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5.3 Beaver Reintroduction

Introduction

The natural retention of water within the landscape can be beneficial to providing better hydrological conditions in an area. Besides artificial impoundments, it is possible to enhance water retention by introducing beavers to appropriate areas. Beaver (the Euro-Asiatic Castor fiber and introduced North American Castor canadensis) are aquatic rodents of the family Castoridae (order Rodentia), and are well known for their dam-building activities (Figure 7).

Figure 7. The beaver and its lodge, which is generally built transverse to a stream course forming an impoundment.

Beavers are thickset animals with small, rounded ears, short legs, and large, webbed hind feet. They may grow to about 1.3 m long, including their flat, scaly, 0.3 m tail, and may weigh more than 27 kilograms. Beavers have a preference for streams and small rivers but also live around the margins of forest-edged lakes. Their dams of sticks, stones, and mud may last for years, impounding pools that sometimes cover many acres, which, as with all lakes, eventually fill in with silt to form meadows. Saplings and even large trees are felled by gnawing, cut into portable lengths, and dragged or floated through beaver-made canals to the pond. Beavers live in colonies, one or more family groups to a lodge. A family consists of a mated pair and two sets of offspring. The food of the beaver usually consists of the tender bark and buds of trees. The beaver is a protected species in Poland.

Technical Description

The method of augmenting water resources through beaver reintroduction is based on ecological engineering principles. In this method, a knowledge of local physiographic conditions and beaver species ecology are used to identify suitable sites to which beaver families may be transferred from overpopulated areas. The choice of the reintroduction site is a crucial stage in this process. Some site investigation and research into local development scenarios should be conducted to avoid those areas which are extensively used for agriculture and forestry. This avoids conflict between the beavers and neighbouring humans. These site investigations should also take into account the fact that should, population growth occur among the introduced family in a few years, young beaver might migrate to another nearby locality. Migration generally occurs along main rivers and their tributaries. Migrating animals can settle anywhere regardless of potentially competing human interests; in such cases, the beavers activities may lead to damages such as flooding of agricultural lands. Beavers can also be a threat to some cultivars, such as beets, which are a favourite food.

Ponding behind beaver dams modifies the hydrological regime in the surrounding area. The scale of change in the water regime depends on the prevailing hydrological and geological conditions. Because beavers also make vertical wells (up to 2 m in depth) to access their lodges, water circulation into and through soil layers may be enhanced. One beaver family can create a pond with a surface area of between 100 and 5 000 m2. In one reported case, a beaver pond covered an area of 200 ha and impounded about 1 000 000 m3 of stored water.

Extent of Use

In Poland, the introduction of beavers is carried out by the University of Pozna and the Ministry of Environmental Protection Natural Resources and Forestry as part of a national programme of beaver protection. A few other universities in Poland also have field stations which are involved in beaver research and which offer beaver-introduction expertise. The known beaver population in Poland is about 12 000 animals. However, these animals are not equally distributed throughout the country. After World War II, beaver populations were sustained only in a few natural stands in the north-eastern part of Poland, and it was due solely to strict protection measures that this species was saved from extinction. This programme, which comprised three voivodships over a 40 year period, allowed the beaver population to achieve a size which now exceeds the ecological capacity of the area, allowing the surplus beaver population to be transferred to other voivodships. In 1995, about 120 beavers (or 30 beaver families) were relocated to new areas. In this process of reintroduction, the voivodship administration takes part in covering the direct costs of reintroduction, in preparing feasibility studies, and in protecting the beavers. Since the beginning of this relocation programme in 1973, 1 800 beavers (400 families) have been relocated to the Oder River basin, and, in the highly industrialized region of the Katowice voivodship, 18 beavers have been introduced in various places.

Implementation of this technology needs the acceptance by the local community of the animals as a positive natural element. Many people in rural areas still view the beaver as a nuisance, and several have been killed (e.g., at Tarnów, Gda sk Voivodship).

Operation and Maintenance

Operation and maintenance during the initial stages of reintroduction involve catching and transporting the animals to new places, and providing protection for the animals during the period during which their colony is being developed. Such protection should be to the standards typically applied in animal conservation and wildlife preservation - protection from poachers, control of land-use changes, monitoring of changes in population, etc. Beavers should be kept away from areas of extensive agriculture and of infrastructure facilities. Sometimes, however, there is a need for a beaver family to be transferred to another site. Losses of animals are about 1% to 2 % of the introduced population, due to predation by animals such as wolves and cats, and human activities. The reproduction index for beaver populations is about 1.8 to 2 animals. Three years are needed for a beaver to achieve sexual maturity.

