The Successful Sea Lions of Los Islotes

The Successful Sea Lions of Los Islotes

Photo by Erika Peterman

by Bryan Jáuregui for the Journal del Pacifico

Swimming with the sea lion puppies at Los Islotes, the southernmost rookery of the California Sea Lion, Zalophus californianus, is truly one of life’s great joys. The puppies are often playful and naughty, nibbling on the flippers and fingers of human visitors, while their teenage siblings like to sidle up to humans for a good belly rub or game of chase. Their mothers may be found sunning themselves on the rocks, enjoying a snooze, while the males who rule the 20 territories of Los Islotes indefatigably patrol the waters to ensure everyone’s safety. It is a scene of utter Baja bliss, and humans can’t help but feel a magical glow from this most wondrous of wildlife encounters.

All of which begs the obvious question: Why are the males working so hard when everyone else is just having a good time?

Claudia J. Hernandez-Camacho, a professor of biology at CICIMAR in La Paz, has been studying the sea lions of Los Islotes and the Sea of Cortez since 1990. In particular, she has studied the entire lifespan of 190 sea lion individuals (94 females, 96 males) who were hot-branded by her professor between 1980 and 1984. Her findings, based on these specific sea lions and others, tell a complicated tale for our pinniped friends.

“Sea lions are polygynous, meaning that one male mates with several females in the territory that he defends on land and sea. It takes an enormous amount of energy to defend this territory, and in the breeding season a territorial male, who is so focused on his job that he barely eats or sleeps, can lose up to 30% of his impressive body weight (400 to 500 kilos, or about a ton) in just a few weeks.”

Photo by Colin Ruggiero for Todos Santos Eco Adventures

One would assume, of course, that the males are spending this incredible amount of energy to defend their harems and offspring, to ensure the survival of their genes. “But this is not exactly the case” says Claudia, “they are defending the territory, not the females.” The science proves this out. “Genetic studies show that just 15% of territorial males are the fathers of the newborns the next breeding season.  It is not just that the females hook up with and get impregnated by wandering, opportunistic males when they slip off for their 4-5 day feeding trips, which they do, but in some cases the territorial males are not even copulating with the females in their territory.” All that work and no sex?

“It’s a little more complicated than that,” says Claudia. “There are 600 individual sea lions at Los Islotes, and every year around 170 pups are born. Almost 30% of the pups die in the first two years, either from disease or because they or their mothers have fallen prey to predators. But that means that 70% are surviving. With this type of situation, many of the sea lions are, by definition, related. It could be argued that the Los Islotes males work so hard not just for their own offspring, but because they are protecting their extended families. This would also explain why they do not copulate with all the females in their territory. They are avoiding inbreeding.” This is an approach to collective living that we generally only associate with high intelligence mammals like primates, elephants and dolphins.

The Los Islotes territorial males are so successful in their defense of the colony, and have made conditions so conducive to survival, that Los Islotes is actually full to capacity now. In fact, two new satellite colonies have been created nearby in recent years by all the young males who are no longer welcome at Los Islotes, but who are still too young and slight to fight older, larger males for territory. Sea lions are philopatric, meaning that they stay in or habitually return to the area of their birth, so it is possible that these satellite colonies will only continue to grow.

What makes this all the more remarkable is that it is happening at a time when the overall population of California Sea Lions in the Sea of Cortez is dropping dramatically. Between 2000 and 2018, 40% of the population of other colonies disappeared. Are those males falling down on the job? Not likely says Claudia. “We are analyzing a lot of

Photo by Colin Ruggiero for Todos Santos Eco Adventures

environmental variables right now to determine the main factor causing the decline of these colonies, but one of the most likely culprits is the food supply” she observes. “It is not that the fish populations in the other parts of the Sea of Cortez are declining, they are not. It is that the fish are moving further south. While the sea lions of Los Islotes, the southernmost California Sea Lion rookery, are benefitting from this trend, it is proving lethal to others. Healthy females will travel up to 60 kilometers away from their colonies to find food, but further than that is not feasible. They need to conserve energy to produce milk for their pups. And even in those more northern locations where there are still fish, there are a very limited number of fish species, and this relatively poor-quality diet means that the females are not gaining enough energy from their food to productively nurse their pups. On the opposite side of the coin, the sea lions of Los Islotes are getting an increasing number of fish species in their diet, with the result that population density has reached an all-time high.”

