Island lizards less scared of people


This video is called Marine iguanas of the Galapagos islandsBBC wildlife.

From Nature:

Islands make animals tamer

Lizard study supports Darwin‘s hunch that lack of predators leads to unwatchful behaviour.

Ed Yong

08 January 2014

When Charles Darwin visited the Galapagos Islands, he noted that many of its animal inhabitants were so unafraid of people that “a gun is here almost superfluous”. He swatted birds with his hat, pulled the tails of iguanas and sat on giant tortoises.

These antics fuelled his famous idea that animals become tame when they live on remote, predator-free islands. Now, William Cooper Jr of Indiana University–Purdue University in Fort Wayne has tested Darwin’s hypothesis on 66 species of lizards from around the world and found that island dwellers tended to be more docile than their continental relatives — the strongest evidence yet for this classic idea. The results are published this week in Proceedings of the Royal Society B1.

Several studies and unpublished reports have shown that particular species are more approachable on islands where there are fewer predators, or quicker to flee on islands that contain introduced hunters such as feral cats. But despite this largely anecdotal evidence for island tameness, “no one has ever established that it’s a general phenomenon in any group”, says Cooper. “We showed that for a large prey group — lizards — there really is a significant decline in wariness on islands.”

Taming of the few

Island tameness is an old idea, but there have been few tests of it,” says Dan Blumstein, a behavioural biologist at the University of California, Los Angeles. “This is a needed paper that convincingly shows some of the drivers of island tameness in lizards.”

Cooper and his colleagues scoured past studies and collated data on the distance at which lizards start to flee when approached by a researcher. They took a conservative approach, discarding studies in which researchers had pointed at the lizards, walked towards the animals faster or slower than a particular fixed speed, or studied populations that were habituated to humans.

Cooper and his team ended up with data for 66 species, from the Eurasian common lizard (Zootoca vivipara) to the Galapagos marine iguana (Amblyrhynchus cristatus). The results clearly showed that humans can get closer to island-dwelling lizards than to mainland ones, and that lizards become more approachable on islands that are farther from the mainland.

Island ecology is so important that it overrides any effect of evolutionary history, Cooper and his co-authors say. They also showed that even closely related lizard species have different escape behaviours depending on where they live, and that their evolutionary relationships were mostly irrelevant.

The results do not explain why island lizards are tamer than those on the mainland, although the relative lack of island predators is the most likely reason. Animals with skittish dispositions can needlessly abandon valuable resources, and natural selection would be expected to weed out such responses if predators are rare or absent.

Cooper wants to test this idea, but says that it is hard to get decent data on the numbers, densities and types of predators on different islands.

See also here. And here.

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Falkland Islands wolves mystery solved


Old Falkland wolf family tree

From Wildlife Extra:

Mystery solved – Where did Falkland Islands wolves come from?

Ancient DNA solves 320-year-old mystery

March 2013. University of Adelaide researchers have found the answer to one of natural history’s most intriguing puzzles – the origins of the now extinct Falkland Islands wolf and how it came to be the only land-based mammal on the isolated islands – 460km from the nearest land, Argentina.
Previous theories have suggested the wolf somehow rafted on ice or vegetation, crossed via a now-submerged land bridge or was even semi-domesticated and transported by early South American humans.

Darwin questions

The 320-year-old mystery was first recorded by early British explorers in 1690 and raised again by Charles Darwin following his encounter with the famously tame species on his Beagle voyage in 1834.

New stuffed specimen found in New Zealand

Researchers from the University’s Australian Centre for Ancient DNA (ACAD) extracted tiny pieces of tissue from the skull of a specimen collected personally by Darwin. They also used samples from a previously unknown specimen, which was recently re-discovered as a stuffed exhibit in the attic of Otago Museum in New Zealand.

16,000 years ago

The findings concluded that, unlike earlier theories, the Falkland Islands wolf (Dusicyon australis) only became isolated about 16,000 years ago around the peak of the last glacial period.

“Previous studies used ancient DNA from museum specimens to suggest that the Falkland Islands wolf diverged genetically from its closest living relative, the South American maned wolf (Chrysocyon brachyurus) around seven million years ago. As a result, they estimated that the wolf colonised the islands about 330,000 years ago by unknown means,” says Associate Professor Jeremy Austin, Deputy Director of ACAD and co-lead author with Dr Julien Soubrier.

