Svalbard reindeer (Rangifer tarandus platyrhynchus)

Svalbard reindeer
Photo: Øystein Overrein / Norwegian Polar Institute

Management of the Svalbard reindeer, which is only found in Svalbard, is an all-Norwegian responsibility. It is monitored because it is a key species in the terrestrial ecosystem in Svalbard, is considered to be sensitive to climate change and is hunted in parts of central Spitsbergen. The working group for the Conservation of Arctic Flora and Fauna (CAFF) also prioritizes reindeer monitoring.

What is being monitored?

Population sizes

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The figure shows the filtered series of the number of reindeer on Brøggerhalvøya. The reindeer population on the peninsula derives from 15 animals released there in 1978. The development, with a relatively rapid growth in the number of animals followed by a collapse in the population, is not unusual where large herbivores are introduced to areas in arctic regions. Studies have shown that the dynamism observed is most influenced by variations in climate. The amount of snow in winter and the summer temperature are the most important factors. In 2006, the total number of reindeer was estimated (not counted) because a lack of sea ice made monitoring of the whole area impossible.

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The figure shows the filtered series of the number of reindeer in Reindalen. In large parts of the monitoring period, the reindeer population in Reindalen varied around a stable average, but with a large variation. The population was large in 2000 and 2001, thus giving a rising tendency towards the end of the period. Studies have shown that the dynamism observed is due to a combination of direct density dependence and variations in climate. A large number of reindeer present one year will normally give a low growth rate the following year and a reduced number of reindeer present the year after. Climate seems to affect the population primarily through snow depths and events of rain-on-snow.

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The figure shows the filtered series (3-year average) of the number of reindeer in Adventdalen. The monitoring data show large annual fluctuations. The time series shows a trend towards a slowly increasing population between 1979 and 1995 compared to a stronger increase from late in the 1990s. Since the year 2000, the numbers have varied between 700 and 1500 . The population is increasing, but there is a large variation between years in the total number of reindeer, the number of carcasses and the number of calves. As in Reindalen, the population is influenced by a combination of direct density dependence and variations in climate linked with ice on the ground.

Status and trend

The Svalbard reindeer occurs in varying densities in most parts of Svalbard that are not covered by glaciers. It is not known how many reindeer that totally live in Svalbard or how many populations there are. Knowledge of the populations in the monitored areas is good

Brøggerhalvøya

In 1978, 15 reindeer were re-introduced to the Brøggerhalvøya: Annual counts show that the Brøggerhalvøya population grew exponentially until the winter of 1993–94 (N = 360).

This lengthy period of growth was probably due to a great deal of high-quality food being available at the time of their release and in the ensuing period. Autumn/winther 1993 was unusually mild and rainy on Brøggerhalvøya, and in combination with cold this led to the formation of a thick layer of ice over large parts of the area. This resulted in a population collapse due to high mortality and because some reindeer left the area. In the following spring (April 1994), only 78 reindeer were found on the peninsula. Since then, the population has stabilised and varied between 85 and 205.

Reindalen

The reindeer monitoring in Reindalen (1979–) includes the valleys of Semmeldalen, Colesdalen and Fardalen, and several nearby, smaller valleys. It began in 1979 with the aim of obtaining reference data from a population that was little affected by people. The density of the population has varied a great deal during the monitoring period and the data show large annual variations in winter survival and the proportion of calves in summer.

Up to the mid-1990s, about 250–650 reindeer were recorded in the monitored area each year. Since then, there has been a marked increase in the numbers, and about 800 have been recorded each year since 2000. The figures recorded for the total number of reindeer, the number of carcasses and the number of calves still vary considerably from one year to another, and the population, for example, may be nearly halved from one year to the next (e.g. 2007 vs. 2008).

There is a controlled, limited hunt in the area.

Adventdalen

The reindeer monitoring in Adventdalen (1979–) takes place in this valley and in branch valleys as far up as Passhytta. During the monitoring period, the population density has varied considerably and the data show large annual variations in winter survival and numbers of calves per female.

The time series shows that the population grew comparatively slowly from 1979 to 1995 compared with the strong increase since the end of the 1990s. Between 700 and 1450 individuals have been recorded since 2000. There is still large inter annual variations in the total number of reindeer, the number of carcasses and the number of calves recorded.

No hunting takes place in the area now.

Causal factors

The Svalbard reindeer lives in a natural environment where predation is virtually non-existent and only limited hunting takes place in Nordenskiöld Land. Combined with the absence of problems caused by insects, few parasites and probably little competition from other herbivorous species, this simplifies the opportunities for finding out which factors influence its population dynamics.

2 factors mainly determine the variation in the number of individuals from year to year:

  1. Density-dependence (competition for food resources)
  2. Variations in climate (e.g. precipitation in winter, especially rain, and summer temperature)

Density-dependence is the link between the number of animals per unit of area and aspects of the life history, such as rates of birth and death and age of sexual maturity. Changes in these parameters affect the growth rate of a population. If the growth rate in a given year depends upon the number of animals that year (or the previous year), there is said to be density-dependence in the population dynamics.

Studies in Adventdalen and Reindalen have clearly shown that increases in population size lead to lower production of calves and higher mortality in the populations. This density-dependence in the population dynamics gives a reduction in the population if this achieves a high density and a growth in the population when the density is low. The Brøggerhalvøya population, by comparison, shows only a slight tendency for density-dependence.

