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 weightthe 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.