This Animal Can Get Pregnant While Still Pregnant
Thu, September 29, 2022

This Animal Can Get Pregnant While Still Pregnant


Many animals hide fascinating skills humans have yet to discover. Since the 1960s, scientists have been trying to investigate the swamp wallabies’ unusual reproductive tactics after they noticed three females engaging in sex very late into their pregnancies. But, Brandon Menzies, a biologist at the University of Melbourne, and his colleagues tackled the mystery using modern imaging technology. And the findings confirmed the decades-long hypothesis that swamp wallabies can conceive another baby while they are still pregnant.


Credits: Nel_Botha-NZ via Pixabay


In 2015, the researchers captured a small troupe of wild wallabies and monitored them through several pregnancies via a portable ultrasound machine. While performing sonograms on swamp wallabies wasn’t easy, the team found a way to monitor the progress of wallaby embryos by calculating their age based on size alone. However, two female wallabies suffered miscarriages during the study but both of them were found harboring embryos that looked almost two weeks old 10 days later. This suggests that the animals were conceived while the older fetuses were still gestating.


Credits: Cazz via Flickr


Thus, the study published in Proceedings of the National Academy of Sciences concluded that female swamp wallabies (Wallabia bicolor) can start a second pregnancy before finishing their first. According to Smithsonian Mag, the official journal published by the Smithsonian Institution in Washington, D.C., these marsupials can gestate nonstop throughout their entire adulthoods by alternating embryo implantations between two reproductive tracts. 

“As soon as they reach sexual maturity, these females are—perhaps, unfortunately—pregnant all the time,” Menzies said. 


Credits: Cazz via Flickr


The researchers also discovered that any new embryo that’s already been conceived will enter a state of dormancy because the mother swamp wallabies have to minimize the energetic demands so she can focus on churning out lots of nutrient-rich milk. Elisa Zhang, a reproductive biologist at Stanford University who wasn’t involved in the study, stated that overlapping pregnancies could also act as a childbearing insurance policy. If a newborn joey dies, the mother has a backup waiting to take its place.




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