Understanding Manta Rays (Documentary) | Blue Realm

These graceful and majestic creatures are manta rays. In an isolated corner of the globe, the enormous animals approach and interact with humans. And where there are mantas, there are sharks. A close relative of sharks, manta rays have highly developed brains and appear to possess unusual intelligence. Researcher Dr. Robert Rubin studies the fascinating behavior and biology of mantas. And the best place to find them is 250 miles southwest of the tip of Mexico's Baja Peninsula. These are the giants of San Benedicto. Most fish are cold-blooded and are not generally considered intelligent. Manta rays, however, appear to be warm-blooded, have very large brains, and are perhaps even smart. The giant animals were once called devil fish because their cephalic fins resembled the horns of a devil. Known to be harmless filter feeders, manta rays prey on nothing larger than tiny fish and plankton. Sometimes measuring over 20 feet across, they glide through the water like seabirds on an ocean breeze. Manta rays are elasmobranchs, fish whose skeletons are made of cartilage rather than bone. They are essentially modified sharks. But unlike sharks, manta rays have highly developed brains, the largest of any fish. In behavioral terms, they are far more advanced than their shark cousins. Found primarily in tropical waters, mantas also occur in cooler subtropical and occasionally even temperate seas. These ocean voyagers are definitely not your average fish. Rays are, for the most part, flattened sharks. They have all the characteristics of sharks with the exception of the fact that their bodies are flattened from top to bottom. They differ from sharks in that they live most of their lives on the bottom as opposed to living in the open ocean. Manta rays are somewhat different than the classic description of the rays in that they're very large in size, they've appeared very recently evolutionarily, and like sharks, they're pelagic. That is, they swim in the open ocean. Evolutionarily, sharks are a very old group, and they appeared about 350 million years ago. And for a long period of time, sharks were the only cartilaginous fish on Earth. During the Triassic period, most sharks experienced a worldwide extinction during a period of time when the seas were not highly productive, there wasn't much food. And when they reappeared a number of millions of years later, rays also appeared. And so rays are much more recent than sharks as a group, and mantas are the most recent. They appear first in the fossil record about 20 million years ago. Dr. Robert Lubin is a college biology professor and also one of the world's foremost authorities on manta rays. Not teaching in Central California, he spends much of his time studying the enigmatic animals. His passion, unraveling the mysteries of this little-known giant. I was attracted to manta rays when I first saw them in the southern Sea of Cortez 30 years ago. I doubt that I've ever seen an animal that has more charismatic grace and elegance. As a biologist, you become very curious about animals at the extremes. I've always been interested in animals that seem to be pushing either environmental limits or evolutionary limits. The beauty and the grace of the animal, coupled with the fact that almost nothing was known about them, and the fact that they seem to live in a very unusual environmental niche, can't help but attract a curious biologist. Mantas have a great deal in common with many species of sharks, especially large filter feeders such as basking and whale sharks. Similarities between the two groups also extend to their preferred foods and habitat. Manta rays and a number of species of sharks are almost always found to coexist in similar habitats. And in large part, this is a function of the availability of food. Most of these offshore reefs and underwater seamounts experience extensive periods of upwelling. It increases the nutrient quality of the water, and the food chain begins with that, and so there's always food. And as the food goes, the mantas and the sharks go as one large pelagic community following the food. Dr. Rachel Alexander studies the biology of manta rays. At her lab in Cape Town, South Africa, she made an unusual discovery. A large devil ray had washed up at one of the local beaches here in Cape Town. And while we were working this animal up, I came across a large network of blood vessels in the pectoral fin. The structure of this plexus suggested that it was used to warm the swimming muscles of the animal, which indicate that this species of ray is warm-bodied. Many scientists believe the evolution of blood-warming in wide-ranging species, such as manta rays, is related to a phenomenon called niche expansion. Most fish that are cold-blooded don't venture very far from their preferred habitat. But when body temperatures are elevated above those of the surrounding sea, animals can migrate into colder waters. These rays have been known to occur in differing water temperatures, colder waters than normally expected for these animals that live in tropical and subtropical regions. There's even an unconfirmed report of manta occurring waters off Alaska. Manta rays appear to heat not just their bodies, but their oversized brains as well. Manta rays have extraordinarily large brains when you scale them to their body size. In fact, their brains are not too dissimilar to what you'd expect from a mammal of that size, not a fish. And as we look at the brains, we see that not only are they large in size, but the specific areas that are expanded to make them large in size are the same areas that are expanded in the mammalian brain. Recent work has supported the fact that they're probably maintained at a higher temperature. So it's a huge step evolutionarily and has allowed them to occupy areas in the world that other rays couldn't be