Awesome Nature: Predator Versus Prey

The Revillagigedo Archipelago is located off Mexico’s Pacific Coast and is comprised of four islands: San Benedicto, Socorro, Roca Partida, and Clarion. Because “Revillagigedo” is a mouthful, most American divers simply refer to the archipelago as “Socorro.” (It’s pronounced “ray villa he HAY dough,” by the way.) In 1994, the Mexican government established the Revillagigedo Archipelago “biosphere reserve” to protect this unique ecosystem. Since 2002, no fishing is permitted within 12 miles of the islands, and visitors are not allowed to set foot upon the islands. These laws prevent humans from harvesting and harassing the larger animals, and allow them to thrive.

San Benedicto is about 230 miles from the Cabo San Lucas harbor. Because of its distance from the mainland, this is obviously a live-aboard trip, and there are several highly reputable dive charter companies offering regularly scheduled trips. It is a rugged volcanic island with a massive shield volcano. This island is known for its manta rays. These are giants, some better than 20-feet across, and are easily approached while they are at cleaning stations at El Boiler. Divers also see schooling scalloped hammerhead sharks here.

Socorro is the largest island and is home to a Mexican Navy Base. This is a great place to dive with bottlenose dolphins, mantas, and if you are lucky in late winter, humpback whales.

Roca Partida is a rocky pinnacle that juts up from deep water about 70 miles west of Socorro. This rock is small and may be easily circumnavigated twice on a single tank. It is home to numerous whitetip reef sharks that rest in depressions in the wall like cordwood, as well as large schools of silky sharks, jacks and the occasional Galapagos shark.

The order Cetacea — dolphins, porpoises and whales — includes two living sub-orders, Mysticeti (baleen whales) and Odontoceti (toothed whales). 

Members of Mysticeti have two blowholes, baleen, no echolocation, and they have a relatively small brain for their body size. Known as the mustached whales, the baleen that lines their mouths is actually hair that serves as a modified filter or strainer they use when feeding on small crustaceans often referred to as krill, and small, schooling fish. The Mysticeti are the largest creatures ever to live on Earth, larger than the largest dinosaur. Ironically, they feed exclusively on some of the smallest creatures in the ocean. These whales have enormous appetites due to their size and the fact that many do not feed for five or more months during their seasonal migrations.

Humpback whales, one of the most prolific of the baleen whales, are found in all the world’s oceans, and may grow to 57 feet and reach 48 tons. They take their common name from the “humped back” they show off as they prepare to dive. Their Latin name, Megaptera novaeangliae, literally means “big-winged New Englander” and refers to the size of their pectoral fins and where they were first encountered. Humpbacks are unique in that they have extraordinarily long pectoral fins that may be a third as long as their body. They undertake one of the longest migrations of any mammal as they travel between their high latitude feeding grounds and their warm water calving/mating grounds. Male escorts, who are not the calf’s father, often accompany mother and calf pairs.

Members of Odontoceti have teeth, a single blowhole, the ability to echolocate, and a rather large brain for their size. These are referred to as the toothed whales and dolphins. All dolphins and porpoises belong to this suborder. Killer whales are the largest living members of the dolphin family. Males typically range from 23 to 30 feet long and weigh in excess of 6 tons. Females are smaller, generally ranging from 20 to 26 feet and weighing 3 to 4 tons. The toothed whales are generally more social animals than the baleen whales and have larger brains. Scientists believe their relatively large brain size is the evolutionary result of needing to handle complex social interaction and to process echolocation data. Killer whales are found in all oceans. Individual populations specialize in particular types of prey. Some feed exclusively on fish, while others hunt small marine mammals as well as baleen whales. Killer whales are regarded as apex predators, lacking natural predators.

As the first rays of sunlight hit Roca Partida the rock began to glow an eerie purplish hue. In the dim light we were barely able to make out the blows of three humpback whales resting in the lee of the rock — presumably an adult female, her new calf, and an escort male. The trip was off to a promising start. As the sun rose higher the crew of the Solmar V was able identify one of the whales — a female that in previous years had brought her calf here to rest and nurse. They described this whale as friendly and approachable.

