Lisle, S. The Ecology and Management of the Eurasian Beaver (Castor fiber). Co-author. In press.

Lisle, S. “The use and potential of flow devices in beaver management.” Lutra 46(2) 211-216. 2003

Czech, A., and S. Lisle. "Understanding and Solving the Beaver (Castor fiber L.)-Human-Conflict: An Opportunity to Improve the Environment and Economy of Poland." Biber: Die Erfolgreiche Rückkehr, J. Sieber, Editor (2003): 91-98.

Lisle, S. "Beaver management at the Penobscot Indian Nation, USA: Using flow devices to protect property and create wetlands." Proc. 2nd European Beaver Symp. Carpathian Heritage Society, Krakow, Poland. 2001.

Lisle, S. "Wildlife programs at the Penobscot Nation." Transactions of the North American Wildlife and Natural Resource Conference. Vol. 65. 1999.

Lisle, S. "Beaver deceivers." Wildlife Control Technology. September-October (1996): 42-44.

Lisle, S. Beaver recolonization in south-central Maine. Diss. MS thesis. University of Maine, Orono, ME, 1994.

Flow device. A general term used for all pipe or steel-mesh fence systems with a level of sophistication that at least attempts to sneak water away from beavers, and to control damming behavior, without the need to eliminate said animals. There are many different types of flow devices, and they have a great range of quality. Their success is always greatly dependent on the skill of the designer, builder, or installer. Structures that have no chance of working as defined above, and are often just meant to protect the culvert long enough for the beavers to be killed (e.g. simple grates), are not true flow devices.

Outlets. Road culverts, bridges, pond overflows, and other kinds of narrow, manmade structures that streams flow through. The most vulnerable points in the infrastructure, they are attractive to beavers because most of the dam is already in place, so the flow can be blocked, and a pond created, quickly and easily. Outlets are one of two distinct site types where flow devices are used.

Roofed outlets. Culverts and bridges. When these are totally blocked, the water will often rise all the way to the top of the road, which can be very high. This can be expensive and dangerous on a number of levels, which gives them the highest defense priority among outlet types.

Filter. The word filter is used interchangeably with “fence.” However, “filter” implies a greater level of subterfuge. This is appropriate, particularly on the end of pipe systems where one tries to stealthily “filter” water away from beavers and into a dam leak, or pipe. It is preferable to the word “cage” because the last thing one wants to do is to capture beavers, or any animals, inside

“Regular” beaver dams. These are the other type of potential flow device sites. These dams are generally less of an immediate threat because they are not connected to, or supported by, manmade structures. Therefore, they are typically longer, grow more slowly, and never have a secondary, higher overflow point like roofed outlets.

Beaver Deceivers™ (BD;1995). These are flow devices completely or partly comprised of a high quality, wood-frame fence built on the upstream end of outlets. The frame uses specific materials, and typically has three basic components: posts, a horizontal “stringer” between the top of the posts, and, if necessary, diagonal braces on the posts. Special types of fencing and fasteners are used. Once known for their trapezoidal shape, BDs have steadily evolved and improved over the decades. Today, they often have relatively small, square fences in front of the culvert; sometimes, a simple “straight fence” is adequate. These culvert fences are usually combined with an upstream pipe system called a Castor Master™. Because outlets vary greatly, and their topography and watershed characteristics are all different, a key concept of BD design is a flexible, mold-to-fit approach that requires skill and experience. BD is a popular name often used, incorrectly, by the general public for all flow devices. In addition to the descriptions given above, the purest one is “an outlet flow-device built by Skip Lisle or Beaver Deceivers International.”

Double-Filter System™ (DFS). This is a term coined to describe flow devices that have some form of fence in front of the culvert (filter #1) combined with a pipe system that extends upstream. At its intake, the pipe is protected with another steel-mesh filter (#2). Most of our modern BDs are DFSs.

Trapezoidal Fence™. A concept associated with BDs from the late 90s that were usually large, stand-alone (no pipe systems) fences. The idea behind a trapezoid is that, among simple shapes with the same front-to-back length, its sides create the most unnatural direction for a dam (furthest from perpendicular to stream flow). Its perimeter also has the longest length, creating the largest area to filter water away from beavers. They were large because, attached directly to the dam (road), and without “separation,” they were vulnerable. Once good pipe systems began being added in 1998, greatly improving security, culvert fences were less crucial and thus began getting smaller, simpler, and easier to build.

Dam-leak separation. A solid pipe represents a powerful concept. Extending upstream, it essentially moves a dam leak to an incongruous location away from the dam. Beavers are programmed to look for dam leaks in dams, and they don’t understand the concept of pipes and hollowness. Nevertheless, pipe intakes also have to have good filters and cannot be noisy.

Castor Masters™ (CM; 1998). These are pipe systems used in conjunction with fences in BDs™. They are also used alone in regular beaver dams. They incorporate a variety of different types of pipes, and use Round Fence™ and Square Fence™ filters.

Round Fences™ (RF; 1998) are upright, self-supporting cylinders of heavy-duty wire mesh. They are used either enclosed (top and bottom), or not. They were the first filter—beavers out, water in—we designed to protect the end of pipes in Castor Masters.

Square Fences™ (SF; 2005). Square or rectangular, they have a wooden stringer at the top. Sometimes posts are added to these for support.

Swept-Wing Fences™ (SWF; 2009) are designed to turn back beavers that are moving upstream along a narrow, vulnerable watercourse like an irrigation ditch. “Area exclusion” is the best approach in a long ditch that beavers could dam quickly at dozens of different points; it would be too expensive to build a new flow device for every potential dam. SWFs have to be combined with a CM on the upstream side so they don’t become a dam site if beavers do get in the canal.

Flow-Device Fish Ladders™ (2001) are small structures placed on the downstream end of pipes in dams or in Beaver Deceivers™ to help get fish through. They are also used on “hanging” road culverts that block fish passage on the downstream end.

Beaver Doors™ (1998) are components of culvert fences that allow larger animals like beavers and big turtles to traverse streams, and pass through the fence, so they are not forced to go across the road. They also have to be designed to prevent beavers from pulling debris through them. They come in a variety of designs and styles.

Misery Multipliers™ (MM; 2010) are a way of adding security to 6-inch-mesh (15 cm) fencing. Small beavers will sometimes pull a lot of debris through these holes, and then into the culvert. MMs can be designed in a number of ways, and basically make the economics less favorable by forcing beavers to go through two walls, and by making the “movement space” more confining for bodies and the transport of debris.

BDI Live Traps™ (2012) are small cages built with BD components (wood and steel mesh). They have a simple gravity door-drop that a beaver triggers once inside. The beaver is not subjected to a violent, spring-loaded door, and has adequate room to move around when caught. The structure doubles as a carrying case for moving the animal elsewhere.

BDI Tree Guard™ (2006). Our method of protecting trees from chewing.

BDI Boardwalks and Decks™ (2009). Unique frame structures and designs for accessing and enjoying wetlands and other beautiful natural areas. (Also, expertise in determining the best locations for these products.)

BDI Dig Guard™ (2011). A simple system to prevent digging in banks.