Mercury Poisoning Makes Birds Act Homosexual

Metal may influence sexual development in white ibises, expert says.

White ibises perch in Galveston Bay near Smith Point, Texas (file photo).

Photograph by Joel Sartore, National Geographic

Christine Dell'Amore

Male birds that eat mercury-contaminated food show "surprising" homosexual behavior, scientists have found.
In a recent experiment in captive white ibises, many of the males exposed to the metal chose other males as mates.
These "male-male pairs did everything that a heterosexual pair would do," said study leader Peter Frederick, a wildlife ecologist at the University of Florida in Gainesville.
"They built their nest, copulated together, stayed together on a nest for a month, even though there were no eggs—they did the whole nine yards."
(Related: "Homosexual Activity Among Animals Stirs Debate.")
Wild white ibises—among the most common birds in Florida's Everglades—are exposed daily to mercury through their diets of crustaceans and other small invertebrates.
The prey animals take up mercury that's long seeped into the Everglades as a byproduct of industrial processes such as waste incineration.
Recent pollution-control measures have "grossly reduced" the contamination, Frederick said. Even so, the new study shows that ibises experience "fairly major reproductive problems at pretty low levels of [mercury]."


Contaminated Birds Produce Fewer Babies
During the five-year experiment, Frederick and colleague Nilmini Jayasena divided 160 young captive white ibises into four groups of equal numbers of males and females.
During the study period, male and female birds were allowed to choose their mates—an experimental first, according to the study authors.
"All other studies that involve reproduction in birds took a male and a female and put them in a cage," Frederick said. "Our finding, while novel, is the first time anybody's looked for it."
Starting at around 90 days of age, each of three groups was fed a diet containing either low, medium, or high amounts of mercury, based on a realistic range of exposures in the wild. A fourth control group ate mercury-free food.
Once the birds had reached sexual maturity at around a year old, homosexual bonding increased in all three groups exposed to mercury. This behavior led to a 13 to 15 percent decline in the number of young, compared to the mercury-free control group.
The metal also impacted heterosexual couples. Overall, female birds exposed to mercury yielded 35 percent fewer babies than the control group.
(Related: "Mercury Pollution's Oldest Traces Found in Peru.")
The biological mechanism for how the metal causes homosexual actions is not totally understood, Frederick added.
Mercury is a known endocrine disruptor—a substance that mimics or blocks the production of natural estrogen. In this case, exposed male birds' bodies produced more estrogen than testosterone as compared with control birds.
(See "Weed Killer Makes Male Frogs Lay Eggs.")
Though hormones can affect sexual behavior, estrogen or testosterone alone usually don't influence how a bird chooses a mate. This makes Frederick speculate that mercury exposure during the birds' sexual development may play a role.


Mercury Mysteries Remain
Many unknowns remain about the study and mercury's effects, Frederick warned.
The team did not have funding, for example, to examine whether taking mercury out of the birds' diets would stop the homosexual behavior.
But "my suspicion is none of the effects we saw are likely to be permanent," Frederick said. In general, mercury flushes from a bird's body within weeks if the animal isn't consistently exposed.
Frederick also emphasized that the study has no ramification for humans.
"There's a great tendency to extrapolate this study in an offhand fashion to mean, Oh if you eat mercury, you're going to be gay," he said.
In addition, the researchers can't say for sure whether homosexual behavior occurs in wild birds exposed to mercury. (See bird pictures.)
But at least one expert praised the white ibis study for showing a plausible effect of mercury poisoning in the wild.
One of the "great frustrations" for scientists is lab studies on environmental contamination that don't predict what happens in the wild, Lou Guillette, a zoologist at the Medical University of South Carolina, said in a statement.
"So a study like this that looks at environmentally appropriate levels of mercury is probably the most powerful kind of study to tell us what's going on in the real world," said Guillette, who was not part of the research.
Study author Frederick added that the research "gives us a very clear prediction to test—to get out and see whether there are males pairing with males in nature."
"This study badly needs to be replicated."

(From National Geographic Daily News)

'Left-handed' coiling snails survive more snake attacks

By Victoria Gill Science and nature reporter, BBC News

Snails with shells that coil anti-clockwise are less likely to fall prey to snakes than their clockwise-coiling cousins, scientists have discovered.

The arrangement of the snakes' teeth makes it difficult for the reptiles to grasp these "left-handed" snails.
The effect of this advantage on the survival of Satsuma snails is so great, say the researchers, that they could separate into a distinct species.
Biologists in Japan report the finding in the journal Nature Communications.

Angle of attack
Satsuma snails come in two forms: those which have shells that coil anti-clockwise, considered sinistral or "left-handed" and those that coil clockwise, considered "right-handed".
Land snails copulate face-to-face, and a snail with a reverse-coiled shell has its whole body reversed - including the position of its genitals.
This means that oppositely coiled individuals are anatomically incompatible when it comes to mating, so the scientists were puzzled as to why "reverse-coiled" snails continued to survive and evolve.

The arrangement of the snake's teeth makes it difficult to grasp the snails.

To investigate, the team, led by Masaki Hoso from Tohoku University in Sendai, set up "predation experiments".

They observed snail-eater snakes' (Pareas iwasaki) as they attempted to eat the snails.
To consume the soft-bodied molluscs, the predators had to extract them from their shells.
"When attacking, the snake always tilts the head leftward," Dr Hoso told BBC News.
The snake grasped the snail with its upper jaw and inserted its lower jaw into the shell to extract the soft body.