These whales had recently completed a long journey from their feeding grounds in the north and spent a great deal of time resting. Resting adults may only breathe every 15 minutes or so and spend much of their time hovering at around 30 feet. Small calves need to breathe more frequently and may take four of five breaths for every one the adults need. This calf took turns resting beneath its mother’s nose, coming to the surface to breath, and interacting with our divers while the mom remained submerged.

The whales seemed to be as curious about us as we were about them. The adults often turned and swam by us as they came up to breathe, but the calf was more active and playful, and checked out each of our divers. It seemed to be full of energy as it explored its world — the school of bottlenose dolphins, the rocky pinnacle, the fish, and us divers. This creature had everything a young whale could hope for: an attentive mother, a protective escort, and all the rich milk it could drink. Life was good.

The feeling of euphoria we felt was hard to describe as we experienced long encounters with this playful calf. Members of our group named the calf “Bubbles” because it always let out a long stream of bubbles on its way to the surface. Everyone in our group was enjoying a “bucket list” experience, photographing and just interacting with the calf, with mom keeping a watchful eye. It’s no secret that certain big animals — like whales, dolphins, elephants and bears — capture our hearts. Researchers have a name for big animals that have popular appeal; they’re called charismatic megafauna, which is a fancy name for big animals that fascinate us.

The next day began like the previous and we all hoped for a repeat of the experience, because there’s no such thing as too much time spent swimming with whales. After the dive we climbed aboard our Zodiac, ditched our scuba gear, and excitedly prepared to snorkel with the whales. Suddenly our excitement turned to confusion. About 100 feet away the ocean erupted in a fury of thrashing fins and bodies. Someone yelled out, “orca!” I saw red. As the ocean surface swirled with crimson, my mind reeled; I was trying to make sense of the gruesome scene unfolding before us.

Two large male orcas had ambushed the humpbacks. In the ensuing battle the mother humpback and escort male slapped their mighty tails on the surface in an attempt to keep the orcas from the calf. The sheer force, the violence, of the encounter was amazing. After all, we’d just spent the previous day with these whales, describing our encounters as “friendly” and “peaceful.” 

To our disbelief, the pair of orcas managed to quickly separate the humpback calf from its mother and the escort male. They proceeded to kill the youngster by taking turns holding it below the surface, drowning it. 

The mother humpback and her escort had, despite their massive size, been no match for the speed and skill of the hungry orcas. When it was all over, we heard the humpbacks making hideous crying sounds as they surfaced. Were their cries an expression of grief? We watched in stunned silence as the orcas began to feed. A few silky sharks joined in, and in less than an hour not much remained of the baby whale.

It would have been easy for me to describe this event as the “good guys” versus the “bad guys.” The humpbacks, a caring mother and brand new baby, against the murderous “killer whales” — I mean, who would hunt down and kill a sweet, defenseless baby? But nature isn’t about good versus evil. Nature is about survival of the fittest. And everybody’s gotta eat.

Anthropomorphism can be defined as the attribution of human motivation, characteristics, or behavior to inanimate objects, animals, or natural phenomena. It is very much part of human nature to anthropomorphize the animals around us. It was easy for me and members of our group to envision the baby whale as a symbol of everything that’s right in this world — new life and hope and curiosity and a promise for a bright, happy future. It’s just as easy to make the orcas out to be the villains — violent bullies picking on a harmless creature. The fact is, animals simply fill their ecological niche; they do what they do to survive. Humpbacks feed on krill, migrate, and nurture their young in warm, calm seas. This group of orcas feeds exclusively on marine mammals. The orcas had no concept of good or evil. They fulfilled their own instinctual need to survive by preying upon a ready food source.

Had the calf been a little stronger or older, or the adults more attentive, perhaps the outcome may have been different. Nature has a way of selecting for characteristics needed for the species to survive. However, I suspect that the ultimate outcome of this encounter was determined within the first ten seconds, since the orcas appeared to have quickly delivered a weakening, if not fatal bite.

I must admit that witnessing this event caused me to feel a deep sadness for the baby whale and its mother. However, I must also say that as a diver, I also felt fortunate to observe such an incredible encounter. Parts of it were awful. But to have the opportunity to experience nature in its real, raw state? That’s awesome. 

The following dive charter companies offer trips to the Revillagigedo Islands:

solmarv.com