Deer readily consume chestnuts, which are a highly preferred food source in many habitats. These nuts are a significant part of their diet where chestnut trees are available. This attraction can lead to conflicts between deer feeding habits and the health of cultivated or restored chestnut trees. Understanding this preference and the timing of deer damage is key to effective protection.
Why Chestnuts Are a Highly Desired Food Source
Chestnuts are nutritionally superior to many other common hard mast foods, such as acorns, making them a highly sought-after energy source for deer. The primary advantage is their high carbohydrate content, which averages around 40% of the nut’s composition, compared to approximately 10% in white oak acorns. This dense energy provides the necessary fuel for the male deer rutting season and allows both sexes to build up the fat reserves needed to survive the harsh winter months.
The nuts also contain a higher percentage of protein, typically around 10%, which is more than double the protein found in most white oak acorns. Additionally, chestnuts lack the bitter tannic acid found in acorns, making them significantly more palatable to deer. Studies have shown deer can prefer chestnuts over acorns by a ratio of 100 to 1 when given the choice.
This combination of high carbohydrates, quality protein, and sweet taste ensures that deer will actively seek out chestnut trees to maximize their energy intake. Finding and consuming chestnuts provides a substantial net gain in energy, which is a critical factor for survival and reproduction.
Seasonal Feeding Habits and Tree Damage
Deer interact with chestnut trees in two distinct ways: consuming the nuts and physically damaging the tree itself. The primary feeding period for the nuts occurs in the fall and early winter, starting when the nuts drop from the tree in a process known as mast production. Deer focus on the fallen chestnuts during this time to prepare for the nutritional stress of winter.
Damage to the tree structure, however, happens year-round, with two peak periods.
Browsing
Browsing involves deer eating the terminal buds, leaves, and young twigs of the chestnut tree, typically on branches less than an inch in diameter. This browsing is particularly damaging to young seedlings and saplings. Repeated loss of their main leader can stunt growth or cause the tree to develop a bushy, multi-stemmed form.
Antler Rubbing
The second, more destructive type of injury is antler rubbing, which occurs primarily in the fall during the rutting season, from early September through December. Male deer rub their antlers against the trunk to remove the velvet covering and to mark territory. This action strips the bark, damaging the thin layer of phloem and cambium underneath, which is responsible for transporting water and nutrients. If the bark is removed completely around the circumference of the trunk, a condition called girdling, the tree will die.
Strategies for Protecting Chestnut Trees
The most reliable way to prevent deer damage is through physical exclusion barriers. Perimeter fencing is the gold standard for protecting large groves, but it must be at least 8 feet tall to prevent deer from jumping. For added security in areas with high deer pressure, a fence height of 10 feet may be necessary.
Protecting Individual Trees
For protecting individual saplings, two methods are highly effective: wire cages and tree tubes. Individual exclusion cages made from welded wire mesh should be constructed at least 5 feet high to prevent deer from reaching the terminal bud. Tree tubes, which are plastic shelters placed around the trunk, protect the bark from browsing and antler rubbing, particularly for young trees up to 6 feet tall.
Chemical deterrents offer a temporary solution for browsing damage, but are less effective against antler rubbing. These repellents work by taste or odor and often contain putrescent egg solids or sulfurous compounds. They must be reapplied frequently, usually every two to four weeks, and especially after rain, since new, unprotected growth will emerge. Their effectiveness decreases in areas with high deer density or when alternative food sources are scarce.