Svalbard rock ptarmigan

Last updated 13 December 2023

The Svalbard rock ptarmigan (Lagopus muta hyperborea) is a subspecies of rock ptarmigan and is the only resident herbivorous bird species in Svalbard. It is endemic to Svalbard in Norway and Franz Josef Land in Russia, making it a species for which Norway has special management responsibilities. Svalbard rock ptarmigan are found in small, relatively stable to increasing populations in very restricted breeding habitats. Knowledge of trends in population size is necessary for their management and rapid climate change requires such trends to be closely monitored.

Status and trend

In 2000, monitoring of Svalbard rock ptarmigan using standardised methods was begun, in order to measure the density of territorial males in the breeding grounds in the study area covering some 1,200 km² in central Spitsbergen (Nordenskiöld Land; Pedersen et al. 2012, Soininen et al. 2016). This monitoring provides a basis for estimating the density of territorial males and thereby the year’s breeding population. Monitoring has shown that, from 2000 to 2013, the number of territorial males was relatively low, with moderate annual variations (from 1 to 3 males per square kilometre; Pedersen et al. 2012, Soininen et al. 2016). Since 2014, there has been a rising trend in the density of territorial males in the monitoring area, which, in the most recent period, has varied between 3 and 5 males per square kilometre (Soininen et al. 2016; Fuglei et al. 2020; Marolla et al. 2021).

The purpose of the Svalbard Environmental Protection Act is to preserve a virtually untouched environment in Svalbard in respect of contiguous areas of wilderness, landscape, flora, fauna and cultural heritage. Within this framework, the Act allows for environmentally sound settlement, research and commercial activities.

For the Regulations relating to harvesting of the fauna in Svalbard, the purpose is that the fauna shall be managed in such a manner that the natural productivity and diversity of species and their habitats are maintained, and Svalbard’s natural wilderness is protected for future generations. Controlled and limited harvesting may take place within this framework. These regulations state that “Harvesting must not significantly alter the composition and development of the population in question.” The precise meaning of the word “significantly” is not stated, but it may be defined as follows:

A “significant” change in demographic structure will be a gender or age distribution that causes the population to decline over time. For Svalbard rock ptarmigan, the hunting statistics show a change in the proportion of juveniles in the population, but it is unclear whether this is due to real changes in the population or changes in hunting behaviour. The proportion of juveniles in the population is determined by aging the wings submitted after the hunt. Validation of the submitted wings is now underway in which we carry out autumn counts of males, hens and chicks, which are compared with the wing data (Fuglei et al. 2019).

A “significant” change in the size of the population will be a significantly clear trend over time. Monitoring data for territorial males shows no clear trend in areas that are hunted relatively hard. The hunting statistics show a decrease in the number of birds shot, but it is unclear whether this is due to real changes in the population or changes in hunting behaviour.

Causal factors

The dynamics of the monitoring data from 2000 to 2013 were partly driven by inter-annual variations in rain-on-snow events that synchronized the ptarmigan’s population dynamics with the populations of Svalbard reindeer and sibling voles (Hansen et al. 2013).
The extent to which interactions with other species in the particularly simple food web in Svalbard are of importance to Svalbard rock ptarmigan dynamics is still being explored, but both predation by Arctic foxes and competition with reindeer and geese probably play a role (Ims et al. 2013, Pedersen et al. 2017).

Limited access to good ptarmigan habitats with less than 4% of the land areas, and with relatively low carrying capacity in the form of important grazing plants probably makes the Svalbard rock ptarmigan sensitive to changes in plant production. This applies to both the quantity of plants and phenological developments such as nutritional quality. As soon as the ptarmigan chicks emerge from the egg, they have a very specialized diet, consisting of the bulbills of the Alpine bistort plant. This specialization can lead to a so-called phenological mismatch between the times of the ptarmigan’s reproduction and the growth and quality of the grazing plants, if the plants develop earlier due to an earlier start to spring/summer.

The impact of climate change on Svalbard rock ptarmigan can be expected to be both direct and indirect. One direct effect is expected to be changes in the frequency of rain-on-snow events. This effect has already been shown to reduce the population’s growth rate (Hansen et al. 2013). In addition, the climate can have a direct effect on the time of egg-laying, as well as the growth and survival of chicks in the spring.

The indirect effects can occur through changes in interactions with grazing plants, competitors and predators. With its highly specialized diet during the breeding season, the Svalbard rock ptarmigan is likely to be particularly vulnerable to a phenological mismatch with its food plants as a result of climate change. The assumption is that an earlier start of spring will lead to faster phenological changes in Alpine bistort, while the start of reproduction in the Svalbard rock ptarmigan (e.g. egg-laying) is expected to be more conservative. Such a mismatch can reduce the growth and survival of ptarmigan chicks due to reduced production and quality of the Alpine bistort’s bulbills.

Svalbard rock ptarmigan can also be affected by competition with increasing populations of pink-footed geese which graze by intensively grubbing vegetation, leading to reduced plant biomass (Pedersen et al. 2013). However, a warmer climate may also increase primary production (the biomass of grazing plants), which may have a positive effect on the ptarmigan population. There may be more predation of Svalbard rock ptarmigan if the Arctic fox population increases due to a warmer climate. This may occur as a result of an increasing density of geese and reindeer, or greater winter mortality of reindeer.