successful in. Where is the best place in the world to study mantas? And how do you track their movements through the sea? To study manta rays, a team of researchers and filmmakers traveled to the southwestern tip of Mexico's Baja Peninsula. The region is a busy tourism and sport fishing destination and the gateway to the remote Socorro Islands. In Cabo San Lucas, the scientist and high-definition video crew boarded the liveaboard diving vessel Solmar 5. It would be their home at sea for several weeks. The expedition included Bob Rubin, his colleague, microbiologist Dr. Gavin Chilcott, and veteran cinematographers Tom Campbell and Dennis Kaufman. Before departure, Rubin and Chilcott prepared their research tools, including acoustic surveillance equipment. Gavin and I built a PVC cage that would fit over one of the skiff's sides that we could attach a hydrophone to. That allows us to actively track the animals around the island so we can use the tags in an active way by following them in the skiff with a hydrophone. So it gives us a daily pattern of the animals' movements. After a 24-hour, 250-mile journey southwest, the expedition reached San Benedicto Island and the Socorro Archipelago. Desolate and inhospitable, the islands offer little refuge and have been spared the ill effects of human settlement. The isolated region is, however, a beacon to sharks, whales, and other pelagic animals. Part of a volcanic undersea mountain range that includes the Galapagos Islands. Lonely outposts in the open Pacific, they rise thousands of feet from the sea floor. While there is little sign of life above the surface, the surrounding sea teems with activity. Volcanic spires swarm with schools of fish. Upwellings of cold, nutrient-rich water deliver a steady supply of plankton. And where there is food, sharks and rays are sure to follow. The main islands in the group, San Benedicto, Clarion, and Socorro, are spread out over hundreds of square miles. It has made dozens of trips to the archipelago. San Benedicto Island, in particular, is arguably the best place on the planet to study the giant rays. We're now into about the 20th year of working on these animals and about the 15th year of working at San Benedicto. We've chosen San Benedicto as a study site because it certainly is unique in the major locations in the world where mantas are found. And the mantas numerically are found in greater abundance here than any place else in the world that I know of. And they come back, so it allows us to take a look at them over a long period of time. At San Benedicto Island, Bob Rubin and Gavin Chilcott explore recent evidence of volcanic activity. The geologists figure that this has been formed in three major events. First, once the big cone came up. And then volcanic dust. And then recently, 1952, this whole lava flow just broke out in here. Split out the side and flowed into the open water. This turns out to be one of the more interesting places in the world. So new that you can study the formation of land plant communities, marine communities. The first time I came here, there was no vegetation on the island at all except some gourds. I've always really liked islands. I think they're really enchanting. This one, I've been on a lot of oceanic islands, but I think this one is one of the most charismatic and intriguing to me. It's just so, another landscape from another time. One of the main goals of the expedition was to track mantas with high-tech acoustic tags. Devices would allow the researchers to monitor the animals' movements and provide a wealth of other valuable data. Recently, in an effort to find out more about manta movements and the way in which they use specific habitats, we've begun to apply small acoustic tags that allow us to track the animals by using underwater listening stations. The listening stations are receivers that are placed at various locations in the habitat around the island and are running continuously. As the animals swim by, they pick up a ping from the tag that's been attached to the animal and record it. And so it gives us a pattern of when animals are in the habitat, what the water temperatures are like when they're there, and also how frequently they're there. Often these shallow bays are places, in the morning particularly, mantas will come in and move around these bays. Interestingly, in the later afternoon, they seem to go around from point to point. Actually what we want is we want to be as close to the tip of the lava flow, right there, as we can get, to get at least one good mark on the GPS. Analyzing the data has shown us that the animals are present somewhat infrequently, and for the period of time that the tags have been out and the animals have been recorded, they're only in the habitat about 2% of the time. The rest of the time they're away from the island, and they may be moving between islands, they may be in deep water. We're not sure where they are, but we know that they're not close to the listening stations. We also have found that they're primarily animals of the early day. During the night we have very, very few hits from our stations, suggesting that during the daylight hours they're present, and during the dark hours they're not around the island at all. Well, this animal is probably right behind this lava flow. We just got several pretty strong signals, and then they're gone now. My only guess is that it's going in and out of those troughs, coming out to get a signal, and when it goes back in we won't get one. Let's go see. To find out where the rays migrate when they are away from the islands, Rubin utilizes a new tagging system based on satellite technology. The devices are attached to the animal's body where they begin to acquire and store information. After gathering data for up to a year, the tags are pre-programmed to detach and float to the surface. They then search for a satellite