Beaver Management in Norway - A Review of Recent Literature and Current Problems
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OriginalversjonParker, H. & Rosell, F. Beaver Management in Norway - A Review of Recent Literature and Current Problems. HiT Publication no. 4/2012. Telemark University College, 2012
Beginning with the total protection of the beaver (Castor fiber) in Norway in 1845, beaver management has undergone numerous changes as population development, resource exploitation goals and management objectives have evolved. Presently, new beaver management by-laws are being developed. This report briefly summarizes the historical development of beaver management in Norway, reviews the recent literature of particular relevance for the development new by-laws and makes recommendations for the future improvement of beaver management. The main goals of beaver management are to maintain populations throughout their natural range at densities sufficient to enhance biodiversity, produce a harvestable surplus and reduce beaver-human conflicts. In addition, beaver management should optimize recreational opportunities for the public and economic opportunities for landowners, e.g. through the lease of beaver hunting. These often opposing objectives sometimes lead to conflict. The beaver has been an important source of fur, food, and castoreum (as medicine) for the inhabitants of Fennoscandia (Norway, Sweden and Finland) and northwest Russia for millennia. While beaver were completely extirpated from Sweden, Finland and northwest Russia in the late 19th century, a remnant population of 100-200 beaver survived in southeast Norway. Following alternating periods of protection and exploitation the population grew slowly. In 1932 the effective leg-hold trap was forbidden in Norway. Live-trapping and hunting with firearms in autumn were still allowed but proved ineffective for controlling populations. With damage complaints increasing, in 1981 the open season was extended to early May. Spring hunting, i.e. with firearms, improved hunting efficiency and has gradually become the main harvest form. Thus the consumptive value of beaver has transformed from commercial furbearer to recreational game species. This same transition to spring hunting has also developed in neighboring Sweden and Finland. Norwegian beaver management is better understood in light of two basic fundaments of Norwegian wildlife management. 1) All wildlife is publicly owned, and therefore wildlife management should seek to maximize the public’s enjoyment and utilization of wildlife. 2) The hunting privilege belongs to the landowner. Once public authorities have determined when, where and how much game can be harvested, landowners can either hunt themselves or lease the hunting rights to others. In the later case, wildlife becomes a source of income to landowners while providing hunting opportunities for the general public. Most of the details of practical beaver management may be found in the “Wildlife Act”, its accompanying by-law for beaver management (by-law FOR 2002-03-22 nr 314: Forskrift om forvaltning av hjortevilt og bever), and the by-laws defining the open seasons for hunting and trapping (by-law FOR-2012-03-01 nr 190: Forskrift om jakt- og fangsttider samt sanking av egg og dun for jaktsesongene fra og med 1. april 2012 til og med 31. mars 2017) and the hunting and trapping methods allowed (by-law FOR 2002-03-22 nr 313: Forskrift om utøvelse av jakt, felling of fangst). These laws outline when, where and how beaver can be trapped and hunted, the organizing of landowners into beaver management units, and how hunting quotas are determined and distributed among landowners. With the exception of an acute need for control of damage and alien species, 4 trapping and hunting are not allowed during the breeding season, though what constitutes the breeding season is not clearly defined in the “Wildlife Act”. This lack of clarity has recently been the cause of some debate concerning when the breeding season for beaver actually starts, and therefore when spring beaver hunting should cease. Harvesting to conserve, manipulate and exploit beaver populations is a central element of Norwegian beaver management. Quota regulation of the harvest has been continually employed since 1855, at which time landowners were also granted the exclusive right to hunt beaver. At present, municipal wildlife managers first decide whether the local beaver population can be harvested based on population information gathered from e.g. landowners, hunters, or autumn counts of occupied lodges. A harvest quota for the entire township is then established and divided among landowners according to how much beaver habitat they own. The amount of beaver habitat on a particular area or estate can be measured in two different ways; either as the area of “beaver habitat” or the length of “beaver-utilized shoreline”. Beaver habitat includes all habitat normally used by beaver; i.e. forest, bog and agricultural landscapes below tree line, usually excluding urban areas, larger lakes and steep mountain hillsides. “Beaver-utilized shoreline” is the length of shoreline in rotational use by beaver, since shoreline habitat presently in use and later abandoned, will normally be reoccupied again at some future time. In order to distribute the municipal quota among landowners, the minimum area necessary to receive one beaver permit is determined by dividing the total area of beaver habitat in the municipality by the municipal quota. Alternatively, the minimum shoreline length necessary is determined by dividing the total length of beaver-utilized shoreline by the municipal quota. Municipal managers may choose between the two alternatives, though the length of beaver-utilized shoreline on an estate is the best predictor of colony density when the area involved is relatively small (Fig. 1). Reliable data on the length of beaver-utilized shoreline in a municipality, however, is more difficult to obtain than the area of beaver habitat. To receive