A unique species of crocodile lives in New Guinea, but in 1989, a researcher suspected that there may be more to the story on the tropical island.
Philip Hall, the University of Florida researcher investigating if the island’s crocodiles belonged to two different species, died before he could finish his work.
Now, researchers have finished up the work that Hall began and their new study shows that he was right. Their study published Thursday in the journal Copeia.
The New Guinea Crocodile was discovered in 1928. But the large island north of Australia is divided by a mountain range, creating distinct habitats in the north and south. The researchers wondered how different the crocodiles might be in these environments.
In 2014, Chris Murray, assistant professor at Southeastern Louisiana University, and Caleb McMahan, a scientist at the Field Museum in Chicago, were at a conference discussing the differences in reptile skulls. They attended a talk that raised Hall’s research and asked for help to finish the investigation distinguishing between the New Guinea crocodiles.
Hall’s work had noted differences in the way the crocodiles nested and mated. McMahan and Murray were more focused on skeletal differences. Together, the information could paint a bigger picture that would differentiate between species.
“Philip Hall really provided the interesting baseline work on these crocodiles, especially for ecological data,” McMahan said. “Our work adds to this with additional morphological insight into how distinctive these two species of crocodiles.”
They analyzed 51 skulls belonging to the New Guinea Crocodile to look for differences between ones that lived in the north of the island versus the south. They studied specimens from seven different museum collections. Many of the skulls were 90 years old. And the crocodiles they belonged to could reach ten feet in length.
“They highlight the beauty of natural history museums,” Murray said. “We didn’t have to go to Papua New Guinea and collect a bunch of specimens, which would have been incredibly difficult anyhow, and very expensive.”
The researchers also went to the St. Augustine Alligator Farm Zoological Park in Florida to see if observing live crocodiles matched up with the differences noted in the skeletons.
“They have live individuals of what’s called novaeguineae, and we were able to look at those and say, ‘Oh yeah, this matches the north and this matches the south!’ I thought that was super cool,” McMahan said.
“We could even look at a skull that they had there and tell what river it came from,” Murray said. “So our analysis really did a good job at teasing apart where these things are from.”
The crocodile species in the south has now been declared a separate species and the researchers named it Crocodylus halli in honor of Philip Hall.
“I think it was really special for me in particular, I’ve been reading his work since the beginning of my career in academia, in my first year as a master’s student, so to come full circle and help contribute to his work was meaningful,” Murray said. “Being able to name the thing that he initially pondered after him was even more meaningful.”
The researchers hope this insight will help with conservation efforts to protect the crocodiles.
“It could be that when we consider crocs on the whole island, they might be okay, but if we start looking at a species north of the highlands and one south of the highlands you might find more habitat degradation and population threats in one over the other. This highlights the importance of attention to ecology and conservation for both lineages,” McMahan said.
Their work also highlights the important of museum specimens.
“There are new species out there but a lot of them are sitting in drawers and cabinets in museums, and it just takes time to look at them and figure that out,” McMahan said.