Swiss research shows why there are no kangaroos in Bali

There are no kangaroos in Asia due to the humid climate. That’s the conclusion of a new study by Swiss researchers in the journal Science. To do this, they used a new model to study 20,000 species of vertebrates.

This finding is important for understanding why certain introduced animal species become invasive, according to a statement from the Swiss Federal Institute of Technology in Zurich (ETH Zurich) on Friday.

The exchange of species between continents is now regular and at an alarming rate as humans move animals and plants across the planet. “In the current biodiversity crisis, this may help better assess the impacts of human-induced invasions,” study co-author Alexander Skeels said in the statement.

There is barely 20 kilometers between the islands of Bali and Lombok. However, the nature on these two neighboring islands is very different. While Australian species such as kangaroos live in Bali, you will not find them in Lombok. The so-called Wallace Line runs between the two islands: this marks the westernmost distribution of Australian animal species.

Until now not all causes of this dividing line were known. A connection to plate tectonics was suspected. 45 million years ago, the Australian plate began to drift north, pushing under the Eurasian plate. This brought two land masses that were previously far apart closer together. However, this does not explain why more species found their way from Asia to Australia than the other way around.

The researchers have now discovered that the climate in the regions of origin plays a major role. Animals from Asia successfully spread to Australia via the Indonesian islands because these islands had a humid tropical climate with which they were already familiar and in which they could thrive. The Australian species, on the other hand, had adapted to a cooler and increasingly drier climate. As a result, they were less able to gain a foothold on the tropical islands. (sda)