and, after receiving a strong signal, begin downloading information. The tags record a number of factors, including water temperatures, dive depths, locations, and, in some cases, even swimming speeds. Satellite monitoring is a dramatic leap forward in manta research. Satellite tracking will allow us not only to determine how the animals use the specific habitats that we know they're found in, but also how they might move between islands and other habitats. We may also see that there's a well-defined migratory pattern that connects groups of islands or different areas of the ocean that become critical areas to protect. A particular tag was set up so that it'll come up on New Year's Day. New Year's Day? Yeah. Oh, wow. Well, we'll get the data. We'll have the computer in one hand and a bottle of champagne in the other. Yeah. We'll give you a call. This is the first time I've ever seen mantas at this site. And, interestingly enough, one of the animals that we know from San Benedicto, we did see here 30 days later. And that's the only other time that I've ever seen mantas at this site. So we know that they move between at least those two sites, and the satellite tag will tell us a little more. Yeah. Maybe they follow some deep ridgeline or something. That could be. All these islands are on the same underwater ridge system, and that may be what they're using as a migratory cue. Yeah. Possibly. Why do manta rays approach and interact with humans? And who are the hitchhikers on their backs? In the Socorro Islands, it doesn't take long to find mantas. Drawn to the sound of boat motors, the animals immediately approach and exhibit their renowned behavior. Even after 20 years of studying the rays, Bob Rubin is still amazed at how the animals court human company. The interactions that exist between manta rays and humans are not only curious, but remarkable. And I think it's fair to say that nowhere else in the world can people interact with wild vertebrates of this size and these numbers. Wild vertebrate animals are not normally curious about humans, except as potential predators or perhaps prey. But mantas seem uniquely curious about human organisms, to the point of courting the interactions, coming very, very close and making eye-to-eye contact, and allowing humans to stroke them, ride them, pet them. Just about every possible type of contact that a person could make is not only possible, but it seems to be promoted by the behavior of many of the animals. The complexity of manta brains suggests that they may be able to carry out a lot of higher functions that we normally associate with mammals. And their behavior seems to reflect some of those characters. I think it's fair to say that they're curious, and curiosity to some degree is a sign of intelligence. One of the most intriguing aspects of manta and human interaction is that the animals appear to favor certain divers. In simple experiments, Rubin has attempted to discover how they choose their favorite playmates. Certain mantas will allow certain individual humans to come close while moving away from others. And we wondered as to how they might be able to tell, and so in small little experiments we've changed diving gear. And they still are able to recognize the person that they would allow come close and the person that they reject. And we also were able to show that by putting tinfoil in our masks, where they couldn't see our eyes, they no longer could tell who the person was that they wanted to ride or the person they'd reject. And so the speculation is that they're recognizing us by our eyes. And their close proximity and the fact that they come right next to you and look eye to eye may in fact support that. Mantas and other large pelagic animals play host to a strange fish called lamora. The hitchhikers attach themselves to their rides with a specially adapted dorsal fin. Whale sharks, such as this 45-foot giant, are frequently covered with dozens of the fish. The bigger the host, the larger the size and number of lamoras. Even a juvenile whale shark has to contend with the pesky freeloaders. Mantas are very much like a floating community in open water. Very big organisms like this attract a lot of other organisms that use manta rays either as shelter, protection from predators, as a source of transport from one spot to another, or perhaps even a guide to take the other species to food. One of the organisms that exists in close association with mantas are large lamora fish that are sometimes called sucker fish. It was thought for a long period of time that lamoras were parasitic and were using the mantas as a point of attachment and cleaning the mantas to some degree, symbiotically taking parasites and sawing off their body, or perhaps just picking up the scraps after a manta meal. To investigate the relationship between the two fish, Ruben enlisted the services of a free diver. Catching one of the wily fish was no easy feat, especially without scuba gear. Even if you do manage to grab onto them, lamoras' iron grip make extraction difficult. They do, however, make great handles for an exciting manta ride. You can see the disc and this is a fin. Yeah, this is the dorsal fin, the same fin that you see in a shark. It's just modified into a sucker. And in a regular fish, the fin rays that go into the fin to hold it up have been modified here into these sucking arrangements. They tie in and then they pull into the skin and create a suction and also a grip. You can feel the reverse spines here. It's kind of like a gill, but of course it's not, and those are just the rays of the fin. The inside of the gills are overlapped. They may be straining plankton in the same way the mantas are. The ramora revealed an exciting discovery. Ramoras, like mantas, appear to have their own hitchhikers. These are copepod parasites. They're very interesting, probably unknown. I would bet this is