The inguinal crocodiles living in the Indopacific region have a bad reputation: they keep falling victim to careless people. Bathing in the distribution area is considered life -threatening. The reptiles occurring in the sweet and salt water also suffered from us humans: Among other things, they were hunted so strongly because of their skin that they were threatened with extinction in large parts of their Australian habitat. In addition to a hunting ban, a change of food caused a strong increase in existence of these large reptiles, Mariana Campbell from Charles Darwin University in Darwin and her team write in the "Biology Letters".
By comparing certain isotope ratios in the bones of old museum specimens and today's saltwater crocodiles, the working group discovered that the animals no longer eat fish as before, but have switched to the meat of terrestrial organisms: The proportion of carbon-13 and nitrogen-15 isotopes in the museum pieces, some of which are more than 50 years old, was therefore significantly higher than in their current counterparts. Both isotopes speak for a strongly oceanic food chain.
With the ban on hunting in the early 1970s, the number of groin or salt water crocodiles began to rise again. At the same time, the inventory of introduced mammals such as buffalos or pigs grew in the northern Australian swamps and river areas. The increased competitive pressure by prey among the reptiles ensured that the animals expanded their food spectrum with these mammals. Due to the improved care, the population recovered faster and stronger, the biologists write.
Especially the pigs are easily victimized, as they are also happy to reproduce and also like to wallow in water and mud, where the crocodiles can lie in wait for them. In this way, the predators help to contain the population of the invasive species. And in addition, they ensure that fresh nutrients get back into the water via food and the resulting digestive products, according to Campbell and Co.
