From faster metabolisms to changing colours and smaller bodies, discover the adaptations animals are acquiring thanks to climate change
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The world is getting warmer. Global temperatures have risen sharply since the late 19th century, with 2025 noted as one of the top-three warmest years ever recorded.
The current warming trend is, of course, not a natural cycle, but instead driven by human emissions of greenhouse gases from burning fossil fuels, deforestation and agriculture.
As the world continues to warm, how are animals coping with such dramatic rises in temperatures? Read on to find out the adaptations occurring around the world – from animals nesting earlier to choosing to change colours to cope with a warming planet…
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Smaller bodies
Multiple scientific analyses have documented that body size decline in birds and other animals is linked with warming climates. In particular, a UCLA-led study found that many North American migratory birds have become smaller across the decades. In the study, 105 birds were analysed, with an average body mass decline of 0.6 per cent across the last thirty years.
The reason behind this is that smaller bodies cope better with heat. Larger animals cool down more slowly during heatwaves and require more food to maintain body mass – so it’s more favourable for an animal to have a smaller body in a warming world.
Nesting earlier
As the climate warms, bird nesting is occurring earlier. For most birds, the timing of breeding is controlled by a combination of day length and temperature. But as spring arrives earlier, birds begin producing reproductive hormones sooner, with egg-laying shifting days or even weeks earlier than historical averages.
Consistent advances in nesting dates have been reported among songbirds, waterfowl and raptors.
A recent university research programme showed that, like birds, sea turtles are nesting earlier in response to rising temperatures. Warmer waters increase turtles’ metabolic rates and accelerate egg development in females. In essence, turtles are being pushed to reproduce earlier.
Marine species heading polewards
A major global study analysing abundance trends across 304 widely distributed marine species found that, over the last century, warming seas have driven species to become more abundant on the poleward edges of their ranges and declining toward the equator.
This shows a general, global pattern of marine organisms shifting polewards to cooler waters in response to rising ocean temperatures. Species do this to avoid the metabolic and reproductive changes that can occur in warmer waters.
However, recent research from Tel Aviv University has found that species heading to the poles may still be struggling. A study covering around 2,500 fish from 146 species found that rapid poleward movement correlates with an overall population decline.
Changing sex ratios
Many reptiles – especially turtles – do not have genetic sex determination. Instead, the temperature at which eggs incubate during development determines whether an embryo becomes male or female.
Climate warming means that, for example, sea turtles produce more females. As global temperatures continue to rise, many populations are becoming highly female-biased.
A global survey across 64 sea turtle nesting sites found that female-skewed sex ratios now dominate at most beaches, with extremely high proportions of females at many locations.
Such a vast difference between the numbers of females and males could threaten population viability unless evolutionary or behavioural responses occur.
Faster metabolisms
A warmer environment typically accelerates many biological processes because temperature influences the rate of chemical reactions inside cells. For animals – especially ectotherms like fish, reptiles and insects – this means their metabolic rate increases with temperature. In other words, they burn energy faster.
A study combining metabolic data from dozens of species of fish found that as water temperatures increased, metabolic rates rose significantly. In reptiles and insects, warmer conditions speed up metabolic rates, often resulting in more rapid turnover of generations, faster growth to reproductive age and shorter lifespans.
Changing colours
In many insects, such as butterflies, dark colours absorb heat faster than lighter ones. In cooler conditions, this can be beneficial, but as temperatures rise, these darker colours can disappear.
A study of the comma butterfly across Europe found that climate warming is associated with changes in wing patterns consistent with thermal adaptation.
In addition, Arctic foxes are also changing colours to adapt to a warming world. Normally, these creatures shift from brown and grey summer coats to white winter coats. However, in regions with reduce snow cover – thanks to climate change – white coats are becoming less advantageous compared to their darker counterparts. As such, some populations show reduce winter whitening and increased persistence of darker coats.
