The pursuit of populations collapses: long-term dynamics of semi-domestic reindeer in Sweden

By Bård-Jørgen Bårdsen & Marius Warg Næss

In Scandinavia there is a growing concern that the reindeer husbandry is in a state of crisis, but results from our recent study indicates that the Swedish reindeer husbandry is in better condition now compared to the past (1945-1965).

rein1

Reindeer herd in a corral. (C) Bård-Jørgen Bårdsen.

We just got paper published in Human Ecology  that looks at population dynamics of Swedish semi-domestic reindeer (or caribou Rangifer tarandus as the species is called in North America) at the herding district-level (‘Sameby’).

We have used data on reindeer numbers from two distinct periods in time, covering ca. 70 years: 1945-1965 (past) and 1995-2012 (present).

Declines have been reported for many Rangifer populations across the Circumpolar North, but population dynamics are highly variable as both declining and increasing trends in population numbers are evident.

Nonetheless, temporal trends in semi-domestic reindeer number in Fennoscandian countries seem rather synchronous during 1980-2000.

In Sweden the number of reindeer has fluctuated, apparently at the scale of decades, around ~225 000 individuals from 1880-2000, to vary between 240 801 to 261 491 animals from 2005 and onwards.

There is currently a debate on whether the reindeer husbandry as a livelihood is threatened, and in Sweden there has been a growing concern of the reindeer husbandry being in a state of crisis due to e.g. land use changes and conflicts; increased predation and climate change.

rein2

Reindeer on the  move. (C) Bård-Jørgen Bårdsen.

The aim of our study was to assess if population dynamics of semi-domestic reindeer have changed during the last 70 years, and more importantly if there were any signs of population collapses (i.e. dramatic reductions in population size) or declines occurring from 1945-1965 to present day.

We documented few indications of changed dynamics comparing 1995-2012 with 1945-1965, and result from this study indicates that the reindeer husbandry is in better conditions at present compared to the past:

  • Populations were more regulated in the past than now as judged from the estimated direct and delayed density dependence (based on autoregressive models fitted to time series of population growth rates).
  • The estimated carrying capacity (fitting the Ricker model to our data) for the different areas was positively related to their past values.
  • There were positive relationships between past and present population-level density. In fact, low-density populations in the past experienced larger growth from past to present compared to populations with comparable high-density in the past.
  • At the national-level, an increase in the number of reindeer, harvested animals and number of owners from 2000 to present indicated a lack of a recent general collapse in the Swedish Reindeer Husbandry (based on data from the Swedish Sami Parliament).
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Reindeer in a fence. (C) Bård-Jørgen Bårdsen

In short, we found no evidence of any population collapses within the Swedish Reindeer Husbandry since World War II.

Furthermore, no evidence of collapses, or crisis, was found when we analysed of the number of owners and slaughtered calved as well as meat production and average carcass mass in Sweden from 1995 and onwards.

Please check out the full publication:

Bårdsen, B.-J., Næss, M. W., Singh, N. J. & Åhman, B. (2017). The pursuit of populations collapses: long-term dynamics of semi-domestic reindeer in Sweden. Human Ecology. http://dx.doi.org/10.1007/s10745-016-9880-3.

Further reading

Bårdsen, B.-J., Næss, M. W., Tveraa, T., Fauchald, P. & Langeland, K. (2014). Risk sensitive reproductive allocation: fitness consequences of body mass losses in two contrasting environments. Ecology and Evolution. 4(7):1030–1038. http://dx.doi.org/10.1002/ece3.1010.

Bårdsen, B.-J., Berglann, H., Stien, A. & Tveraa, T. (2014). Effekten av høsting på produksjon og lønnsomhet i reindriften. NINA rapport 999: pp. 44. (in Norwegian with English summary). goo.gl/qWyMpP.

Næss, M. W., Bårdsen, B.-J. (2013). Why Herd Size Matters – Mitigating the Effects of Livestock Crashes. PLoS ONE 8(8): e70161. http://dx.doi.org/10.1371/journal.pone.0070161.

Næss, M. W., Bårdsen, B.-J. & Tveraa, T. (2012). Wealth dependent and interdependent strategies in the Saami reindeer husbandry, Norway. Evolution and Human Behavior 33(6): 696-707. http://dx.doi.org/10.1016/j.evolhumbehav.2012.05.004.

Bårdsen, B.-J., Henden, J.-A. Fauchald, P, Tveraa, T. & Stien, A. (2011). Plastic reproductive allocation as a buffer against environmental stochasticity – linking life history and population dynamics to climate. Oikos 120:245-257. http://dx.doi.org/10.1111/j.1600-0706.2010.18597.x.

Næss, M. W., Bårdsen, B.-J., Pedersen, E. and Tveraaa, T. (2011). Pastoral herding strategies and governmental management objectives: predation compensation as a risk buffering strategy in the Saami reindeer husbandry. Human Ecology 39(4):489-508. http://dx.doi.org/10.1007/s10745-011-9398-7.

Næss, M. W., Bårdsen, B.-J., Fauchald, P., & Tveraa, T. (2010). Cooperative pastoral production – the importance of kinship. Evolution and Human Behavior 31(4):246-258. http://dx.doi.org/10.1016/j.evolhumbehav.2009.12.004.

Næss, M. W., and Bårdsen, B.-J. (2010). Environmental stochasticity and long-term livestock viability – herd-accumulation as a risk reducing strategy. Human Ecology 38(1):3-17. http://dx.doi.org/10.1007/s10745-009-9288-4.

Bårdsen, B.-J., Fauchald, P., Tveraa, T. Langeland, K., Yoccoz, N. G. & Ims, R. A. (2008). Experimental evidence for a risk sensitive reproductive allocation in a long-lived mammal. Ecology 89:829-837. http://dx.doi.org/10.1890/07-0414.1.

Bårdsen, B.-J. (2009). Risk sensitive reproductive strategies: the effect of environmental unpredictability. PhD thesis. University of Tromsø, Norway. goo.gl/BbPasb.

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