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Thomas Vignaud of Marseille, France took this photograph, labeled Young fish dart by a jellyfish in the sea, in the Mediterranean Sea in September 2007. With it, he won the Natural World Category of Smithsonian magazine’s 5th Annual Photo Contest.

Have you taken an amazing photograph? Hurry up and enter our 7th Annual Photo Contest. The deadline is Tuesday, December 1, 2009, at 2pm Eastern Standard Time (EST).

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Falkland sheep have no need to worry about wolves these days (courtesy of Flickr user ShimShamB)

When Charles Darwin’s reached the Falkland Islands on his famed voyage, he discovered there a “large wolf-like fox” found nowhere else in the world. “As far as I am aware,” he would later write in The Voyage of the Beagle, “there is no other instance, in any part of the world, of so small a mass of broken land, distant from a continent, possessing so large an aboriginal quadruped peculiar to itself.” The human population on the island, however, was quickly increasing and the canid’s numbers were dwindling. Darwin predicted the species would soon go the way of the dodo, and he was right. The species went extinct in 1876, killed off for its fur and to protect the sheep population.

Since Darwin’s time, scientists have puzzled over his wolf-like canid, now known as the Falklands wolf. The species was the only native terrestrial mammal found on the island; there were no mice or porcupines or deer. And the islands lie 300 miles from the mainland. Where did the wolf come from and how did it get to the Falklands? Could Native Americans have brought the wolves to the island?

To get a picture of the wolf’s history, scientists isolated DNA from four museum specimens of the Falklands wolf, including one that had been collected by Darwin himself. (Their study appears in Current Biology.) They compared the DNA of their specimens with that of other canids, including several South American species (foxes, the maned wolf, and the bush dog) and members of the Canis genus (which includes the gray wolf and coyotes). With the DNA data, they created a phylogenetic tree that let the scientists see which species were the most closely related to the Falklands wolf and when the Falklands wolf branched off as a new species (that is, when they became isolated on the islands).

The four museum specimens diverged from their closest relatives about 70,000 years ago, which the scientists think is when the species came to the Falkland Islands. That was during the last ice age and long before humans showed up in the area (nixing the Native American theory). The wolves probably floated to the islands on ice or logs or perhaps walked over a glacier. Once on the islands, they would have feasted on penguins, geese and pinnepeds.

The scientists now have a new mystery: The analysis revealed the maned wolf to be the Falklands wolf’s closest relative, but the two species diverged from each other over 6 million years ago, several million years before canids populated South America from the north. There aren’t yet any canid fossils from this time period—something to look for.

Roosters are funny-looking creatures. They have a red bit that sticks out from the top of their heads—the comb—and another that dangles beneath their chin—the wattle. And then they perform this little dance called “tidbitting” (see first part of video below), in which they make sounds (food calls) and move their head up and down, picking up and dropping a bit of food.

Why does a rooster have a wattle?

Research has shown that when hens are choosing a mate they prefer roosters that have larger, brighter combs and ones that frequently perform the tidbitting behavior. This makes sense because the characteristics of the comb have been shown to correlate with how healthy the male is, and tidbitting behavior provides the hen with nutritionally important food items and shows the male’s status. But the presence of the wattles has long been a puzzle because they haven’t been shown to serve a similar purpose.

Carolynn Smith (a friend and former colleague) and her current colleagues at Macquarie University in Australia set out to discover the purpose behind the wattle by studying red junglefowl (Gallus gallus), which are the wild brethren of the chickens we eat (their study appears in the journal Animal Behaviour). Cutting off the wattles of roosters and seeing how the behavior of hens changed wasn’t an option. Instead, Smith created four animated roosters. The animated roosters (see second part of the video below) all acted the same, performing the tidbitting routine over and over, and they all looked the same, except for their wattles. One had a normal wattle, one was missing his, a third had a wattle that didn’t move, and the fourth had an extra floppy wattle.

A test chicken would be placed inside a test pen with two “audience hens,” a couple of buddies intended to make the test hen more comfortable in the less familiar surroundings (fowl are social creatures). One of the videos was then played for the test chicken and her response was recorded: How quickly did she respond to the animated rooster? How quickly did she start searching for food (the normal response to a male tidbitting)? And how long did she search for food?