The "right-handedness" of this sequence of movements, Dr Hoso explained, means that the snake "cannot grasp [left-handed] or sinistral snails well".

The scientists wrote: "This study illustrates how a single gene for reproductive incompatibility could generate a new species by natural selection."

(From BBC News)

Giant fossil bird found on 'hobbit' island of Flores

By Emma Brennand Earth News reporter

Artist’s impression of the size of the giant stork next to a Homo floresiensis hobbit

A giant marabou stork has been discovered on an island once home to human-like 'hobbits'.

Fossils of the bird were discovered on the Indonesian island of Flores, a place previously famed for the discovery of Homo floresiensis, a small hominin species closely related to modern humans.
The stork may have been capable of hunting and eating juvenile members of this hominin species, say researchers who made the discovery, though there is no direct evidence the birds did so.
The finding, reported in the Zoological Journal of the Linnean Society, also helps explain how prehistoric wildlife adapted to living on islands.

Tall and heavy
The new species of giant stork, named Leptoptilos robustus, stood 1.8m tall and weighed up to 16kg researchers estimate, making it taller and much heavier than living stork species.

Palaeontologist Hanneke Meijer of the Smithsonian National Museum of Natural History in Washington DC, and affiliated to the National Museum of Natural History in Leiden, the Netherlands, made the
discovery with colleague Dr Rokus Due of the National Center for
Archaeology in Jakarta, Indonesia.

Finding large birds of prey is common on islands, but I wasn't expecting to find a giant marabou stork Palaeontologist Hanneke Meijer

They found fossilised fragments of four leg bones in the Liang Bua caves on the island of Flores.

The bones, thought to belong to a single stork, are between 20,000 to 50,000 years old, having been found in sediments dating to that age.
The giant bird is the latest extreme-sized species to be discovered once living on the island, which was home to dwarf elephants, giant rats and out-sized lizards, as well as humans of small stature.

"I noticed the giant stork bones for the first time in Jakarta, as they stood out from the rest of the smaller bird bones. Finding large birds of prey is common on islands, but I wasn't expecting to find a giant marabou stork," Dr Meijer told the BBC.
Only fragments of wing bones were found, but the researchers suspect the giant stork rarely, if at all, took flight.

Instead, the size and weight of its leg bones, and the thickness of the bone walls, suggest that the now extinct stork was so heavy that it lived most of its life on the ground.
It is thought to have evolved from flying storks that colonised the relatively isolated island.

Map showing the location of the Liang Bua caves on the island of Flores

"Flores has never been connected to mainland Asia and has always been isolated from surrounding islands. This isolation has played a key role in shaping the evolution of the Flores fauna," says Dr Meijer.
Many species on the islands evolved into either giants or dwarfs.
This phenomenon is known as the "island factor", and is thought to have been triggered by few mammalian predators being on the island. That led to abundant prey species becoming smaller, and other predators becoming larger.

"Larger mammals, such as elephants and primates, show a distinct decrease in size, whereas the smaller mammals such as rodents, and birds, have increased in size," explains Dr Meijer.
Among the giants evolved the giant stork, and the giant rat, Papagomys armandvillei, as well as Komodo dragons, the largest surviving species of lizard.
Dwarf species included the dwarfed elephant, Stedgodon florensis insularis, and the human species , popularly known as the 'hobbit' H. floresiensis.

BIG BIRDS More pictures of the bones of the now extinct giant stork (pictured above) can be viewed at the Zoological Journal of the Linnean Society (subscription required) Remains of the earliest known pelican, including a preserved beak, were discovered earlier this year in France Watch video of modern storks and other long-legged wading birds

Indeed, the remains of the giant stork were found in the same section of cave as the remains of H. floresiensis.
Discovered in 2004, H. floresiensis is thought to be a new human-like species standing just 1m tall, which survived until around 17,000 years ago.

It is thought to be descended from a prehistoric species of human - perhaps H. erectus - which reached island South-East Asia more than a million years ago.
"The status of this human contemporary has been subject of intense debate since its discovery," says Dr Meijer. "But in my opinion, the associated fauna is crucial in understanding the evolution of H. floresiensis."
The distinct difference in size between the 1.8 m-tall giant stork L. robustus and 1m-tall the tiny hominin H. floresiensis raises some interesting questions.

Would the hominin have eaten the giant stork?
Direct evidence of H. floresiensis 's diet is hard to come by, but it is suspected of hunting animals on the island for meat.
However, modern marabou storks mainly eat carrion, but they do take fish, frogs, and small mammals and birds.
So would the giant stork have eaten the hominin?

A modern, smaller marabou stork (Leptoptilos crumeniferus)

"Whether or not this animal may have eaten hobbits is speculative: there is no evidence for that," Dr Meijer told the BBC.
"But can not be excluded either."
The giant storks towered over the hobbits.
More importantly, juvenile hobbits were no bigger than giant rats that existed on the island, which themselves may have fallen prey to the giant stork, she adds.
As yet is it unclear why the giant stork, and the pygmy elephants and hobbit hominins, went extinct.
"But we have several clues," says Dr Meijer.
"All the bones of the giant marabou as well as those of the pygmy elephants and the hobbits are found below a thick layer of volcanic ash," suggesting a recent volcanic eruption.
"Second, the giant marabou and its contemporaries go extinct right before modern humans appear at the cave."
Around 15,000 years ago, the climate of Flores went from dry to being wetter, and a combination of any of these factors may have been enough to drive species on the islands to extinction.

(From BBC News)