Huggin’ Trees by Design

By Tim Ross (Own work) [Public domain], via Wikimedia Commons

By Tim Ross (Own work) [Public domain], via Wikimedia Commons

How do you survive if you’re not the most dominant canine in an area? If you have to share space and potential food with your faster and sometimes much larger cousin, how do you and your kin thrive day in and day out? These are questions the gray fox, Urocyon cinereoargenteus, must answer.

The common gray fox is a crepuscular and nocturnal canid whose home range averages around 1.5 square miles. This range contracts during the spring when they mate and have pups and then expands during the fall while they search for food. Their diet, like both red foxes and coyotes, consists of small mammals and even birds. Unlike other canids, the gray fox’s digestive system is better equipped to handle much more fruit.

In many parts of the southeast, including Statesville, gray foxes live with both red foxes and coyotes. Not much is known about how red foxes and gray foxes divide habitat in areas where they overlap. What is known is that red foxes seem to prefer more open terrain while gray foxes stick to the woods. it’s certainly possible that these two species use time-share strategies to avoid interactions.

Having to share space and resources with coyotes, however, could cause major, or fatal, problems for the foxes. Coyotes have been implicated in the decrease of red fox populations in certain areas (Cypher 1993). However, gray fox populations do not seem to be impacted as much by the larger coyote. Our small data set from greenway patches seem to support the idea that gray foxes tolerate coyotes better than red foxes. The following shows the number of pictures of each species we have collected from two camera traps from August to December during both 2015 and 2016:

                               Camera A             Camera B
Coyotes             25                         10
Gray fox            24                           2
Red fox                1                           2

Is the explanation just that the diets of gray foxes and coyotes are different or is it that gray foxes avoid coyotes spatially and/or temporally?

Both Cypher (1993) and Neale and Sacks (2001) found that there was actually a high dietary overlap among coyotes and gray foxes year-round. The implication is that this means, more than likely, that there is interspecific competition when they live in the same area. Neale and Sacks (2001) also used scat analyses to determine that gray foxes did not avoid coyotes in space. Our data (Figure 1) suggest that gray foxes don’t avoid coyotes in a temporal (time) dimension either.

rplot

Figure 1. Gray fox versus Coyote

The answer to how gray foxes avoid coyotes seems to be found in their evolutionary past. Gray foxes were the first canid to diverge from the rest of the canid family. They are a primitive species that branched off from the rest of the canids around ten million years ago (Lindblad-Toh et al. 2005). As a matter of fact, there is scientific support that states that the gray fox should not even be considered a canine or a vulpine (red fox). The gray fox is what geneticists call a basal canid, meaning it represents an ancient lineage.

Gray fox climbing in Statesville

Gray fox climbing in Statesville

As a result of this ancient lineage, the gray fox has many unique characteristics. Some features are only shared with another ancient species, the raccoon dog (Nyctereutes procyonoides). Gray foxes have hooked claws and the ability to rotate their forearms. This, coupled with the fact that they have the shortest leg-to-body ratio of any wild canid, allows them to easily hug tree trunks or branches and climb. Ecologically, they are more like cats. When pursued, gray foxes are not really interested in running. They would rather scamper up a tree. It’s this ability that helps them minimize conflict with coyotes.

Next time you are out in the forest, take the time to look up into the trees. You may get a peek at one of these cat-like dogs.

Gray fox foraging

Gray fox foraging


Cypher, B. L. 1993. Food Item Use by Three Sympatric Canids in Southern Illinois. Transactions of the Illinois State Academy of Science, 86: 139-144.

Lindblad-Toh et al. 2005. genome sequence, comparative analysis, and haplotype structure of the domestic dog. Nature, 438: 803-819.

Neale, J. C. C. and Sacks, B. N. 2001. Food habits and space use of gray foxes in relation to sympatric coyotes and bobcats. Canadian Journal of Zoology, 79:1794-1800.

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