By Ken Bevis, DNR Stewardship Wildlife Biologist, ken.bevis@dnr.wa.gov
Food, water, cover — the three core needs for wildlife to survive and succeed on any given home range.
In forest management we seldom attempt to address food, assuming that our wildlife will be able to exist with the plants or prey species that naturally occur. Water is sometimes provided with streams, puddles or ponds, but also is usually not directly addressed for wildlife. Both of these factors are usually adequate on most forest lands for wildlife to exist.
Cover, however, is sometimes a limiting factor. Particularly in scenarios where fuel reduction is an objective. It is also something easily addressed by providing hiding places for wildlife to rest and reproduce. But what type of structures makes good cover? Examples include: Hollow logs or trees; dense shrubs and shrub clumps; clumps in tree crowns, such as mistletoe brooms; down wood; concentrations of down wood and branches; and piles of forestry generated materials
Let’s look at piles.
I like to say there are three basic kinds of piles:
- Slash piles – unconsolidated debris from logging or land clearing, with big chunks, stumps and dirt all jumble together, often in huge piles and burned in winter.
- Brush piles – generally small diameter branches and pieces of discarded vegetation, tossed randomly into a pile with intention of disposal via chipping, burning or simple decomposition.
- Habitat piles – material deliberately arranged to optimize habitat availability for local wildlife, and positioned on the land with intention of retention for wildlife long term.
So what is a habitat pile?
Simply stated, habitat piles consist of big material crisscrossed or carefully arranged on the lower levels forming a core that provides cavities and openings, with smaller material piled on the top to form a roof.
Sometimes dens are created inside of piles too. Imagine what sort of a cave would be the right size for a rabbit, bobcat, coyote, raccoon or porcupine. Lay the base layer of logs in such a way to create a cavern in the middle. Perhaps dig a hole to help them get started before lying the wood. Put a solid layer of smaller diameter pieces over the cavity as a roof. Layer with small branches, but leave an outside entrance, maybe somewhat hidden. It can be surprising what will use these den sites.
Logs can be piled in linear arrangements to provide hiding places for snakes and small mammals, fully in contact with the soil. Others are arranged on top of these lowest levels to create overhead cover.
Small animals, including mammals such as deer mice; reptiles, such as fence lizards; and amphibians, such as salamanders, can greatly benefit from strategically placed piles.
Tyler Larsen has been working with habitat piles on a private forest near Cle Elum for the past three years. They were included deliberately in a fuels reduction project sponsored by DNR and coordinated by the venerable forestry consultant, Phil Hess.
There are lots of anecdotal accounts of wildlife using piles, but we asked how this use could be systematically documented. Tyler and his team (including his colleague and friend, Adam Hess) are working on a research project, using trail cameras pointed at constructed Habitat Piles to document use. It is an experimental design created with the help of retired U.S. Forest Service scientist, Dr. Peter Singleton. The research uses paired sets of cameras; one set of cameras on a habitat pile, another in a parallel location, not on a pile. The results have been remarkable, showing high wildlife use of these structures. Species using these piles include ground squirrels, chipmunks, marmots, a flying squirrel, snakes, many birds including juncos and white crowned sparrows, deer, and many others. Larsen and Hess are working on a research publication to describe the results of this work.
Incorporating habitat piles into fuels reduction projects, and in thinnings or other activities generating woody material, can provide habitat complexity to support wildlife in nearly any setting.
I sent him a set of questions in preparation for this article. Larsen offered these thoughts on his habitat pile project. Thanks to Tyler for his good work. Stay tuned for the research results.
Send me good photos of your habitat piles!
Habitat Pile Thoughts
Tyler Larsen, forest health scientist, central Washington
What are some design elements of your piles?
When I design a pile, I try to integrate as much complexity as I can. I have a feeling for which animals in our area use our piles the most, so I try to accommodate them. Having a variety of opening and chamber sizes will allow a greater diversity of species to benefit from the pile. I try to overcome my human desire for neatness and symmetry and make a complex and haphazard – but structurally sound – pile.
