by Whit Gibbons

September 20, 2009

Among the most common of questions people ask about alligators is How big do they get? A new twist on this question was asked recently: How accurate was William Bartram's statement that he had seen a 20-foot-alligator?

The William Bartram referred to was the author of the famous book from 1791 "Travels through North and South Carolina, Georgia, East and West Florida." Bartram traveled over land and through waters of the Southeast before the rest of us humans got our hands on them. He told us about plants and animals before we had depleted some of their numbers to the point of rarity or near-extinction. Many of today's would-be naturalists dream of traveling with Bartram and chronicling their adventures. Appreciating his travels is easy for anyone who thrives on wild things and wonders what it would have been like to experience an abundance of wildlife that seemed nearly endless.

However, Bartram has been criticized by some modern biologists, as well as some in his own time, for supposed leniency in describing certain reptiles, especially alligators. His reference to the maximum size of alligators has been repeatedly challenged for almost a century. One writer in the 1920s declared that "the accumulated testimony of travelers and naturalists does not support Bartram's statement."

What is the biggest alligator Bartram saw? He says he saw some "twenty feet in length." Few biologists have believed his claim. A noteworthy observation, however, is that an equal lack of acceptance has been accorded E. A. McIlhenny (the name you read on a bottle of Tabasco Sauce) who in the 1930s reported killing an alligator in Louisiana that was more than 19 feet long. Like Bartram, McIlhenny wrote of his numerous natural history observations, most of which are accepted in full—but not the maximum size he reported for an alligator. How can assertions that alligators could be 19 to 20 feet long be reconciled based on what we know today?

Adult female alligators characteristically are 6 to 9 feet in length, whereas males commonly attain lengths of about 12 to 13 feet and can weigh more than 500 to 600 pounds. Exceedingly large alligators, above 14 feet, appear to be rare or absent in today's world. In fact, a study based on skull sizes a few years ago concluded that no alligator has ever reached a length of 15 feet.

Could the absence of the giants reported from yesteryear simply be a consequence of the elimination of most older, larger individuals beginning in the nineteenth century and continuing until alligators became formally protected as endangered species in the 1960s and 1970s? Or were the extreme sizes reported in the past a result of unintentional misreporting or mismeasurement? Whatever the true maximum size any alligator has ever attained, 12- to 13-foot individuals weighing more than a quarter of a ton are around today.

But could these already rather large individuals still be growing and be capable of reaching much larger sizes of 19 to 20 feet? Alligators are believed to have what is referred to as indeterminate growth, which means they continue growing throughout their lifetime, albeit at an ever-diminishing rate. However, the maximum longevity of alligators is unknown. Some have been documented to have lived to be 70 years old. Could they perhaps live much longer than this if the older individuals were not killed by gator hunters? And would they keep getting bigger?

Old records give an idea of the massive slaughter of alligators and indicate how we could indeed have eliminated the giants. Alligators were nearly obliterated throughout their range by hide hunters between the 1870s and the early 1900s. McIlhenny documented hunts for a large area in Louisiana where in the summer of 1916 more than 1,000 alligators were killed—per day! Presumably, such massacres were going on throughout the alligator's natural range in the Southeast. Maybe before humans began their siege, a few Methuselah gators were still around that had been getting bigger and bigger for many decades.

Were the leviathans that Bartram and McIlhenny saw actually 20 feet long? Maybe if alligators are protected for a few more decades, such a claim may be made again—and validated.

If you have an environmental question or comment, email

(Back to Ecoviews)