Young Cold-Bloodied Animals Struggle to Adapt to Rising Temperatures, Study Shows

New research shows that young cold-blooded animals are struggling to cope with rising global temperatures, making them more vulnerable to climate change than adults. The study examined ectotherms, which make up over 99 percent of animals on Earth and include fish, reptiles, amphibians and insects. Their body temperature depends directly on outside conditions, leaving them at risk of dangerous overheating during heat waves.

Study Findings

The research drew on 60 years of data covering 138 ectotherm species from around the world. Findings show that embryos and juvenile animals increased their heat tolerance by an average of just 0.13 degrees Celsius for each degree of warming. Young land-based animals proved worse at acclimatising than aquatic species, potentially because land animals rely more on moving to cooler spots rather than physiological adaptation. The work also revealed that past exposure to high temperatures does not necessarily help young animals withstand future heat.

Species Examples

Specific examples from the study highlight these risks. For instance, young Lesueur's velvet geckos from cooler nests of 23.2 degrees Celsius tolerated temperatures up to 40.2 degrees, while those from warmer nests of 27 degrees only tolerated up to 38.7 degrees. Similarly, adult male mosquito fish from eggs incubated at 32 degrees showed lower heat tolerance than those from 26-degree environments. These patterns indicate that warmer early conditions can produce adults less capable of handling future heat.

Context

Ectotherms rely on external environmental sources to regulate their body temperature, unlike warm-blooded animals that generate their own heat internally. Because global temperatures are rising faster than species can evolve across generations, understanding how these animals adapt within a single lifetime is vital for protecting wildlife. Conservation efforts that preserve shady natural shelters like trees, burrows and rocks remain essential for helping vulnerable species survive intense heat waves.