When I walk my dog, which tend to encourage most animals to avoid the path I take (I also tend to walk mid-day and both foxes are more night time, dusk and dawn animals), I have seen a Gray Fox in the heavily forested areas, Red foxes in the more open area near the local High School (Which is right next to the large Forested area). I have always suspected that the difference was more do to the natural of the two then anything else.
The problem with Red Foxes adopting a more Gray Fox life Style is that the physical ability of both is different. The Gray Fox has claws that permit it to climb straight up a tree without any tree limbs. Its claws are tough enough to dig into the trunk of a tree and climb that tree. Red Foxes do NOT have that same claw and thus can NOT climb up trees as well as the Gray Fox. Red Foxes may very well emulate Gray Foxes, but only to a degree, you can NOT duplicate what you can NOT do, and the Red Fox can NOT climb up a trunk of a tree, it can jump into the lower branches and climb from that point, but NOT crawl right up the trunk like a gray fox can. Below is a New York State Department of Environmental Protection article on Gray Foxes and point out the eastward expansion of Coyotes had had almost no affect on Gray Foxes, who tend to den in Deep woods and high in trees, but have has lead to a drop in Red Fox population do to the Coyotes viewing Foxes as food and the Red Fox inability to climb trees as well as the Gray Fox.
This sight has picture of a Gray Fox climbing a tree just using its claws to dig into the tree, please note the pictures are halfway down in the site so you have to go by a lot of pictures of Gray Fox paw prints before you get to the pictures:
http://www.bear-tracker.com/grayfox.htmlMore on the Gray Fox tree climbing ability
http://retrieverman.wordpress.com/2010/08/20/the-tale-of-two-foxes-in-west-virginia/http://www.dec.ny.gov/animals/63058.htmlhttp://books.google.com/books?id=Ef-v7YQHAcUC&pg=PA255&lpg=PA255&dq=Gray+Fox+Tree+Climbing+PA&source=bl&ots=-UINKKNIgk&sig=eqLcDgnaYdF2Q8jDbbFjM75Hc8c&hl=en&ei=Itn1TLKULIS0lQeBpdTKBQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CCUQ6AEwAQ#v=onepage&q&f=falsehttp://www.outdooralabama.com/hunting/articles/climbingfox.cfmhttp://www.tpwmagazine.com/archive/2006/jun/legend/http://www.nationaltrappers.com/grayfox.htmlRed Foxes tracks:
http://www.bear-tracker.com/redfox.html