An increasing number of studies of the monitored populations have shown that variations in the climate largely shape the population dynamics of the Svalbard reindeer. The climate mainly influences the Svalbard reindeer by affecting the growth of plants in summer and the availability of food in winter. Studies of all the monitored populations have shown that ice-covered ground in winter is the most important factor helping to shape the population dynamics. Winters with a great deal of ice give a reduction in the population because the ice covers the vegetation so that the reindeer cannot gain access to sufficient food. This results in increased mortality and reduced calf production. Frequent and heavy rainfall in winter is the main cause of significant icing some years. High reindeer mortality one winter is generally succeeded by less mortality and fewer carcasses the next winter because the weakest individuals have died. Higher summer temperature increases the plant biomass and leads to a longer growing season, which has a positive effect on the population growth rate the following year.

The population development in the areas monitored in Nordenskiöld Land has shown a tendency to rise even though the frequency of icing in winter has increased during the monitoring period. The reason for the increase in these populations has not been clarified, but the most important hypothesis is that it has to do with positive effects resulting from a significant rise in the summer temperature in Svalbard in the same period. This may have led to more plant production in summer and longer snow-free growth seasons (earlier springs and/or later autumns).

A major international research project, REINCLIM, led by the Norwegian University of Science and Technology (NTNU) and financed by the Norwegian Research Council (NORKLIMA grant), is underway (2012–2015) to try to understand and predict the net effect of climate change on the Svalbard reindeer. The results are not published yet.

Consequences

Meteorological data from Svalbard show that the frequency of rainy weather in winter has increased over the past 30 years. New climate models predict that the temperature will continue to rise and there will be more precipitation in winter, which will lead to more frequent rainy weather resulting in ice on the ground. This is a trend that may lead to a decline in the populations. At the same time, a warmer climate will probably result in spring starting earlier and longer growth seasons. These changes have direct effects on the plant communities in the shape of more plant growth and changes in phenological development. Such changes may bring better growth conditions for the reindeer populations and probably buffer or counter the negative effect of rainy winters.

The effect on the Svalbard reindeer of changes in biomass and the length of the growing season has so far only been studied on a limited scale in Svalbard. A study from Ny-Ålesund has shown that some of the variation in the growth rate of the population is a response to variation in the plant growth and the grazing plants on offer. A very recent study, that includes the Adventdalen population, has shown that the growth rate was positively influenced by the summer temperature. The outcome of a warmer climate on the reindeer will be determined to a large extent by the degree to which increased plant growth and longer growing seasons will affect the fitness of the reindeer and thus counteract the negative effects of rainfall and icing in winter. So far, it seems that the net effect of climate change varies locally, which is reflected in the rising population trend in Adventdalen and Reindalen, for example.

The Svalbard reindeer impacts the tundra ecosystem through effects on several trophic levels. For instance, it modifies the composition and structure of the vegetation. The tundra in Svalbard presently has little lichen and is dominated by grasses and herbs, but in the absence of reindeer it would to a large degree be covered by thick lichen mats. On Brøggerhalvøya, for example, grazing conditions have changed on both the species and the community levels since reindeer were introduced in 1978. In the future, the effect of density is likely to become stronger because the competition for limited grazing will increase.

In winter, carcasses constitute a substantial and important part of the arctic fox diet and a positive connection has been found between the number of carcasses available and the reproduction and population size of the arctic fox. Because of these trophic interactions, the Svalbard reindeer probably has a significant indirect influence on several other species through competition for food and varying predation pressure on ground-nesting birds due to changes in the arctic fox population.

The reindeer eat the same food as several herbivorous birds, including the Svalbard ptarmigan, which occur in low densities, and the migratory geese, chiefly barnacle geese and pink-footed geese, which occur in large, growing populations. The pink-footed goose eats many of the same plant species as the Svalbard reindeer. It removes plants with their roots and surrounding moss and directly affects the composition and structure of the vegetation locally, which may in turn lead to increased competition for the food resources between the species.

Recent studies have shown that the impacts of the winter climate lead to synchronous declines in the populations of the most important herbivorous species and arctic foxes. The interactions between the herbivores in the tundra ecosystem in Svalbard have still been little studied.

Both Adventdalen and Reindalen experience considerable human traffic by both snowmobile and on foot. The populations have grown in the monitoring period and studies have shown that the reindeer have a good ability to adapt to human traffic. This does not mean that human traffic has no significance, since it is impossible to know how the population dynamics would have been without that traffic. However, it seems realistic to believe that the populations in these areas are still not particularly vulnerable to human traffic on the present scale.

About the monitoring

The Svalbard reindeer is an endemic species (existing only on Svalbard). It is the largest herbivore and a key species for the tundra ecosystem because it affects and changes the vegetation and the population dynamics of the top predator, the arctic fox.

Even though polar bears have sometimes been recorded killing reindeer, the Svalbard reindeer lives in an ecosystem practically without predation and with almost no hunting. Hence, changes in the population of Svalbard reindeer can be a signal of changes in other parts of the arctic ecosystem.

Research shows that variation in the number of animals per area (density) and climate variation are the most important factors regulating populations. These factors controls the different populations monitored in different ways.

Svalbard reindeer can also be a possible parameter for monitoring the effects of disturbance from human traffic. This would require studies designed for this purpose, and no such studies are planned. Population data from the current monitoring will, however, provide an important basis for such studies.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring