Weather conditions and nonhuman animals

This page is about ways weather conditions affect animals living in the wild. For information about what animals’ lives are like in the wild, see our section on the situation of animals in the wild.

Weather, especially temperature, plays a major role in influencing whether animals can survive and be healthy in certain habitats. Fluctuations in temperatures in certain regions can result in the deaths of entire populations. Cold-blooded animals (e.g., fishes, amphibians, reptiles, and invertebrates) are particularly susceptible to sudden changes in temperature. Young animals who cannot migrate or live in shallow waters that get cold more quickly are especially at risk.

When weather conditions are sufficient to maintain a certain population of animals, they can reproduce for generations until conditions become unfavorable for survival.1 Even though an environment may meet animals’ survival needs, they can still experience extreme discomfort. Let’s consider a scenario in which some animals can only survive if the temperature remains between 40ºF (4ºC) and 90ºF (32ºC). If the temperature stays within this range, the animals will continue to live and reproduce. However, if the temperature fluctuates too much above or below that range, they might survive but will suffer from the extreme heat or cold.2

The optimal situation for the wellbeing of the animals would be for them to only colonize areas in which they can live comfortably. Unfortunately, this situation is far removed from the realities of nature. Many animals, especially those reproducing in high numbers, may colonize a certain area when weather conditions are fit for them to live there, only to die later when weather conditions change.

We might suppose that when all the members of a population die in a particular area, it will never be populated by those animals again. However, animals tend to re-colonize the same areas because scarce resources, or other inhospitable conditions, force them to find a new place to live. This can result in a continuous cycle of colonization, suffering, mass death, and re-colonization.

Biologists studying meta-populations refer to this as the dynamics of “sources and sinks.” A meta-population is a group of a certain species of animal that lives in different areas. Often the animals of that species have the means to survive in some of those areas but not in others. They would become permanently extinct in those areas (the “sinks”) if they did not continually migrate to them from the other areas (the “sources”).

 

Temperature changes

Many animals suffer due to changes in temperature. They may be fine during part of the year but experience great discomfort and hardship during a particularly hot summer or cold winter. In temperate areas – such as large parts of North America, Europe, and Asia – there can be big differences between the minimum and maximum temperatures during the summer and the winter. Animals who don’t hibernate or become dormant in cold weather have to endure large variations in temperature. The temperatures may fall within a tolerable range but may nevertheless be very uncomfortable. This may weaken their immune systems and make them more susceptible to illness.

Of course, humans would suffer similar discomfort due to weather conditions if it weren’t for our ability to adapt to changes in temperature by wearing suitable clothing and using heating and cooling. Nonhuman animals lack the technologies that we humans have at our disposal and, as a result, they can suffer greatly when weather conditions are extreme. When there are deadly heat waves that kill some humans in an area, there may be many other animals who also die due to the heat or complications from it, such as dehydration.3

Cold weather leads to loss of life more routinely than hot weather. It’s common for large portions of a population of mammals to die every winter, and more than half can be wiped out during a particularly harsh winter. Unlike many other animals in temperate climates, deers don’t migrate or hibernate in the winter. They try to crowd into the few spots that provide some shelter from the cold, wind, and snow. Food is also scarcer for them during the winter. The harshness of winters is the biggest limiting factor in determining whether a habitat is viable for deers.4

Animals who hibernate are also more vulnerable during the winter due to an increased risk of disease or starvation before the winter’s end. For example, bats can suffer from frostbite or starve to death if they awaken during their winter hibernation and fly around too much, depleting the fat stores they need to get them through the rest of the winter. They are more likely to wake up during warmer periods of the winter if they have contracted a fungal infection called white-nose syndrome.5

Crickets, like many other insects, can survive the winter in diapause (dormancy). Whether they survive or not typically depends on which stage of their life cycle they are in and how unstable the winter temperatures are. Some insects can withstand being frozen solid because they produce cryoprotective chemicals similar to antifreeze. However, if they thaw out due to sudden warming temperatures, they may not survive a refreeze.6