The test hens responded more quickly to the tidbitting males that had the normal or stationary wattles, less quickly to the one with the extra floppy wattle (the wattle moved so much that it swung up the side of the rooster’s head and appeared much smaller than it was) and slowest to the male lacking wattles. After the hen’s attention was gained, though, she reacted about the same to each of the four animated chickens. Smith suggests that the wattle helps a rooster gain a hen’s attention when he is tidbitting, rather like a human guy wearing flashy clothes while doing his best dance moves to try and pick up chicks.

Photos and video courtesy of Carolynn Smith.

A European hoopoe (via Wikimedia Commons)

Birds produce special chemicals in their preen gland that they spread over their skin and feathers to protect themselves from pathogens and parasites. The secretions of European hoopoes (Upupa epops) and green woodhoopoes (Phoeniculus purpureus), however, are different from those of other birds. The substance they produce is brown in color instead of white and it is especially pungent.

Scientists in Spain, reporting in Proceedings of the Royal Society B, have discovered that the hoopoes are not entirely responsible for the smelly secretions. The preen glands of these two species harbor symbiotic Enterococcus bacteria that produce helpful chemicals that the birds use in defense against pathogens like the Bacillus licheniformus, a bacterium that degrades feathers.

How do the biologists know the bacteria were responsible? They injected nestling hoopoes with antibiotics that prevented the Enterococcus bacteria from taking up residence in their preen glands. Birds that grew up without the bacteria lacked most of the helpful chemicals.

A zebra longwing on a sage flower (via Wikimedia Commons)

Zebra longwing butterflies (Heliconius charithonia) can be found flitting about the southern United States through Central and South Americas. Like several other species of the Heliconius genus, male zebra longwings often find a mate before she has emerged from the pupal stage of life, guarding her until she becomes an adult and ready for mating. (Only one other species outside this genus is known to perform pupal guarding, as scientists have named this behavior.) But when this species of butterfly is in the pupal stage, males and females look alike, and researchers have wondered how the males know which ones to guard.

Biologists from Texas and Germany, reporting in the Proceedings of the Royal Society B, found that the male and female pupae emit different chemicals when they near the end of this stage of life. Males emit linalool and females linalool oxide. Adult males likely use visual clues to find pupae and then use these short-range olfactory cues (that is, they smell these two chemicals) to determine whether they’ve found a male or a female.

The male adult butterflies, however, aren’t entirely successful in their identification; in the biologists’ experiments, nearly a third of male pupae were under guard. The technique, however, is usually a good one that assures a male gets to mate.

The females, meanwhile, seem to have gotten the short end of this deal. They have no choice in their mates. But could they also benefit from this strategy? Yes, the scientists say. The adult males have to compete for the opportunity to guard a female pupa and, thus, only the bigger, stronger males would win that spot. These larger males will likely gift the female with a spermataphore that has more nutrients and chemical defence. So even if she doesn’t get a choice in the matter, the female butterfly—and perhaps more importantly, her offspring—still gets an advantage in life.

Ball pythons Boa constrictors (courtesy of flickr user Nicovangelion)

Any report on invasive species is bound to have bad news, it seems, and a new report from the U.S. Geological Survey analyzing the threat from nine giant snake species is possibly even worse because we’re talking about GIANT SNAKES (and I’m not generally scared of snakes). These snakes have already made their way here to the United States—as pets or hidden in cargo (Snakes on a Plane was NONFICTION?! -Ed.), usually—and pose a threat to the ecosystems where they might or have already become established. There are five identified as high risk (details below) and four medium risk species (reticulated python, DeSchauensee’s anaconda, green anaconda, and Beni anaconda). There are no low risks, the USGS notes, because all nine “share several traits that increase their risk of establishment, increase the damage they might do, or make eradication difficult.” (Worryingly, the report notes that there are no control tools for eradicating these species once these have become established.)