Female sea lions are not only philopatric, i.e., prone to stay in the area where they were born, they are attached to very specific real estate in that area, with many staking one specific rocky outcropping for their own. So with the increasing density of the population at Los Islotes, it is not surprising to learn that sea lion attitudes are becoming a bit more aggressive. Add to that the fact that the entire colony of females either a) goes into estrus, or b) has newborn pups to defend at exactly the same time and breeding season, which generally takes place June 1 to August 31, becomes a time when human body parts might best be kept at a distance from the sea lions of Los Islotes.  In fact, Los Islotes is now closed to snorkelers and scuba divers during this period.

Los Islotes is regularly listed as one of the top diving/snorkeling spots in the world, and Claudia and her students are launching a study to evaluate the effects of all these visitors on the sea lions. The tourism hiatus being imposed by the authorities during breeding season offers them the perfect opportunity for their research. “We have already collected fecal samples from the sea lions during the tourist season, and will now do so again when the colony is closed to tourists. We will then test the level of cortisol, a stress indicator, in both sets of fecal matter to determine if tourism increases stress in sea lions. We have already observed some differences in behavior in the sea lions at Los Islotes. While at other, more remote colonies, the sea lions will copulate during the day, at Los Islotes they only engage in this behavior at night. We hope to be able to determine if tourism is having an impact on the sea lions.”

Claudia at Los Islotes

Of course, liking your loving in the evening time is a common enough attribute of many healthy mammals, but if other colonies are also enjoying some afternoon delight, have the sea lions of Los Islotes gone too far in adapting to the presence of humans? Will the territorial males one day snap back to impose a more natural environment for their territories? Human males have certainly done battle over lesser issues.

Tourists have been visiting Los Islotes on a regular basis for roughly three decades, and sea lion males live an average of 19 years. There is therefore not yet a deep institutional knowledge about humans among the territorial males, and they could still be giving us the opportunity to demonstrate our worthiness as visitors to their home. Will we make the cut? We can’t be sure what the sea lions have learned about humans over the years, or what Claudia and her team will demonstrate, but the strong pull of Los Islotes on humans is easy enough to understand: it is a place where joy and spontaneity rule, and we thrill to that vibrancy.  While the territorial males are likely not motivated by their roles as life coaches for humans, it is enticing to think that maybe just one of the reasons they work so hard is to protect such a joyful lifestyle for their families. Claudia and her team are working hard to do the same.


Todos Santos Eco Adventures is the leading eco adventure company in Baja California Sur. On Isla Espiritu Santo we operate Camp Cecil, a luxury tent camp, and Camp Colossus, a moveable glamping operation. Claudia and her students will be spending time with us at our camps throughout the season as they conduct their sea lion research, so you may find them at the dinner table if you spend time with us at the island!

© Copyright Sergio and Bryan Jauregui, Casa Payaso S de RL de CV, 2018

The Star of the Sea of Cortez: Estrella Navarro Holm

The Star of the Sea of Cortez: Estrella Navarro Holm

by Bryan Jáuregui, Todos Santos Eco Adventures

This article first appeared in Janice Kinne’s Journal del Pacifico

She’s been free diving since before she could walk, but every time she gets in the water for a competition she reflects on the old nightmare: She’s swimming peacefully at the shore when the ocean suddenly starts retracting away from the beach at great speed like it does before a tsunami. She’s caught in the enormous power of the angry water, completely out of control. She’s filled with dread of the cold and the dark, terrified of being so absolutely alone.