Birds can usually tolerate a relatively wide range of temperatures. Yet if they are sick or injured and unable to fly to a warmer place or can’t keep up their body heat in the winter, they can suffer from frostbite which can be serious if left untreated. They can also suffer from crash landings on ice or wet pavement that they mistake for water. Swans and other birds who can’t move well out of water sometimes get stuck on ice and injure their wings trying to flap them against the hard surface.7

Cold-blooded animals like fishes, amphibians, and reptiles have to expose themselves to warmer or cooler water or air to regulate their body temperature. As a result, they are more vulnerable than mammals and birds to heat stress or hypothermia due to sudden temperature changes. Although marine environments generally have smaller temperature fluctuations than terrestrial ones, there can be a large variation in temperatures between bodies of water. Freshwater habitats are generally smaller, and, as a result, have larger seasonal temperature variations.8 Some animals can survive in both saltwater and freshwater environments. Just as land animals migrate to inhabit new areas, marine animals can move into habitats that are colder or hotter than what is optimal for their bodies. Floods and heavy winds can also displace marine animals so they end up in inhospitable environments.

In response to warmer temperatures, the metabolism of some marine animals slows down – enabling them to better adapt. However, many marine animals experience heat stress that impairs their ability to consume oxygen. While they can recover from the stress this causes to their bodies to an extent, if temperatures remain too high for too long, they will be unable to survive.

Rapidly cooling temperatures can be dangerous as well. For example, sea turtles commonly experience “cold stunning” when there is a rapid change in temperature or the water remains too cold for too long. Cold stunning occurs when decreased heart rate and circulation result in shock and lethargy that can be fatal. At its worst, turtles stop moving altogether and their systems shut down to such an extent that rescuers can’t tell if they are dead or alive. Young turtles are especially at risk because they often live in shallow water that gets cold faster.9 The condition can be further complicated by frostbite. Affected turtles are more susceptible to diseases like pneumonia and are also more likely to be injured or preyed upon. Cold stunning often happens during unusually cold spells, but in some areas it is chronic, occurring every winter and killing more than 60% of the turtles who aren’t able to migrate.10

In extreme cases, or when there are changes in the climate that occur progressively over longer time periods, entire populations may die off, suffering a great deal in the process. Animals dying from extreme weather conditions can experience a lot of pain in addition to losing their lives.

 

Other weather conditions apart from temperature

Many factors other than extremes of temperature can affect animal populations. Some animals require a certain level of humidity to thrive and can suffer a great deal in arid regions. For others, too much humidity or rain can be harmful. Although there are many animals who are not affected by rain, or who actually like rain, there are others who are bothered by it or have illnesses or physical conditions that are worsened by it. Just as rain, snow, and strong wind can negatively impact human wellbeing, they can cause similar discomfort and stress to animals living in the wild. Even if these uncomfortable weather conditions don’t kill them, just as they usually don’t kill us, they can still cause suffering for nonhuman animals. Without access to adequate shelter or medical care, complications that would be minor for humans can be severe for animals living in the wild.

Several other weather phenomena can have a huge impact on animals, and can wipe out entire populations. Their effects can combine with other factors such as the availability of food and water, the presence of predators, and diseases. Consider, for example, droughts, heavy snows, and flooding. These extreme conditions can kill animals directly, for example by drowning, or indirectly, for example by damaging the food supply (to read more about this, see Animals in natural disasters). Weather conditions can also cause diseases or trigger epidemics among animals. Many animals get weaker during the winter due to the harsh weather, which makes them more susceptible to becoming sick. For example, many birds carry avian cholera that is inactive. Very cold weather or high water forcing birds to leave their habitats are common stressors that can activate the disease in infected birds. Lobsters living in warmer water are more susceptible to lobster shell disease, which weakens their shells and makes them more susceptible to injury and predation. Other animals suffer from diseases that are transmitted by flies when certain weather conditions occur.11

Animals who are struck by disease may be able to survive, but it may depend on the weather conditions in which they are fighting the disease. The effect would be similar for humans. If you didn’t have a house and clothes, you might be able to recover easily from the flu in the summer, but it might be much harder for you to overcome it in the cold of a harsh winter. It is the same for nonhuman animals in the wild. Warm-blooded animals, like birds and mammals, can only generate more heat internally if they eat enough calories, and food tends to be harder to find in the winter. Thus, an injury or illness that restricts movement can be fatal if it prevents an animal from moving around to keep warm.

