The most significant information I have learned over the last 12 years of research is animals have developed an early warning system when predators enter their domain. It starts with the birds which are usually high in the trees. They see or hear some type of movement, then they locate and identify what is approaching. Once they identify the predator, they signal others in their group to warn them of the approaching individual. This is relatively simple, the birds identify the predator and then take steps to (depending on the predator call) stay in the trees, or fly down to the brush and take cover. After reading many textbooks and science journals I learned that many primates can recognize bird and other animal predator calls and also take the appropriate action. Here is one example. A raptor flying above a trees is spotted by another type of bird, this bird broadcasts a warning call to the other birds that a predator is flying above them. Not only do the other birds take evasive action, the monkeys also take evasive action without even looking up. They can identify and associate the birds warning call with a raptor flying in the area. So it seems that many animals can associate calls made by other species and use them to their advantage. While conducting research alone in the woods one day I heard some crows making all kinds of calls. It seemed the crows were mad at something so I decided to investigate it. I moved forward in advance of whatever they were following and concealed myself in some brush. Within a couple minutes two men walked by carrying shovels and metal detectors, I could tell they were checking the local streams for gold. I’m not sure why but the crows were still following them making a racket. I stayed still and let them and the crows pass. If the Bigfoot creatures can associate bird and animal predator calls then they can anticipate trouble, just like I did and take evasive action. I know I am out on a limb saying this but if other creatures can do this why not Bigfoot. If anyone is interested, I will forward the name of the book that contains the information I am referencing. Another interesting point was made in this book. Primates usually send warning calls to other primates only when family members or offspring are nearby. If they are alone when a predator approaches, they stay sill and quiet. It is possible the Bigfoot creatures do the same. I do believe these live below ground in burrows they dig. The temperature is always a cool 56 degrees Fahrenheit and the burrow can provide needed cover when raising their young. It also provides an “out of sight, out of mind thinking”. I have tested tree knocking while recording audio in a mine shaft. The tree knocking provides sound above ground, but also transfers the energy below ground into the root system where it continues on through the soil, rock and water table. If you spend enough time in the mine shaft, you can hear the controlled tree knocking and actually tell the direction in which it originated. This testing was very basic in nature and would require more accurate documentation before it could be presented in a scientific paper, but it does prove tree knocking could provide an early audio alarm both above and below ground.