Beaver damage to trees: pencil-pointed stumps at the water's edge, as extension services describe it

This page reports what the official source says. It is not legal advice: ask the office named here. Control, trapping and relocation of beavers are regulated and differ by state and province, and the state or provincial wildlife agency is the office that applies; Purdue, quoted below, says to ask the state agency. The page describes what the sources say the damage looks like and the guards they list. It does not say what to do about any tree or animal. For protected species and nests in tree work, see the guide on wildlife and the law.

What the damage looks like

Purdue University and the USDA Forest Service (FNR-216, hardwood plantations) say beavers cut small to fence-post-sized trees to build dams and will gnaw on almost any tree. Trees they cut off have the look of a sharpened pencil, and the signs are found on the banks of streams near a plantation. The damage is typically limited to the edge of a planting beside the stream the beavers live on. The Utah State University Extension Swaner Preserve information sheet shows tooth marks on aspen with a hand for scale, and says a beaver can take down a tree of that size or larger in one night.

The University of Maryland Extension (Woodland Wildlife Spotlight: American Beaver, updated February 15, 2023) explains why: beaver incisors grow throughout life and must be worn down by daily use, so beavers gnaw trees at the water's edge, working so the tree falls into the water, then gnaw the branches off larger trees or take the trunks of saplings to build dams and lodges. It says the animal is mostly nocturnal and feeds on leaves, woody stems and aquatic plants, and that construction happens mainly in spring and summer.

Which trees the sources name

The Swaner sheet says aspens, willows and cottonwoods are preferred, because they evolved alongside beavers and sprout quickly after chewing, and that conifers tend to be left alone if other trees are readily available. It says brush-sized willows without a large main stem are left unfenced at the preserve because chewing stimulates new growth. Purdue's wording is broader: almost any tree.

Whether the sources call it harmful

North Carolina State Extension (Managing Beaver Ponds, reviewed May 28, 2024) says beavers are viewed negatively in some situations because of the flooding and girdling of trees, yet that their presence may ultimately be beneficial since they create wetlands. It lists benefits of active ponds, including better downstream water quality, breeding areas for amphibians and fish, and dead trees (snags) for birds, bats and other mammals, and says beavers use and expand a pond until the food supply runs out, usually up to 10 years or more, after which the old pond silts in and returns to forested wetland. Maryland says some property owners consider beavers nuisance animals while they contribute to healthier ecosystems, and reports Maryland research linking beaver behavior to reduced sediment loads in streams. The flooding side connects to the page on flooding and waterlogged soil, where Iowa State University Extension says how long water stays over roots matters.

Guards the sources list

The Swaner sheet says tree damage by beavers can be prevented with physical barriers, and lists exterior latex paint mixed with sand on the lower bark as a short-term measure that may not deter beavers forever, and individual fencing of trees or clumps of trees as the main method. It says a fence with a small grid of heavy wire resists force, that larger-grid fencing lets beavers reach through, that chicken wire is not strong enough, and that plastic sheaths around trunks are not effective. The sheet adds that lethal removal is not a permanent solution because recolonization is rapid where habitat remains, and that relocation is difficult and costly with few facilities and experts available. Purdue lists an electrified wire added low on a plantation fence where beavers are a problem, or tree cages, and says trapping can limit beaver damage. It points to the state Department of Natural Resources or a similar agency for information and regulations on beaver trapping.

The other animals in this group are listed on the wildlife damage to trees page.