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Thursday, April 21, 2022

food chain ~ dingoes as conservation tools ~ feral cats and dusky hopping mouse !

Ever seen this ….it is dusky hopping mouse – photo courtesy : Ben Moore,

Cricket World Cup is just over ~ many Indian fans travelled to Australia for witnessing the matches – now it is IPL – many players from Australia, New Zealand, West Indies, South Africa, Sri Lanka are in India representing various sides.   The dingo (Canis lupus dingo) is a free-ranging dog found mainly in Australia. Its exact ancestry is debated, but dingoes are generally believed to be descended from semi-domesticated dogs from East or South Asia, which returned to a wild lifestyle when introduced to Australia.

Contrary to popular belief, Australia may not have been as isolated for the 40,000 years prior to European colonisation as once thought, according to a new study which has found evidence of substantial gene flow between Indian populations and Australia about 4000 years ago. The research also suggests the dingo might have arrived on Australian shores about that time – along with tool technology and food processing – though other experts are sceptical.  The study, published in the journal PNAS, says it was commonly assumed that Australia remained largely isolated following initial colonisation some 40,000 years ago, though the genetic history of Aboriginal people has not been explored in detail.  Researchers of  Max Planck Institute for Evolutionary Anthropology in Germany, joined colleagues in analysing large-scale genotyping data from Aboriginal Australians, New Guineans, Island Southeast Asians and Indians that suggest a new possibility.  The researchers say this supports the view that these groups represent the descendants of an ancient southwards migration out of Africa.   The authors suggest that Indian genes might not have come directly from Indian and they are too uniformly spread across northern Aboriginal genomes to have come from European colonists.

Some are sceptical though contending - genetic data for dingoes suggests they came from Island Southeast Asia, not India. So linking the human genetic evidence to the idea that they also imported a range of new technologies and dingoes is something that needs further investigation,”  they say.  Away from dingoes, feral cats are causing devastation to more than 400 native species, according to a new survey of their impact.  A large collaboration of researchers analysed faeces and stomach contents of feral cats across the entire continent to ascertain the diets of these feline pests. What they found was bad news for our wildlife.

From a total of 49 published and unpublished data sets, the researchers determined that the menu of feral cats is more extensive than previously thought. In a similar study in Europe data from different islands around the world showed a less varied menu. "On 40 islands across the globe where feral cat diet data was available, they recorded cats killing and eating 179 species; whereas here in Australia we have 400 different species," says lead author Tim Doherty, a wildlife ecology PhD candidate at Edith Cowan University in Perth.  In Australia feral cats have already contributed to the extinction of 16 mammals. Small and medium native animals have been declining catastrophically, and huge ferals are wreaking havoc in areas like Arnhem Land.

Another quite significant finding of the study was that across the continent, where cats eat [fewer] rabbits, they eat more native small mammals.  It is called  'prey-switching', according to them.  This means that culling a local rabbit population may inadvertently lead to cats eating more of the native animals in that area.  Getting back, Dingoes may be the unlikely saviour of the native and endangered dusky hopping mouse (Notomys fuscus), new research reveals. Higher numbers of the dusky hopping mouse have been recorded in Central Australia's Strzelecki Desert, which has a healthy population of dingoes, compared to other areas the native mouse inhabits. An apex predator, the dingo seems to be offering indirect protection to the dusky hopping mouse by hunting on its predator: feral cats.  That is a two-way effect ! – the dingoes suppress cat abundance by outcompeting for food resources; cats also provide a food resource for them" says lead authour of the study, Christopher Gordon, from the University of Western Sydney.

The numbers of dingoes, cats and hopping mice were detected using nocturnal spotlight and sand plot techniques, over 47 sites. The dingoes' presence also encouraged behavioural changes in dusky hopping mice, says Christopher. With fewer feral cats around, the dusky hopping mice were less fearful of coming out to forage for food.  Christopher tested this concept by placing small feeding trays in open areas where either feral cat or dingo numbers were high. Feeding trays containing 40 hopbush seeds were filled each night before dusk, and counted the following morning. Significantly more seeds were consumed at the sites where dingoes rule.

The study provides evidence that 'size-dependant predation' occurs when dingoes are absent or in low-density, says Christopher. This is where smaller predators, such as feral cats and foxes, whittle down populations of prey species like the dusky hopping mouse, which are too small to be hunted by apex predators.  The study suggests dingoes could be introduced to areas with small mammals that are hit hardest by feral cats, which hunt more than 400 of Australia's animal species.

Dingoes as conservation tools !!!  - that takes back to the ‘food chain’ concept –  a linear sequence of links in a food web starting from "producer" species (such as grass or trees) and ending at apex predator "decomposer" species (like grizzly bears or killer whales). A food chain also shows how the organisms are related with each other by the food they eat.  Food chains were first introduced by the African-Arab scientist and philosopher Al-Jahiz in the 9th century and later popularized in a book published in 1927 by Charles Elton, which also introduced the food web concept.

Interesting indeed.

With regards – S. Sampathkumar
8th Apr 2015.

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