“But competitive free diving is at least 70% mental” says Mexican free diving champion Estrella Navarro Holm. “And it was free diving that finally put that old nightmare to rest. In competition they allow us a few minutes on the rope at the surface before the dive, and I use that time to do my deep breathing, face any fears I may have, and relax into the dive. Once the count reaches zero, the rules allow only 30 seconds to get your face in the water, so you have to be ready.” Ready to dive 70 meters (230 feet) into the black of the ocean with no oxygen, no light, no friends,  just the air in your lungs and your wet suit to protect you? Fear is the only rational response.  “Yet”, says Estrella, “once my face is in the water the training kicks in and my diving reflex is activated. My whole system has a physiological response to my mental state and I am completely prepared to go. The first few meters are hard because my body is heavy and buoyant with air, and I have to really work to get down. But then at about 30 meters the free fall starts. It’s as if the wet suit and my skin fall away, and the water in my body merges with the water of the ocean.  Each molecule of water feels very intense. It’s like flying, but in slow motion. The free fall is the most beautiful, spiritual experience – it’s what makes people free diving junkies.” Knew there had to be a payoff.

And that payoff has paid off big time for Estrella. The La Paz native has broken the Mexican national free diving record 21 times, she was the first Mexican on the medal podium in a free diving world championship, and she’s the first woman in Latin America to medal in the discipline of constant weight no fins. And unlike most world champion athletes, she didn’t enter her first major competition until she was 24. This gave her the time to earn a degree in marine biology from the Autonomous University of Baja California Sur (UABCS) in La Paz, widely acknowledged as one of the best marine biology programs in the country. And she’s using that degree to pursue her other great passion in life, ocean conservation. Among other accomplishments, she is co-author of a paper titled Global Economic Value of Shark Ecotourism: Implications for Conservation, that appeared in Oryx, The International Journal of Conservation, published by Cambridge University Press. Yes, the one in England.

It is often the case in life that we don’t fully appreciate what we have at home until we travel elsewhere. And as Estrella traveled the waters of the globe for competitions, she found that her fellow athletes scarcely believed her when she described the riches of the Sea of Cortez, marveling – some skeptically –  when she told them about diving with sea turtles, sea lions, whale sharks, whales, dolphins and more. Their wonderment (incredulity) gave her an idea for combining her passions: invite the best free diving athletes in the world to La Paz to share the wonders of the Sea of Cortez and, at the same time, promote ocean conservation. Says Estrella, “I sent out 250 personal invitations via Facebook to my free diving friends, and I was so thrilled that 24 of the best athletes in the world accepted the invitation to compete in our program, Big Blue. But I was even more excited that they took up the call to be ocean ambassadors, to return to their home countries and promote strong ocean conservation measures. This is really the success of Big Blue.”

Indeed, as part of the Big Blue program in November 2015, Estrella, working in coordination with the tourism board of Baja California Sur, organized a conference on ocean conservation where she presented the shark research in which she and her co-authors demonstrated that shark ecotourism around the world currently generates US$314 million a year and supports 10,000 jobs – a vastly higher and more sustainable number than those associated with shark landings each year. That is to say, as is generally the case when speaking of wild flora and fauna, the living, breathing resources of the world are worth more to mankind alive than dead.

Estrella wants to keep bringing that message to the world, and plans to make Big Blue an annual event in La Paz, her home town and a great staging area for exploring the Sea of Cortez.  Estrella is part of a growing cadre of world class athletes that grew up in La Paz and the Sea of Cortez (Mexican board diving champion and Olympian Paola Espinosa’s dad was actually Estrella’s competitive swimming trainer when she was a little girl, and the two champions remain friends) and their love for their home town is helping to fuel growing interest in La Paz as a destination for top competitions in many sports including stand up paddle boarding, water polo, swimming and, of course, diving.