Since 2014, the population trend of Svalbard rock ptarmigan has been increasing, with considerable variation between years. Marolla et al. (2021) translated the conceptual food web model of COAT (Climate-Ecological Observatory for Arctic Tundra) for Svalbard rock ptarmigan into statistically descriptive models to obtain estimates of the different relationships between the species in the food web and the effects of drivers such as hunting and climate on population dynamics (i.e. changes in density from year to year). Several of the effects were relatively weak, such as a negative effect of harvesting (i.e. the number of birds shot), the amount of precipitation in July, which can affect chick survival, when winter starts (shorter season of snow), and the quantity of reindeer carcasses, which is believed to have an indirect effect through predation from Arctic foxes.

The largest and clearly significant estimates in the model were a negative density dependence and a positive effect of winter temperature. Strong negative density dependence is a consistent feature of populations that have territorial individuals, which can help reduce (compensate for) the effect of hunting. Concerning the effect of winter temperatures, this relates to these having greatly increased over recent years in Svalbard. Warmer winters with extreme mild weather events can also, for example, reduce the effects of rain-on-snow events, because the ice on the ground melts and facilitates access to the grazing plants. Higher winter temperatures probably also lower metabolic costs, and thus enable an increase in winter survival among the Svalbard rock ptarmigan population.

For the time being, it appears that rising average winter temperatures have a strong positive effect on the growth rate of the Svalbard rock ptarmigan population, which outweighs the negative impact from other climate-related changes, such as rain-on-snow events. It also seems as the ptarmigan population can compensate for the current harvesting level (Marolla et al. 2021).

Consequences

The Svalbard rock ptarmigan may be vulnerable to changes in climate because it can lose out in the competition for important grazing plants with growing populations of geese. Ptarmigan may also be exposed to a mismatch between the phenological development of their grazing plant, alpine bistort, and the timing of the hatching of their chicks.

Predation pressure from the Arctic fox depends on the development in the geese and reindeer populations. This is related to the climate. We have shown that the winter climate in Svalbard, with periods of mild weather in winter with precipitation as rain, synchronises the entire community of herbivores in Svalbard – ptarmigan, reindeer and sibling vole. Vegetation covered with ice results in higher mortality and poorer production of offspring, due to less food being available. The reduction in the populations of the three herbivores is perfectly synchronised and coincides with the rainy winters.

One way to improve our understanding and management of the consequences of today’s rapid climate change is to use the long time series from our monitoring to create frequently updated and short-term predictions of the ecosystem responses. Based on estimated predictions in Marolla et al. (2021), we found that the models’ short-term predictive abilities improved with long time series. By including ecological explanatory variables, we improved the model’s ability to predict abrupt changes in next year’s population density, thereby demonstrating the importance of ecosystem-based monitoring. Overall, this study illustrates the strength of integrating short-term predictions into monitoring systems in order to improve the understanding and management of wild populations exposed to rapid climate change.

The results of the model analyses show that there are many factors that influence the population development of Svalbard rock ptarmigan. These may include the negative effects of heavy precipitation in the summer and increasing access to reindeer carcasses in winter. Many of the effect estimates are admittedly weak and currently uncertain (not statistically significant). This may partly be due to the fact that a monitoring series of less than 20 years is relatively short for detecting cause and effect. The analysis results must also be assessed in the context that climate change is so far quite moderate compared to the expectations for the relatively near future. Today’s models are not able to predict the effect of these future changes.

We therefore recommend a precautionary approach and not increasing the take by hunting of Svalbard rock ptarmigan. As of today, the daily quota of 10 ptarmigan per day is not filled, and there are no quota restrictions over the season. Within the hunting period from 10 September to 23 December, Svalbard rock ptarmigan can be hunted throughout Svalbard unless otherwise specifically stipulated in law or statutory regulations. In reality, this means that the hunt for Svalbard ptarmigan is not quota regulated.

Another factor militating against increasing the take of Svalbard ptarmigan is that the regulations for quota setting in Svalbard are inflexible, i.e. changes in quota setting are slow to implement (often taking several years), and it will not be possible to capture rapid changes in the population development by means of rapid management measures. In other words, under the current regulations it is not feasible to operate dynamic adaptive management in Svalbard. It can be argued that the rapid climate change we are facing in Svalbard will require a more dynamic quota setting tool that is adjusted annually based on population counts before hunting takes place, as is practised on the Norwegian mainland. The current quota regulations for Svalbard rock ptarmigan have remained unchanged since 2003.

About the monitoring

The Svalbard ptarmigan is a ptarmigan subspecies and is the only herbivorous bird species that lives in Svalbard year-round. It is endemic to Svalbard and Franz Josef Land, making it a species for which Norway has special management responsibility.

There is low genetic diversity among Svalbard ptarmigan, which indicates that they have been isolated in the archipelago for a long time. Habitats vary throughout the year and the ptarmigan live in distinct areas during the breeding season and in the winter months. Access to suitable breeding habitats may therefore be a limiting factor for the population, since < 4% of the ice-free land areas in Svalbard constitute medium to good habitats for the ptarmigan (Pedersen et al. 2011; 2017).

The Svalbard ptarmigan is hunted annually and is the most harvested game species in Svalbard. Between 500–2,000 ptarmigan are taken per year in central parts of Spitsbergen and in the hunting areas north of Spitsbergen.

Information on the population density of cocks in the spring is important to allow the Governor of Svalbard to regulate the hunt when required. With today’s rapid climate change, knowledge of the size and development of the population over time is important for ensuring sustainable harvesting levels in a new climate.

Because Arctic foxes are the most important ptarmigan predator, and increasing predation can occur as a result of more reindeer carcasses, the management of both Arctic foxes and Svalbard reindeer must be assessed in the context of the development of the Svalbard ptarmigan population.

Competition for resources from rising goose populations may have a negative impact on Svalbard ptarmigan, and the management of geese should therefore also be assessed in the context of the development of the Svalbard ptarmigan population.