In my searchings I have found reference to a creature found in the woods of New Hampshire. Back in the 30's they called it the "Wood devil or Stick Men". The one thing in common is they are able to blend into trees to avoid being seen.
Also there is mentioned way back in the 1700's, in a report by Roger and his Rangers that "as they were traveling in Vermont from an attack on a French Fort in Canada, they were followed by a thing they called Old Slippery Skin ( a skinny thing) which threw rocks and branches down on them from the ridges above the valley floor they were traveling on. It did't make much of an impression on them , it seemed to be just a pest.
The witness supplied these two drawings:
Once the witnesses had passed the animal and turned their aluminum canoe around, it had already begun climbing the tree. It was ten feet up the trunk near the lowest branch, moving slowly like a sloth. It crawled onto the branch and moved its head to look at them again. Then it tucked its chin down into its chest and appeared to blend in with the reddish brown bark on the tree. The witness said that, once it blended into the tree, "The shape didn't have any definition to it."
The witness described it again to me in writing: "As soon as it put it's head down into it's underbelly, it looked like a large bump on the branch. If you hadn't seen it move it's head you would not know it was anything but a large branch. When it bent over on the branch blending in with the bark of the tree, it's fur had a pine bark look too."
During this sighting the witness felt no fear, however he did feel that there was a "boundary line," or a certain area between him and the animal that should not be encroached upon.
The witness' brother was contacted and he corroborated his brother's story, although his recollection of the sighting was not as detailed. He said that the creature was about four feet tall, and both sloth-like and orangutan-like in appearance, although he did not see its face. He doesn't remember seeing the creature standing on the shore before it climbed the tree; nor does he remember seeing it tuck its head down and "blend in" with the tree as his brother did.
According to the witness, several years later two girls, one of which is a lifeguard at a nearby YMCA camp, saw something they called "Monkey Boy" jumping on and off a wall. Attempts to locate and contact these witnesses have thus far been unsuccessful.
Update 11/7/2009: Another witness may have seen the same or another one of these creatures. See the email sent to the BFRO below. [Mike Aragona, BFRO Investigator New Jersey]
To whom it concerns: My girlfriend told me of an experience she had at Lake George 11 years ago when she saw a "monkey boy" at Lake George. I immediately searched for "monkey boy lake george" and found your case #2405:http://www.bfro.net/GDB/show_report.asp?id=2405 The description there is a striking match with her story, and in the same area. In fact, she worked at Silver Bay (the "YMCA camp" referenced in the report) and that is where she had her sighting. Her physical description is downright identical to the one provided by the witnesses in #2405. She saw the picture in the report and said, "That's him." The one difference is that she remembers the animal having a short tail. She doesn't want to contact you but I told her I would anyway. There's even a chance that she is one of the two girls mentioned in your report in reference to the YMCA camp, though her experience did not occur with another girl but with her boyfriend at the time.