From New Guinea to Florida, one of these crocs is not like the others

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  • Scientists have described the newest crocodilian species known to science, the Hall’s New Guinea crocodile, previously considered a population of the already known New Guinea crocodile.
  • The discovery was nearly 40 years in the making, sparked by the late herpetologist Philip Hall, who, in the 1980s, began questioning the differences between the southern and northern populations of crocodiles on the island of New Guinea.
  • To describe the new species, named in honor of Hall, scientists studied and compared New Guinea crocodile skulls held at museums across the U.S.
  • They also found some members of this new species hiding in plain sight: at an alligator farm in Florida that’s famous for having specimens of all known crocodilians.

The St. Augustine Alligator Farm Zoological Park in Florida prides itself on having every species of alligator and crocodile in the world. By 2019, scientists had recognized 26 crocodilian species worldwide, with the alligator farm housing live specimens of all 26. Yet, little did they know that a 27th species lurked in plain sight.

A close-up photo of Hall’s New Guinea crocodile, the 27th crocodilian species known to science, found at the St. Augustine Alligator Farm. Image courtesy of John Brueggen.

In September last year, scientists announced the discovery of that 27th crocodilian, a species native to New Guinea, the world’s second-largest island, and named it Hall’s New Guinea crocodile (Crocodylus halli). For nearly a century, the species was thought to be a population of the New Guinea crocodile (Crocodylus novaeguineae). Published in Copeia, the discovery was nearly 40 years in the making.

Philip Hall, a late scientist at the University of Florida, first speculated in the 1980s that the New Guinea crocodile might actually be two species. In particular, Hall noted that the New Guinea crocodiles on the northern half of the island mated and nested differently from the crocodiles on the southern half. New Guinea is an island sprawling with unique landscapes and unmatched biodiversity, such as birds-of-paradise and tree kangaroos. The country of Indonesia claims the western half of the island, while Papua New Guinea claims the east. The New Guinea highlands divide the island laterally, creating distinct ecosystems in the northern and southern halves of the island.

When Hall passed away, there was still no official conclusion on the existence of a second species.

In 2014, Chris Murray, an assistant professor at Southeastern Louisiana University, and Caleb McMahan, a scientist with the Field Museum in Chicago, teamed up to tackle Hall’s unfinished work.

While Hall’s research focused on the differences between the northern and southern crocodiles’ behavior, Murray and McMahan took a different approach. They studied 51 New Guinea crocodile skulls kept at museums around the U.S. The researchers intensively analyzed the structural differences between crocodiles from the northern and southern halves of the island.

“We used a tool called geometric morphometrics to look at structural differences of the skulls between the two species,” Murray said. “The visible differences are that Novaeguinea [the New Guinea Crocodile] has a more narrow and longer skull, while Halli [Hall’s New Guinea crocodile] has a shorter and wider skull.”

A comparison between the skull structures of the New Guinea crocodile, left, and Hall’s New Guinea crocodile, middle and right. Image courtesy of the American Society of Ichthyologists and Herpetologists.

In describing the new species, Crocodylus halli, Murray and McMahan felt it was best to name the crocodile after the scientist whose work they sought to finish.

After publishing their groundbreaking discovery, Murray and McMahan wanted to see the reptile in real life next. However, the species’ native island of New Guinea was a little out of the way for them, located more than 13,000 kilometers (8,000 miles) from the U.S and around 160 km (100 mi) north of the Australian mainland.

The scientists decided on a closer, cheaper, and more convenient location that might just have the species without even knowing it.

That location was none other than the St. Augustine Alligator Farm Zoological Park in Florida. “The Alligator Farm is known for having every crocodile species in the world,” Murray said. “So, if anyone was going to have them, it was going to be them.”

His hunch was right. When he and McMahan made the trip to St. Augustine, they were pleased to see the newly described crocodile species in the flesh.

“It was really exciting for Caleb and I to see that some of the crocodiles were obviously Halli, as we could clearly see the differences in the skulls that they had,” Murray said.

Caleb McMahan, second left, and Chris Murray, second right, pose with a Hall’s New Guinea crocodile at the St. Augustine Alligator Farm in Florida. They’re flanked by Jen Brueggen, the farm’s social media manager, and John Brueggen, the farm manager. Image courtesy of Chris Murray.

Of course, it’s much easier for someone to identify the minute differences between crocodile skulls if they’ve been studying them for years. John Brueggen, the manager of the St. Augustine Alligator Farm, noted how Hall’s New Guinea crocodile “is not drastically different looking than the animals on the other side of the mountain range in New Guinea, which is why it has taken so long to distinguish it from the other.”

The process to discover Hall’s New Guinea crocodile may have taken nearly four decades, but the work is not over yet. This discovery raises important questions about the actual conservation statuses of the New Guinea crocodile and Hall’s New Guinea crocodile, especially since the IUCN Red List previously listed the New Guinea crocodile as being of least concern.

“We now have two species instead of one,” McMahan said. “If habitats or stressors are different in northern and southern portions of the island, these species could be impacted in different ways.”

In general, wildlife in New Guinea suffer from a variety of human-caused threats, including the logging and mining industries, the destruction of habitats for agricultural plantations (such as for palm oil), and the introduction of non-native wildlife.

Since the publication of Murray and McMahan’s paper last year, the IUCN Crocodile Specialist Group has been reassessing the two New Guinea-based crocodile species and their unique habitats more closely.

“Understanding differences can tell us more than just how to tell the two species apart,” McMahan said. “It gives us important information that can lead to new questions and hypotheses about the evolution and ecology of these crocodiles.”

 

Citation:

Murray, C. M., Russo, P., Zorrilla, A., & McMahan, C. D. (2019). Divergent morphology among populations of the New Guinea crocodile, Crocodylus novaeguineae (Schmidt, 1928): Diagnosis of an independent lineage and description of a new species. Copeia107(3), 517-523. doi:10.1643/CG-19-240

This story first appeared on Mongabay

South Africa Today – Environment


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