Jan 31

Non-native Burmese pythons are believed to be the cause of severe mammal declines in the Florida Everglades, according to new research.

Photo of Asiatic rock python (Python molurus bivittatus) resting in shallow water

Asiatic rock python (Burmese python) resting in water

Escaped pets

Also known as the Asiatic rock python, the Burmese python (Python molurus bivittatus) is a large constricting snake native to Asia. The exact origins of the pythons in the Everglades are unknown, but many have been imported into the United States through the pet trade, and some are likely to have escaped or been released into the wild.

In the absence of natural predators, the Burmese python population has exploded. Since 2000 the species has been recognised as being established across large parts of southern Florida, where it is known to eat a wide variety of mammals and birds.

Close up photo of Asiatic rock python showing heat receptors

Close up of Asiatic rock python showing heat receptors, used to detect the body heat of prey

Worrying mammal declines

In new research published in the journal PNAS, a team of scientists studied the number of live and dead mammals spotted along roads in the Everglades National Park. The team compared mammal surveys performed before and after the pythons became common, and found a strong link between the spread of the snakes and a decrease in many mammal species.

In particular, observations of racoons and opossums dropped by about 99%, while white-tailed deer fell by 94% and bobcats by 87.5%. No rabbits or foxes were seen during more recent surveys, despite rabbits being one of the most common mammals in earlier studies.

Most of these mammal species have been recorded in the diet of Burmese pythons in the Everglades National Park, with raccoons and opossums being particularly vulnerable to ambush as they often forage at the water’s edge.

Photo of Asiatic rock python with hog deer prey in water

Asiatic rock python killing hog deer

The decline in mammals was found to coincide with the spread of the pythons, with mammals being more common in areas were the pythons have only recently arrived, and most common outside of the python’s current range. The pythons are also likely to be eating other types of prey, including alligators.

We have documented pythons eating alligators, we have also documented alligators eating pythons. It depends on who is biggest during the encounter,” said Professor Michael Dorcas, one of the authors of the study.

Ecosystem impacts

The exact number of Burmese pythons in the Everglades is unknown, but their numbers are increasing year by year.

Any snake population – you are only seeing a small fraction of the numbers that are actually out there,” said Professor Dorcas. “They are a new top predator in Everglades National Park – one that shouldn’t be there.”

Photo of Asiatic rock python (Python molurus bivittatus) resting on foliage

Although a problem where it has been introduced in the US, the Asiatic rock python is classified as Near Threatened in its native Asia

Professor Dorcas has also stated that more research is needed to assess the potential impacts of the large mammal declines. “It’s not unreasonable to assume that any time we have major declines in mammals like this it’s going to have overall impacts on the ecosystem. Exactly what those are going to be, we don’t know. But it’s possible they could be fairly profound.”

Import ban

Earlier this month, it was announced that the US was poised to approve a ban on the import of Burmese pythons and on the sale of the snake across state lines. Another species that has been found in the Everglades, the African rock python, is also likely to be added to this list of “injurous” species.

Although reptile breeders and collectors have challenged the ban, and it would come too late to reverse the situation in Florida, Professor Dorcas has pointed out that it could help prevent the species from invading other suitable habitats in the United States, such as in southern Louisiana and south Texas.

Read more on this story at BBC – Pythons linked to Florida Everglades mammal decline.

View photos and videos of the Asiatic rock python on ARKive.

Liz Shaw, ARKive Species Text Author