Sunde, P., Olesen, C.R.
Summary
The moose (Alces alces L.) went extinct in <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> around 2.600 BC. but migrants from <st1:country-region w:st="on"><st1:place w:st="on">Sweden</st1:place></st1:country-region> occasionally swim over Øresund strait and live in the Danish nature for days, months or years. The existence of dense moose populations few kilometres from the Danish boarder and the fact that individuals from the Swedish population from time to time reach Danish territory has raised a debate whether <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> in the future again may – or shall - host viable moose populations funded by spontaneously arrived immigrants or introduced individuals. This report evaluates (i) the likelihood that moose populations may establish themselves in Denmark from spontaneous immigration events, (ii) the approximate population potentials for moose in various forested regions based on estimated food supply as well as the possible consequences for the present flora and fauna and (iii) society implications: the danger potential of aggressively behaving individuals, economic damage to farm crops and forestry interest and, not least, traffic collision risk.
Population establishing through natural immigration to Jutland from central Europe seems to be unlikely as long as no populations exist in <st1:country-region w:st="on"><st1:place w:st="on">Germany</st1:place></st1:country-region> . Natural immigration from Sweden to Sealand remains a (very) small theoretical possibility: a simulation model, based on the immigration rate 1930-2006, suggests that preconditions for a population establishment (reproduction in three subsequent years) even under the most favourable conditions will occur once every 239 year and possibly as infrequent as once every millennium. As the chances of a spontaneous immigration resulting in the establishing of a population, very much depends on the survival and ability for finding a mate, attempts could be made to prevent traffic-kills or emigration from optional moose areas. However, in practise, the likelihood of natural colonization within a reasonable time is probably so small that this offers no acceptable management option. Re-introduction programmes are therefore the most feasible option to re-establish moose populations in <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> .
In order to be robust to extinction, a future Danish moose population is considered to be comprised by at least 75 individuals, but should number >200 individuals to maintain a robust population from catastrophic incidents (e.g. epidemics) and loss of genetic diversity. As moose are mobile individuals, a future Danish moose population may possibly exist as a meta-population consisting of several smaller populations (15-50 individuals) exchanging individuals at regular intervals.
Analyses based on the presence of potentially suitable natural types in 25 evaluated areas, representing the largest areas with continuous woodland, indicate sufficient habitat to sustain self maintaining moose populations in at least six areas in <st1:place w:st="on">Jutland</st1:place> and in two areas on Sealand. The potentially largest population would be able to live in the central <st1:place w:st="on">Jutland</st1:place> (estimated food supply sufficiently for up to 1,673-1,992 individuals). However, it does seem that the locality of Thy offers sufficient conditions for a moose population to maintain itself (782-893 individuals), in mid Sealand (642-659 individuals), on Djursland (293-360 individuals), in north Sealand (266-276 individuals), in the most southwest of Jutland (252-278), in east Himmerland (Rold forest – Lille Vildmose: 248-311) and in the triangle between Skagen, Frederikshavn and Hirtshals (225-272 individuals). As these potential population figures are based on a maximum exploitation of the estimated food supply, only a fraction of this maximum number is probably acceptable in places where forestry is intensively managed. However, even if the populations were to be kept at one third of what food supply offers, a viable population is supposed to be able to maintain itself in most of the above mentioned areas. If moose is able to adapt itself in smaller woods, spreading from population in large wood complex may be possible and thus more or less constant population could establish themselves in other parts of the country.
The moose occupies - to a great extent - an empty ecological niche (leaves, buds and twigs in the interval 1-3 metre height) why only limited food competition with roe- and <st1:City w:st="on"><st1:place w:st="on">red deer</st1:place></st1:City> is expected. The competitiveness of species frequently browsed by moose is expected to be reduced. These ecological effects are, of course, dependent on the population density which is to be regulated by shooting.
Aggressive moose are not assessed to pose any serious threat to man. However, it must be expected that some threatening incidents may occur in confrontations with people and dogs. As the majority of “moose attacks” are provoked feints, confrontations with “aggressive” moose can be avoided by informing the public of a sensible behaviour.
With the present Danish road infrastructure, free ranging moose are considered to pose major threats to traffic safety, no matter where an unfenced population of moose may live. Unless comprehensive actions are taken in planning of road infrastructure, collision with cars (locally also trains) is unavoidable and consequently may incur personal injury. If moose-traffic collision rates from roads in SE-Sweden (1990-99) are extrapolated to Danish landscapes, individual moose are expected to run an annual risk of being involved in traffic collision of 8-38%, dependent on local variation in road density (mean = 15%). In terms of accidents resulting in human injury, a Danish moose will run a 0.7-1.9% annual risk of causing human injury through a car collision. In one area (the woods of Helsingør) traffic collision rates are expected to be so high (38% per moose per year) that it would outweigh the entire reproductive potential of any moose population. In the most secure areas, the estimated annual risk of collision of 8-10% per moose is 5-6 times higher compared to the average risks exposed to Swedish moose. Sixty percent of the collisions are predicted to occur on secondary roads why fencing of the larger roads reduces the total expected number of accidents by 23-40% depending on the region in question. Further reductions in accidents demand speed control in exposed stretches. If politically feasible, a speed reduction to 60 km/h in the dark hours on road stretches with high collision risk potential might eliminate the number of accidents resulting in human injury to a very low level.
The moose is expected to induce financial loss to the forestry such as bite damage to young stands. The accurate extent of this loss is impossible to predict as it depends on local conditions such as moose population density, the commercial value of forest, fencing actions and alternative forage. Income from moose hunting will probably compensate for a great deal of these costs, at least in certain areas.
The moose is supposed to inflict only very little damage on agricultural crop.
In a final chapter it is discussed how Danish moose populations could be planned and managed in order to outbalance the potential problems they may cause to society interests.
Full report in pdf-format (2.788 kB)
