Decoding Deer Distress: A Guide to Unusual Deer Behavior & Health Concerns

As someone who’s spent over a decade exploring the backcountry and working with outdoor enthusiasts, I’ve seen a lot of deer. And while most encounters are peaceful, sometimes you come across a deer exhibiting truly bizarre behavior – or physical abnormalities. From reports of arterial worms in deer to unsettling sightings of deer with strange growths, it’s natural to be concerned. This guide aims to help you understand some of the more unusual things you might observe in whitetail and mule deer, what might be causing them, and when to report your findings. We’ll cover everything from common parasites to neurological diseases, and even address some of the more visually disturbing reports like a deer head exploding (which, thankfully, is rarely literal, but often related to serious illness).

Understanding Common Deer Health Issues

Before diving into the truly unusual, let’s cover some common deer health concerns. These can sometimes manifest as odd behavior, and understanding them provides a baseline for recognizing something more serious. Chronic Wasting Disease (CWD) is a major concern in many states (see National Park Service CWD information). It’s a fatal neurological disease that affects deer, elk, moose, and caribou. Other common issues include Lyme disease, ehrlichiosis, and various parasitic infections. These can cause weakness, lethargy, and changes in behavior.

Parasites: More Common Than You Think

Parasites are a frequent cause of distress in deer. While muscle worms in deer (Trichinosis) are a concern for hunters consuming the meat, other parasites can cause external symptoms. Mange, caused by mites, leads to hair loss, thickened skin, and intense itching – resulting in a whitetail deer with mange appearing quite distressed. Ticks are another common parasite, transmitting diseases and causing irritation. You might also notice black spots on deer, which can be caused by ticks, fungal infections, or even localized skin irritation. It’s important to note that black spots on deer meat during processing should always be reported to your state’s wildlife agency, as they could indicate a serious disease.

Nutritional Deficiencies & Genetic Anomalies

Poor nutrition, especially during winter months, can weaken a deer’s immune system and make it more susceptible to disease. Genetic anomalies, while rare, can also lead to unusual appearances. A piebald mule deer, for example, is a deer with patches of white fur due to a genetic mutation. These deer are often visually striking, but can sometimes have compromised immune systems. Similarly, white spots on deer can sometimes be linked to genetic factors, though they are more often associated with fungal infections or skin conditions.

Decoding Bizarre Deer Behavior: What Does It Mean?

Now, let’s address the more unsettling observations. I’ve received countless questions from trail camera users and hunters about deer exhibiting strange behaviors. Here’s a breakdown of some of the most common reports.

Neurological Issues: When Something is Seriously Wrong

Perhaps the most concerning observations involve neurological symptoms. A deer with tongue hanging out, or a deer with mouth hanging open, can be a sign of several serious conditions, including CWD, brain abscesses, or poisoning. Seeing a deer smashing head on rock repeatedly is extremely alarming and almost certainly indicates a severe neurological problem. This behavior, while seemingly self-destructive, is often a result of disorientation and loss of coordination. Brain abscess syndrome deer is a relatively new concern in some areas, causing similar neurological symptoms. The term “deer head exploding” is often used to describe the advanced stages of CWD or other severe neurological diseases, where the brain becomes severely compromised.

Unusual Physical Manifestations: Growths, Swellings, and Deformities

Reports of trail cam deer with tumors are unfortunately becoming more frequent. These growths can be benign or malignant, and their cause can be difficult to determine without a biopsy. Seeing a deer with a hole in its back is also deeply concerning and could indicate a severe infection, injury, or cancerous growth. The bumps on deer antlers, while sometimes normal velvet development, can also be caused by abscesses or other growths. It’s crucial to report any deer with significant physical deformities to your state wildlife agency.

Strange Locomotion & Repetitive Behaviors

Beyond neurological symptoms, other unusual behaviors can indicate a problem. Why do deer walk in circles? This behavior can be a sign of neurological disease, poisoning, or even a brain tumor. Seeing a deer walking on bones (meaning appearing extremely emaciated) is a clear indication of starvation or a debilitating illness. And while less serious, a pregnant deer belly can sometimes appear unusually large or asymmetrical, potentially indicating a difficult pregnancy or multiple fawns.

The Case of Arterial Worms: A Growing Concern

The recent increase in reports of arterial worms in deer is particularly troubling. These parasitic worms, Elazma curialis, live in the arteries of deer and can cause significant health problems. They’re often found during hunting season, and while they don’t typically pose a risk to humans, their presence indicates a stressed deer population. The worms can cause inflammation and block blood flow, leading to weakness, lethargy, and even death. The increased prevalence of these worms is thought to be linked to climate change and the expansion of the snail population, which serves as an intermediate host. You can find more information on this from the USDA Forest Service (USDA Forest Service Arterial Worms).

Addressing the "He Can't Even Skin a Buck" Phenomenon

I’ve seen this comment online a lot – often in response to photos of deer with unusual conditions. It’s a dismissive and frankly unhelpful attitude. The reality is, encountering a deer with a serious health issue can be distressing, and proper handling and reporting are crucial. It’s not about skill; it’s about recognizing a problem and doing the right thing.

Reporting & Responsible Outdoor Practices

What should you do if you encounter a deer exhibiting unusual behavior or physical symptoms? Here’s a checklist:

1. Document it: Take photos or videos if possible. Note the date, time, and location.
2. Report it: Contact your state’s wildlife agency immediately. They will be able to investigate and potentially collect samples for testing.
3. Do not approach: Maintain a safe distance from the deer. Do not attempt to handle or treat it yourself.
4. Practice Leave No Trace: (Leave No Trace) Avoid disturbing the area around the deer.
5. Hunter Specific: If you harvest a deer with any signs of illness, report it to your state wildlife agency before field dressing.

As outdoor enthusiasts, we have a responsibility to be observant and report any unusual wildlife activity. By working together, we can help monitor deer populations and protect their health. Understanding these potential issues, from arterial worms in deer to the more devastating neurological diseases, is the first step in responsible stewardship. For more information on deer health and disease, consult your state’s wildlife agency and resources like REI Expert Advice (REI Deer Health).

Remember, a healthy deer population is a sign of a healthy ecosystem. Let’s all do our part to ensure their well-being.