How does climate change impact migration and hibernation?
Different climatic seasons are experienced throughout the year because the amount of sunlight changes as the Earth revolves around the Sun. Animals and plants have adapted their life cycles (birth, growth, reproduction, etc.) to the seasons and resource availability. Some animals have developed behaviors to cope with winter conditions, conserve energy and deal with food scarcity by migrating to a warmer climate or hibernating. Both migration and hibernation are sensitive to weather and climate, and climate change poses a challenge to migratory and hibernating species.
- Climate change can alter the length of climatic seasons, which affects resource availability (food, shelter, etc.) and the amount of time animals have to prepare for subsequent seasons and life stages.
- Climate change can alter the cues used by species to regulate their behavior. For example, yellow-bellied marmots rely on air temperature as a cue to come out from hibernation. With warming temperatures, they are emerging earlier than usual.
- Climate change can disrupt the timing and synchrony between animal behaviors or life cycles and resource availability. For example, warmer sea temperatures affect the life cycle of small animals and plants that live in the ocean and are eaten by fish. This creates a mismatch between Atlantic cod migration and food availability. Food scarcity when cod arrive at specific spawning sites has lowered the number of cod reaching adulthood.
- Climate change can affect the distribution of species due to warming temperatures. Analyses performed by the National Audubon Society have shown that over the last four decades, 58 percent of birds have shifted their distribution northward into higher latitudes.
Migration usually occurs between breeding and non-breeding areas, utilizing a network of habitats to travel back and forth. Migrating species need to prepare to cross ecological barriers such as deserts, mountains and oceans, which requires high amounts of quality food in a short period of time. If they are not able to prepare, they may arrive in poor physical condition, affecting their survival and ability to reproduce. Climate change is changing weather factors such as temperature and precipitation, and increasing the frequency of some extreme weather events. This increases the risk for migratory species that depend on food availability and suitable habitats in multiple locations. Hibernating species are being affected by warming temperatures to the extent that some species are spending less time hibernating by delaying the onset of hibernation or emerging earlier; being abnormally active can force them to use stored energy before they can replace it. In other cases, species such as the Columbian ground squirrel delayed emergence from hibernation due to late spring snow falls, reducing the time they have to prepare for the next winter.
Photo: Yellow-bellied marmot, courtesy of U.S. Fish and Wildlife Service.
(Source: Inouye, D.W., B. Barr, K.B. Armitage, and B.D. Inouye. 2000. Climate Change is Affecting Altitudinal Migrants and Hibernating Species. Proceedings of the National Academy of Science 97(4):1630-1633. and Robinson, R.A, H.Q.P. Crick, J.A. Learmonth, I.M.D. Maclean, C.D. Thomas, F. Bairlein, M.C. Forchhammer, C.M. Francis, J.A. Gill, B.J. Godley, J. Harwood, G.C. Hays, B. Huntley, A.M. Hutson, G.J. Pierce, M.M. Rehfisch, D.W. Sims, M.B. Santos, T.H. Sparks, D.A. Stroud, M.E. Visser. 2009. Travelling Through a Warming World: Climate Change and Migratory Species. Endang Species Res 7:87-99. and Frank, C.L. 2011. The Relationship between Climate Warming and Hibernation in Mammals. Temperature Adaptation in a Changing Climate: Nature at Risk. eds K.B. Storey and K.K. Tanino and National Park Service. Denning and Hibernation Behavior. Accessed Online 31 October 2013. http://www.nps.gov/yell/naturescience/denning.htm and National Audubon Society. 2009. Birds and Climate Change: Ecological Disruption in Motion. Accessed online 31 October 2013. http://web4.audubon.org/news/pressroom/bacc/pdfs/birds%20and%20climate%20report.pdf and Science Daily. Hibernation Altered by Climate Change Takes a Toll on Rocky Mountain Animal Species. Accessed online 1 November 2013. http://www.sciencedaily.com/releases/2012/08/120808132707.htm)