their portion of the municipal quota, landowners must first organize beaver management units. Because Norwegian estates average small (≈ 50 hectares), landowners must usually group together in order to attain the minimum area necessary to receive a quota of at least one beaver. Typically, the minimum area required to receive one beaver would be 300-500 hectares. Thus beaver management units almost always entail many landowners, creating challenges with respect to e.g. landowner cooperation and organization. Once organized and approved by the municipal authorities, each beaver management area is allotted its portion of the total municipal quota based on the relative amount of beaver habitat or beaver-utilized shoreline it encompasses. Management areas too small to meet the required minimum area or minimum shoreline length do not receive a quota, which serves to motivate landowners to merge into larger units. Management units for cervids (moose Alces alces, red deer Cervus elaphus and roe deer Capreolus capreolus) in most instances also function well as management units for beaver, though usually not in farmland. This is because most management units for cervids do not involve farmland, though farmland is usually good habitat for beaver. The present national distribution of beaver (Fig. 2) extends from mid-Norway south through the eastern and southern counties. As of 2003, Troms and Finnmark no longer have beaver, despite several releases of new animals in recent decades. The national population size is thought to be about 70,000 individuals and still growing. On a scale of 5 about 200-500 km2, newly established populations appear to peak after 35-40 years, followed by an abrupt fall (phase 1, Fig. 3). This pattern closely mimics the Riney-Caughley model for introduced ungulates. Populations are thought to eventually enter a more stabile carrying-capacity phase (phase 2, Fig. 3). Over-browsing is thought to be the main cause of the initial abrupt decline (Fig. 3). Though information is limited, colony density seems to vary considerably between landscape types, being greatest along low-gradient rivers and in farmland, and least in alpine regions (Table 1). A suggested mean colony density for all landscapes combined (excluding alpine) once populations have stabilized is 0.25 colonies per km2, or one colony per 4 km2. A central goal of the “Wildlife Act”, the “Nature Diversity Act”, and of Norwegian forest owners is the conservation of biodiversity at the genetic, species, landscape and ecosystem levels. As an ecosystem engineer, beaver physically change the landscape primarily through dam-building and tree-felling, significantly modifying the geomorphology, hydrology, ecological succession and species composition of the landscape. Locally however, species biodiversity may temporarily decline. Modern clear-cut forestry, though detrimental to many wildlife species, may actually benefit beaver by stimulating the shoreline growth of broadleaf species favored by them. Municipal wildlife managers are required to arrive at a municipal beaver quota, which requires information on population size. Since sites occupied by beaver are highly visible in autumn, information is usually gathered then. Population size is usually expressed as number of colonies rather than number of beaver, as the number of beaver in each colony is difficult to determine. When an estimate of the actual number of animals in the population is necessary, a mean colony size of 4 is usually employed for the Eurasian beaver. Five methods used to estimate population size on a municipal scale are briefly described in this report. Reliable harvest information is important for population management. The national beaver harvest figures for 1984-85 – 2010-11 (Fig. 4) reveal an unexpected pattern consisting of an initial 3-fold increase the first 5 years, followed by a gradual 3-fold decline and leveling-out. During this same period, the range of the beaver throughout Norway has slowly expanded and presumably the population size as well. Therefore a gradual increase in the national harvest would also be expected, but for some reason the data indicate a decline. From 1985 - 2000 the harvest estimation methods employed changed several times, suggesting dissatisfaction with them. We suspect that these changes in methodology may lie behind the unexpected abrupt rise and fall observed. From 2001- 2011, however, the same sampling methodology has been employed, suggesting that the decline shown for the last 10 years may better reflect the true harvest size and trend. Since most of the national harvest has occurred in only 4 of the 11 counties where beaver are hunted (Fig. 5), the key to the trend seems to lie with these 4. The harvest data for each individual county (Fig. 6) shows significant harvest declines in 5, no change in 4, and significant increases in 2. The 5 counties showing declines, i.e. Vest-Agder, Aust-Agder, Telemark, Hedmark and Vestfold, are the counties with the oldest populations, all having had beaver for at least 50 years. We therefore suspect that populations in these 5 had entered phase 2 and stabilized (Fig. 3) before the decline in harvest numbers occurred (Fig. 6). Thus the observed harvest decline in these 5 counties does not seem to reflect the actual population trends in them. Neither is there reason to 6 believe that a prolonged over-exploitation has been occurring in these counties that could explain the decline. Rather, based on contact with hunters and municipal wildlife managers, we suspect that falling hunter effort, due to difficulty in finding a place to hunt, is the main cause of the harvest decline. Though the total number of hunters in Norway has increased slowly during the past 10 years, mean age is increasing and recruitment of new hunters into the population has begun to decline. In our experience, beaver hunters tend to be younger than average because beaver hunting is less expensive than other forms. This ageing of the hunter population, together with a declining recruitment of