But unlike her fellow champions in other sports, Estrella doesn’t worry so much about the march of time. One of the greatest female free divers of all time, Natalia Molchanova, became the first woman to dive 100 meters (328 feet) at the age of 44, and continued to dominate the sport for another decade. (Her son Alexey swept the Big Blue competition in La Paz and is the reigning world champion.) So that means that for the foreseeable future, Estrella can continue to both compete in oceans around the world, and create the knowledge and ambassadors to help protect them. Saving it all for the generations to come. That’s what truly makes the champion Estrella Navarro Holm the Star of the Sea of Cortez.

To learn more about Estrella and Big Blue please visit:


The Largest Animal to Ever Inhabit the Earth: Meeting a Blue Whale in Baja

by Todos Santos Eco Adventures

Imagine a fellow mammal with a body so magnificent, so enormous, so dominant that it takes a heart the size of a Mini Cooper to power it.

Imagine a fellow creature with a voice so commanding, so forceful, so potent that it can be heard up to 1,000 miles away.

Click to compare the size of a blue whale to the space shuttle, dinosaurs and more.

Imagine the bone structure of a fellow vertebrate so long an NBA basketball court can’t hold it, that weighs so much 8 DC-9 aircrafts can’t lift it, and that is so loud it drowns out the noise of a jet engine.

Imagine arteries so large that an adult human can swim through them; imagine a heart beat so powerful it can be heard two miles away; imagine a tongue as large as an elephant!

If you can do all that then you’re able to conceive of the largest animal ever to inhabit the earth, the blue whale. And as so often happens here in Baja, you don’t have to visit your imagination to encounter some of the planet’s most remarkable beings – you can see them right here. Please enjoy this video of our blue whale encounter on a recent outing in the Sea of Cortez, video courtesy of our guests the Moffats: [youtube=]

With this enormous size you can well imagine that blue whales have few predators, but it doesn’t mean that they’re not under attack. To learn more about how ship strikes are harming blue whales and what you can do about it, please click here and visit the Great Whale Conservancy website.

The blue whale fun facts in this article are all part of National Geographic Channel’s Kingdom of the Blue Whale video program. They have a great interactive piece comparing the size of the blue whale to various animate and inanimate objects that you can reach by clicking on the blue whale image above.

Swimming with Whale Sharks in the Sea of Cortez

This article by Todos Santos Eco Adventures was published in the Spring 2012 issue of Janice Kinne’s Journal del Pacifico.

If you sift back through the catalog of parental admonitions that were meant to ensure you a long and happy life – you know, “don’t stick your tongue on frozen metal”, “don’t eat yellow snow”, “don’t drink your father’s last bottle of beer” – somewhere buried in there your mother must surely have added “and oh yes dear, don’t swim with sharks”.

Very  sound advice to be sure but swimming with sharks – whale sharks that is – in the Sea of Cortez is truly one of life’s great (and, sadly for you danger junkies, very safe) adventures.  While whale sharks have thousands of teeth in hundreds of rows in their enormous mouths (imagine armed shark mouths 4 to 5 feet wide), they can neither bite nor chew. That’s right, they are happy to forego all human body parts in favor of plankton, krill and small fish. Go figure!

Whale Shark Mouth! Photo by Deni Ramirez

So now you feel safe but even if you were on the varsity swim team you’re probably wondering how you could actually keep pace with a shark in the water. Well, the whale shark got its moniker because it is the only fish that is literally as big as a whale; mature adults can reach 60 feet in length and 50 tons in weight. Reaching these proportions requires an immense amount of energy, which the whale shark gets by consuming huge volumes of plankton-rich water, then straining it out through its gills. In fact, to get the food it needs it is not unusual for a whale shark to filter 400,000 gallons of water an hour. To conserve this hard-won strength – and continue eating – whale sharks tend to do a lot of hanging about in the water, or, if moving, doing so at a very slow pace. This lollygagging is what makes it possible for non-bait types like humans to jump in and swim alongside them for a bit. Of course, when they want to put on the speed they certainly can so when a whale shark tires of your company all you will see is a swishing tail receding into the distance.

