Rattlesnakes silently shook their tails before evolving rattles

Rattlesnakes silently shook their tails before evolving rattles:

Shake, rattle and strike. It is possibly one of the most terrifying sounds in the animal kingdom, but how the rattlesnake evolved its chilling warning signal is a mystery. Now a study suggests the rattle evolved long after the tail-shaking behaviour.

The evolution of the rattle has baffled scientists because, unlike other complex physical traits like eyes or feathers, it has no obvious precursor or intermediate stage.

“There is no half-rattle,” says David Pfennig at the University of North Carolina at Chapel Hill.

One theory is that ancestral snakes shook their tails to warn off predators, and the noise-making rattle – which is made of a series of hollow, modified keratin scales – evolved later as a more effective signal that took advantage of the pre-existing behaviour. This may be why many rattle-less snakes also shake their tails.

To test the idea, Pfennig and his colleague prodded 56 species of venomous and non-venomous snakes with a fake rat on a stick and recorded their defensive tail shakes.

They found that the more closely related a snake was to the rattlesnake, the more similar its tail shake was in speed and duration.

“This suggests the defensive tail vibration came first, perhaps as a physiological response to stress, and that became a reliable cue to predators that the snake was about to strike,” says Pfennig. “When the rattle evolved, it became an even more effective signal.”

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New fossil shows birds and pterosaurs flew side-by-side

New fossil shows birds and pterosaurs flew side-by-side:

Some pterosaurs were the largest flying animals ever seen on Earth. These extinct flying reptiles that lived above the dinosaurs’ heads could grow wingspans of up to 11 metres and dominated the skies of the late Cretaceous period, the last age of the giant reptiles.

Earlier pterosaurs are also known to have been as small as a metre across, but few such fossils from this period have been found. This has led to the idea that small-bodied pterosaurs disappeared because they were out-competed by early birds who forced them to evolve into much bigger animals.

But an exciting new pterosaur fossil has added to the growing body of evidence that small pterosaurs did continue to exist alongside their much bigger cousins.

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Blood-Guzzling Brain Key To Evolution Of Human Intelligence

Blood-Guzzling Brain Key To Evolution Of Human Intelligence:

The human brain is a fuel hog, and that, it turns out, is key to how our intelligence evolved. It has long been believed that the evolution of human intelligence was simply related to increasing brain size, but a team of researchers from South Africa and Australia have overturned that assumption.

By calculating how blood supply to the brains of human ancestors changed over time, the researchers were able to show that the human brain not only evolved to become larger, but also more blood-thirsty. And the need for blood outpaced the volume increase of the brain itself.

“Brain size has increased about 350% over human evolution, but we found that blood flow to the brain increased an amazing 600%,” project leader Roger Seymour, from the University of Adelaide, said in a statement. “We believe this is possibly related to the brain’s need to satisfy increasingly energetic connections between nerve cells that allowed the evolution of complex thinking and learning.”

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Tasmanian devils are evolving rapidly to fight their deadly cancer

Tasmanian devils are evolving rapidly to fight their deadly cancer:

FOR THE PAST 20 years, an infectious cancer has been killing wild Tasmanian devils, creating a massive challenge for conservationists. But new research, published today in Nature Communications, suggests that devils are evolving rapidly in response to their highly lethal transmissible cancer and that they could ultimately save themselves.

Cancer is usually a disease that arises and dies with its host. In vertebrates, only two known types – Canine Transmissible Venereal Cancer in dogs and Devil Facial Tumour Disease (DFTD) – have taken the extraordinary evolutionary step of becoming transmissible. These cancers can grow not just within their host but can spread to other individuals. Because the cancer cells are all descendants of one mutant cell, the cancer is effectively immortal.

To grow in the new host, the tumour cell must evade detection and rejection by the immune system. Both the devil and dog transmissible cancers have sophisticated mechanisms for hiding from the host’s immune system. Our research suggests that the devil is nevertheless evolving resistance to the disease.

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Meet some of the species we’ve found in 2016

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Single mutation changes a species’ mating

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New theoretical work suggests women co-opted orgasms for happy endings

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Cactus bugs compensate for lack of weapons with bigger balls

Cactus bugs compensate for lack of weapons with bigger balls:

Species: Leaf-footed cactus bugs (Narnia femorata)

Habitat: prickly pear cacti around the southern US and Central America

Silver linings can be hard to come by, but for the leaf-footed cactus bug – who appear to grow larger testes in response to losing their sparring weapons – life could certainly be worse.

Leaf-footed cactus bugs – or Narnia femorata – generally grow to between 14 and 19 millimetres and live on prickly pear cacti around the southern US and Central America. The insects feed on the fruit and joints of the cacti on which they reside – and fight their existential battles.

Males compete over territory and mates by swivelling around and grappling one another using their barbed hind legs in an attempt to wrestle and kick their rival off the cactus pad arena.

Normally, when a wild animal loses its weapon the outcome is poor, if not fatal, as it can no longer compete for resources.

But a study by Paul Joseph and Christine Miller at the University of Florida in Gainesville suggests that for the leaf-footed cactus bug, disarmament leaves the insects far from helpless.

“Males may encounter problems that negatively affect weapon growth during development to adulthood, like self-amputating a limb as a self-defence mechanism to escape predators,” says Joseph. “We wanted to see if these males, who dropped a weapon, allocate more resources to another trait that increases reproductive success – testes.”

Joseph and Miller divided young males into control and weapon-less groups and allowed them to reach sexual maturity. They found that young males that dropped a weapon during development grew 20 per cent larger testes than the control groups.

“Larger testes create more sperm, so males with larger testes – but lacking a weapon – may be able to compensate by fertilising more eggs in the few mating opportunities they do achieve than males with intact weapons but smaller testes,” says Joseph. The team presented its findings at the 53rd Annual Conference of the Animal Behaviour Society in Missouri on 31 July.

The existence of such a trade-off is intriguing, says Clint Kelly at the University of Quebec in Montreal, Canada.

“If larger weaponry increases a male’s mating success, and larger testes increase a male’s fertilisation success, then why do males not invest more into each of these traits at the expense of some other non-sexually-selected trait, such as middle legs?” he asks.

“In all likelihood it does not pay for a male to increase investment in both traits concurrently, perhaps because males with larger weaponry face reduced levels of sperm competition and thus have no need to boost the size of their ejaculates, which are energetically expensive to produce.”

Kelly says the study will help identify whether this strategy only occurs in cactus bugs or “is a deeply rooted developmental strategy among animals”.

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Welcome to the age of ancient DNA sequencing

New tech gives us a sharper view of how people lived 12,000 years ago. sci tech news Continue reading Welcome to the age of ancient DNA sequencing

Orangutan learns to mimic human conversation for the first time

Orangutan learns to mimic human conversation for the first time:

An orangutan has shown an ability to emulate human speech for the first time — a feat that gets us closer to understanding how human speech first evolved from the communications of ancestral great apes.

‘Rocky’ the ginger ape has astonished experts by producing sounds similar to words in a “conversational context”.

“This opens up the potential for us to learn more about the vocal capacities of early hominids that lived before the split between the orangutan and human lineages to see how the vocal system evolved towards full-blown speech in humans,” says lead researcher Adriano Lameria, from the University of Durham, UK.

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