Whether deer consume cannabis plants, often called “weed,” is a matter of plant chemistry and animal biology. Deer generally avoid eating the Cannabis sativa plant. Their strong natural aversion stems from the plant’s robust chemical defense system, which renders it unpalatable and potentially toxic to the selective herbivore. This interaction suggests that while deer may occasionally browse out of desperation, the plant is not a preferred food source.
Typical Deer Forage and Dietary Habits
Deer are classified as “concentrate selectors,” meaning they seek out high-quality, easily digestible forage rather than grazing on low-nutrient roughage like grass. Their diet is primarily composed of browse (tender leaves and twigs of woody plants) and forbs (broad-leaved herbaceous plants). These animals require a high-protein diet to support their rapid metabolism and physiological demands, such as antler growth and lactation. Their narrow snout and long tongue allow for highly selective browsing, enabling them to pick the most nutritious parts of a plant. This specialized digestive system makes them particularly sensitive to plant compounds that may interfere with digestion.
Chemical Deterrents in the Cannabis Plant
The primary reason deer avoid cannabis is the plant’s strong chemical profile, which acts as a powerful feeding deterrent. The Cannabis sativa plant produces a dense array of volatile organic compounds, including a complex mixture of terpenes. Terpenes are aromatic hydrocarbon molecules that give the plant its characteristic pungent odor and flavor, serving as a first line of defense against herbivores.
These secondary metabolites are highly volatile, meaning their strong scent can be detected by deer before the plant is even tasted. For a selective browser, this potent aroma acts as an immediate warning sign of poor palatability or potential toxicity. Additionally, the plant produces bitter-tasting compounds that reinforce the initial olfactory aversion. This two-pronged sensory defense system is highly effective at convincing a discerning animal to seek forage elsewhere.
The Biological Impact of Cannabinoids on Ruminants
If a deer were to consume a significant amount of cannabis, the cannabinoids present, such as cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC), would have a biological effect. Deer are ruminants, like cattle, and research on livestock provides insight into this physiological response. These compounds interact with the body’s endocannabinoid system, which helps regulate various functions, including mood, pain, and immune response.
Studies on cattle fed industrial hemp byproducts have noted that the plant material has low palatability, often leading to reduced feed intake. While the effects on wild deer are not specifically studied, ingesting high concentrations of cannabinoids could potentially affect their nervous system, leading to altered behavior or impaired coordination. Furthermore, cannabinoids can accumulate in the animal’s system, and in high doses, they can induce changes in stress and inflammatory biomarkers within the ruminant’s body.
Strategies for Protecting Cultivated Plants
Despite their general aversion, a hungry deer may still browse on cultivated plants, making physical protection necessary for high-value crops.
Physical Barriers
The most reliable method of exclusion is the installation of a physical barrier, such as a sturdy fence. Deer are capable jumpers, so a fence must be at least seven feet high to be fully effective at preventing entry into a restricted area.
Sensory Deterrents
Cultivators can also employ sensory deterrents that rely on a deer’s acute senses and skittish nature. Motion-activated sprinklers or noise-makers can startle the animals, encouraging them to leave the area immediately. Repellents that use strong odors or tastes, such as those based on predator scents or putrefied egg solids, can be applied directly to surrounding vegetation or boundary markers. To prevent deer from becoming accustomed to any single method, it is often recommended to rotate the type of repellent used and reapply it frequently, especially after rain.