White-tailed deer are common North American herbivores known for their adaptable, generalist diet. They consume a wide array of plants, including woody shoots, stems, leaves, grasses, and various cultivated crops. Ragweed, specifically common ragweed (Ambrosia artemisiifolia) and giant ragweed (Ambrosia trifida), are prevalent in disturbed areas. These plants are known for their prolific growth and wind-borne pollen, a significant allergen for many. Given deer’s diverse foraging habits, their consumption of this widespread plant is often questioned.
Deer and Ragweed Consumption
White-tailed deer generally do not prefer ragweed as a primary food source. While deer are opportunistic feeders whose diet varies with seasonal availability and nutritional needs, ragweed is a low-preference browse. Deer diets include forbs (broadleaf herbaceous weeds) and browse (leaves and tender twigs of woody plants). Although ragweed is a forb, studies rarely show it as a major dietary component.
Deer may consume ragweed when preferred forage is scarce or when plants are very young. Common ragweed can offer 17-18% crude protein, making it a potentially valuable food source, especially during high-stress periods. However, this consumption is often a “last resort.” While some observations note deer browsing on giant ragweed, particularly its nutritious seeds, it is not consistently favored across all regions.
Factors Influencing Deer Foraging
Several factors explain why deer avoid ragweed despite its widespread availability. A primary reason is the presence of secondary metabolites, specifically sesquiterpene lactones. These compounds give ragweed a bitter taste, deterring many herbivores, including deer. The concentration of these bitter compounds varies with the plant’s growth stage and environmental conditions, influencing palatability.
Beyond taste, ragweed’s nutritional profile may not be optimal compared to other available forage. While not toxic and potentially high in protein, deer almost always choose other readily available plants. More palatable and nutritionally rich alternatives mean ragweed often serves as a fallback food. Younger ragweed plants might be slightly more palatable before their chemical deterrents fully develop, but their desirability decreases with maturity.
Ragweed’s Ecological Role and Management Considerations
Ragweed acts as a pioneer species, thriving in disturbed habitats like roadsides, fields, and cultivated areas. Its rapid colonization and prolific seed production contribute to its widespread presence. Ragweed is also known for its highly allergenic pollen, a major cause of hay fever in North America. A single plant can produce billions of pollen grains, easily dispersed by wind over long distances.
Given deer’s low preference for ragweed, relying on them to control populations is ineffective. Deer are not a viable solution for managing its spread due to their selective foraging habits. Effective ragweed management involves human-led strategies. Common methods include regular mowing before flowering to prevent seed production, hand-pulling for smaller infestations, and herbicide application. These interventions reduce pollen release and limit seed spread, as seeds can remain viable in soil for several years.