The study spent several weeks tracking
kangaroos and tracking their energy
needs.
Image: iStockphoto

A comparative study of the energy requirements of kangaroos and sheep has concluded roos have far less impact on the environment than once thought.

The study, quoted on the University of Sydney’s website, has given new weight to calls for the increased use of roos for everything from eco-tourism to human and pet food consumption.

Dr Adam Munn, from the university’s School of Veterinary Science, spent weeks tracking kangaroos and recording their energy needs.

"We found the kangaroos were consuming only 13 per cent as much water a day as sheep," he said.

In the rangelands, a sheep’s diet consists mainly of saltbush.

Dr Munn’s main collaborator on the project, NSW Department of Primary Industries’ Dr Steve McLeod, says sheep feeding on saltbush will drink approximately 12 litres of water a day, as opposed to kangaroos, which drink approximately 1.5 litres a day.

The study also shows kangaroos consume approximately one-third of the energy of sheep and therefore have much less of an impact on the environment, Dr McLeod said.

The researchers injected isotopes into the animals to compare their energy requirements, with a blood sample taken after 10 days.

The animals’ energy levels were then calculated by comparing the quantity of remaining isotopes.

"This showed that a kangaroo will turn over about 5000 kilojoules per day, with sheep turning over about 15 000," Dr Munn said.

As kangaroos have significantly lower energy requirements than sheep, this indicates they need less food than sheep, thus their environmental impact is lower, say the researchers.

"With climate change, most rangelands are going to need to look at diverse options for land management for sustainability," Dr Munn said.