younger hunters, may be having some effect on hunter effort, though hardly sufficient to explain the near 50% decline in the harvest since 1994. New beaver management by-laws were established in 1997 and 2002, and though new laws are intended to improve existing laws, this may not always happen. In particular, the extra effort required to organize many small landowners into beaver management units in farmland, i.e. outside of management units for cervids, seems to discourage many landowners from organizing. Without management units no quotas are issued and the harvest suffers. Spring hunting is the dominating harvest form in Fennoscandia. Beaver, however, cannot be sexed or reliably aged under spring hunting conditions, so hunters normally shoot the first animal seen. The sex-ratio of spring-shot animals does not deviate significantly from 50:50 in any age class. However adults, and in particular pregnant females, are more likely to be the first individuals shot from colonies. Most pregnant females shot in late April have visible fetuses, an experience many hunters are uncomfortable with, and a situation that challenges the general management principle of not hunting during the reproductive season. The best way to limit the takeoff of pregnant females is to shoot the quota from as few colonies as possible, as each colony usually contains only one. Hunting predominantly in damage colonies will help accomplish this goal, plus reduce damage. Many factors including e.g. habitat quality, reproductive rates, and selection for sex and age groups affect the sustainable harvest rate. Results from recent field experiments suggest that the level of sustainability for spring-shot Eurasian beaver is around 10-20%, a figure lower than that suggested for trapped populations. Once the colony number for a municipality has been determined, we suggest that the initial annual quota be set at one beaver per colony. At a harvest success of about 50%, which in our experience is seldom attained, and an average of 4 animals per colony, this would lead to a take-off of around 10-15%. Future quota size can be adjusted when necessary. If unwanted over-harvesting should occur, populations are likely to rebound quickly (Fig. 9). Since recreation rather than economic gain is the prime motivation for hunting beaver, hunting effort will likely fall as populations decline, thereby counteracting any tendency to over-harvest. Limiting damage caused by beaver is a central management goal. Initially, all beaver dams and lodges are protected by the “Nature Diversity Act” and removing them requires permission from municipal authorities. In general, there is a direct relationship between the number of colonies and reports of damage. Methods to limit both colony number and damage include 1) avoiding the commonly experienced population “over-shoot” (phase 1, Fig. 3) by starting to harvest early in the initial population growth phase (Fig. 8); 2) by concentrating the harvest effort to sites where damage is often reported (Fig. 8) and 3) 7 implementing non-lethal control methods to limit damage where this is practical. Municipal beaver management plans should include maps that show hunters where damage is often a problem. Central problems facing Norwegian beaver management and their potential solutions include the following. 1) Many landowners perceive the beaver to be a problem species with little positive economic value. Increased tolerance will likely develop with increased knowledge of the beaver’s ecological role and potential economic value through more education at all age levels. The Norwegian Federation of Forester’s recent course on ways to increase biodiversity in managed forests, including the beaver’s role, is a good example of this. 2) Many non-hunters and hunters alike object to the shooting of females in the late stages of pregnancy. Most sexually mature female cervids (moose and deer) are also pregnant when shot, a practice hunters rarely object to since most are killed early in pregnancy before fetuses are visible. If female beaver were shot from new-born young this would certainly violate accepted animal welfare practice, but this has never been documented within the present hunting season limits. In the absence of spring hunting, few animals would be harvested and beaver management would essentially be reduced to damage control. Hunters must accept that pregnant individuals can be shot and try to avoid this based on methods outlined here. 3) An invasion of Norway and Sweden by the North American beaver from Finland (Fig. 10) is almost guaranteed if appropriate action to hinder this is not taken within the next few years. The imminent question is whether coexistence or the competitive exclusion of one species by the other will ultimately result, with the possible regional extirpation or eventual extinction of the Eurasian beaver. The spread of this alien throughout Eurasia can still be prevented if the will to do so exists. 4) In our experience, the main problem facing today’s beaver harvest management derives from the lack of interest that landowners, and to some degree municipal wildlife managers, have for this species. Few landowners hunt beaver themselves and few are willing to organize the lease of beaver hunting when its market value is so low. In addition, numerous small landowners must often cooperate to form beaver management units, a process many find difficult. When beaver management units are not formed, quotas do not get issued and many beaver hunters have no place to hunt. In contrast, beaver hunting functions well when organized by single, large landowners, either private or public. Landowners are a key element in the harvest management process and somehow must be motivated to take this responsibility more seriously. Together with municipal wildlife managers they need to take greater responsibility for creating hunting opportunities for non-landowners and for recruiting young hunters into an ageing hunter population. Making beaver hunting more accessible is one way to do this.