Specifically, these snakes:

1. Grow rapidly to a large size (some individuals of these species surpass 20 feet in length and 200 pounds in weight);
2. Are habitat generalists (they can live in many kinds of habitats and have behaviors that allow them to escape freezing temperatures);
3. Are dietary generalists (can eat a variety of mammals, bird, and reptiles);
4. Are arboreal (tree-living) when young, which puts birds and arboreal mammals such as squirrels and bats at risk and provide another avenue for quick dispersal of the snakes;
5. Are tolerant of urbanization (can live in urban/suburban areas);
6. Are well-concealed “sit-and-wait” predators (difficult to detect, difficult to trap due to infrequent movements between hiding places);
7. Mature rapidly and produce many offspring (females can store sperm and fertilize their eggs—which in some of these snakes can number more than 100—when conditions are favorable for bearing young);
8. Achieve high population densities (greater impact on native wildlife); and
9. Serve as potential hosts for parasites and diseases of economic and human health significance.

Had they not possessed these features, they might have constituted a low risk.

A Burmese python (courtesy of flickr user aehack)

The five high risk species:

Burmese python (Python molurus)
Native to: Southeast Asia, from Pakistan and India to China and Vietnam to Indonesia
Size: on average, grows to 18 feet and 160 pounds
Eats: terrestrial vertebrates, including lizards, birds and mammals; has been known to attack and kill humans
U.S. states with suitable climate: Alabama, Arkansas, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, Oklahoma, North Carolina, South Carolina, Texas
Already established in: Florida, in the Everglades

Northern African python (Python sebae)
Native to: central Africa from the coasts of Kenya and Tanzania to Mali and Mauritania, and north to Ethiopia and Eritrea; in arid regions, only near permanent water
Size: a typical adult is around 16 feet
Eats: antelopes, warthog, porcupine, caracal, birds, fish, crocodiles, lizards, frogs
U.S. states with suitable climate: southern half of Florida, southern tip of Texas, Hawaii
May already be established in: southern Florida

Southern African Python (Python natalensis)
Native to: ranges from Kenya southwest to Angola and south through Namibia and eastern South Africa
Size: a typical adult is around 16 feet, but can grow bigger than the Northern African python
Eats: antelopes, warthog, porcupine, caracal, birds, fish, crocodiles, lizards, frogs
U.S. states with suitable climate: southern half of Florida, along much of the southern border of Texas, Hawaii

Boa constrictor (Boa constrictor)
Native to: much of central and South America, from Mexico to Argentina
Size: adults are around 13 feet long
Eats: mammals, birds, lizards, fish
U.S. states with suitable climate: Arizona, Florida, Georgia, Hawaii, New Mexico, Texas
Already established in: southern Florida

Yellow anaconda (Eunectes notaeus)
Native to: Argentina, Bolivia, Brazil, Paraguay, Uruguay
Size: 10 to 12 feet on average
Eats: fish, turtles, aquatic birds, rodents
U.S. states with suitable climate: Florida, southeast Georgia, southern and eastern Texas, southern California, Hawaii

Scientists from Britain and Japan used sophisticated techniques to study the feeding behavior of the black-browed albatross (Thalassarche melanophrys) at sea. A lot of useful information came out of this study, but the single item you will likely hear most about is a really cool photograph, taken by the albatross itself, of a killer whale.

It is difficult to study albatross because they fly hundreds of kilometers across open ocean, flying faster than a boat can sail, to find food. Since you can’t just follow them, and since their open ocean feeding area is very large, observing albatross feeding behavior can’t be done reliably.

The new study addressed this problem by using miniature digital cameras attached to the backs of four birds breeding at colonies on Bird Island, South Georgia in the Southern Ocean. The resulting pictures showed albatrosses foraging in groups while at sea to collect food for their chicks. The cameras included a depth meter and a thermometer. The depth information was intended to indicate when the albatross would dive underwater for food, and the temperature meter indicates when the bird is settled on the sea surface or dives into water.

The following diagram shows what these information resulting from an instrument-fitted albatross flight looks like:

Diagram of albatross flight, courtesy of PLoS One

The X-axis is time, showing that this particular flight that took over two hours. The squiggly line along the top indicates temperature and the vertical lines along the lower part of the chart indicate depth. The bird appears to make four dives and later on sits on the water for a while (indicated by the cooling down without a dive event). The camera took photographs on a regular basis, and the Xes in the diagram indicate a photograph with another organism in it, generally another albatross. This shows that the albatross tracked in this diagram dived and presumably fed in the vicinity of other birds. The X with the red circle indicates a photograph of special interest, this one:

Albatrosses following an orca. Courtesy of PloS One

Here you can see two birds, one higher and one lower than the bird with the camera, and the three birds together seem to be closing in on a whale. This is an orca, a.k.a. killer whale.

