robusta, a tapeworm which is classified as Rare under the Tasmanian Threatened Species Protection Act 1995. This tapeworm is found only in devils. In late 2020, Tasmanian devils were reintroduced to mainland Australia in a sanctuary run by Aussie Ark in the Barrington Tops area of New South Wales. This was the first time devils had lived on the Australian mainland in over 3,000 years. 26 adult devils were released into the protected area, and by late April 2021, seven joeys had been born, with up to 20 expected by the end of the year. Ecology and behaviour The Tasmanian devil is a keystone species in the ecosystem of Tasmania. It is a nocturnal and crepuscular hunter, spending the days in dense bush or in a hole. It has been speculated that nocturnalism may have been adopted to avoid predation by eagles and humans. Young devils are predominantly crepuscular. There is no evidence of torpor. Young devils can climb trees, but this becomes more difficult as they grow larger. Devils can scale trees of trunk diameter larger than , which tend to have no small side branches to hang onto, up to a height of around . Devils that are yet to reach maturity can climb shrubs to a height of , and can climb a tree to if it is not vertical. Adult devils may eat young devils if they are very hungry, so this climbing behaviour may be an adaptation to allow young devils to escape. Devils can also swim and have been observed crossing rivers that are in width, including icy cold waterways, apparently enthusiastically. Tasmanian devils do not form packs, but rather spend most of their time alone once weaned. Classically considered as solitary animals, their social interactions were poorly understood. However, a field study published in 2009 shed some light on this. Tasmanian devils in Narawntapu National Park were fitted with proximity sensing radio collars which recorded their interactions with other devils over several months from February to June 2006. This revealed that all devils were part of a single huge contact network, characterised by male-female interactions during mating season, while female–female interactions were the most common at other times, although frequency and patterns of contact did not vary markedly between seasons. Previously thought to fight over food, males only rarely interacted with other males. Hence, all devils in a region are part of a