As if Australians didn't have enough pesky species to worry about, a new study finds their country is effectively crawling with feral cats.
Research by more than 40 of Australia's top environmental scientists - and drawing on evidence from nearly 100 studies - has concluded feral cats cover more than 99.8 per cent of Australia's land area, including almost 80 per cent of the area of its islands.
"Australia's total feral cat population fluctuates between 2.1 million when times are lean, up to 6.3 million when widespread rain results in plenty of available prey," said study author Dr Sarah Legge, of the University of Queensland.
The study also looked at what caused variation in cat densities, finding rates were especially higher on smaller islands.
Inland areas with low rainfall and more open vegetation had higher cat densities than most coastal, wetter areas, but only after extensive rain.
"Our study highlights the scale and impacts of feral cats and the urgent need to develop effective control methods, and to target our efforts in areas where that control will produce the biggest gains."
New Zealand faces a similar problem with an estimated 2.5 million feral cats - pests that have been blamed for wiping out six endemic bird species and more than 70 localised subspecies.
A recent study found that, by 2070, climate change could widen the range of areas suitable for feral cats, bringing them closer to conservation hotspots in new places like the central North Island, and the top and central areas of the South Island.
Why chooks aren't so bird-brained
Chickens aren't as bird-brained as we believe them to be, with researchers finding they have distinct personalities and can outmanoeuvre one another.
But they know their place in the pecking order and can reason by deduction - an ability that humans develop by the age of seven.
"Chicken intelligence" was therefore unnecessarily underestimated and overshadowed by other avian groups, say scientists who have just reported their findings in the journal Animal Cognition.
"They are perceived as lacking most of the psychological characteristics we recognise in other intelligent animals and are typically thought of as possessing a low level of intelligence compared with other animals," said study author Lori Marino, a senior scientist with the US-based Someone Project.
"The very idea of chicken psychology is strange to most people."
Research has already shown that chickens have also some sense of numbers, with experiments with newly hatched domestic chicks revealing they can discriminate between quantities.
They also had an idea about "ordinality" - or the ability to place quantities in a series, as demonstrated by another experiment.
Five-day-old domestic chicks presented with two sets of objects of different quantities disappearing behind two screens were able to successfully track which one hid the larger number by apparently performing simple arithmetic in the form of addition and subtraction.
Weirdest galaxy in the universe?
Approximately 359 million light-years away from Earth, there's a galaxy with an innocuous name - PGC 1000714 - that doesn't look quite like anything astronomers have observed before.
New research provides a first description of a well-defined elliptical-like core surrounded by two circular rings - a galaxy that appears to belong to a class of rarely observed, "Hoag-type" galaxies.
Hoag-type galaxies are round cores surrounded by a circular ring, with nothing visibly connecting them.
The majority of observed galaxies are disc-shaped like our own Milky Way, and galaxies with unusual appearances give astronomers unique insights into how galaxies are formed and change.
While the researchers found a blue and young (0.13 billion years) outer ring, surrounding a red and older (5.5 billion years) central core, they were surprised to uncover evidence of a second inner ring around the central body.
To document this second ring, researchers took their images and subtracted out a model of the core.
This allowed them to observe and measure the obscured, second inner ring structure.
"We've observed galaxies with a blue ring around a central red body before, the most well-known of these is Hoag's object," explained study co-author Patrick Treuthardt, an astrophysicist at the North Carolina Museum of Natural Sciences in the US.
However, the unique feature of the galaxy was what appears to be an older diffuse red inner ring, he said.
"Whenever we find a unique or strange object to study, it challenges our current theories and assumptions about how the universe works - it usually tells us that we still have a lot to learn."