Abstract
The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain-on-snow) can cause 'icing', restricting access to forage, resulting in starvation, lower survival and fecundity. Since body condition is a 'barometer' of energy demands relative to energy intake, we explored the causes and consequences of variation in body mass of wild female Svalbard reindeer (Rangifer tarandus platyrhynchus) from 1994-2015, a period of marked climate warming. Late winter (April) body mass explained 88% of the between-year variation in population growth rate, because it strongly influenced reproductive loss, and hence subsequent fecundity (92%), as well as survival (94%) and recruitment (93%). Autumn (October) body mass affected ovulation rates but did not affect fecundity. April body mass showed no long-term trend (Coefficient of variation, CV = 8.8%) but was higher following warm autumn (October) weather, reflecting delays in winter onset, but most strongly, and negatively, related to 'rain-on-snow' events. October body mass (CV =2.5%) increased over the study due to higher plant productivity in the increasingly warm summers. Density-dependent mass change suggested competition for resources in both winter and summer but was less pronounced in recent years, despite an increasing population size. While continued climate warming is expected to increase the carrying capacity of the high Arctic tundra, it is also likely to cause more frequent icing-events. Our analyses suggest that these contrasting effects may cause larger seasonal fluctuations in body mass and vital rates. Overall our findings provide an important 'missing' mechanistic link in the current understanding of the population biology of a keystone species in a rapidly warming Arctic. This article is protected by copyright. All rights reserved.
| Original language | English |
|---|---|
| Pages (from-to) | 1374–1389 |
| Number of pages | 16 |
| Journal | Global Change Biology |
| Volume | 23 |
| Issue number | 4 |
| Early online date | 6 Aug 2016 |
| DOIs | |
| Publication status | Published - 1 Apr 2017 |
Bibliographical note
ACKNOWLEDGEMENTSWe thank the Governor of Svalbard for permission to undertaker the research. We are especially grateful to Steve Coulson, and the logistical and technical staff at the University Centre in Svalbard (UNIS) for supporting the field campaigns. The data collection would not have been possible without the contribution of numerous field assistants, including veterinary students from the Norwegian School of Veterinary Science. Statistical advice was provided by Mark Brewer and David Elston, BioSS. The work was supported mainly by grants from U.K. Natural Environment Research Council the Norwegian Research Council, and the Macaulay Development Trust. Additional financial support has come from the Amundsen Foundation, Centre for Ecology and Hydrology, The Macaulay Institute, the NINA, UNIS, and the Norwegian School of Veterinary Science
Keywords
- Climate change
- density dependence
- extreme events
- icing
- nutrition
- primary production
- Rangifer
- Reindeer
- Svalbard
- weather
Access to Document
- Contrasting effects of summer and winter warming on body mass explain population dynamics in a food-limited Arctic herbivore
© 2016 The Authors. Global Change Biology Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.