Animal damage is common in winter. Most of the damage is from feeding. While the damage is distressing to gardeners, it is important to realize that plants make up the entire diet of many animals, and our gardens are tempting.
As the food supply decreases, animals will search for food wherever they can find it. Evergreen needles and leaves are particularly tempting to browsing animals, like deer. Small mammals, like mice and voles, find the thin bark of young trees and shrubs to their liking. These small animals can hide under the snow and cause damage unseen. Squirrels often chew buds and small stems for water.
Deer
Deer can cause two types of damage to plants: rubbing antlers against bark and browsing on stems and leaves.
Antler rubbing usually occurs prior to the deer’s rutting (mating) season, in late summer and early fall. Male deer, or bucks, rub their antlers against trees that are two to three inches in diameter and larger. Rubbing against young trunks can severely damage the bark, causing girdling and dieback of branches.
Browsing can occur throughout the year, but becomes more noticeable during late fall and winter when other foods are less available. A hungry deer in a cold winter will eat anything. One adult deer can consume up to four pounds of woody twigs a day.
Management for Deer Damage
Fencing is the most reliable deer control solution, but not always the most practical or aesthetically pleasing. Deer are good jumpers, and it is commonly recommended to use at least eight-foot-high fencing.
Metal wire cages placed around individual plants will help deter deer from browsing, provided the cage is tall enough to prevent deer from reaching over the top.
Protecting trees with plastic collars and tree guards in late summer may provide some protection from deer rubbing. Be sure to remove any trunk guards or collars in spring to allow the trunk to expand normally and avoid damage to the trees.
Several commercial repellents are available for short-term solutions. Spray repellents work by emitting an odor or taste that deer don’t like. These products may reduce the level of feeding, but may not totally eliminate deer browsing. Reapplication may be necessary depending on rainfall.
Deer-Resistant Plants
If they are starving and food is scarce enough, deer will eat almost anything. There are a number of plants, however, that deer don’t find especially palatable. Using deer-resistant plants in your landscape is often the most cost-effective, least time-consuming, and most aesthetically pleasing solution.
Mice and Voles
Mice and voles are small rodents that do most of their damage to trees and shrubs during the winter, when food supplies are scarce.
In winter, they can gnaw on trunks and roots, usually below the snowline or under a layer of mulch touching the base of the tree or shrub. The damage to the bark cuts off the plant’s water supply, causing a slow decline and potentially the death of the plant.
In spring, shallow trails from voles may be seen in mulch and in lawns. The trails in lawns will fill in as the lawn resumes growing in spring.
Management for Mice and Vole Damage
The success in reducing rodent damage lies in taking action before damage occurs.
In autumn, look for nests or vole runs in grass and other vegetation close to the soil surface. Push mulch away from the base of trees and shrubs. Place cylinders of hardware cloth (1/4-inch mesh) around plants. Be sure to extend the cylinder deep enough into the soil to prevent mice and voles from digging under the screen. Commercial animal repellents may also reduce mouse and vole damage, but may need to be reapplied, depending on rainfall.
Rabbits
Rabbits damage plants in winter by eating small twigs and buds or chewing bark at the base of plants.
Twigs clipped by rabbits exhibit a clean, 45-degree slant or knife-like cut. Trunk damage shows up as scarred areas with paired gouges from the rabbit’s front teeth.
Rabbits generally feed no more than two feet above the ground, but they can travel on top of the snow to feed at higher points.
In other seasons of the year, rabbits will feed on a wide variety of garden and landscape plants, again cutting stems at a 45-degree angle.
Small plants may be eaten completely down to the ground.
Management for Rabbits
One of the best ways to protect against rabbits is to secure a fence of chicken wire or wire mesh around plants needing protection. The fencing needs to be at least 18 to 24 inches high and should be buried into the ground about two to three inches, or staked firmly into the ground to prevent tunneling underneath.
Individual cylinders of hardware cloth can protect valuable trees from damage. The cylinders should extend above the expected snow line and stand one to two inches from the tree trunk.
There are commercial repellents available for management of rabbits. Those that are taste repellents discourage rabbit browsing, but only protect the parts of the plant they contact. New growth that emerges after application is not protected. Heavy rains may require reapplication of some repellents.
Sapsuckers
The yellow-bellied sapsucker is a member of the woodpecker family. This migratory bird, about the size of a starling, is present in the Chicago area during April, and again in September and October.
An individual sapsucker often picks a favorite tree and returns to it repeatedly. Favorite trees include pine, apple, maple, poplar, and birch, though it may attack other species as well.
The appearance of holes on the trunk or branches of trees is often an indication of borers. However, if the holes have a regularly spaced pattern in neat side-by-side rows, the damage is caused by the sapsucker.
The bird feeds on the sap and insects trapped in the sap. Sapsuckers may make just a few rows of holes on some trees or make repeated attacks on the same area of a specific tree. If the rows of holes extend completely around the trunk of the tree, the water-conducting tissue under the bark is disrupted. This can cause the area to be girdled, and the portion of the tree above the affected area can die.
Management for Sapsuckers
To discourage sapsuckers from damaging a tree, wrap hardware cloth or burlap around the area being damaged. Remove it once the birds have migrated out of the area.
Hanging balloons, reflective bird tape, or other things that move may scare the birds away.
The yellow-bellied sapsucker is protected by the Migratory Bird Treaty Act and cannot be harmed or killed.
Squirrels
Squirrels damage trees by clipping, gnawing, and stripping the twigs and bark.
Twigs are clipped during the collection of seeds and buds. The clipped twigs often litter the area beneath the tree, and the ends of the twigs appear as though they were cut with shears.
The bark on larger branches may be gnawed or stripped in winter or early spring when food supplies are reduced. During the summer, squirrels may occasionally strip bark from main stems and larger branches for nesting material.
Management for Squirrels
Squirrels are very adept at climbing and jumping, so management is difficult and is seldom fully effective. To prevent loss of fruit from fruit trees, bird netting can be draped over small fruit trees. The bottom of the netting would need to be tied off to keep squirrels from entering.
Pruning tree branches back from rooftops at least ten feet will limit the ability of a squirrel to access the roof and possibly cause damage to it.
Taste repellents may reduce plant damage by squirrels, but may require reapplication after rains. Repellents that contain capsaicin can be used on seeds and bulbs at planting, and on trees and shrubs as well. Capsaicin-based taste repellents can also be mixed with birdseed to discourage feeding by squirrels. Capsaicin does not harm birds.
In Illinois, squirrels are protected under the Illinois Wildlife Code. A nuisance animal removal permit is needed in urban areas to trap and release a squirrel.