a new species. These kinds of parasites are species specific. So it could be that this kind of copepod parasite, this species, is found only on ramoras. There are similar copepods like this, but they have much longer tail structures, tail-like structures, that are found on the dorsal fins of sharks. Back at his lab, Ruben made a more thorough examination of the unusual fish. His findings have helped to disprove many long-held theories about ramoras and their relationship with their hosts. One of the things that's kind of interesting about them is that when you look at the mouth of the animal, the mouth is disproportionately large. It has a really big mouth for a fish of this size. And then you look at the gills of the animal here, and see how large the gills are? They're really big, almost like the fish were some kind of a pelagic swimmer, like a tuna. Among mantas, and also among the great whales, we see exactly this sort of thing. That suggests that instead of feeding on fish, as one might expect, that they've been feeding on some kind of planktonic organism. And I think this is a fairly reasonable verification of the fact that these animals are planktivores, just like the mantas. And they just use the manta rays as taxi cabs to the restaurant. A very unusual fish, one of the great feats of evolutionary design in the marine world. How do you tell mantas apart? Are they a potential source of new miracle drugs? And what is the most popular attraction at one of the world's largest aquariums? Despite the fact that manta rays are very large in size and widely distributed, relatively little is known about their biology or genetics. Mantas are considered to be members of a single species. Although they are sometimes referred to as either a Pacific or an Atlantic manta ray, depending on where they're encountered. The rays also have two distinct body patterns. Manta rays occur in two different color types. One of them with white on the back and a large V at the base of the dorsal fin, and we call those chevron mantas. And others are solid black like large stealth bombers. And we call those black mantas. The black mantas are not found typically in warmer tropical waters. Whereas the chevron pattern seems to be the most common pattern worldwide. Individual manta rays, like orcas and humpback whales, have distinguishing characteristics. These subtle and sometimes dramatic differences enable the researchers to utilize photo identification. Each animal has a different marking, very much like an individual fingerprint. By looking at these through time, we've been able to establish that they don't change. And so that once you have a photograph of an animal's undersurface, you can enter it into a catalog and you can match it time after time to new photographs. We've identified now 146 individuals, and of that 146 animals, we've seen about 40 animals more than once. Some of the animals we know for as long as 15 years. The photo identification system allows us to get an estimate as to how big this population is, and whether it's what biologists call an open or closed population. And that really means are animals moving in and out of it from other sources, or does this population represent one large group of animals that are genetically related like large families. Bob Rubin and Gavin Chilcott's research includes DNA sampling of metatissue. These clues help the researchers piece together a difficult genetic puzzle. Acquiring a DNA sample requires a specially tipped spear that extracts a plug of tissue the size of a pencil eraser. A quick jab from a sharp spearhead, not unlike a mosquito bite, secures the sample. The difficult part is trying to catch the speedy mantis. In sampling small amounts of skin and surface tissue, we're able to bring that tissue back to the laboratory and analyze the sequences in the DNA of the cells. Those sequences, when compared to other samples, will tell us the kinship similarities between individual mantis and also between groups of mantis, for example, those found in one group of islands as opposed to those found in another. Boy, that was about the most cooperative manta you'll ever find in your life. Yeah, that was successful despite a false start there. You didn't get the DNA sample in the first go, did you? Well, the tissue didn't retain. We did get a good punch, but the tissue didn't come out with the tip, and I'm not sure why. So, we changed the tip, and the second tip was successful. So, you got a good sample now? Got a good sample. The research team also collected samples of the mucus coating of mantis. The potential healing properties of the mucus may one day be the source of new wonder drugs. Elasmobranchs as a group, the sharks and the rays, seem to have a remarkable capacity for wound repair and tissue regeneration. Manta rays are covered with a very fine mucus film. One of the new things we've become interested in is the role that this mucus might play in protecting manta rays from pathogens, from bacterial invaders. And so recently, we've collected some of this mucus and brought it back for laboratory analysis. It's possible that mucuses of this type may have antibacterial qualities not only for the mantis, but also for human skin as well. And it's theoretically possible that things like this could be produced by pharmaceutical companies and used to enhance wound repair and decrease the potential for infection. We know that we've extracted a lot of natural products, drugs and things that have been very useful in the human condition from tropical rainforests. And the sea seems to be the next frontier for that. The Atlantis Resort and Casino in the Bahamas boasts one of the world's largest aquariums. And the number one attraction for the past few years has been bubbles, an Atlantic manta ray. Of course, sharks are a top draw for visitors, but their graceful cousin consistently ranked as the