to 29% for humans. This part of the brain in humans is thought to be used for planning and analytical behaviour, leading to debate as to whether the echidna has reasoning and strategising ability. Experiments in a simple maze and with a test on opening a trap door to access food, and the echidna's ability to remember what it has learnt for over a month, has led scientists to conclude its learning ability is similar to that of a cat or a rat. The echidna shows rapid eye movement during sleep, usually around its thermoneutral temperature of 25 °C, and this effect is suppressed at other temperatures. Its brain has been shown to contain a claustrum similar to that of placental mammals, linking this structure to their common ancestor. Ecology and behaviour No systematic study of the ecology of the short-beaked echidna has been published, but studies of several aspects of their ecological behaviour have been conducted. They live alone, and, apart from the burrow created for rearing young, they have no fixed shelter or nest site. They do not have a home territory they defend against other echidnas, but range over a wide area. The range area has been observed to be between 21 and 93 ha, although one study in Kangaroo Island found the animals there covered an area between 9 and 192 ha. Overall, the mean range areas across the various regions of Australia were 40–60 ha. There was no correlation between sex and range area, but a weak one with size. Echidnas can share home ranges without incident, and sometimes share shelter sites if not enough are available for each animal to have one individually. Short-beaked echidnas are typically active in the daytime, though they are ill-equipped to deal with heat because they have no sweat glands and do not pant. Therefore, in warm weather, they change their patterns of activity, becoming crepuscular or nocturnal. Body temperatures above 34 °C (93 °F) are believed to be fatal, and in addition to avoiding heat, the animal adjusts its circulation to maintain a sustainable temperature by moving blood to and from the skin to increase or lower heat loss. In areas where water is present, they can also swim to keep their body temperatures low. The "thermoneutral zone" for the environment is around 25 °C (77 °F), at which point the metabolism needed to maintain body temperature is