Now you’d think it’d be a relatively simple matter to learn about a mammoth fish the size of a school bus dawdling through the water eating up everything in its path. But the fact is that scientists still know relatively little about the whale shark, and La Paz resident Dení Ramirez of Whale Shark Mexico is trying to change all that.  Originally from Mexico City, Dení has been studying whale sharks in La Paz since 2001, and completed her Ph.D. in marine biology last year. The whale shark’s skin is covered in a pattern of pale yellow spots and stripes that is unique to each animal, a type of fingerprint if you will, so Dení has been able to track some of the inhabitants of La Paz Bay. In fact, she has been tracking the young sharks Flavio, Tikki Tikki and Tango for almost a decade now, and has determined that they are true Baja residents. While whale sharks have been spotted across the globe from Australia to Djibouti, from the Philippines to Mozambique, Dení’s juveniles appear to travel only in the Sea of Cortez, from the Bay of La Paz to Bahia de Los Angeles – roughly 600 miles. We asked Dení why we seem to be seeing the whale sharks around La Paz so much more over the last couple of years than we ever did before.

Whale Shark Feeding in the Sea of Cortez: Photo by Deni Ramirez

“It’s really just a question of food. Over the last two to three years the conditions in the Bay of La Paz have been just right to produce an enormous amount of plankton for the whale sharks to feed on. The wind, currents, mangrove conditions – all these have combined to create an excellent environment for plankton growth that we just didn’t have for such extended periods in earlier years. Also, in the Bay of La Paz the plankton is rich in the coastal waters, and these relatively shallow waters give the young sharks in my group a certain amount of protection.” Dení is happy to take visitors with her on her research trips and share some of her extensive knowledge of whale sharks and research methodology.

Dení is currently doing a lot of work with the pregnant females who inhabit the deeper waters around Espiritu Santo Island and have found that they have much larger migrations than the young sharks due to their different needs as mothers, mothers who surely will work to ensure the long life and happiness of their offspring by admonishing “and dear, don’t try to eat the humans. They’ll just clog up your gills.”

TOSEA guest Mary Winzig recounts her whale shark adventure:

“Swimming with whales sharks is the most amazing thing I have ever done in my life. They are such magnificent animals and I felt so lucky to be in their presence. I was scared—to see something so large and to know you are jumping in the water with them made me pause for a moment. My heart seemed to be almost leaping through my wetsuit – I asked the guide to make sure they were whale sharks because their dorsal fins were so huge! But after watching them and seeing their polka dots, I realized I had to swim with them. You can’t be afraid of anything with polka dots! Jumping in and seeing them through the snorkel was magical. Once I was in the water, I wasn’t afraid. I have no idea how long I was in the water with them, 2 minutes? 15 minutes? I was transfixed. Their mouths look like the grill of a ‘57 Chevy. I have never felt so small or insignificant, but also so powerful. I have decided I have to do everything in my power to help save these magnificent creatures. Thank you Todos Santos Eco Adventures for this wonderful opportunity. I look forward to swimming with the sharks again!”

Mary Winzig After Swimming with Whale Sharks

© Copyright Sergio and Bryan Jauregui, Casa Payaso S de RL de CV, 2012

El Mechudo and the Pearl of the Sea of Cortés

by Sergio and Bryan Jauregui, Todos Santos Eco Adventures

June through November are the best months for diving and exploring the Sea of Cortés – “the aquarium of the world” – as the warmer water temperatures mean an (even more) incredible variety of fish, superior visibility and calmer seas.  But a word of warning for those of you who do venture to the depths of the Sea of Cortés: there is one truly scary thing that you should know about – and be constantly on the alert for – and that is El Mechudo. There are many variations on the story of this wild-haired free diver, but this is the one that the old fishermen around Punta Mechudo tell…

