October 8, 2010
Ten years ago a group of marine scientists founded the Census of Marine Life and set out to answer three questions: What did live in the oceans? What does live in the oceans? What will live in the oceans? More than 2,700 scientists would participate in the Census on more than 540 expeditions around the world. They found nearly 250,000 marine species, upping the count by about 20,000; they estimate there are at least a million marine species in the oceans and tens to hundreds of millions of kinds of microbes.
There were schools of fish the size of Manhattan and animals that commuted like clockwork up and down the water column. There were living things in every bit of ocean the scientists looked at, from the deep dark depths to frozen seawater to waters so hot they would melt lead. There were mats of bacteria that extended for hundreds of kilometers.
But there was bad news, too. Scientists documented what used to live in the seas by checking historical records of sightings and catches, and also restaurant menus. Many species had declined in numbers, sometimes within one human generation. Phytoplankton, which sits at the base of the food web, has also declined in the last century.
This first Census is officially done, but it wasn’t complete. The Census has no records for about 20 percent of the ocean’s volume, and records are sparse for some large areas.
But the Census has already had a huge effect, not only in introducing us to thousands more of the species with which we share the planet (some were featured recently in our story Weird Creatures of the Deep), but also by setting a baseline against which we can measure our impact on the oceans. We fish some species too much, pollute the waters and change ocean chemistry through climate change. At least now we can get a good idea of how bad the situation is becoming.
September 24, 2010
Call them panthers, mountain lions, cougars or pumas, the Americas’ largest cat species has been dwindling in eastern North America for hundreds of years. They were extirpated from everywhere but some shrinking habitat in Florida between Naples and Miami. And even there, the panthers were not doing well. By the mid-1990s, the population consisted of just a couple dozen adult cats, and they were suffering from the problems of inbreeding: low reproduction rates, sperm quality and testosterone levels; heart defects; kinked tails; and high loads of parasites and pathogens. It wasn’t looking good for the Florida kitties.
In 1995, conservationists tried to bolster the Florida population by introducing eight female panthers from Texas. The two subspecies used to intermingle, so transferring a few females would restore some of the natural gene flow. Fifteen years later, scientists are declaring the program a success. The addition of just a few new kitties to the gene pool resulted in a more diverse population that no longer suffered from the problems of inbreeding. And the population tripled in size. (The study appears in today’s issue of Science.)
Florida’s panthers, like so many cat species, still face serious challenges to their survival, including habitat loss and disease. But it’s heartening to see that relatively simple solutions—transferring a handful of cats combined with efforts to preserve habitat and reduce deaths from car accidents—can have such a positive effect on a population.
Earlier this week, the BBC announced the discovery of tigers in Bhutan living high above the treeline, far from where anyone had expected the cats could survive. Scientists hope to create a corridor connecting small, scattered tiger populations, such as this one in Bhutan, with others across much of Asia. The idea being that, like the Florida panthers, Asia’s tiger populations would get stronger from increased genetic diversity.
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September 15, 2010
Just how long has the world’s oldest living thing been on this planet? That would be Siberian actinobacteria, and they’ve been here for some 400,000 to 600,000 years, longer than our species has existed.
Photographer Rachel Sussman is keeping track of these ancient specimens. She’s been photographing organisms that are 2,000 years old and older around the world (nicely mapped out here). There’s the world’s oldest predator (also the biggest), the 2,400-year-old Armillaria fungus in Oregon, which kills trees. And a 2,000-year-old brain coral off the coast of Tobago. And a clonal creosote bush that’s been living in the Mojave Desert for 12,000 years.
Sussman is blogging about her adventures. She’s currently in Sicily, trying to figure out the age of an ancient chestnut tree. She estimates she’s got maybe two more years to go on the project. Why spend so much time photographing old things? She explains in her recent TEDTalk (above):
The oldest living things in the world are a record and celebration of our past, a call to action in the present and a barometer of our future. They’ve survived for millennia in desert, in the permafrost, at the tops of mountains and at the bottom of the ocean. They’ve withstood untold natural perils and human encroachments, but now some of them are in jeopardy, and they can’t just get up and get out of the way. It’s my hope that, by going to find these organisms, that I can help draw attention to their remarkable resilience and help play a part in insuring their continued longevity into the foreseeable future.
I look forward to seeing what she makes of the project.
July 30, 2010
Many of the poster animals of Australia—kangaroos, koalas, wombats and wallabies, to name a few—are marsupials, animals best known for carrying around their young in a pouch. Marsupials can also be found in the Americas; in the United States, the Virginia opossum is the only one, but there are dozens of species in Central and South America.
