The gray fox is the only canid in North America that climbs trees. It goes up a trunk to eat fruit from the branches, comes back down, and plants the next generation of that tree in its scat.
No other fox, coyote, wolf, or wild dog on the continent can do what the gray fox does with a vertical surface. It has semi-retractable claws, the only canid with this feature, and forearms that rotate in a way no other dog relative's do, allowing it to grip bark and push itself up a trunk the way a cat does. Gray foxes have been documented climbing more than sixty feet into a tree canopy to den, to escape coyotes, or to reach fruit that no other ground-level carnivore can access. They will sleep in a tree hollow, raise pups in a cavity forty feet off the ground, and jump between branches in pursuit of squirrels.
The fruit eating is where the biology turns unexpected. The U.S. Forest Service fire effects database lists persimmon, black cherry, blackberry, manzanita berries, juniper cones, cascara berries, and California fan palm fruit in the Sonoran Desert as confirmed gray fox foods. In some seasons and some habitats, gray foxes eat more fruit than meat. They are functionally frugivorous, a word that describes animals whose diet centers on fruit, and which nobody associates with a member of the dog family.
A 2020 study published in Ecology and Evolution examined gray fox scat in a temperate forest in Mexico's Sierra FrΓa and found that 93 percent of gray fox scats contained seeds. The average was 185 seeds per scat, mostly manzanita and juniper. The gray fox dispersed far more seeds per scat than the coyote, the ringtail, or the bobcat, all of which share the same landscape and eat some of the same fruit. The study tested the seeds for viability and germination after gut passage. Seeds that had passed through a gray fox germinated as well as or better than seeds that had not. The digestive process scarified the seed coat just enough to promote sprouting without destroying the embryo. The fox eats the fruit, walks a mile through the forest, defecates, and leaves behind a packet of viable seeds in a mound of nitrogen-rich fertilizer, deposited in a location away from the parent tree where competition for light and water is lower.
This is not an accident. The relationship between carnivores and the plants they disperse is an active area of research, and the gray fox is emerging as one of the most effective mammalian seed dispersers in North American temperate and arid forests. A study on the Edwards Plateau in Texas found gray foxes and other carnivores dispersing Texas persimmon and Ashe juniper seeds in large numbers, with few seeds destroyed by digestion. The pattern holds across the species' range: the fox eats fruit when it is available, sometimes preferentially, and deposits viable seeds miles from the source.
The gray fox has lived in North America for roughly 3.6 million years, making it one of the oldest surviving canid lineages on the continent. It predates the red fox, the coyote, and the wolf. Its tree-climbing ability and its fruit-heavy diet may be remnants of an older ecological niche, one that existed before the larger, faster, ground-running canids evolved and pushed it into the margins. Today it lives in brushy woodland, rocky hill country, and forest edges from southern Canada to Venezuela, and it is still the only dog in the hemisphere that goes up a tree to pick its dinner and comes back down carrying the seeds of the next forest in its gut.
Source: U.S. Forest Service, Fire Effects Information System / Ecology and Evolution (2020) / Edwards Plateau seed dispersal study / Smithsonian National Zoo / Animal Diversity Web.
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