Florida’s Invaders: Armadillo

The prehistoric-looking Armadillo is such a familiar part of the Florida landscape (most often as squashed roadkill along the highways) that it has become accepted as a normal part of the scenery. In reality, it is an invader in Florida, but one of the very few that got here on its own as a natural extension of its normal range.

Armadillo_USFWS

Nine-Banded Armadillo                                                photo from US FWS

The Armadillos are a group of about 20 mammals in the family Dasypodidae, an ancient group related to the sloths and anteaters dating back to the time just after the dinosaurs, which is characterized by a turtle-like leathery shell studded with small bone platelets that form a protective armor. At this time, sea levels were higher than they are now, so most of what is now Panama was underwater, and North and South America were separated from each other and went their separate evolutionary ways. Then about 3 million years ago, ocean levels dropped and tectonic forces pushed the land up to form the Isthmus of Panama, connecting the two continents. The result was what paleontologists refer to as the Great American Interchange, when wildlife from each continent now had a land route to the other. Deer, horses, camels, tapirs, bears and cats went south, while sloths, armadillos, giant birds and giant rodents went north.

During the Ice Ages, Florida and the rest of the southern US was inhabited by huge versions of Armadillos known as Glyptodonts, which reached the size of a Volkswagen and weighed two tons. About 10,000 years ago, however, the giant armadillos in North America died out, and only a handful of their former glory remained, in the lower half of South America.

One of these South American survivors is the Nine-Banded Armadillo, Dasypus ovemcinctus. Measuring about two feet from nose to tail and weighing about 15 pounds, this species is marked by the nine narrow flexible bands of skin across its back which act as a hinge and allow the animal to curl up its bony outer shell for protection. The Nine-Banded Armadillo proved to be more adaptable than its fellow species, and over the years it invaded nearly all of South America, where it adapted to habitats ranging from rainforest jungle to open grassland (only the snowy peaks of the Andes Mountains were too much for it).

When the Spanish invaded South America in the 1500’s, they encountered these odd-looking animals and were baffled–they had never seen anything like it before. The Aztecs had called them “turtle rabbits”: the Spanish took to calling them armadillos (“little armored ones”).

Like all the other armadillo species, the Nine-Banded Armadillo is mostly crepuscular, sleeping up to 16 hours a day and hunting at dusk and dawn, using its keen sense of smell to locate and dig up worms, insects and other soil-dwelling prey. The legs are very strong and the claws are very stout, and the Armadillo is an excellent digger, excavating subterranean chambers as shelters. Mating occurs in the summer, when the ovulating female releases one egg cell into the uterus. Once fertilized, the egg delays implantation for a few months until the weather is suitable, then it splits into four zygotes which each develops into an embryo over the next four months, producing a litter of identical quadruplets. The youngsters are weened after about four months and wander off on their own at about nine months old.

Despite their ungainly appearance, Armadillos can run surprisingly fast. They can cross streams and rivers by holding their breath and simply walking across the bottom, but if the river is very wide, they can gulp air and float at the surface, allowing them to swim across. In South America, their primary predators are large cats like Jaguars and Cougars, which hunt them by ambush. To escape an attack, Armadillos can jump straight up into the air from a standing start, to a height of 3-4 feet. This allows them to dodge the cat’s leap, and then run away. In North America, the Armadillo’s only real enemy is the automobile–where their instinctive jumping response doesn’t help them very much. So dead Armadillos are a common sight along roadways all across the South. In some areas, Armadillos are eaten: it is known as “poor man’s pork”.

At the time of the Spanish, the natural range of the Nine-Banded Armadillo lay entirely within South America. But as tough and adaptable generalists, they were already expanding their natural range, and since they were inconspicuous and harmless, the Spanish settlers mostly left them alone. By the 18th century they had expanded through Central America into Mexico, and by around 1850 they had reached the Rio Grande and crossed into the United States into Texas. Armadillos had spread into New Mexico by 1905, and reached the Florida Panhandle by 1920 and the rest of Florida by the 1950’s. From there, lacking any large predators, they spread quickly northward. By 1995 the Armadillo was firmly established in Oklahoma and across the Gulf coast states, and was found in Colorado, Kansas and South Carolina. The species is expected to eventually cover most of the United States, limited only by the cold temperatures it will encounter in the areas north of Pennsylvania and Nebraska.

For the most part, the Armadillo has been a benign invader, although some people resent its habit of digging holes in the lawn or garden, and its tendency to get hit by cars. Although it is considered a “non-native” by the State of Florida and has no legal protections, the state has taken a hands-off attitude to the “little armored one”, and is making no effort to control or remove it. Since it got here naturally, it is not really considered an invasive.

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