A two-feet “leopard eel” was hiding in US swamps; Scientists took years to identify it

The murky waters of Northwestern Florida and Southern Alabama had been giving up an odd creature for years. It was long like an eel, marked with dark spots that looked like a leopard’s, and fringed with frilly gills around its head. People called it the “leopard eel”. The name was wrong on both counts. The animal was a salamander, and scientists eventually established that it belonged to a species nobody had formally described.

The reticulated siren, also known as the “Leopard Eel”, is a fully aquatic mammal and can grow up to 60 centimeters. According to the paper published in PLUS ONE on December 5, 2018, described it as drawing on years of collecting specimens, comparing various physical features and analysing DNA. What stands out is how long it stayed unclassified. A specimen had been collected as far back as 1970.

The clue had been sitting in a museum

According to the paper, the first known specimen was collected on April 15, 1970, from the Fish River in Baldwin County, Alabama, and placed in a museum collection. A later examination noted that it did not match the description of the greater siren, a related salamander.


That did not lead to a formal identification. The animal is hard to find and hard to study. Sirens spend much of their time underwater, often in shallow, muddy wetlands where researchers cannot easily observe them.

The case moved forward on September 4, 2009, when biologist David Steen caught one while trapping turtles at Eglin Air Force Base in Florida. He and fellow researcher Sean Graham had already been following reports of a spotted siren that did not seem to match any known species.

National Geographic reported in 2018 that the two worked on the question over several years, largely in their own time and without official funding for the project. One animal was not enough. They needed more specimens to tell whether the unusual appearance meant a distinct species or simply variation within a known one.

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Five years between the first catch and the next breakthrough

Later attempts to collect the animal at several sites failed. Then, on June 8, 2014, the researchers found three more in a freshwater marsh near Lake Jackson, Florida.

Along with preserved museum specimens, these gave the team material to compare. Graham, Steen and their co-authors studied the animals’ physical characteristics and genetic evidence. Their analysis supported the conclusion that the animal was genetically distinct from other recognised siren species.

They named it Siren reticulata. “Reticulated” refers to the network-like pattern on its body. The scientific name is also more accurate than “leopard eel”, because despite its eel-like shape the animal is a salamander. The paper gave its maximum known size as nearly 60 centimetres. It has an elongated body and external gills, it has no hind legs, and like other sirens it is adapted to life in water.

What makes it so hard to study?

The paper noted that they are common in parts of the southern United States, yet their evolutionary relationships and natural history have received relatively little study.

The animal’s habitat adds to the problem. It lives in freshwater marshes, swamps and other wet places where the water is cloudy and its bottom is muddy. A creature that stays below the surface are unlikely to turn up in regular wildlife surveys.

This also shows why appearance alone cannot settle whether an animal is a new species or already available. The researchers doing the study also compared body measurements and analyzed genetic materials to show that it was distinct. A specimen present in a museum can offer a hint, but confirming a new species may require evidence that holds up against known animals.

A discovery, not the end of the story

The 2018 paper did not answer every question. The animal’s diet, behaviour, distribution and other aspects of its biology still needed study. The researchers hoped that describing the species could encourage more research and work on reticulata siren, a group whose diversity might be greater than earlier recognised.

It was also a reminder that gaps in science are not always in distant places. Sometimes all we need is some research about what is happening and what is missing, as evidence is already there in a museum, even local people may have seen the animal near its habitat.

The “Leopard Eel”, also known as “reticulated siren”, may not be the only new species hiding out in the swamps. It took a specimen, years of fieldwork and genetic analysis to establish what it really was. In the end, the creature did not need to be found in an unexplored wilderness to surprise scientists. It only needed someone to keep asking why it did not fit.

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