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Crocodiles and their ancient relatives have survived major changes in Earth’s climate and several mass extinction events over hundreds of millions of years. But how did these animals survive when many other groups, including non-avian dinosaurs, disappeared? A study by Chiarenza et al. (2026), published in Science Advances, investigated how climate influenced the evolution, geographic distribution, and survival of crocodiles and their relatives. The researchers found that these animals maintained a strong preference for warm environments throughout much of their evolutionary history. This long-lasting relationship with climate may help explain why some crocodile relatives survived environmental disasters that eliminated many other species.

To investigate this relationship, the researchers studied more than 400 living and extinct species of crocodiles and their ancient relatives. They combined fossil records, evolutionary family trees, information about modern crocodile habitats, and computer simulations of ancient climates covering approximately 245 million years. Their analysis examined how temperature and rainfall influenced where these animals could live. The results showed that crocodile relatives generally followed suitable climates instead of developing entirely new climate preferences. During warmer periods, their geographic ranges expanded into regions farther from the equator, while cooler periods pushed them back toward warmer tropical areas. Scientists call this pattern climatic niche conservatism, meaning that a group of organisms maintains similar environmental preferences over long evolutionary periods.

One important finding concerns the mass extinction event that occurred approximately 66 million years ago, when an asteroid impact contributed to the disappearance of non-avian dinosaurs. The researchers used climate simulations to examine whether suitable environments remained available to crocodile relatives following the impact. Their models suggested that tropical and subtropical regions could have remained warm enough to support some crocodile relatives, even as environmental conditions became unsuitable across many other regions. These warmer areas may have served as refuges where populations survived and later expanded. However, the researchers did not conclude that climate alone explains their survival. Other characteristics, including smaller body sizes, flexible diets, semiaquatic lifestyles, and relatively low energy requirements, may also have contributed. The study also identified periods when some crocodile lineages evolved different temperature or rainfall preferences, showing that their climate requirements were not completely fixed.

The findings provide a better understanding of how climate can influence animal evolution and survival over millions of years. They suggest that crocodiles and their relatives often responded to changing temperatures by moving into regions with suitable environmental conditions rather than rapidly adapting to entirely different climates. This historical pattern may also have implications for crocodiles living today. As modern climate change alters temperatures and rainfall patterns, some species may need to move to new habitats to survive. However, human activities such as urban development, agriculture, and habitat fragmentation can make these movements more difficult. Although the research does not predict exactly how modern crocodiles will respond to future climate change, it highlights the importance of protecting suitable habitats and maintaining connections between ecosystems. Overall, the study demonstrates how long-standing environmental preferences can influence the survival and evolution of animal groups.

References

Chiarenza, A. A., Howard, A. F. C., Varnham, G. L., Farnsworth, A., Valdes, P. J., & Mannion, P. D. (2026). Climatic niche conservatism shapes the macroevolution, extinction, and survivorship of crocodile-line archosaurs. Science Advances, 12(43), Article eaeg2217. https://doi.org/10.1126/sciadv.aeg2217

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