and drummed out if they even talked to higher ups about seeing UFO, and they certainly could not go public. Of course the UFO field has changed some since Dec. of 2017 when those radar pics of Tic Tac UFOs were released. And pilots such as Lt. Commander David Fravor and Lt Ryan Graves that saw these craft flying and bouncing around and accelerating at instantaneous speeds and making right angle turns at hundreds of miles per hour with no visible means of propulsion or heat signatures in ways that are outside the laws of physics as we know them, has contributed mightily to the UFO field. The Navy now states it encourages their pilots to come forward, however I am most sure their is still great reluctance.
To answer your question.
1. The acidic soils of forest go not give up remains very easily and are decomposed quickly, and bones picked over by porcupines and such. Few fossils of the great apes are found, and no one is finding bear remains in our forests unless it has been recently shot. The History Channel series from 2007 to 2009, Monster Quest, in one episode about Bigfoots, staked out a dead dear and filmed it while it decomposed. It took about a week for remains to disappear.
In the fossil record is what I, and many think, is the ancestor to Bigfoot. Anthropologist have named it Gigantopithicus ( Blacki ). All that has been found ( in southern China, over their it is known as the Yeren ) are some large teeth and a few jaw bone fragments in a cave. They have determined from these fossils that it was an 8 to 10 foot tall primate, and probably a member of the Orangutan family that went extinct 100,000 years ago. I disagree that it was an Orangutan member simply because it had to be. The modern day Bigfoot is not an Orangutan, instead a closest cousin to us on the ever expanding hominid branch, in my opinion which is based in part from DNA sequences.
2. They bury their own. They live in family units and even clan units and hunt and live together. Their upper body strength is off the charts and their fingernails are like chisels. Janice Carter Coy witnessed the male Fox and female Sheeba burying their child that had passed. She stated the hole they dug was extremely deep, maybe 10 feet. For days Sheeba wailed and mourned and for days they brought offerings of food and laid it on the grave. To me this means they also are spiritual like us.
To conclude and make it a Cop Corner offering I will offer up this docu drama from 2011 from the show Paranormal Witness - Watched in the Wilderness. In it Deputy Sheriff, Jeff Boiler, is hiking the Cascades of Oregon when his frightening sighting and ensuing " escorting out of the area " occurs. This escorting is quite common in their forest environments, if they do not want you around. You really are not in danger as Jeff thought he was, but it certainly is best to leave and everyone does. Usually this is achieved by paralleling you in the forest. They are much faster than humans ( as Jeff witnessed ) and this one could have had Jeff at any time if it desired, but they do not. They just want you gone. His adventure starts at the 31 minute mark. Paranormal Witness, Watched in the Wilderness.