section_path: Ecology and behaviour/Reproduction
section_name: Reproduction
paragraph_text: Reproduction
  
  There is evidence for at least some year-round breeding (cull records show joeys discovered in the pouch at all times of the year), although the peak breeding season was in winter and spring. They would produce up to four joeys per litter (typically two or three), carrying the young in a pouch for up to three months and protecting them until they were at least half adult size. Early pouch young were hairless and blind, but they had their eyes open and were fully furred by the time they left the pouch. The young also had their own pouches that were not visible until they were 9.5 weeks old. After leaving the pouch, and until they were developed enough to assist, the juveniles would remain in the lair while their mother hunted. Thylacines only once bred successfully in captivity, in Melbourne Zoo in 1899. Their life expectancy in the wild is estimated to have been 5 to 7 years, although captive specimens survived up to 9 years.
  
  In 2018, Newton et al. collected and CT-scanned all known preserved thylacine pouch young specimens to digitally reconstruct their development throughout their entire window of growth in their mother's pouch. This study revealed new information on the biology of the thylacine, including the growth of its limbs and when it developed its 'dog-like' appearance. It was found that two of the thylacine young in the Tasmanian Museum and Art Gallery (TMAG) were misidentified and of another species, reducing the number of known pouch young specimens to 11 worldwide. One of four specimens kept at Museum Victoria has been serially sectioned, allowing an in-depth investigation of its internal tissues and providing some insights into thylacine pouch young development, biology, immunology and ecology.