The idea of “cannibal deer” can be quite startling, conjuring images of these typically docile herbivores engaging in unexpected and aggressive behaviors. This phenomenon challenges common perceptions of deer as strictly plant-eating animals. Understanding this behavior requires exploring the true nature of their dietary habits.
What “Cannibal Deer” Really Means
The term “cannibal deer” is a misnomer, as deer do not actively hunt and consume other live deer. The observed behavior is primarily osteophagia, the consumption of bones, or occasional scavenging. Deer have been documented gnawing on various animal remains, including bones, antlers, and even carcasses of birds or fish. This is distinct from predatory actions and reflects a different nutritional motivation. For instance, white-tailed deer have been observed gnawing on human bones at forensic research facilities, an activity attributed to seeking minerals.
This behavior has been observed in various deer species, including red deer, Axis deer, and white-tailed deer, across different geographical locations, such as Costa Rica where they consume sea turtle bones. The gnawing patterns left by deer on bones, such as a “forked pattern” or zigzag marks on the ends, are distinct from those left by carnivores. This scavenging activity is a documented part of their broader feeding ecology, despite their classification as herbivores.
Why Deer Eat Bones and Carcasses
Deer engage in osteophagia primarily to supplement their diet with essential minerals that may be lacking in their regular plant-based forage. Calcium and phosphorus are important for deer, playing a significant role in bone formation, antler development in males, and successful reproduction and lactation in females. While most of their diet comes from vegetation, plants often do not provide sufficient quantities of these minerals, especially phosphorus.
Deer can store calcium and phosphorus in their skeletons, but these reserves alone are often not enough to meet peak demands, such as during antler growth or gestation and lactation. For example, white-tailed deer antlers are composed of approximately 22-24% calcium and 10-11% phosphorus. When mineral deficiencies occur, deer will seek out alternative sources, including bones and shed antlers, to obtain these necessary elements. The consumption of bones can also provide other trace minerals that contribute to overall health.
Potential Links to Disease and Environment
The consumption of animal remains by deer raises questions about potential disease transmission, particularly concerning Chronic Wasting Disease (CWD). CWD is a fatal neurological disease caused by misfolded proteins called prions, which can accumulate in bodily tissues. While CWD prions are known to persist in the environment for extended periods, direct evidence for significant CWD transmission through deer consuming infected bones or carcasses is still under investigation.
Transmission of CWD is thought to occur primarily through direct animal-to-animal contact or indirectly through contact with contaminated environments, such as soil or water sources where infected animals have shed prions. Although the concentration of prions in excreta might be low, their accumulation in the environment can be substantial because they do not easily degrade. Scavenging by various vertebrates, including deer, plays an ecological role in removing carcasses from the environment, which can help limit the spread of potentially infectious materials, thus contributing to ecosystem stability.