guest favorite. Our sharks, I'd say, rate number two in terms of attraction for the guests. And what outranks the sharks for us is our impressive manta ray that we have right here in the ruins tank. That's always the biggest draw for the guests is to watch the manta ray. And because of the size, right now this one that we have in the tank is just over 13 feet in width. Bubbles easily acclimatized to her new surroundings. But with daily feedings, she dramatically increased in size. Once Bubbles reached a wingspan of almost 15 feet, it was clearly evident that she had outgrown her artificial home. A reluctant decision was made to release her back into the wild. Capturing and transporting such a huge animal was no easy feat. Timing was critical and a helicopter waited on standby. Released within just a few minutes, she quickly bolted into the depths. Basically, she just outgrew the aquarium. They grow really quick. They almost double their size in the first year. So we had to release her. It went very well. It was a great effort, great team effort. A few days later, a six-foot juvenile manta was caught off Rose Island. Like Bubbles before her, the new ray, appropriately named Rose, will be a top attraction at Atlantis. How does such an endearing animal find itself on an endangered species list? In February 1994, members of the conservation group Sea-Watch visited the Socorro Archipelago. They were there to scuba dive and snorkel with the famed mantas. On Valentine's Day, Mexican fishing boats appeared and started pulling in nets off the southern tip of San Benedicto Island. Mantas that the group had been interacting with the day before were hopelessly trapped in gill nets. The entangled rays destroyed valuable fishing gear and enraged fishermen killed the animals. Sea-Watch brought the disturbing video footage to the attention of the Mexican media. Influential television programs began airing the story and networks from around the world quickly seized on the dramatic images. The footage was brought to the attention of the head of fisheries and the Mexican president. Government and public reaction was swift. Within two months, the Pacific manta ray was put on an endangered species list. It is now a crime to kill a manta ray in Mexico. The islands are highly desirable as a fishing ground because they are so highly productive. And in the recent past, fishermen have used the islands to take large quantities of billfish, sharks and a variety of other species including manta rays. Manta rays were taken rather indiscriminately and killed rather viciously by fishermen because they were contaminating the nets. Mantas worldwide need protection because as you look at them biologically, they're first large animals that don't reach reproductive maturity until late in life. That's true of most sharks and rays. They are also characterized by giving birth to a single pup. And so it's then likely that a single female will give birth to maybe only 10 or 12 pups in her entire lifetime. Large animals like mantas can't survive without a conscious human conservation effort. We got a very good measurement of one. A complete measurement of both the width and the length. After nearly a month at sea, it was time to return to Cabo San Lucas. For Bob Rubin and the rest of the team, leaving was bittersweet. But the expedition revealed many new insights into manta biology, distribution and behavior. After returning to his lab at Santa Rosa Junior College, Rubin began to receive results from his satellite tagging program. We recently received information from two tags that had been out for approximately a month. And it translates into 890 pages of data. Speculation suggests that these animals are probably well away from the island in deep water. And all the indications that we have imply that the animals move away from the island at night into deep water to feed. And then return to the island during the daylight hours. And we know that in some cases we see animals at one island within a few days to several weeks. We see the same animal 100 kilometers away. The animals are present for a few years at a time and then often gone for several years at a time. So they may be perhaps thousands of miles away from these sites during other times of their life history. And the satellite tags will allow us to identify those trends. The Socorro Archipelago and nearby Sea of Cortez were up until recently some of the richest waters on Earth. The undersea ecosystem in the region is now in danger of collapse. Industrial scale gill netting dramatically depletes resources. And when fishing boats discard damaged nets, they continue to kill. Sharks, sea lions and mantas are no match for the nearly indestructible lines. Long lining produces a huge bycatch of non-targeted species. Almost all the fish and other animals caught are incidental. Worthless to fishermen. And Asian demand for shark fin soup fuels a wasteful industry. There is hope. Due to the conservation efforts of groups such as Sea-Watch and the Save Our Seas Foundation and scientists like Bob Rubin, mantas have a fighting chance of survival. The Socorro Archipelago is now a protected biosphere of Mexico. Manta rays are one of the most incredible organisms the planet has ever spawned. And to watch them, to be around them, to have the ability to study them and know more about their biology is exciting beyond belief. I'm very optimistic about the future because I think some of the work that we're doing and the work of others will result in a much better understanding of who they are and how important they are in the structure of pelagic communities and the world's oceans as a whole. Working with mantas is one of the most exciting things that anybody could do. And I love doing it every day. I hope to continue to do it as long as I'm here and as long as they're here. And I hope that they're here a lot longer than I am.