rhamphotheca:

_____________________________________________________

Early humans linked to large-carnivore extinctions

Hominins could have triggered broad changes to the numbers and diversity of meat-eaters in Africa, researcher says.

by Jeff Tollefson  (26 April 2012)

Animal lovers around the world know modern otters as cute, playful and unthreatening. But the mustelid’s giant cousins in ancient Africa may have engaged in a life-and-death competition with humanity’s ancestors — and come out on the losing end.

The demise of the gigantic ‘bear otter’ (Enhydriodon dikikae) was part of a broader decline in large-carnivore diversity in Africa, which accelerated around 2 million years ago — roughly the time that the first representatives of the genus Homo appeared on the scene. Lars Werdelin, a curator at the Swedish Museum of Natural History in Stockholm has been building a case that our forebears had something to do with the change. Although direct evidence of any causal connection is sorely lacking, Werdelin says, the transition in the carnivore fossil record coincides nicely with advances in tool-making and dietary shifts among early hominins.

“The way I see it, this is one of the first ways in which we manipulated our environment on a large scale,” says Werdelin, who presented his latest findings at a symposium on human evolution and climate change at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York. Werdelin argues that hominins may have competed indirectly with some of these carnivores by occupying prime habitat, thus forcing the animals to change their behavior without ever coming into direct contact with them. In some cases, the hominins may have out-competed carnivores directly by forcing them to surrender fresh kills. Regardless, the emergence of early humans could have cascaded through the food chain — ultimately wiping out many of Africa’s larger meat-eaters…

(read more: Nature)              

(images via NovaTaxa: TR - Victor Leshyk; B - Cal. Academy of Sci.)

kecobe:

Walton Ford (American; 1960– )

Dying Words

Hardground etching, aquatint, spit bite aquatint, drypoint, scraping, and burnishing on white Rives paper, 2005

The New York Public Library, Wallach Division, Print Collection

biomedicalephemera:

Megatherium americanum - The Giant Ground Sloth

The skeleton of Megatherium set up in the London Natural History Museum, and a depiction of a possibility of Megatherium behavior in life.

Though the population was already decreasing when the first humans arrived in South America, the disappearance of the Giant Sloth was helped along by the new immigrants. Using mammoth-hunting skills, this large and lumbering creature was an ideal kill for a human tribe. It was one of the many Pleistocene megafauna that went extinct during the Quaternary extinctions.

Extinct monsters. H. N. Hutchinson, 1896.

(via biomedicalephemera)

biomedicalephemera:

Canada Goose - Branta canadensis

Can you believe that this incredible nuisance of a bird was once on the verge of extinction - and not in the distant past? Hunting and slaughter by farmers in the late 1800s led to the critical endangerment of the entire Branta canadensis species, until the International Migratory Birds Treaty was passed in 1918.

While the species as a whole began a slow recovery process at that point, several of the subspecies were still on a rapid decline due to habitat loss, and by 1962, both the Aleutian and Giant Canada Goose were believed to be functionally extinct. However, the discovery of a wintering flock of Giant Canada Geese in Rochester, MN, that year, and the discovery of two small Aleutian Canada Geese flocks the next year, kicked off a conservation movement to restore the habitat and flyways for the entire species.

Well, the movement worked, obviously. In less than 40 years, all seven subspecies have been removed from the endangered species list, and the species as a whole is now considered a nuisance bird in many areas.

As they prefer open spaces with water, they’re often present in the same area as humans: around beaches, airports, and golf courses; their toxic droppings (not to mention their big ol’ engine-clogging bodies) have caused many problems over the past decade or so. In fact, they were the cause of the birdstrike that resulted in the “Miracle on the Hudson” a few years back. So far, culling and extermination efforts have only had limited effects on the overall population.

Voegel, aus Asien, Africa, America, und Neuholland in Abbildungen nach der Natur mit Beschreibungen. Carl Wilhelm Hahn, 1818.

lindahall:

Illustrations from The Dodo and It’s Kindred by H. E. Strickland, 1848.

biomedicalephemera:

Przewalski’s Horse - Equus prjevalskii [disputed, generally accepted as Equus ferus przewalskii]

The Przewalski’s horse, or takhi, is the only “true” wild horse remaining in the world, and is distinct from Equus ferus ferus, the domesticated horse. Though Przewalski’s horses and domesticated horses can interbreed and produce fertile offspring, the Przewalski’s horse has an extra pair of chromosomes, distinctive dentition, and a convex profile (“Roman nose”) uncommon in most breeds of domestic horse. The subspecies is believed to have diverged from Equus ferus ferus around 125,000 years ago, but the two groups interbred for at least 25,000 years before true geographical isolation began.

The discovery of the takhi in the Mongolian steppes in 1881 was followed by the collection of entire herds through hunting and rounding up to be kept in zoos. The last wild herd was spotted in 1967, and the last individual was spotted in 1969. The most genetically diverse captive herd (living in Askania-Nova in Ukraine) was slaughtered by former German soldiers in the late 1940s for unknown reasons.

Fortunately for conservation efforts, the very few individuals remaining in the world by 1977, when the species was declared “Extinct in the Wild”, proved to be very healthy, at least in terms of genetic vitality. Careful breeding programs started by the Foundation for the Preservation and Protection of the Przewalski’s Horse (FPPPH) in that same year ensured that the genetic diversity remained as strong as possible, given the tiny population. Twelve to fifteen individuals managed to produce small herds in several zoos and preserves, and the population grew at a steady pace for a decade and a half, before the first individuals were re-introduced to the wild, in 1992. Despite

After that first herd of 16 genetically distinct individuals from several zoos was introduced into the Gobi Desert, and successfully formed a herd with numerous healthy foals, Przewalski’s horse was re-classified from “Extinct in the Wild” to “Critically Endangered”. As of 2008, three stable-and-growing herds exist in the wild, in Mongolia and the prohibited-access zone around Chernobyl, Ukraine (a surprisingly good wildlife preserve!). They’re currently considered “Endangered”, and their population outlook is positive, with genetic diversity programs continuing in both zoos and the wild herds.

Proceedings of the Zoological Society of London. 1902.

bibi:

The Dodo,the Auk and the Oryx by Tolstoy2007 on Flickr.

(via dendroica)

crookedindifference:

Shark Extinction: The Shocking Truth

Ocean lovers everywhere, we are at crisis point. The top predator species in the food chain of our oceans is being hunted to extinction. Some shark specie populations are estimated to have declined by over 99% since the 1970′s!

The repercussions for marine eco-systems are dramatic and have devastating consequences down the food chain. To name but one example, species of Rays and Skates can explode leading in turn to the shocking decline of shellfish fisheries and a rapid reduction in water quality. And that’s just for starters!

(via creewillow)

biomedicalephemera:

2000: The last Pyrenean Ibex (Bucardo), named Celia, is found dead near the French border, her skull crushed by a fallen tree. The reason for the extinction of the species is unknown, as their habitat was protected since 1918. Since that time, approximately 40 individuals existed at any given…