What is poisonous to deer?

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Deer, while seemingly adaptable, can be surprisingly susceptible to certain toxins found in common plants, chemicals, and even improperly stored food. Understanding what is poisonous to deer is crucial for landowners, gardeners, and anyone concerned with deer welfare, and avoiding these substances can help protect these animals.

Understanding the Dietary Habits of Deer

Deer are primarily herbivores, meaning their diet consists mainly of plants. However, their feeding habits are opportunistic, leading them to sample a wide variety of vegetation. This exploration, while beneficial for nutrient intake, also increases their exposure to potentially harmful substances. They browse, consuming leaves, twigs, fruits, and nuts. This diverse diet, influenced by seasonal availability and geographic location, creates challenges in predicting and preventing accidental poisonings.

Common Poisonous Plants for Deer

Many ornamental and wild plants contain toxins that can harm deer if ingested. Recognizing these plants is vital for preventing unintentional poisoning.

Rhododendrons and Azaleas: Contain grayanotoxins, causing digestive upset, weakness, and neurological problems.
Oleander: Highly toxic, containing cardiac glycosides that can lead to heart failure.
Yew: All parts of the yew plant, except the red aril surrounding the seed, contain taxines, which are deadly to deer.
Cherry Trees (Wilted Leaves and Twigs): Under certain conditions, such as after frost or drought, wilted cherry leaves and twigs can produce cyanide, a rapidly acting poison.
Nightshade Family (Tomatoes, Potatoes, Eggplant – foliage and green fruits): Contains solanine and other alkaloids that can cause gastrointestinal distress and neurological symptoms.
Buttercups: Contain protoanemonin, which irritates the mucous membranes and can cause blistering and digestive upset.

Identifying Chemical Hazards for Deer

Beyond plants, certain chemicals commonly used in gardens and agriculture pose significant risks to deer.

Pesticides and Herbicides: While designed for specific targets, these chemicals can inadvertently poison deer through direct contact or ingestion of treated plants.
Fertilizers: Over-application of fertilizers, especially those containing high levels of nitrogen, can lead to nitrate poisoning.
Rodenticides: Deer may indirectly consume rodenticides by eating poisoned rodents or contaminated bait.
Antifreeze: Ethylene glycol, a common ingredient in antifreeze, is extremely toxic and attractive to deer due to its sweet taste.

Spoiled or Improperly Stored Food

Deer are also susceptible to poisoning from spoiled or improperly stored human food.

Moldy Grain or Hay: Can contain mycotoxins that cause various health problems, including neurological damage and liver failure.
Fermenting Fruits: Excessive consumption of fermenting fruits can lead to alcohol poisoning.
Table Scraps and Garden Waste: While seemingly harmless, certain food scraps, such as onions and garlic, can be toxic to deer in large quantities.

Mitigation Strategies: Protecting Deer from Poisonous Substances

Preventing deer poisoning requires a proactive approach, focusing on removing or mitigating potential hazards.

Plant Selection: Choose deer-resistant plants for landscaping and gardening to reduce the risk of accidental ingestion of toxic species.
Fencing and Barriers: Construct fences or barriers to exclude deer from areas where poisonous plants or chemicals are present.
Chemical Storage: Store pesticides, herbicides, fertilizers, and antifreeze in secure, deer-proof containers.
Proper Waste Disposal: Dispose of spoiled food, garden waste, and other potentially toxic materials properly to prevent deer from accessing them.
Monitoring and Observation: Regularly monitor deer populations for signs of poisoning, such as unusual behavior, weakness, or digestive upset.

Recognizing Symptoms of Poisoning in Deer

Early detection of poisoning is crucial for improving the chances of survival. Symptoms vary depending on the toxin involved, but common signs include:

Lethargy and Weakness: Noticeable decrease in energy levels and difficulty moving.
Digestive Upset: Diarrhea, vomiting, or abdominal pain.
Neurological Symptoms: Tremors, seizures, incoordination, or paralysis.
Difficulty Breathing: Rapid or labored breathing.
Excessive Salivation: Drooling or frothing at the mouth.

If you suspect a deer has been poisoned, contact a wildlife rehabilitator or veterinarian immediately. Prompt action can often save the animal’s life.