As was stated previously, some educational programming or activities may be needed to inform the public about these animals. This programming can be provided by the foresters, who usually are responsible for beaver protection, and who are well acquainted with the local people.

Level of Involvement

Government and its institutions must be involved in supervising the programme as a whole, securing the legal status of this animal, backing scientific research, disseminating instructions and information, providing materials, and assisting financially. In addition, local and regional administration involvement is required in the process of introduction, in site selection, covering local costs, providing consultancy, and in adapting and integrating the species into the new area. Local and regional authorities can also assist in local community education.

Costs

Costs include the cost of catching the animals in their natural environment (at sites overpopulated by the species), and transporting the animals to the new site. There are also costs associated with acquiring the necessary scientific expertise, and providing educational services. The direct cost for a beaver family transfer is made up of labour (10 days x 6 persons) and miscellaneous costs like transportation, cages, etc. Additional costs may be incurred as a result of natural migration or when uncontrolled development of a colony threatens human activities (the local administration in Poland, according to the law, is obliged to pay for damages caused by the beavers' activities, as they are a protected species).

Effectiveness of the Technology

Effectiveness depends on the natural physiographic conditions in the area to which a beaver family is introduced. The most effective sites are those with a shallow watertable, such as a flat-bottomed or valley-shaped surface with a low rate of water outflux. Streams, small rivers, and natural, seminatural and artificial water courses with woodland vegetation comprise ideal places for beavers. Under these conditions, reintroduction of beavers is an effective means of enhancing water retention within catchment areas, and of raising the watertable.

Advantages

The main advantage of this technology is enhanced retention of surface water in the area, and the raising of the associated watertable. This additional source of groundwater can be productively used as a freshwater resource (e.g., as in Kielce Voivodship, Poland). Additional advantages include the facts that the beavers are an important biocoenotical element, their activities can efficiently enhance the water purification capacity of the ecosystem and contribute favourably to changes in the local microclimate and biodiversity within the stream system (as has been observed in the Gda sk Voivodship following beaver reintroduction). These modifications contribute also to general changes in the forest environment which are important in improving the fire resistance of the forest, improving soil conditions, and enhancing carbon fixation (as a result of the gradual accumulation of organic matter in the pond). Beavers can be efficiently used in land reclamation schemes (as in Przemy l Voivodship where beaver resettlement and activities in an abandoned gravel pit enhanced the restoration of the natural landscape).

Disadvantages

The disadvantage of this technology is the land-use changes which beavers can initiate. Such changes, in cases of where highly productive agricultural lands are flooded, forest stands decimated, or infrastructure like roads and railway crossings flooded or undermined, may result in conflicts between the beavers and their human neighbours (e.g., as in one not very serious case in Katowice Voivodship).

Further Development of the Technology

Beaver reintroduction in Central and Eastern Europe could be one means of creating better general retention of water within the landscape. In comparison to artificial dams, this technology provides a decidedly more natural, effective and, in the longer term, less expensive approach. In addition, beavers can repair the damage caused by human activities (such as dewatering of bogs and wetlands). Beavers from the Polish populations of Euro-Asiatic species can be slowly re-introduced to many Central and Eastern Europe countries, and could mirror the success of other Polish wildlife species protection efforts, such as the restoration of breeding populations of the European Bison (Bison bonansus), from remnant populations in the Bia owie a forests. In comparison to this example, the beaver has an especial importance because of the role that this animal plays in preserving and augmenting water resources.

Information Sources

Prof. Ryszard Graczyk, Academy of Agriculture, Zootechnical Department, ul. Wojska Polskiego 71c, 60-625 Pozna , Poland, Tel. (48-061) 224901 ext. 28.

Dr Zygmunt Krzemi ski, Ministry of Environmental Protection, Natural Resources and Forestry, Department of Nature Protection, Wawelska 52/54, 00-922 Warszawa, Poland, Tel. (48-22) 256204, fax: (48-22) 254705.

Janusz Krupanek, Institute for Ecology of Industrial Areas, ul. Kossutha 6, Katowice, Poland, Tel.(48-3) 154 6031, fax: (48-3) 154 1717, e-mail: jan@amnesia.ietu.us.edu.pl.

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