Climate variability poses a threat to cold blooded animals, research indicates

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A new Murdoch University study has found that cold-blooded animals (ectotherms) are unable to adjust physiologically to daily temperature fluctuations, a limitation that could leave them increasingly vulnerable as climate change drives even greater temperature variability. Daily temperature variations are a common feature in natural environments, ranging from subtle to extreme depending on the geographic location, season, and local climate patterns.

Ectotherms, which include almost all fish, reptiles, and invertebrates, rely on external sources to regulate their body heat. Their internal temperature closely mirrors the temperature of their environment, making daily temperature variations highly consequential.

Based on the existing scientific framework, it was previously assumed that ectotherms adjusted physiological factors like their metabolism, movement, heart function, and enzyme activity to become less sensitive to temperature changes—to essentially become more stable in fluctuating conditions.

However, a study led by Dr. Daniel Gomez Isaza from the Harry Butler Institute, reveals this was not the case. The work is published in the journal Philosophical Transactions B.

To understand how cold-blooded animals responded to everyday temperature swings, the research team combined data from 26 separate studies and compared how different species performed under constant versus fluctuating temperatures.

"By analyzing metabolic, locomotor, cardiovascular and enzyme activity across a wide range of ectotherms, we expected to see signs that these animals adjust their physiology to become less sensitive to daily temperature change," Dr. Gomez Isaza said.

"Instead, we found the opposite. There was no consistent evidence that ectotherms fine-tune their physiology in response to these predictable fluctuations.

"This suggests that ectotherms have limited capacity (or need) for regulating their internal physiology to cope with short-term environmental fluctuations."

Dr. Essie Rodgers, a co-author and Lecturer at Murdoch University's School of Environmental and Conservation Sciences, believes this vulnerability could pose a threat to ectotherms in the long-term.

"This inability could expose the vulnerability of ectotherms to unpredictable daily temperature fluctuations, which are becoming increasingly common with the progression of climate change," she said.

"Because ectotherms aren't adjusting their physiology to daily temperature swings, it's likely they'll have to depend more on behavioral strategies—like seeking shade, sun, or cooler microhabitats—or on rapid, short-term stress responses to cope with these changes.

"Over the longer term, their resilience may hinge on genetic adaptation rather than day-to-day physiological flexibility, which raises real concerns as temperature variability continues to increase."

More information

Daniel Gomez Isaza et al, Unresponsive to change: Ectotherms fail to adjust physiology to daily temperature variation, Philosophical Transactions B (2026). DOI: 10.1098/rstb.2025.0055

Key concepts

effects of climate changeanimal behaviorAdaptation, BiologicalBody Temperature RegulationTemperatureClimate Change

Provided by Murdoch University