Scientists trying to draw the marsupial family tree have been perplexed by contradictory evidence: DNA studies suggested that the Australian branch was an offshoot of South American animals that migrated to Australia when the two continents were connected and part of Gondwana. Fossil studies, though, seemed to show that some of the Australian marsupials had made their way back to South America.
In a new study in PLoS Biology, researchers from Germany set out to make a marsupial family tree using retroposons, a kind of jumping gene—pieces of DNA that are copied and pasted at random within the genome. The more closely related two species are, the more retroposons they will share.
Comparing the retroposons of the 21 marsupials showed that they all shared 10 jumping genes, thus confirming that they shared one ancestor. But the South American and Australian marsupials formed distinct groups; the Australians shared retroposons that their South American relatives lacked. The researchers were also able to determine that the South American branch was older (meaning that the Australian marsupials had come from South America) because the South Americans lacked two retroposons shared by everyone in the Australian branch.
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November 10, 2009
While writing about the Falklands wolf and the Labrador duck, I was reminded that they are only two of the dozens, maybe hundreds, of creatures that have gone extinct in recent human memory (that is, the last few hundred years). Here are seven more creatures that exist only in pictures or as museum specimens:
Dodo (Raphus cucullatus)
The dodo has become synonymous with extinction. To “go the way of the dodo,” for example, means that something is headed out of existence. The three-foot-tall, flightless bird lived on the island of Mauritius in the Indian Ocean. They probably ate fruit. Though the birds did not fear humans, hunting was not a huge problem for the birds as they didn’t taste very good. More troublesome were the other animals that came with people—like dogs, cats and rats—that destroyed dodo nests. Human destruction of their forest homes was also a contributor to the dodo’s decline. The last dodo was seen on the island sometime in the late 1600s.
Steller’s sea cow (Hydrodamalis gigas)
Georg Steller first described his sea cow in 1741 on an expedition to the uninhabited Commander Islands off the coast of Kamchatka. The placid sea creature probably grew as big as 26 feet long and weighed around 8 to 10 tons. It fed on kelp. Just 27 years after Steller’s discovery, however, it was hunted to extinction.
Great auk (Pinguinus impennis)
Millions of these black-and-white birds once inhabited rocky islands in some of the coldest parts of the North Atlantic, where the sea provided a bounty of fish. Though their population numbers probably took a hit during the last Ice Age, it was the feathers that kept them warm that led to their downfall. The soft down feathers were preferred pillow filling in Europe in the 1500s and in North America in the 1700s. The dwindling birds were further doomed when their eggs became a popular collector’s item. The last live auk was seen in Newfoundland in 1852.
Passenger pigeon (Ectopistes migratorius)
The passenger pigeon was once the most numerous bird species in North America, making up 25 to 40 percent of all birds on the continent. There were as many as 3 to 5 billion of them before the Europeans arrived. They would migrate in huge flocks consisting of millions of birds. In the 1800s, however, they became a popular food item. Tens of thousands could be killed in a day. By the end of that century, when laws were finally passed to ban their hunting, it was too late. The last wild bird was captured in 1900. Martha, the last of her kind, died in 1914 at the Cincinnati Zoological Garden.
Carolina parakeet (Conuropsis carolinensis)
The eastern United States once had its own native parrot, the Carolina parakeet. But farmers cut down their forests and made fields, and then killed the birds for being pests. Some birds were taken so that their feathers could adorn ladies’ hats, and others became pets. The last wild parakeet was killed in 1904 in Florida. The last captive bird, which oddly enough lived in the same cage in which the passenger pigeon Martha died (above), died in 1918.
The thylacine wasn’t really a tiger, though it got that name for the stripes on its back. The largest carnivorous marsupial, it was once native to New Guinea, Tasmania and Australia. It had already become rare by the time Europeans found Australia, confined to the island of Tasmania. In the 1800s, a bounty was put on the species because it was a danger to the sheep flocks on the island. The last wild thylacine was killed in 1930, though some may have survived into the 1960s.
Golden toad (Bufo periglenes)
They lived in the Monteverde Cloud Forest Preserve in Costa Rica. Most of the year, they were hard to find, and scientists think they may have lived underground. But during the rainy season of April to June, they would gather in small, temporary pools to mate. The population crashed in 1987 due to a bad patch of weather and none have been seen since 1991. No one is sure what happened, but climate change, deforestation and invasive species have all been suggested as possible culprits.