There are many ways we can, and already do, help animals living in the wild who are threatened by weather condition and other natural factors.


Further readings

Abe, A. S. (1995) “Estivation in South American amphibians and reptiles”, Brazilian Journal of Medical and Biological Research, 28, pp. 1241-1247.

Bowler, D. E.; Haase, P.; Hof, C.; Kröncke, I.; Baert, L.; Dekoninck, W.; Domisch, S.; Hendrickx, F.; Hickler, T.; Neumann, H.; O’Hara, R. B.; Sell A. F.; Sonnewald, M.; Stoll, S.; Türkay, M.; van Klink, R.; Schweiger, O.; Vermeulen, R. & Böhning-Gaese, K. (2017) “Cross-taxa generalities in the relationship between population abundance and ambient temperatures”, Proceedings of the Royal Society B: Biological Sciences, 284 (1863) [accessed on 19 June 2019].

Bradshaw, S. D. & Death, G. (1991) “Variation in condition indexes due to climatic and seasonal factors in an Australian desert lizard, Amphibolurus-Nuchalis”, Australian Journal of Zoology, 39, pp. 373-385.

Brown, C. R. & Brown, M. B. (1998) “Intense natural selection on body size and wing and tail asymmetry in cliff swallows during severe weather”, Evolution, 52, pp. 1461-1475.

Dillon, M. E.; Woods, H. A.; Wang, G.; Fey, S. B.; Vasseur, D. A.; Telemeco, R. S.; Marshall, K. & Pincebourde, S. (2016). “Life in the frequency domain: The biological impacts of changes in climate variability at multiple time scales”, Integrative and Comparative Biology, 56, pp. 14-30 [accessed on 19 June 2019].

Forbes, B. C.; Kumpula, T.; Meschtyb, N.; Laptander, R.; Macias-Fauria, M.; Zetterberg, P.; Verdonen, M.; Skarin, A.; Kim, K.-Y.; Boisvert, L. N.; Stroeve, J. C. & Bartsch, A. (2016) “Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia”, Biology Letters, 12 (11) [accessed on 19 June 2019].

Grigg; G.; Geiser, F.; Nicol, S. & Turbill, C. (2016) “Hibernation”, science.org.au [accessed on 19 June 2019].

Hansen, T. F.; Stenseth, N. C. & Henttonen, H. (1999) “Multiannual vole cycles and population regulation during long winters: An analysis of seasonal density dependence”, American Naturalist, 154, pp. 129-139.

Hansson, L. (1990) “Ultimate factors in the winter weight depression of small mammals”, Mammalia, 54, pp. 397-404.

Huitu, O.; Koivula, M.; Korpimäki, E.; Klemola, T. & Norrdahl, K. (2003) “Winter food supply limits growth of northern vole populations in the absence of predation”, Ecology, 84, pp. 2108-2118.

Kay, R. N. B. (1997) “Responses of African livestock and wild herbivores to drought”, Journal of Arid Environments, 37, pp. 683-694.

Maxwell, S. M; Jeglinski, J. W. E.; Trillmich, F.; Costa, D. P. & Raimondi, P. T. (2014) “The Influence of Weather and Tides on the Land Basking Behavior of Green Sea Turtles”, Chelonian Conservation and Biology, 13, pp. 247-251.

McDermott Long, O.; Warren, R.; Price, J.; Brereton, T. M.; Botham, M. S. & Franco, A. M. A. (2016) “Sensitivity of UK butterflies to local climatic extremes: Which life stages are most at risk?”, Journal of Animal Ecology, 86, pp. 108-116 [accessed on 19 June 2019].

