Study estimates Tyrannosaurus rex body temperature at about 97°F
Analysis of fossil teeth suggests the iconic predator maintained a body temperature similar to modern warm-blooded animals, supporting the view that it was an active, endothermic species.
Researchers have measured the body temperature of Tyrannosaurus rex for the first time, estimating it at roughly 97 degrees Fahrenheit (36 degrees Celsius). The result, published in Science Advances, was derived from chemical signatures in two small samples of tooth enamel taken from a nearly complete T. rex skeleton housed at the Natural History Museum of Los Angeles County.
The method relies on the ratio of carbon and oxygen isotopes in enamel, which varies with temperature during formation. By drilling out a few milligrams of material, the team could infer the temperature at which the tooth grew, effectively using the fossil as a prehistoric thermometer.
"It’s probably the most direct and least complicated constraint on the actual body temperature of a T. rex that’s been possible before," said Robert Eagle, a geobiologist at UCLA and coauthor of the study.
The estimated temperature places T. rex within the range of modern endotherms, hotter than contemporary reptiles but cooler than many birds. The finding aligns with previous evidence, such as a 2022 T. rex footprint discovered in Alaska, that the species could thrive in cooler climates.
"A warm-blooded T. rex is a T. rex that can go almost anywhere on the continent, including the Arctic," said Aradhna Tripati, a climate scientist at UCLA and senior author.
Paleoclimate modeling suggests the dinosaur could have inhabited a broad swath of North America, from present-day Mexico to Alaska. The higher metabolic rate implied by a warm body temperature would have required greater food intake and could have allowed the predator to sustain activity longer than cold-blooded reptiles.
Vertebrate paleontologist Thomas Holtz Jr. noted that the temperature data, when compared with contemporaneous crocodiles and clams, give high confidence that T. rex maintained a high body temperature, reinforcing the hypothesis of endothermy.
The researchers aim to apply the same technique to other extinct species, potentially shedding light on the evolution of warm-bloodedness across dinosaurs and early mammals.