“Understanding melanism can give us insight into how global manta ray populations are connected, and how certain traits spread across different locations. Melanism is typically a heritable trait that is passed down from generation to generation, yet scientists are still trying to identify the genes that are responsible for melanism in manta rays. “This study also highlights the benefits of long-term photo-ID catalogs and collaborative citizen science platforms like MantaMatcher, which enables research of this kind to take place,” added Dr. Researchers made use of MantaMatcher – a global database for manta rays where scientists and members of the public record encounters – to access identification photos of individuals from a range of locations. The study also found evidence that melanism may spread between neighbouring populations through gene flow in giant manta rays, which occurs when individuals travel between locations. It is likely that the variation in melanism percentages across locations may be a result of more random evolutionary processes such as genetic drift, where traits occur in a population by pure chance. The findings suggest that predation does not influence melanism in these populations. Despite being less camouflaged, we found that predators don't appear to target black mantas more than normal colored mantas, as survival rates were equal,” said Dr Andrea Marshall, co-founder and principal scientist of MMF’s global manta ray program. “Because of their size, manta rays don’t have many predators, mainly larger sharks and orcas. To begin to answer this question, the study also looked at whether survival rates were different for melanistic mantas when compared to typical-colored manta rays. While black manta rays may look stealthy to us, their darker coloration could, in fact, make them more visible to predators. But scientists questioned whether it could have any benefits or disadvantages to manta rays. In some terrestrial species, melanism has been linked to improved camouflage or increased thermoregulation. While melanism is relatively common in terrestrial animals, like black panthers (which are in fact leopards or jaguars), it is rare in marine species. Although they are often mistaken as a different species, these melanistic individuals are simply a different color variation (or ‘color morph’) within a species.

Melanism occurs when an increase in darker pigments in an animal’s skin or fur results in darker-colored or entirely black individuals. Their research, which is published today, found that the frequency of melanism varied across the studied locations, and that this variation was more likely a result of random evolutionary processes such as genetic drift, as opposed to selection by predation. In a new study – the first to investigate melanism in a marine species – scientists from the Marine Megafauna Foundation (MMF), University of Western Australia, University of Papua, Udayana University, Murdoch University, and Macquarie University set out to learn more about this fascinating color variation. Have you ever seen a black manta ray and wondered what makes it that color? Or whether the darker coloration has any effect on the way the animal lives and behaves?

Giant manta ray face