Prepared By: Lake Simcoe Region Conservation Authority (LSRCA)

Introduction

The beaver is the largest rodent in North America, with the average adult weighing from 16 to 32 kg and measuring up to 1.3 m long.

A beaver’s life is inextricably connected to cutting trees—for sustenance and for habitation. In nature, beaver activity plays an important ecological role. However, their ingenuity and need to build dams, brings them into direct conflict with humans when their activities take place within stormwater infrastructure, where activities can adversely affect its functionality, putting people and property at risk of flooding. Beavers can also interfere with planting through vegetation removal. As a result, management options may be necessary to deter them from interacting with these features.

There are several recommended, humane management practices to address concerns beavers may present in and around stormwater management features. Management practices for beaver control at stormwater management features should be reviewed on a site-by-site basis. Municipal teams should determine the best

strategy for effective, proactive strategies as a priority, exercising humane removal and relocation efforts only if more reactive measures are needed.

Stormwater management wet ponds remove pollutants and provide flood control. When properly maintained, ponds also provide ecological benefits that support ecosystem health. Stormwater management features, including ponds, must comply with provincial approvals to maintain functionality. Consequently, when ponds are adversely impacted by beaver activity, a compliance issue may be created.

Each Lake Simcoe Watershed municipality should consider developing longer-term strategies incorporating a proactive approach. This technical bulletin highlights key beaver issues and how to best address and manage these issues.

Key Issues

1. Damming: beaver dams within stormwater management ponds can block inlets, outlets or other sections of the feature that adversely impact the functionality of the pond including reducing active storage.
2. Removal of Vegetation: beaver activity may cause trees to fall, posing a safety issue to the public and potential damage to infrastructure.
3. Trapping and Removal: the practice of trapping beavers is often a concern among members of the public.

How to Address these Issues

The illustration below summarizes a recommended sequence of actions for beaver management. This sequence can also act as a foundation for municipalities to develop an overall strategy from upfront planning to annual inspection and maintenance activities.

Proactive

Planting Considerations

Design considerations include developing a planting scheme that incorporates trees and other vegetation within the stormwater management feature area that do not appeal to the beaver community. Examples of plantings to consider and avoid are as follows.

Plantings to Consider:

• Ninebark 6 5 3 *
• Red-osier (twig) dogwood 6 *
• Elderberry 6 5 3 *

* Native hardwood tree species accepted by municipality and conservation authority, consult with a qualified specialist

Plantings to avoid:

• Aspen
• Willow
• Cottonwood
• Alder
• Apple
• Cherry
• Birch
• Sugar maple
• Poplar
• Cattails
• Water lilies
• Sedges

Tree protection

• Wrap trees with wire in 1.5 m high field fencing, hardware cloth, or multiple layers of chicken wire.
• Paint tree trunks with a sand and paint mix (i.e., 120 gm of masonry-grade sand per litre of latex paint).

Pond & Culvert Protection

If a stormwater management feature is enclosed in fencing, keep the bottom of the fence flush to the ground to help prevent beavers from entering the block area.

Tubular culvert protectors confuse beavers, preventing them from creating a dam. A protector is constructed from two lengths of concrete reinforcement wire extending from the outside of the culvert and rounded to a close at least 2.5m from the end of the culvert.

Light rods should be fixed inside the mesh to stabilize the protector and maintain the cylindrical shape. This tubular protector requires inspection at least once per year, and is known to only require periodic maintenance (e.g., clean-out of debris caught on wire every few years). It may need to be repaired if damaged by ice in the winter. Tubular culvert protectors should be used to prevent beavers from colonizing or recolonizing an area that is known to be favourable habitat.

Older, wet stormwater management ponds or other features may incorporate culverts as inlets or outlets. The wire mesh configurations have also been implemented for beaver deterrence for other types of structures including inlet headwalls.

Reactive

Dam and Lodge Removal

Beavers typically do not remain in unsuitable areas. If their dams are breached and their lodges are damaged on a regular basis, they typically move on to another location. For instance, beaver lodges and dams may be removed by simple mechanical methods over two to three seasons. Once these structures are destroyed, regular maintenance of the facilities is often adequate to prevent their activity from becoming a future problem (Environmental Protection Agency, 2009).

Keep in mind the dam removal method and timing is important. A slow and methodical approach should be taken, to reduce the impacts of downstream erosion and the release of sediment. Dam removal in late fall or winter may endanger overwintering beavers as they typically rely on deep water to store and access food caches. Likewise, dam removal during the spring and early summer months could endanger young beaver kits. Therefore, removal is typically best in the summer to early fall period.

Beaver Baffle Application

A final consideration for minimizing the impact of beaver activity within a stormwater management feature includes the application of a beaver baffle. A beaver baffle is a pond-levelling device, consisting of a pipe and a cage, to help control flooding. While controlling flooding, a beaver baffle also stifles the sound of flowing water, which fools beavers into thinking the stormwater pond is not a suitable location to build a dam.

This approach may be implemented for an interim period before other measures, including relocation, are carried out. The baffles help reduce the impact of rising water levels, providing a manual method for changing the water levels in the dammed areas of the stormwater management feature. Thus, maintaining overall intended functionality of the stormwater management feature until a more permanent solution is realized.

Trapping and Relocation of Beavers

Only engage licensed animal specialists to perform trapping and relocation efforts once you have exhausted all other efforts. This approach should only be used as a last resort. It should also be noted that multiple beavers may find the features within a stormwater management pond appealing, continued trapping on a seasonal basis is to be expected.

Effective beaver relocation is expensive and often poses significant challenges. Not only is it difficult to find suitable areas for relocation nearby, the Ontario Ministry of Natural Resources requires beavers must be released within 24 hours of being captured and cannot be relocated more than 1 km from where they have been captured. If it becomes known that this method is being used public pressure can become an issue.

Additional References

For more information to support beaver management efforts please visit:

1. https://www.ontario.ca/page/wild-animal-control-information-for-municipalities
2. https://www.ontario.ca/page/preventing-conflicts-beavers
3. City of Portland (COP) Environmental Services. (2020). Beaver Management Plan.
4. DuBow, T. 2000. Reducing beaver damage to habitat restoration sites using less palatable tree species and repellents. Masters Thesis, Utah State University.
5. Jefferson county Conservation District. (2017). Chimacum creek adaptive beaver management plan.
6. King County Department of Natural Resources and Parks. (2017). Beaver management tools literature review and guidance.