Table: Common Poisonous Plants and Their Effects on Deer

Plant	Toxin(s)	Symptoms
———————-	—————–	—————————————————————————-
Rhododendrons/Azaleas	Grayanotoxins	Digestive upset, weakness, neurological problems
Oleander	Cardiac glycosides	Heart failure
Yew	Taxines	Sudden death
Wilted Cherry Leaves	Cyanide	Rapid breathing, tremors, convulsions, death
Nightshade	Solanine	Gastrointestinal distress, neurological symptoms
Buttercups	Protoanemonin	Irritation of mucous membranes, blistering, digestive upset

Understanding Regional Variations

It’s important to remember that the specific plants and chemicals that pose a threat to deer can vary depending on the geographic location. Local knowledge and consultation with wildlife experts are essential for identifying and mitigating risks in your particular area. What is poisonous to deer in one region might be relatively harmless in another due to differences in plant species, agricultural practices, and environmental conditions.

Frequently Asked Questions (FAQs)

What are the most common signs of poisoning in deer?

The most common signs of poisoning in deer include lethargy, weakness, digestive upset (diarrhea, vomiting), neurological symptoms (tremors, seizures), difficulty breathing, and excessive salivation. Early detection is crucial for increasing the chances of survival.

Can deer develop immunity to certain poisons?

While deer can develop some tolerance to certain plants over time, they do not develop immunity to highly toxic substances like cyanide or cardiac glycosides. Continued exposure to even small amounts of these toxins can still be harmful.

Is it safe to feed deer human food?

Feeding deer human food is generally not recommended. While some foods may be harmless in small quantities, others, like onions, garlic, and chocolate, can be toxic. Spoiled food can also pose a risk. It is always best to let deer forage for their natural food sources.

How can I protect my garden from deer without using harmful chemicals?

Several methods can protect your garden from deer without resorting to harmful chemicals. These include installing fences, using deer-resistant plants, applying natural repellents (such as soap or garlic sprays), and employing scare tactics (like motion-activated sprinklers).

What should I do if I find a dead deer and suspect poisoning?

If you find a dead deer and suspect poisoning, contact your local wildlife agency or veterinarian. They may be able to perform a necropsy to determine the cause of death and identify potential sources of poisoning.

Can deer get poisoned from eating grass treated with weed killer?

Yes, deer can be poisoned from eating grass treated with weed killer. The toxicity depends on the type of herbicide used and the concentration. Always follow the manufacturer’s instructions carefully when applying herbicides and allow sufficient time for the treated area to dry before allowing deer access.

Are acorns poisonous to deer?

While acorns are a natural food source for deer, excessive consumption of certain types of acorns, particularly green or unripe ones, can cause digestive upset due to the presence of tannins. Deer typically adapt to acorn consumption over time, but sudden changes in diet can be problematic.

What kind of fencing is best for keeping deer out of my property?

The best type of fencing for keeping deer out of your property is typically a woven wire fence that is at least 8 feet tall. Deer are excellent jumpers, so height is crucial. Slanted fences or electric fences can also be effective.

How do I know if a plant is deer-resistant?

You can determine if a plant is deer-resistant by consulting local nurseries, extension offices, or online resources. Many websites and publications provide lists of deer-resistant plants for specific regions. Look for plants with strong scents or prickly leaves, as deer tend to avoid these.

Are pets at risk if a deer has been poisoned?

Pets can be at risk if a deer has been poisoned, especially if the poison is something they could ingest directly, such as rodenticides or antifreeze. If you suspect a deer has been poisoned, keep your pets away from the area and contact your veterinarian if they show any signs of illness.

Can water sources be a source of poisoning for deer?

Yes, water sources can be contaminated with toxins from agricultural runoff, industrial waste, or improperly stored chemicals. Ensure water sources near deer habitats are protected from contamination.

What role does climate change play in deer poisoning?

Climate change can indirectly affect deer poisoning by altering plant distributions and increasing the frequency of droughts and floods. These changes can impact the availability of food resources and potentially increase the risk of deer consuming poisonous plants or contaminated water sources. Understanding what is poisonous to deer is even more critical in a changing climate.