Swamp crocodiles and crocodiles in the Ganges turn orange, and scientists think the cause lies in the amount of iron in the water in the area where they live.
Orange crocodiles were discovered in Chitwan National Park at the foot of the Himalayas. To find out why alligators have this strange color, Phoebe Griffith, a researcher at Leibniz Institute of Inland Fisheries and Freshwater Ecology, and a collaborator with the Mecistops project. This is a conservation project dedicated to protecting and reintroducing the narrow-nosed crocodile (Mecistops cataphractus) in Côte d'Ivoire and western Africa.
An orange crocodile in Chitwan National Park. (Photo: Phoebe Griffith).
The team found that some of the rivers and streams that flow through the national park have extremely high levels of iron. Swamp crocodiles and Ganges crocodiles spend a lot of time in streams or near estuaries, gradually becoming dark orange. Some areas in Chitwan have high concentrations of iron in the water, which reacts with oxygen to form an orange compound called iron oxide. Due to living mainly in the water, the Ganges crocodile is not well adapted to walking on land and only crawls on sandy shores to warm up in the sun or nest. Iron-rich rivers can cause their scales and teeth to cover a temporary layer of rust particles.
The Ganges crocodile (Gavialis gangeticus) is a critically endangered freshwater crocodile with an elongated snout and a large tumor at the tip. Males can be 5 m long and weigh up to 250 kg. The Ganga crocodile population in Nepal has dropped 98% since the 1940s due to overhunting, according to the Zoological Society of London. Most of the remaining 200 live in Chitwan National Park, where they face many other risks such as pollution, open fishing and declining fish numbers.
Swamp crocodiles (Crocodylus palustris) are more common, inhabiting marshes and waterways stretching from southern Iran to the Indian subcontinent. They have a wide snout and are similar in size to the Ganges crocodile, but can weigh twice as much depending on the bust. According to zoologist Lala Aswini Kumar Singh, rust particles attached to the crocodile's body can automatically drift away in cleaner water.
A 2016 study in the African Journal of Ecology found that the cave-dwelling dwarf crocodile (Osteolaemus tetraspis) in Gagon can turn orange due to exposure to bat droppings containing large amounts of urea, a compound that has the Discoloration forms when proteins break down in the liver.
