dwells in dry environments, whilst the long-beaked echidna, which lives in moist environments, is intermediate between the other two monotremes. Biofluorescence In 2020, research in biofluorescence revealed that the platypus glows a bluish-green color when exposed to black light. Distribution, ecology, and behaviour The platypus is semiaquatic, inhabiting small streams and rivers over an extensive range from the cold highlands of Tasmania and the Australian Alps to the tropical rainforests of coastal Queensland as far north as the base of the Cape York Peninsula. Inland, its distribution is not well known. It was considered extinct on the South Australian mainland, with the last sighting recorded at Renmark in 1975, until some years after John Wamsley had created Warrawong Sanctuary (see below) in the 1980s, setting a platypus breeding program there, and it had subsequently closed. In 2017 there were some unconfirmed sightings downstream, outside the sanctuary, and in October 2020 a nesting platypus was filmed inside the recently reopened sanctuary. There is a population on Kangaroo Island introduced in the 1920s, which was said to stand at 150 individuals in the Rocky River region of Flinders Chase National Park before the 2019–20 Australian bushfire season, in which large portions of the island burnt, decimating all wildlife. However, with the SA Department for Environment and Water recovery teams working hard to reinstate their habitat, there had been a number of sightings reported by April 2020. The platypus is no longer found in the main part of the Murray-Darling Basin, possibly due to the declining water quality brought about by extensive land clearing and irrigation schemes. Along the coastal river systems, its distribution is unpredictable; it appears to be absent from some relatively healthy rivers, and yet maintains a presence in others, for example, the lower Maribyrnong, that are quite degraded. In captivity, platypuses have survived to 17 years of age, and wild specimens have been recaptured when 11 years old. Mortality rates for adults in the wild appear to be low. Natural predators include snakes, water rats, goannas, hawks, owls, and eagles. Low platypus numbers in northern Australia are possibly due to predation by crocodiles. The introduction of red foxes in 1845 for hunting may have had some impact on its numbers on the mainland. The platypus is generally regarded as nocturnal and crepuscular, but individuals are also active during the day, particularly when the sky is overcast. Its habitat bridges