(1) Climate: temperatures within "urban cores" are typically warmer than the surrounding non-urban landscape. All of that black top, concrete, and etc. absorbs heat and retains it for longer than vegetation and soil. Obviously for ectothermic (cold-blooded) species, this may be more problematic. But it poses challenges to endotherms as well.
(2) Water: Hydrology may be significantly altered in urban areas. In cities surrounded by arid landscapes (such as deserts), water may be more plentiful in town than out-of-town (due to garden ponds, sprinklers, fountains, golf courses, etc.). Urban/suburban areas in any part of the U.S. also usually have storm-water retention ponds. These collect rain run-off, which occurs in excess when lots of concrete is present, that blocks rain from being absorbed by the ground. That rain must go somewhere. Often natural wetlands act as a catchment area for rain-runnoff. But, as we fill in wetlands for a variety of purposes related to development, that water is more likely to end up in basements, etc.. So artificial retention ponds are often built in urban/suburban areas to act as an artificial catchment for excess rain water. These are not natural, but may attract wildlife just the same. Amphibians breed in them, fish are introduced into them, while mammals and birds find them for drinking purposes. Some semi-aquatic mammals and birds (i.e., mink and herons) may actually take up more permanent residency in artificial retention ponds. In some cases hydrology is massively altered in the form of stream corridors, river corridors and lakeshores being rearranged and re-directed to suit the needs of the people living within a given area.
(3) Light: We often do not think of light pollution. Street lights, billboards, neon signs all create artificial light that illuminates urband/surburban areas, making them much brighter at night than in more rural areas. Many mammal species likely learn to avoid areas that are lit up at night, or at least skirt around in the shadows. Although for carnivores like fox and coyotes, their major prey (small mammals) may become less active on bright nights, which can cause them problems. For some species, particularly certain reptiles and amphibians, artificial light sources can be a more serious problem. They have been known to artificially attract adults during the breeding season, or juveniles recently hatching from eggs.
(4) Noise: Something else we take for granted. We're used to constant traffic, lawn mowers, leaf-blowers, and car stereos. The inlfuence of this is not well-studied, but animals that rely heavily on hearing must be affected. See Gehrt (2010) for some examples.
(5) Habitat Fragmentation: Loss of habitat is the number one cause for the global reduction of biodiversity that we are experiencing. Habitats become fragmented into smaller isolated "islands" due to a variety of reasons. Conversion of previously "undisturbed" habitat into agriculture or housing/commercial land is one cause of fragmentation. Also, construction of roads through previously undisturbed habitat is another cause of fragmentation (for a good general overview of fragmentation see Franklin et al., 2002, What is Habitat Fragmentation? in Studies in Avian Biology). Obviously, some animals are more heavily affected by it than others. Small vertebrates are particularly susceptible to mortality when a large undisturbed plot of woodland gets bisected by a road (for example). They tend not to be quick enough getting across and will either not attempt to cross the road (and become stranded in a habitat island of inadequate size) or get smacked when trying to cross. Some species may remain in habitat fragments (or islands of "undisturbed" habitat surrounded by development) for some period of time. But the retention rate of species within these fragments depends on the size of the fragment and the avialble resources within that fragment. So, if food becomes scarce, animals will be required to make forays into the disturbed suburban or urban landscape to meet this need. Larger, more mobile vertebrates can likely get across these boundaries with greater ease than small mammals, reptiles and amphibians. Some species do well in fragmented landscapes, so long as there are still small buffers and "green spaces" for them to move along and hide in among the homes and businesses associated with suburbia.
(6) Biota: Native wildlife species in urban/suburban landscapes also likely come into contact with many types of flora and fauna that are unfamiliar. Exotic pets, exotic ornamental plants, domestic dogs & cats, etc. all pose the potential for interactions with wildlife that live in such a landscape that don't exist in "natural" areas. Ornamental plants, shrubs, bushes, may provide cover for certain species. On the other hand, large manicured lawns reduce cover. Newer developed areas may lack any type of vegetation that has grown enough to provide real cover for many medium and large vertebrates, while older suburbs and city parks (with older trees, shrubs, etc.) may be adequate.
Alright...so...I was talking about gray fox, right? Gray fox seem to be a very adaptable little critter.
