April 16, 2009 9:55:07 am
Kangaroos who consume less water and energy than sheep can reduce environmental impact of farming,a recent Australian survey has found.
According to University of Sydney,the study that tracked and recorded Kangaroos energy requirements concluded that kangaroos consumed only about 13 per cent as much water as sheep and has vital implications for grazing practices.
Adam Munn,a lecturer in Sydney’s faculty of veterinary science,spent five weeks on the study,’The Australian report said in Melbourne.
He hoped his research will encourage greater uses for kangaroos. “With climate change,most rangelands are going to need to look at diverse options for land management for sustainability,” he says.
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Knowing the reduced impact of kangaroos on the environment gives graziers these options. “You could use kangaroos for eco-tourism without the environmental impact once thought,or increase the use of kangaroo for human and pet food consumption.”
A sheep’s diet consists mainly of saltbush.
“Sheep feeding on saltbush will drink around 12 litres of water a day,as opposed to kangaroos,which drink around 1.5 litres per day,” Munn said adding ‘The discrepancy between the water requirements is attributed to their different diets and bodily functions. Kangaroos are better at concentrating their urine,and sheep eat more saltbush.”
The quantities of salt in saltbush have “to be flushed out the body and this is done by drinking and urinating”.
According to the study,kangaroos also consume only one-third of the energy of sheep.
“In the past it has been thought that kangaroos used 70 per cent as much energy (as) sheep. But we’ve shown that when kangaroos and sheep are studied at the same time period,in the same environmental conditions,kangaroos only use 0.3 to
0.35 per cent of the amount of energy as sheep” Munn said.
Earlier studies calculating the energy requirements of kangaroos were based on assumptions about the resting metabolic rate of marsupials compared with non-marsupial mammals.
Researchers assumed that free-ranging kangaroos used 70 per cent of the energy of sheep. These estimates did not consider the body size of the animals,or their movements.
“This is the first study of the metabolic rate of kangaroo in the field,not in the resting state,” he said.
The researchers used isotopes to compare the animals energy requirements. “We used a doubly-labelled water method,which uses stable isotopes of hydrogen and oxygen,” Munn said.
Isotopes are atoms of the same element that have different numbers of neutrons. A blood sample is taken from the animals. “Then isotopes are introduced into the animal and you let it range freely for eight to 10 days,” he said.
A final blood sample is taken,and the animal’s energy use can be calculated comparing the quantity of isotopes in the two samples.
“The kangaroo will turn over around 5000 kilojoules per day,and a sheep will turn over about 15,000” Munn said.
Knowing the energy requirements of kangaroos and sheep allows researchers to calculate the amount of plant each animal will eat. These calculations were the next step in Munn’s research.
“If you know what they are feeding on,you can measure the standard energy content of the food they are eating,” he said.
“We can then look at how much energy they need from a real,on-the-ground food source” he added.
As kangaroos have significantly lower energy requirements than sheep,it’s expected they will need less food than sheep and their environmental impact will be lower. “It’s important to get the message out there that kangaroos may not have as great an impact as people once thought,” Munn said.
Munn’s research has been partially funded by the NSW,South Australian and West Australian state bodies controlling kangaroo management,NSW Western Catchment Management Authority,the NSW Department of Primary Industries and the National Geographic Society.
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