Milner, J. M.; Elston, D. A. & Albon, S. D. (1999) “Estimating the contributions of population density and climatic fluctuations to interannual variation in survival of Soay sheep”, Journal of Animal Ecology, 68, pp. 1235-1247 [accessed on 19 June 2019].

Munguia, P. (2015) “Role of sources and temporal sinks in a marine amphipod”, Biology Letters, 11 (2) [accessed 19 June 2019].

Salman, M. D. (2003) “Chronic wasting disease in deer and elk: Scientific facts and findings”, Journal of Veterinary Medical Science, 65, pp. 761-768.

White, T. C. R. (2008) “The role of food, weather and climate in limiting the abundance of animals”, Biological Reviews, 83, pp. 227-248.


Notes

1 See for instance Sasvari, L & Hegyi, Z. (1993) “The effects of parental age and weather on breeding performance of colonial and solitary tree sparrow (Passer montanus (L.))”, Acta Oecologica, 14, pp. 477-487; Bradley, M.; Johnstone, R.; Court, G. & Duncan, T. (1997) “Influence of weather on breeding success of peregrine falcons in the Arctic”, The Auk, 114, pp. 786-791.

2 Hardewig, I.; Pörtner, H. O. & Dijk, P. (2004) “How does the cold stenothermal gadoid Lota lota survive high water temperatures during summer?”, Journal of Comparative Physiology, 174, pp. 149-156. Stevenson, R. D. (1985) “Body size and limits to the daily range of body temperature in terrestrial ectotherms,” The American Naturalist, 125, pp. 102-117.

3 One study found that “[a] brief but intense heat wave on 9 June 1979 caused catastrophic chick mortality in a population of Western Gulls on Santa Barbara Island, California, USA. Mortality ranged from 0 to 90% in different areas of the colony”: Salzman, A. G. (1982) “The selective importance of heat stress in gull nest location”, Ecology, 63, pp. 742-751. Some recent examples of life-threatening heat stress include McCahill, E. (2018) “Baby hedgehogs could die of thirst in heatwave – here’s how you can help them”, Mirror, 7 Jul [accessed on 23 May 2019]; Scully, R. P. (2019) “Thirsty koalas need bowls of water to survive increasingly hot climate”, NewScientist, 5 June [accessed on 28 October 2019]. See references for more information about heat stress.

4 Wooster, C. (2003) “What happens to deer during a tough winter?”, Northern Woodlands, February 2 [accessed on 14 October 2019].

5 National Park Service (2017) “What is white-nose syndrome?”, nps.gov [accessed on 19 June 2019].

6 Callahan, R. (2018) “How do crickets go into a hibernation state when cold?”, Sciencing, October 17 [accessed on 23 June 2019].

7 Brown, C. R; Brown, M. B. (1998) “Intense natural selection on body size and wing and tail asymmetry in cliff swallows during severe weather”, Evolution, 52, p. 1461-1475. Raddatz, K. (2018) “Frigid temps pose danger to local wildlife”, CBS Minnesota, January 4 [accessed on 19 June 2019].

8 Hardewig, I.; Pörtner, H. O. & Dijk, P. (2004) “How does the cold stenothermal gadoid Lota lota survive high water temperatures during summer?”, op. cit.

9 Gabriel, M. N. (2018) “Hundreds of sea turtles ‘cold-stunned’ by frigid temperatures in Gulf waters”, Pensacola News Journal, Jan 4 [accessed on 19 June 2019].

10 Foley, A. M.; Singel, K. E.; Dutton, P. H.; Summers, T. M.; Redlow, A. E. & Lessman, J. (2007) “Characteristics of a green turtle (Chelonia mydas) assemblage in northwestern Florida determined during a hypothermic stunning event”, Gulf of Mexico Science, 25 (2) [accessed on 19 June 2019].

11 Henning, J.; Schnitzler, F. R.; Pfeiffer, D. U. & Davies, P. (2005) “Influence of weather conditions on fly abundance and its implications for transmission of rabbit haemorrhagic disease virus in the North Island of New Zealand”, Medical and Veterinary Entomology, 19, pp. 251-262.

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