Last Stages of Pregnancy Can Put Stumpy-Tailed Lizards at Risk

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Pregnancy poses considerable challenges to human mothers-to-be. But those pale in comparison to what expectant stumpy-tailed lizards endure. Indeed, new research on the Australian reptile reveals that as the female nears full term, her life may be in danger.

The main problem, Suzy Munns of Adelaide University reports, is that by the time of birth, the creature is carrying baby stumpies amounting to 35 percent of her body weight¿the human equivalent of bearing a six-year-old child. To make matters worse, the pregnant stumpy's body does not expand as the babies grow. As a result, the developing fetuses (stumpies give birth to between one and four young) take up more and more of their mother's body cavity, which leaves less and less room for her lungs and digestive tract.

"What I found was that their ability to breathe properly became less the further they went into the pregnancy, and in the last six to eight weeks before birth both breathing frequency and the volume of breath are reduced quite significantly," Munns remarks. By the last four weeks of the stumpy's five- to six-month pregnancy, she moves very little, making her an easy target for predators. Foraging is likewise difficult. In fact, Munns found that the stumpy-tailed lizard eats hardly anything at all.

Kate Wong is an award-winning science writer and senior editor for features at Scientific American, where she has focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for nearly 30 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home to the shores of Kenya’s Lake Turkana in search of the oldest stone tools in the world, as well as to Madagascar on an expedition to unearth ancient mammals and dinosaurs, the icy waters of Antarctica, where humpback whales feast on krill, and a “Big Day” race around the state of Connecticut to find as many bird species as possible in 24 hours. Wong is co-author, with Donald Johanson, of Lucy’s Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow her on Bluesky @katewong.bsky.social

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