Habitat piles can be constructed with a specific species in mind. We have multiple populations of breeding frogs and salamanders with little cover around their ponds. So, with the advice of a biologist who has had success with this, we created piles to benefit amphibians. We did this by burying habitat piles about three feet underground, then building another pile on top of them, making sure to leave underground access points. Being underground will help with moisture retention throughout the year and hopefully help reduce temperature extremes.
Like most habitat piles, they begin with a base of logs cut to a manageable length. I’ll toss these into a pile, letting them fall where they may, while making sure they don’t roll away or collapse. I like to make piles at least six feet across and three to four feet high. A crucial element of the pile is a layer of slash on top. This will better insulate the pile, providing better thermal cover, while also sheltering the animals from predators and the elements. Smaller branches sticking up from the top provide perches for birds. I also like to incorporate snags or large shrubs within the pile to add structure and complexity.
The most important element in creating habitat piles in my opinion is placement, but I’ll get to that later.
What wildlife species have you observed using your piles?
Using our cameras, we have observed at least 20 species using our piles. The main users are small mammals like chipmunks, squirrels, mice, marmots, and skunks. We have observed a variety of birds perching on the piles such as: western tanagers, American kestrels, white-crowned sparrows, Townsend’s solitaires, spotted towhees and hairy woodpeckers. Another common occupant is the western fence lizard, we regularly see them basking on the logs within the piles.
Other animals use piles in ways that I hadn’t thought of before. Larger mammals can take advantage of the protection of the piles. We see that deer and elk bed down next to them. Whether they provide a wind break, or just a sense of security, deer seem to like them. They also promote shrub growth within and in the shade of the piles, which we have observed deer taking advantage of.
What suggestions can you make to landowners for the most effective habitat piles?
Building habitat piles is more of an art than a science. There are no set rules, and even a few logs on the ground can provide habitat value for some species. Be creative and make piles that you think look good and seem like they would be a good place for a critter to hide. Think about the species in your forest and what their sizes are. Small animals like to be in spaces that they can fit into, but their predators cannot. Also, give them some time. It can take a while for animals to colonize new habitat features, and eventually they will carve out a space for themselves.
How long have you been an advocate for habitat piles?
As an undergraduate I studied snake ecology. One of the best ways to find snakes is to look under cover — natural and artificial. I would flip over logs, rocks, and boards to increase the chances of finding snakes. I also observed many other types of animals using this cover, such as insects, rodents, lizards and more. This taught me the importance of cover for small animals and showed me that there is an entire community of semi-fossorial organisms — which are adapted to living partly underground — that you can find by looking under logs and rocks. Natural and artificial cover creates the interface connecting fossorial and terrestrial species, helping to reinforce those connections in the food web. Modern forest thinning can leave very little cover in the form of downed wood on the forest floor. Forest landowner goals revolving around fire mitigation tend to encourage more open space and less fuel left in the forest. This can result in a deficit of cover for animals, which are an important factor in forest health. We are in an age of biodiversity loss and mass extinction. Anything that can be done to promote wildlife habitat, especially in lower trophic species, is a worthwhile endeavor. Habitat piles and wildlife trees are probably the best ways to do that in forest ecosystems.
Do you have any suggestions on pile placement?
You don’t want your piles to become ladder fuels in case of a fire. If a fire were to burn through the forest, the burning piles will produce high flame lengths and can torch nearby trees. Because of this I think it is best to place piles at least 30 feet away from any tree that could torch and cause a crown fire. If a tree is isolated and wouldn’t ignite a neighboring tree, then this is less important.
The proximity to other types of cover or habitat features is crucial. Some of our piles, while well-constructed, were not used because they were so isolated and had no other cover nearby. Now, if we place piles in a large opening, we will build several in the area so the critters can move from pile to pile without being exposed for too long. After seeing how deer use the habitat piles, we have placed them near rows of large shrubs, hoping deer can take advantage of the wind protection and security.
By Molly Darr, Washington State University Extension Forester, 
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