Threats: Technical encroachments/disturbances
In Norway, the original wild reindeer mountains consisted of four main regions. There was probably a great deal of internal cross-movement of animals within these regions. The regions represent areas with clear climatic differences from west to east and from south to north. The mild, high-precipitation areas along the coast were good for calving and spring/summer grazing grounds, while the cold, low-precipitation inland areas provided attractive winter grazing with little snow and large amounts of lichen.
The Dovre/Rondane region is a good example of a formerly continuous habitat with a clear east/west gradient. The eastern parts of the region (Rondane, Sølnkletten and Knutshø) were formerly important winter grazing grounds, while the eastern areas (Dovrefjell and Trollheimen) were spring and summer grazing grounds.
Today, the situation is very different. The presence of the railway and the E6 road across Dovre has blocked the original migration route between east and west. In addition, there have been a number of encroachments and disturbances which have led to the original Dovre/Rondane region now being divided up (fragmented) into seven more or less separate areas.
The normal protection instinct of wild reindeer is to move away. In order to find grazing grounds all year, a reindeer's natural behaviour pattern is move to new or better grazing grounds. In the current situation where infrastructure and human activity bar the old migration routes, wild reindeer have fewer migration options.
This situation applies to all four of the original regions in Norway. So today we have 23 more or less separate wild reindeer areas in mainland Norway.
We currently differentiate between at least four different effects linked to technical encroachments and disturbances:
Loss of habitat as a direct result of encroachment
These effects are directly related to the encroachment itself and are often of limited scope. The exceptions are cases in which the physical encroachment covers large areas or where the encroachment itself has the effect of creating a barrier. Examples that show that such encroachment can have severe consequences for wild reindeer are the hydroelectric reservoirs created in special reindeer grazing grounds, and holiday cabin developments that interfere with important migration routes.
Physiological and behavioural reactions in individual animals
Such effects have been documented in a number of species, and most often in connection with experimental studies in which animals are exposed to a number of different stimuli. These effects are directly linked to a specific disturbance and often disappear quickly. An example of this is accelerated metabolism and reduced hunting time as a result of human traffic.
These effects can either arise as a result of major changes in the reindeer’s habitat or the building of longitudinal barriers that block normal migration between areas. Roads, railway lines, power lines or oil pipelines are examples of such barriers. The reduced exchange of genetic material, changes in grazing load and changed access to seasonal grazing grounds or important habitats (e.g. calving areas) are biological effects of the creation of such barriers.
Total effects of various disturbances and encroachment
The sum of the different disturbances, encroachments and limitation to the natural environment is often referred to as the cumulative effects. The cumulative effects have a measurable impact on wild reindeer in the form of impeded growth, reproduction and survival.