Koalas need to balance their requirements for food and shadeSubmitted by editor on 1 April 2014.
You would think that once a koala found a good tree for feeding, they would stay put. This is not the case according to a new study by Mathew Crowther and colleagues.
By fitting 40 koalas with portable GPS units, the research team could locate where the koalas were every four hours. Their results provided some new insights on how koalas use the landscape. The koalas use very different trees during day and night, and different trees as temperatures became hotter. Koalas, during the day, and at warmer temperatures, used larger trees, with more shelter and in gullies. These were often non-food trees like Belah and Kurrajong. This meant that koalas had to sacrifice feeding in their favourite trees in the area, such as River Red Gums and Bimble Box, to find trees to protect them from the heat.
The cost for those koalas not having access to these shelter trees could be enormous, and in 2009, a weeklong heat-wave of temperatures in excess of 40oC caused around a quarter of the population to perish. This could be even more extreme in the future when periods of excessive heat are predicted to increase in south eastern Australia.
Crowther M. S., Lunney D., Lemon J., Stalenberg E., Wheeler R., Madani G., Ross K. A. & Ellis M. (2014) Climate-mediated habitat selection in an arboreal folivore. Ecography. DOI: 10.1111/j.1600-0587.2013.00413.x