Reasons for the disappearance of tigers

The dwindling population of wild tigers has always been of great concern. While several efforts are being made to control the illegal poaching of tigers in India, the decline in the number of tigers is also strongly affected by other factors like the loss of habitat. Scientists from the Kalakkad Mundanthurai Tiger Reserve (KMTR), Tamil Nadu and the Salim Ali School of Ecology and Environmental Sciences, Puducherry have studied the natural causes that led to the near complete absence of tigers in KMTR for over two decades. The scientists believe that such an absence is linked to the low numbers of large hoofed herbivores, which are the primary prey for tigers.

They looked at how the banning of cattle grazing in the KMTR plateau affected the populations of large carnivores and their prey. They argued that ban would leave more vegetation for the prey and lead to an increase in their population. This would mean that the tiger population would increase too.

However, while there were improvements in the prey population, their density was still low. The scientists found that the plateau had large herbivores enough to only sustain around 11 tigers per 100 square km area. This study might help us better understand the complex dynamics between predators and preys in a forest.


Similar prey, but two very different necks

It was a question that dogged biologists: Why the neck? Imperial cormorants, lanky, long-necked creatures that live on the southern coasts of Argentina and Chile, spend much of their time immersed in the frigid waters of the ocean. They dive to chilly depths to hunt fish.

But the cormorants have neighbours: Magellanic penguins. Their stout, well-insulated bodies seem like a much better choice for hunting in this unforgiving environment, while the slender, exposed necks of cormorants are like gloveless hands in January. "They would lose heat," says Agustina, a researcher at the Instituto de Biologia de Organismos Marinos in Argentina. "So what's the advantage?" As it turns out, that long, flexible necks offer real benefits when you hunt like a cormorant, according to a paper published in Proceedings of the Royal Society B.

While cormorants shed heat in the ocean, this energy loss may be offset by being able to move only their head, not their whole body, when they snap up prey. Cormorants prowl among the rocks and see their prey only when they are very close, their heads shooting out to grab it. Researchers found that a cormorant uses half as much energy by just moving her head and not her whole body.

A long neck does mean a certain amount of heat is lost, and the cormorant's gawky profile is not as streamlined as a penguin's form. But in a species that moves a bit slower than penguins, the benefit of being able to hunt more efficiently may outweigh these downsides.


Developing in two generations

A study of Darwin's finches, which live on the Galapagos Islands in the Pacific Ocean, has revealed direct genetic evidence that new species can arise in just two generations. The arrival of a strange bird to a remote island in the Galapagos archipelago 36 years ago has provided direct genetic evidence of a novel way in which new species arise.

In a recent issue of the journal Science, researchers from Princeton University, USA and Uppsala University, Sweden report that the newcomer belonging to one species mated with a member of another species resident on the island, giving rise to a new species that today consists of roughly 30 individuals.

The study comes from work conducted on Darwin's finches, which live on the Galapagos Islands in the Pacific Ocean. The remote location has enabled researchers to study the evolution of biodiversity due to natural selection.



In geological terms, we're currently living in the Holocene stage of the Earth's existence; a period of time when all the elements have proven most beneficial to our species. But our unfettered growth has left a massive footprint upon our planet, and its ramifications may soon usher in a new geological epoch. Anthropocene, a short documentary produced by the ABC-TV Catalyst series, examines the characteristics and the consequences of this oncoming age.

From singular events such as the first nuclear weapons test of 1945 to the unprecedented industrialisation that's occurred in nearly every region of the world, our Earth has undergone more rampant change in recent times than any other period in its history. Geologists call this period the anthropocene.

In the midst of the climate change debate, Anthropocene examines the crisis our planet faces from a fresh perspective that is not often considered by the mainstream. To watch the documentary, visit

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