Showing posts with label invasive snakes. Show all posts
Showing posts with label invasive snakes. Show all posts

Sunday, March 27, 2011

Cold Weather & Pythons

Predictions that freezing weather will remove invasive pythons from  the Florida Everglades seem to have been wrong given the following story. Python bivittatus is an exceptionally resilient animal that lives in a wide range of habitats, including the foothills of the Himalayas.

Freezes fail to kill off pythons in Everglades
By David Fleshler, Sun Sentinel
5:25 p.m. EDT, March 26, 2011

Record freezes and a fearsome drought have failed to kill off the Burmese pythons that have colonized the Everglades.

Six of the non-native, constricting snakes were found last week in sections of the Everglades in which they had not turned up before, including an area north of Alligator Alley, according to the South Florida Water Management District. This further dashed hopes by scientists that the past winter's cold weather could kill off the snakes, which are native to the warmer climate of southern Asia.

The snakes, which arrived in the Everglades either through intentional or accidental releases by exotic pet owners and breeders, consume native wildlife, including deer, wading birds and small alligators.

"Almost nothing stops them," said Dan Thayer, the water management district's director of vegetation and land management in a statement. "It tells us they're tough and rugged. The survival of an invasive species often depends on its ability to endure extremes. The Burmese python is overcoming a wide range of conditions in Florida, including extreme colds and a water shortage."

Thursday, March 17, 2011

Scientists find that non-native snakes are taking a toll on native birds

The Everglades National Park in Florida is home to hundreds of species of native wildlife. It has also become the well-established home of the non-native Burmese python—known to be a predator of native species. Now scientists, for the first time, have conducted a detailed analysis of the avian component of the python's diet and the negative impact the snakes may have on Florida's native birds, including some endangered species.

The Burmese python (Python molurus bivittatus), native to Southeast Asia, was first recorded in the Everglades in 1979—thought to be escaped or discarded pets. Their numbers have since grown, with an estimated breeding population in Florida in the tens of thousands. As researchers investigate the impact of this snake in the Everglades, scientists from the Smithsonian Institution, South Florida Natural Resources Center and the University of Florida examined the snake's predation of the area's birds. They found that birds, including endangered species, accounted for 25 percent of the python's diet in the Everglades.

"These invasive Burmese pythons are particularly hazardous to native bird populations in North America because the birds didn't evolve with this large reptile as a predator," said Carla Dove, ornithologist at the Smithsonian's Feather Identification Lab in the National Museum of Natural History. "Conversely, the python is able to thrive here partly because it has no natural predator to keep its numbers in check."

The scientists collected 343 Burmese pythons in Everglades National Park as part of their study between 2003 and 2008. Eighty-five of these snakes had bird remains in their intestinal tract. From these remains the team identified 25 species of birds by comparing feathers and bone fragments with specimens in the Smithsonian's collection. The results reflected a wide variety of species, from the 5-inch-long house wren to the 4-foot-long great blue heron. Four of the species identified (snowy egret, little blue heron, white ibis and limpkin) are listed as "species of special concern" by the Florida Fish and Wildlife Conservation Commission. The team also identified the remains of a wood stork, which is a federally endangered species.

"These pythons can also inhabit a wide variety of habitats, so their impact is not restricted to just the native species within the Everglades," Dove said. "The python's high reproductive rate, longevity, ability to consume large prey and consumption of bird species are causes for serious conservation and control measures."

Monday, April 12, 2010

Human Fascination With Large Snakes is Ancient

There is evidence that humans have been moving the large snakes around for at least two millennia. Strabo’s encyclopedic work Geography is a description of the ancient Greco-Roman world. In this 2000 year old text the author reports seeing a snake in Egypt that was 9 cubits long (about 13 feet or about 4 m) that had been brought from India. The same appears true for the African Python complex (Python sebae). Bodson (2004) described, what she considers, the first herpetological expedition to capture a large African Python organized under Ptolemy II (290 to 246 BC). The expedition captured a large specimen in the area known as the Island of Meroe, which is not really an island but the area between the White Nile, the Blue Nile and the Atbara River (14-16°N latitude). This area is within the known range of Python sebae. There are no firsthand accounts of the 3rd century BC effort and Bodson's account is based on information in a ms from the 1st century BC, at least 200 years after the event. Therefore it is not surprising that the size and abilities of the snake were exaggerated. Accounts from the turn of the 19th century suggest people in the Philippines were using Reticulated Pythons (Broghammerus reticulatus) to control rodents, keeping them in their houses and places of business. This may have lead Brown and Acala (1970) to concluded that the presence of reticulatus on virtually all Philippine islands were the result of human transport. It is therefore not surprising that 15 foot Burmese Python (P. bivittatus) was found in Riverside, California's Lake Evan over the week end (April 9) and an 11 ft python of an unstated species was found in Cornwell, England on April 11. Of course people keep giant snakes as pets or for commercial breeding projects today. Human fascination with snakes is ancient and undeniable.

Friday, February 26, 2010

Thoughts on Cold Weather and Invasive Snakes.

The cold weather experienced in southern Florida has damaged crops causing economic damage to orange growers. It has also been proposed that the cold weather would solve the python problem. A January 1, 2010 Miami Herald article by Robert Samuels states,
"Scientists have waited for years for this moment. They are hoping that the extended, freakishly bitter cold just might accomplish what trappers have been unable to do: thin the population of pythons and other invaders running roughshod over the fragile environment and native species. Or at least slow their explosive growth."

The same article quotes University Florida Wildlife scientist Frank Mazzotti saying,  "Today has been what I would consider a game changer...The pythons are going to be stunned by this kind of weather."

Other articles report 50% of the Burmese Python found were dead, describe the invasive Green Iguana as falling out of trees, and state that many invasive freshwater fish have died.

The cold snap undoubtedly brought about a die-off of individual animals that were exposed to the cold but some individuals will have been in shelters where they would be protected from the cold. They may have learned how to survive the cold weather. But, some of them, maybe just a few, have a physiology that allows them to better withstand the cold. These snakes will survive, reproduce, and leave offspring that are also able to survive cold snaps. Overtime the populations of invasive constricting snakes will adapt to the local climate that includes the occasional cold front that sags into southern Florida. Just as bacteria become resistant to antibiotics, snake populations will become resistant to cold. If the Burmese Python, African Python, Boa Constrictor populations are large enough they too will likely become cold resistant.  Natural selection works this way. It should not be a surprise to any biologist.