Some snakes lack the ‘hunger hormone.’ Experts are hungry to know why

Some snakes lack the ‘hunger hormone.’ Experts are hungry to know why Skip to content Subscribe today Every print subscription comes with full digital access Subscribe Now Menu All Topics Health Humans Anthropology Health & Medicine Archaeology Psychology View All Life Animals Plants Ecosystems Paleontology Neuroscience Genetics Microbes View All Earth Agriculture Climate Oceans Environment View All Physics Materials Science Quantum Physics Particle Physics View All Space Astronomy Planetary Science Cosmology View All Magazine Menu All Stories Multimedia Reviews Puzzles Collections Educator Portal Century of Science Unsung characters Coronavirus Outbreak Newsletters Investors Lab About SN Explores Our Store SIGN IN Donate Home INDEPENDENT JOURNALISM SINCE 1921 SIGN IN Search Open search Close search Home INDEPENDENT JOURNALISM SINCE 1921 All Topics Earth Agriculture Climate Oceans Environment Humans Anthropology Health & Medicine Archaeology Psychology Life Animals Plants Ecosystems Paleontology Neuroscience Genetics Microbes Physics Materials Science Quantum Physics Particle Physics Space Astronomy Planetary Science Cosmology Tech Computing Artificial Intelligence Chemistry Math Science & Society All Topics Health Humans Humans Anthropology Health & Medicine Archaeology Psychology Recent posts in Humans Artificial Intelligence Real-world medical questions stump AI chatbots By Tina Hesman Saey6 hours ago Health & Medicine A simple shift in schedule could make cancer immunotherapy work better By Elie DolginFebruary 12, 2026 Health & Medicine This baby sling turns sunlight into treatment for newborn jaundice By Elie DolginFebruary 12, 2026 Life Life Animals Plants Ecosystems Paleontology Neuroscience Genetics Microbes Recent posts in Life Animals Some snakes lack the ‘hunger hormone.’ Experts are hungry to know why By Andrea Lius2 hours ago Oceans Evolution didn’t wait long after the dinosaurs died By Elie DolginFebruary 13, 2026 Animals A sea turtle boom may be hiding a population collapse By Melissa HobsonFebruary 13, 2026 Earth Earth Agriculture Climate Oceans Environment Recent posts in Earth Oceans Evolution didn’t wait long after the dinosaurs died By Elie DolginFebruary 13, 2026 Earth Earth’s core may hide dozens of oceans of hydrogen By Nikk OgasaFebruary 10, 2026 Animals Some dung beetles dig deep to keep their eggs cool By Elizabeth PennisiFebruary 4, 2026 Physics Physics Materials Science Quantum Physics Particle Physics Recent posts in Physics Physics Physicists dream up ‘spacetime quasicrystals’ that could underpin the universe By Emily Conover24 minutes ago Physics A precise proton measurement helps put a core theory of physics to the test By Emily ConoverFebruary 11, 2026 Physics The only U.S. particle collider shuts down – so a new one may rise By Emily ConoverFebruary 6, 2026 Space Space Astronomy Planetary Science Cosmology Recent posts in Space Astronomy This inside-out planetary system has astronomers scratching their heads By Adam MannFebruary 12, 2026 Space Artemis II is returning humans to the moon with science riding shotgun By Lisa GrossmanFebruary 4, 2026 Physics A Greek star catalog from the dawn of astronomy, revealed By Adam MannJanuary 30, 2026 News Animals Some snakes lack the ‘hunger hormone.’ Experts are hungry to know why The gene for ghrelin is missing in serpents, yet present in other fasting reptiles Certain snakes, such as members of the Colubridae family (one shown), lack genes encoding the “hunger hormone” ghrelin and the enzyme that activates it. kuritafsheen/RooM/Getty Images By Andrea Lius 2 hours ago Share this:Share Share via email (Opens in new window) Email Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Print (Opens in new window) Print Snakes would do great on Survivor. These animals can last weeks — even months — without food. A couple of recently discovered genetic changes may help. Certain snakes and some other reptiles lack the gene encoding ghrelin, commonly known as the hunger hormone, researchers report in the Feb. 1 Open Biology. The gene encoding an essential enzyme that activates ghrelin is missing too. But ghrelin’s complicated relationship with hunger and its presence in other reptiles that can also withstand long fasts make the trend hard to interpret. Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday. The researchers’ findings are “striking,” says Todd Castoe, an evolutionary geneticist at the University of Texas at Arlington who was not involved in the work. Many scientists, including himself, had missed the “really cool pattern.”Evolutionary geneticist Rui Pinto and colleagues stumbled on the discovery when comparing the genomes of 112 reptile species, including snakes, crocodiles and chameleons, which they obtained from a public database. Genes for ghrelin and its activating enzyme were absent in 32 snake species. Surprisingly, the researchers also observed this pattern in some species of chameleons and lizards called toadhead agamas, which eat quite regularly. On the other hand, crocodiles, which can go more than a year without food — even outlasting snakes — still have both genes. Snakes’ lack of ghrelin may have nothing to do with hunger, says Pinto, of the Interdisciplinary Centre of Marine and Environmental Research in Porto, Portugal. Other studies show that mice lacking ghrelin experience no change in appetite or food intake. And in mice and humans, levels of the key activating enzyme and ghrelin’s active form rise after a meal. If ghrelin’s main function is to stimulate hunger, why would its activity surge after the sensation has been sated? To Pinto, this suggests that the absence of ghrelin in snakes probably has more to do with metabolism than hunger. Researchers have also linked ghrelin to the regulation of fat storage and response to insulin. Maybe snakes’ metabolism is just so different from mammals’ that they have no need for ghrelin, Pinto says. Other experts caution against overemphasizing ghrelin’s importance for metabolism. Like all hormones involved in appetite and satiety, ghrelin has metabolic effects, but there’s no evidence those effects are profound, says Tobias Wang, a zoophysiologist at Aarhus University in Denmark. Study author Rute Fonseca, an evolutionary geneticist at the University of Copenhagen, acknowledges that the analyses that she and her colleagues performed are not meant to tell a complete story about ghrelin’s functions. Understanding ghrelin’s many roles and how its absence impacts different animals will require more experiments. For example, Wang is curious about what will happen when researchers delete the ghrelin gene in crocodiles or give the hormone to snakes. Castoe says that such studies might reveal a thing or two about human met