The black-tailed deer, represented by the Columbian and Sitka subspecies, inhabits the Pacific Northwest, ranging from northern California to coastal Alaska. As a ruminant, this mammal possesses a four-chambered stomach, which dictates its feeding strategy. The deer is primarily a browser, consuming the leaves, buds, and shoots of woody plants and shrubs, rather than grazing grasses like cattle.
Essential Forage: Browse and Forbs
The black-tailed deer’s annual diet relies on two categories: browse and forbs. Browse refers to the tender twigs, leaves, and buds of woody plants, constituting about 65% of their annual food intake. Highly utilized browse species include salal, vine maple, trailing blackberry, and red huckleberry. These woody materials provide necessary fiber for the deer’s digestive system.
Forbs are non-woody, broad-leafed herbaceous plants that typically account for about 25% of the diet. Examples include fireweed, deer fern, and various clovers, which are selected for their high protein and nutrient concentration. The deer’s relatively small rumen size necessitates this selective feeding strategy, targeting small volumes of nutrient-dense food rather than low-quality roughage.
Seasonal Changes in Their Diet
The black-tailed deer’s diet shifts between the growing and dormant seasons, driven by plant availability and nutritional quality. During spring and summer, deer maximize their intake of high-energy and high-moisture foods to build fat reserves. They prefer tender, new growth, succulent shoots, and abundant forbs, which offer digestible protein and carbohydrates. Berries, such as salmonberry and thimbleberry, are also consumed as soft mast, providing a rich source of sugars.
Winter requires a switch to evergreen foliage and woody browse, such as Douglas fir and western red cedar, as herbaceous plants die back. The nutritional value of this winter forage is lower, and the deer’s digestive microbes must adapt to process the higher fiber content. Consequently, the deer’s metabolism slows, and its overall food intake decreases, relying on fat reserves accumulated during warmer months.
Critical High-Value and Mineral Sources
Specialized foods provide concentrated nutrients available seasonally. Hard mast, such as acorns, is consumed in the fall and winter, offering a dense source of fat and carbohydrates that is immediately stored as energy. Fungi, including various mushroom species, are sought after for their protein and phosphorus content. Furthermore, arboreal lichens, like old-man’s-beard, become a significant component of the winter diet. While lichens themselves are not highly nutritious, their chemical composition aids in the digestion and utilization of the low-quality woody browse, effectively acting as a digestive supplement.
Mineral sources are also a necessary supplement to the diet, particularly sodium, calcium, and phosphorus. Deer seek out natural mineral licks or salt sources, especially during the spring and summer. This timing correlates with the demands of reproduction and growth; does require high levels of calcium and magnesium for gestation and lactation. For bucks, the rapid growth of antlers necessitates a substantial mineral supply, with calcium and phosphorus being temporarily mobilized from their skeletal structure and then replenished through their diet and mineral intake.
Deer and Human Landscapes
As black-tailed deer increasingly interface with human habitation, their foraging behavior often extends into managed landscapes. Ornamental plants, vegetable gardens, and fruit trees become attractive, high-value food targets due to their palatability and ease of access. Common garden targets include roses, hostas, cedar hedges, and young fruit tree saplings, which are browsed for their tender tips and buds. This shift in foraging is a direct result of resource availability and can lead to property damage.
The presence of humans also introduces the significant danger of artificial feeding, which can be unintentionally lethal. Foods like corn, hay, and commercial grain pellets are not compatible with the deer’s specialized digestive system, especially in winter when their stomach microbes are adapted to high-fiber woody browse. Ingesting large amounts of low-fiber, carbohydrate-rich food can cause a condition called gut acidosis or enterotoxaemia, where the rapid change in gut chemistry kills the beneficial bacteria, leading to starvation despite a full stomach. Furthermore, artificial feeding congregates deer in unnaturally high densities, increasing the risk of disease transmission and habituating the animals to humans and roadways.