“Critically, however, these early studies hadn’t included an extinct relative from the mainland, the fox-like Dusicyon avus. We extracted ancient DNA from six specimens of D. avus collected across Argentina and Chile, and made comparisons with a wide group of extinct and living species in the same family.”

ACAD’s analyses showed that D. avus was the closest relative of the Falkland Islands wolf and they separated only 16,000 years ago – but the question of how the island colonisation came about remained. The absence of other mammals argued against any land bridge connection to the mainland.

Eureka moment

“The Eureka moment was finding evidence of submarine terraces off the coast of Argentina,” says study leader Professor Alan Cooper. “They recorded the dramatically lowered sea levels during the Last Glacial Maximum (around 25-18,000 years ago).”

“At that time, there was a shallow and narrow (around 20km) strait between the islands and the mainland, allowing the Falkland Islands wolf to cross when the sea was frozen over, probably while pursuing marine prey like seals or penguins. Other small mammals like rats weren’t able to cross the ice.”

The study was published in Nature Communications.

Chinese dinosaur age bird discovery


This video is called The Fabulous Chinese Fossils— Chaoyang, Liaoning Province.

Sulcavis geeorum skull, photo credit: Stephanie Abramowicz

By Alan McStravick for redOrbit.com – Your Universe Online:

First Fossil Bird Discovered With Teeth For A Tough Diet

January 7, 2013

A trip to the Galapagos islands will bring you face to face with 14 closely related species of finch that Charles Darwin discovered on his adventure abroad in the 1830s. The finches he noted, still referenced in essentially every biology textbook, had beak sizes of varying lengths and sizes. This was true of both the ground- and tree-dwelling birds, and Darwin postulated that differing diets might have required the birds’ unique beaks for their specialized feeding tasks.

It was these birds, catalogued in 1835, that first helped Darwin to arrive at his theory of evolution. He was able to realize that each of the finch species had originally arisen from one ancestral form and that each of the successive forms – with their individual ecological niches and diets – were what he considered the most perfect examples of adaptive radiation, the process where one species undergoes several distinct changes to survive and thrive in a wider variety of habitats.

If Darwin had lived some 121-125 million years ago, he might have experienced the same sense of wonder at the site

rather: sight

of a Sulcavis geeorum, a species of early bird that existed in the Liaoning Province of what is now modern-day China. It was here that a new fossil discovery was made showing that these early ancestors of the dinosaurs

This should be “descendants of the dinosaurs”. Dinosaurs were ancestral to birds; not the other way round.

had evolved teeth adapted to their specialized diets.

In a report of the finding published in the latest issue of the Journal of Vertebrate Paleontology, researchers say they believe that S. geeorum existed on a so-called ‘durophagous diet’, one that included lots of prey with hard exoskeletons such as insects or crabs.

S. geeorum was an enantiornithine bird, a primitive group of early birds that were abundant in the Mesozoic era and carried over into the Cretacious.

Cretaceous

With the discovery of S. geeorum, researchers are enjoying their own Darwin-like moment as they see this discovery as representing a huge leap forward in the known diversity of tooth shape in early birds. This diversity of shape also leads them to believe that they may have stumbled upon an as yet unrecognized degree of ecological diversity.

According to the research team, S. geeorum is the first fossilized bird discovery that has ornamented tooth enamel. Looking back to the specific dinosaurs from which birds are believed to have evolved, researchers find that their tooth structure was specialized mainly for a carnivorous diet. The enanitiornithine family of birds have undergone the most minimal tooth reductions from their dinosaur cousins compared to any other extinct or extant groups of birds, and they also displayed a wide diversity of individual dental patterns.

In this newest enantiornithine discovery, researchers say that they have discovered a robust set of teeth that are marked with grooves on the inside surface. It is from these grooves, they hypothesize, that the teeth received their strength that allowed them to ingest harder food items.

“While other birds were losing their teeth, enantiornithines were evolving new morphologies and dental specializations. We still don’t understand why enantiornithines were so successful in the Cretaceous but then died out – maybe differences in diet played a part,” according to Jingmai O’Connor, lead author of the new study. One thing that is known is that until this discovery, no previous known bird species had preserved ridges, striations, serrated edges, or any other form of dental ornamentation.

“This study highlights again how uneven the diversity of birds was during the Cretaceous. There are many more enantiornithines than any other group of early birds, each one with its own anatomical specialization,” said the study’s co-author Luis Chiappe, from Natural History Museum of Los Angeles County.