With the IPCC predicting global temperature rises of 0.2°C per decade, many species are facing an uncertain future. How they will respond and whether they have the flexibility to adapt is unclear. Alexander Riek from the University of Göttingen, Germany, and Fritz Geiser from the University of New England, Australia, explain that temperature is already known to have a dramatic effect on animals, with related creatures from higher latitudes tending to be larger than animals from the tropics. But what effect could temperature have on an animal’s development? As minute baby marsupials can be exposed to a wide range of temperatures during development, the duo decided to find out how developing at different temperatures affects dunnart pups (p. 1552).
Explaining that dunnart pups are born 12 days after fertilization into a rather exposed open pouch, the duo collected new dunnart mums and transferred them to temperature-controlled rooms, at either 16 or 22°C, until their youngsters were weaned 2 months later. Measuring the independent youngsters’ vital statistics, the duo found that the cold-reared pups had longer bodies and heads than their warm-reared counterparts: even though the animals weighed the same regardless of the temperature. Also, the team found significant differences in the animals’ metabolic rates depending on the temperature to which they were exposed during development. At cooler temperatures the cold-reared animals had a lower metabolic rate than the warm-reared animals, although the two groups had essentially the same metabolic rate at 30°C. Finally, when the team assessed how often the youngsters became torpid to conserve energy, they found that at an environmental temperature of 16°C, the cold-reared animals used torpor more often and for longer than the warm-reared youngsters.
So, the young dunnarts had responded quite dramatically to the colder conditions, which not only affected their body shape but also had an effect on their metabolism. Riek and Geiser say, ‘A rapid adjustment to environmental conditions... could be a major determinant in a species’ ability to cope with climate change’, and they suspect that animals that hibernate or conserve energy through torpor may have sufficient metabolic versatility to be able to adjust rapidly to environmental change. ‘Animals employing some form of energy-saving mechanism stand a better chance of surviving during adverse climatic or environmental conditions’, they say.