The Griffith University A new research finding reveals the reason behind the seemingly unexplained increase in the number of polygonal crocodiles: the success story of keeping Australia’s largest predator appears to be due to ostracized pigs.
The Biology Letters In a study published in the journal, experts compared specimens made for 50 years of living in the same place in museums. In contrast, carbon and nitrogen isotopes indicative of animal food were examined.
“The museum specimens were collected when the polygonal crocodiles got very few votes because they were being hunted a lot,” said Professor Stuart Boone, one of the research participants. Hunting supposedly drove the crocodiles away from the shores and they only got to find their prey in the sea water. However, there has been a clear change in the past 50 years: reptiles have moved away from the diet of the sea. “When their numbers began to grow again, they returned to the floodplains and the extensive river system in parallel, and they appear to be more dependent on today’s wild food sources,” the researcher added.
Aborted pigs, without conscious reproduction, are increasingly similar to the ancestors of wild boars.
Source: Wikimedia Commons
This change could be caused by two things: competition among crocodiles for food, and the presence of increasingly common hooves, such as feral pigs, on the banks of rivers. “Without the local increase in pig populations over the past 50 years and the change in crocodile diet, pig populations would not have increased significantly.”
Fixation isotope analysis can be used to very accurately determine the diet of an organism, in which case there was a clear shift from the marine diet to the mainland.
The increase in the number of crocodiles is also helping to control the numbers of extinct pigs, which are causing severe damage to both wildlife and agriculture. Captain Cook released the first pair of pigs in Australia.
