Hammerhead Sharks in Costa Rica
October 26th, 2012
Manta rays (Manta birostris) or manta for short, are found all over the tropical waters of the world. But there are some places where the existence of mantas are endangered, not by natural predation, but by fishing. Yes, you read it right. They are harvested in big numbers and has even become a local delicacy where some has said that its meat goes best when cooked in coconut milk, chili and other spices.
As far as the manta fishery is concerned, most of the manta catch will end up in someone else’s plate while a lucky few had gotten away. But these surviving mantas can be injured brought about by the fishing method used where you can see fishing lines entangled in its body. This fishing lines may not necessarily come from manta fishing but also from other fishing lines targeting high value species like tunas.
If you are diving in Costa Rica, there is a high chance of seeing a manta ray. Some divers are amazed by the huge size of this creature which looks like a B2 Bomber of the US Air force. But some divers have noticed, and even video recorded, the existence of fishing lines entangled in a mantas body. Here is a sample of that video where divers are trying to help a manta free from an entangling fishing line.
From the video, some have said that the reason why the manta came near to the divers is that it is asking for help while some have doubted if the manta was really asking for help.
Using the brain to body ratio, it is not conclusive that mantas are intelligent enough to ask for help. In fact, the behavior of mantas coming close to a group of divers is part of their natural behavior as they become curious of our existence underwater, us being the strange creature. But what can possibly be conclusive is that the manta has sensed that something, which is supposedly not to be there, is now entangled in its body.
Since mantas are passive feeders, one good indicator that the manta was presenting itself for diver assistance was the furling of the cephalic lobe, or horns as they commonly call it. Second, when the manta sensed that the diver was taking hold of the fishing line while it is being removed, the manta most probably sensed that this decent-sized creature with a black and white coating that expels bubbles is actually helping her. Yes, the manta was a female due to the absence of claspers, the male reproductive organ. That was also the reason why the manta momentarily paused from swimming giving time for the diver to completely take the fishing line off. This scene is comparable to a cleaning station where you can see motionless mantas being taken cared by cleaner wrasse while removing parasites and dead skin cells from its body.
At the end of the day, I think what is important is not about mantas asking for help or not, but us humans, who are intelligent enough to help this gentle giants.