X-ray images of two newborn woolly mammoths from the Arctic reveal details of their violent deaths: they both died after inhaling mud and suffocating.
Lyuba and Khroma are the most complete and best preserved baby mammoth specimens ever found. "This allowed us to document the changes that occur as the mammoth body develops," University of Michigan’s Daniel Fisher says in a news release. "And since they are both essentially complete skeletons, they can be thought of as Rosetta Stones that will help us interpret all the isolated baby mammoth bones that show up at other localities."
The two calves lived more than 40,000 years ago and belonged to populations 3,000 miles (4,800 kilometers) apart. Lyuba was found by reindeer herders in 2007 along the Yuribei River in northwest Siberia; Khroma was found in 2008 in permafrost near the Khroma River in northeast Siberia. In addition to fully articulated skeletons, the mummies held preserved muscle, fat, connective tissue, organs, skin, and even clotted blood inside intact blood vessels.
To avoid destroying tissue, Fisher and an international team of researchers used medical computed tomography (CT) scans to analyze their anatomy in 3D. And because of Lyuba’s size (110 pounds, or 50 kilograms), the team also turned to Ford Motor’s industrial scanner, designed to find flaws in car transmissions.
To estimate their ages when they died, the team counted daily growth layers (like tree rings) in scans of their teeth. Lyuba died 30 to 35 days after birth, and Khroma died between 52 and 57 days. They were both born in the spring. Khroma had a slightly smaller brain than a newborn elephant, suggesting a shorter gestation period for mammoths. Additionally, they found differences between the two calves that could reflect their one-month age difference: Lyuba's skull is narrower and her upper jawbones are more slender, while Khroma's shoulder blades and foot bones are more developed.
Both calves appear to have died from suffocation after inhaling mud. A solid mass of fine-grained sediment blocked air passages in the middle of Lyuba’s trunk, and sediment was also seen the throat and bronchial passages. Slightly coarser sediment was found in Khroma's trunk, mouth, and throat. Since both animals appear to have been healthy, the researchers think a "traumatic demise" is the most likely cause of their deaths. You can see the sediment in the airways of Lyuba (top) and Khroma (bottom).
If Lyuba crashed through the ice while crossing a lake during the spring melt, her reflexes may have shifted blood from the extremities to vital organs like the brain and heart, which explains the small iron phosphate nodules on the facial tissues. Since Khroma’s remains contained undigested milk in the stomach, she was nursing less than an hour before her death. She and her mother may have been on a riverbank that collapsed, which would also account for the fractured spinal column.
Images: University of Michigan Museum of Paleontology (CT images) & Francis Latreille (Lyuba’s external appearance)