This image showed that the killer whale broke the surface and that three other albatrosses were also apparently following the whale. This image was, unfortunately, followed by subsequent images that were obscured by feathers. However, the rapidly decreasing external temperature suggests that the bird landed on the sea surface after the encounter with the killer whale…

The camera is small, weighing about 82 grams. Although the camera slightly changes the aerodynamic shape of the albatross, it did not affect the breeding success of the study birds. In all, over 28,000 pictures were taken with the albatross mounted cameras. According to Dr Richard Phillips from British Antarctic Survey (BAS), “These images are really interesting. They show us that albatrosses associate with marine mammals in the same way as tropical seabirds often do with tuna. In both cases the prey (usually fish) are directed to the surface and then it’s easy hunting for the birds.”

Cape Buffalo and calf. Photo courtesy of Wiki Commons

Greg Laden is guest-blogging this week while Sarah is on vacation. You can find his regular blog at Scienceblogs.com and Quiche Moraine.

We are talking mainly about bovids (cattle and antelope), which grow horns over their lifetime, and deer, which grow antlers every year. In most well known bovids and cervids, only the males grow the horns or antlers, but there are a few species where the females do as well.

For example, male and female cattle (including the many wild versions such as the African Cape Buffalo) and wildebeest (a kind of antelope) have horns, while in most other bovids only the males have horns. Both male and female caribou (a kind of deer) grow antlers each year, while in most other deer only the males do so.

This is actually a very complicated issue, and a new study of this question offers a new possible answer. But first, what did we think before this study?

There is one factor that explains most instances of female horns or antlers. The tiny monogamous deer and antelope tend to be much more “monomorphic” (that is, males and females look similar) than larger deer and antelope. These are small, pair-bonded, forest-dwelling species, and their horns or antlers are effective tools for defending territory or defending the young against small forest predators such as cats. Both the males and females have the horn or antler because they both use them, and for similar purposes. That is not particularly enigmatic.

It is also not hard to explain why in the vast majority of large cattle, antelope and deer species males and females are dimorphic (that is, males and females look different) in this trait, with only the males having the big appendages on their heads. In most of these species, males compete with each other, either in direct male-male competition or using a more show-off strategy to impress the females, in which the horns or antlers play an important role.

What’s harder to explain is this: In a small number of these large species, where the males compete over females, why do females also grow horns or antlers?

One early theory suggested that females in larger species could use these appendages for anti-predator defense. In other, smaller, species the females are better off hiding or running away. In my personal experience with wild Cape buffalo, this makes sense.  On many occasions while working in the Semliki Valley in the Congo, I encountered small herds of female buffalo with their young. As I would draw nearer in my vehicle, they would gather more closely and form a circle with the young in the center, watching me suspiciously and looking rather formidable, and the horns were very much part of that look. However, this does not seem to hold true for deer. In the largest deer species, females do not have antlers.

Another previous hypothesis, proposed by Richard Estes, who works with wildebeest in East Africa, suggests that horned or antlered females benefit by confusing adult males as to who the young males in the group are. This is a strategy to keep the young males in the group longer, so they can grow bigger before heading out on their own. Essentially, this is a trait that benefits mom (it makes her son more successful) but is manifest in her daughters. According to this idea, female horns or antlers should be found in species where competitive males are forced to hang around with each other more than in other species because they live in large herds that consist of “family” groups. This is, in fact, what is found in caribou and wildebeest, two of the prime example of antlered or horned females.

The new theory, proposed by Ted Stankowich of the University of Massachusetts and Tim Caro of the University of California at Davis, is that females benefit from having horns or antlers if they are of a body size or live in a habitat that makes it hard for them to hide. The more conspicuous the female, the more benefit they gain from horns or antlers, which would be needed for defense against predators.  (They may also benefit from competition with members of their own species for grazing spots.) This would explain caribou and wildebeest nicely, as they both live in very open country, as well as a lot of other species. This study was done by looking at a large sample of animals for traits related to body size and vegetation cover in the habitats they live in.  The sample included 82 species with female horns or antlers, of which 80 were “very conspicuous.”  According to the authors, who feel the two species that did not fit for reasons that can probably be explained, that is a nearly perfect match between theory and data.

More information on this story can be found here.