Some snakes worldwide appear to be growing ever larger, and reptile experts believe people may be helping to drive the growth.
A nearly 18-foot-long Burmese python, for example, was recently discovered in the Florida Everglades. It is one of the largest ever pythons found there.
"The maximum size of Burmese pythons in the Florida Everglades has been increasing by 6 inches to a foot a year for the past five to six years," J.D. Willson, assistant professor of biological sciences at the University of Arkansas, told Discovery News, adding that he expects a 20-footer to be found there before long.
As their name suggests, Burmese pythons are not native to Florida. Instead, they are native to Southern and Southeast Asia. Willson explained that they were all the rage in pet stores back in the day.
"From the 70's to the 90's, you could buy baby Burmese pythons in pet stores," he said.
Some escaped, or were released into the wild. The Florida Everglades has turned out to be a good habitat for them -- at least initially -- and their population has been established there since at least the year 2000.
Willson said that, unlike mammals, snakes continue to grow as they age. He thinks that the recently caught python in the Everglades was at least 10 years old.
Two other invasive species, African rocky pythons and non-native boa constrictors, have also been found at huge sizes in Florida. Boa constrictors have also established a breeding population in Puerto Rico.
Non-native boas can exceed 10 feet and 75 pounds, according to U.S. Geological Survey director Marcia McNutt. She said island ecosystems are particularly vulnerable to snake invasions.
Very large brown tree snakes have been found on yet another island, Guam. Willson explained that brown tree snakes probably were accidentally introduced to the island during World War II, when they might have stowed away in cargo.
The trend seems to be that non-native snakes grow very large at first and then become smaller as their food supply diminishes. Brown tree snakes already have driven many native birds and lizards on Guam to extinction.
Climate change may also be contributing to snake sizes.
University of Illinois researcher Patrick Weatherhead and colleagues recently found that warming temperatures benefit ratsnakes in Canada, Illinois and Texas. Weatherhead expects ratsnakes to become more active at night and to expand their ranges northward.
The invasion of Burmese pythons in Florida's wetlands pose an existential challenge to the state's native wildlife as these apex predators. National Park Service
The largest snake on record, Titanoboa, weighed 2,500 pounds and conservatively measured 42.7 feet from its nose to tail tip.
Researchers from the Smithsonian Tropical Research Institute and the Florida Museum of Natural History believe that warmer temperatures during Titanoboa's lifetime, 60 million years ago in South America, helped to fuel and maintain its astounding growth. The temperature was about 5 degrees warmer, on average, than it is now.
It is little wonder that Titanoboa was a top predator of its day. Now, in the Florida Everglades, an epic battle is underway.
"Alligators and Burmese pythons are duking it out for the top predator spot," said Willson, who explained that the animals eat each other.
Burmese pythons have been known to eat humans while in captivity, but probably because they mistakenly identified their owner as food (food smells can get on the person during feeding times, and snakes possess a very keen sense of smell). Burmese pythons are consuming rabbits, raccoons, possums, bobcats, deer and rodents in the Florida Everglades.
One Burmese python was found with two endangered Key Largo woodrats in its gut.
"That's roughly 1 percent of the entire known population of this rodent, so the snakes have become a real problem in Florida," Willson said.