Take a look at their traditional geographic range, extending from Canada to Panama. It is often reported to prefer wooded habitats, or areas of dense cover (thickets, woodlands, wooded wetlands, etc.). It is also a very adept climber, which means it can eat birds and their eggs, as well as any arboreal or ground-residing mammals, birds, insects, and etc (they'll also eat a fair amount of berries, and other vegetable matter throughout the year). They are great mousers, which makes them beneficial in natural ecosystems (and may control rodent populations in towns and cities, although I could find little information on this. Their generalist's attitude towards diet, range and habitat features means it can be a frequent inhabitant of surburan and urban areas. Plenty of food is provided in the form of vegetable gardens, backyard birds, squirrels, dog food that's been left outside, and perhaps scraps of meat in a trashcan.
Although they can handle disturbed habitats, it may not be good for them. They are more likely to come into contact with domestic dogs and either contract, or spread, diseases such as canine distemper (which is fatal in wild canines that can't visit the vet) and rabies. They also often run afoul of folks that keep poultry in rural and suburban settings. Them chickens are easy pickins!
Yet, despite all of this, the International Union for Conservation of Nature (IUCN) lists them as being of "Least Concern". Globally, this is accurrate, as in many areas they are relatively common. IUCN also lists the major threat to this species as loss of habitat (which probably affects just about all species). Becuase it apparently does not have a desirable coat for trappers/hunters, it is not often a target species in those areas. It is worth noting, however, that this species may be considered rare regionally. For example, although common where I live now....in my home state of Wisconsin, this is a more rare species that is legally protected by the state.
I have captured so many pictures of gray fox on my camera traps over the last year that I hardly know how to start posting them all! So..I'll post some of my more recent pics that I've obtained. These are, appropriately, from my own back yard. We live in a suburban environment, but one with alot of "green space" in between the houses (mostly in the form of small wooded corridors). Also, some of the development in our area is relatively old and the Shrubs and trees larger for more cover.
My first experience with a gray fox near our home came in the car with the wife and kid. One day last spring, as we drove home form somewhere in the middle of the day, I was shocked to see a grey streak shoot in front of the car, followed by a gang of angry ravens. Not sure what happened, but I can only imagine the fox was after young or eggs (because they can climb...a nest in a tree is no problem!). That night, I took the dog out for his nightly evacuation and I happened to see one run along our lot line (just in the shadows of an area illuminated by our street lamp) before bolting off between the houses. Not a week later, I saw two running in the neighbor's yard one night (and the next morning found a dried husk of a squirrel roadkill they had probably drug into our yard, which I had to quickly dispose of before it got into my young daughter's curious line-of-sight). Then, activity in the yard stopped. At one point last July, I half-heartedly tried putting a camera trap in the yard to see if they were around, but after two weeeks of brutal heat realized they weren't going to be very active and pulled the cam.
This spring, however, I started testing out new cameras in the back yard and guess who decided to show?
In this first picture below, I was still testing which direction the camera should face for the best pics. So, I caught only a glimpse of the fox, off to the left of the field of view. In the second picture, I had figured out which angle was better. With the help of Sampson (my dog), who emptied his bladder in front of the cam, I was able to get some of these urban fox to come in for a close up.
Not two days ago, we (my wife, the kid, the dog and I) were enjoying a very mild spring afternoon. It was nearing evening, and the sun was going down, but our daughter was enjoying alittle play time outside before bed. Suddenly, I noticed movement along our back lot line and without any hesitation, a gray fox silently trotted out, walking along the neighbor's driveway. He moved with a purpose, but didn't seem to pay us much heed, and didn't run as I said "hey, look...a gray fox!" to my wife and kid. In a matter of seconds, and before the dog had even noticed, the fox had quickly moved across the street and into the wooded green space between the houses on the other side.
I have many, many more gray fox pictures that I will share with you. Most from more natural settings. But these are some of my favorites.
Further Reading on Gray Fox:
Chapman and Feldhammer (editors). 1982. Wild Mammals of the World. Johns Hopkins University Press.
Macdonald and Sullero-Zibiri (editors). 2004. The Biology and Conservation of Wild Canines. Oxford Uuniversity Press.