Long ago, when La Paz was the pearl capital of the world, there lived a Yaqui Indian known as El Mechudo, The Hairy One. In those days there were many pearl divers of great skill and daring in La Paz, men and women who could hold their breath for long stretches at a time and knew the secrets of finding large and magnificent pearls. Each year the companies that sold La Paz pearls around the world would hold a contest to see which diver could find the largest and loveliest pearl. The diver who won was awarded the great honor of having his or her pearl presented to the Virgin of Guadalupe. For as many years as anyone could remember, El Mechudo, with his wild flowing black hair, had won the contest; he could hold his breath longer and dive deeper than any of the other divers and he always knew where to find the most fantastic pearls.

Then one year El Mechudo failed to appear at the beginning of the contest. They waited for him for several hours but finally had to hold the event without him. By the time El Mechudo arrived to compete, the contest was over and a winner had been declared. Enraged, El Mechudo insisted on diving. His friends begged him not to risk his life and to simply wait until the following year to prove himself the champion once again. The organizers warned that even if he found the biggest, blackest pearl of all time that they would not crown him the winner, nor would they present the pearl to the Virgin. Unfazed, El Mechudo dove into the water. Time passed. After many minutes he still had not returned to the surface. His friends jumped into the water to search for him and saw a sight that would haunt them for the rest of their lives: the lifeless body of El Mechudo with his hand caught in a giant oyster.


The man known as El Mechudo is dead, but he is not gone. To this day divers, kayakers, fishermen and snorkelers in the Bay of La Paz are visited by the ghost of El Mechudo. There are regular reports of unexplainable touches in the night, rearranged camp sites and voices in the wind. And aspiring pearl divers should beware. Word is that if you go into the Bay of La Paz looking for pearls, El Mechudo will find you and offer you the largest, blackest pearl you can imagine. If you accept, your final resting ground will be the depths of the Bay of La Paz, right beside El Mechudo.

So how did La Paz become the Pearl Capital of the World in

the days of El Mechudo? Tony Burton of MexConnect* explored that story by reaching back to the early 1530s when the explorers of Hernán Cortés sailed into the Sea of Cortés searching for the earthly Paradise of California.  The first peoples they encountered on the Baja Peninsula were Pericú Indians. The Spanish explorers were immediately struck by the Pericú’s necklaces which were strung with berries, shells and blackened pearls. As the Pericú did not have metal knives they had been retrieving pearls by throwing oyster shells into a fire, charring the pearls in the process. The Spanish explorers soon determined that opening the oyster shells with their knives gave them access to lustrous, milky-white pearls on par with those to be found in Asia or the Middle East.  A robust pearl industry was born, and thousands of pearls were sent from Baja to Europe where they were used in the royal regalía of many European courts. While the Jesuits tried to restrict pearl collection during the period of their missions in Baja (1697 to 1768) due to the poor conditions inflicted in the native Indian divers (see story of El Mechudo above), traffic in the pearls persisted. It was estimated that by 1857, 95,000 tons of oysters, that yielded about 2,770 pounds of pearls, had been removed from the Sea of Cortés. The coves around La Paz and Isla Espiritu Santo were the center of the Baja pearl industry.

Pearl diving was revolutionized after 1874 when larger vessels, equipped with diving suits and accompanying equipment, first entered Mexican waters. The new equipment lengthened the season to include the cooler winter months and had the added benefit of reducing shark attacks. But new dangers emerged: divers confined to diving suits for hours at a time frequently suffered rheumatism, paralysis (due to compression and sudden temperature changes) and partial deafness. Equipment failure led to many deaths. (Never fear new divers – Jacques Cousteau radically enhanced the functionality and safety of scuba gear and since his first Aqua-Lung in 1943, equipment safety has increased dramatically.) Despite the problems faced by the divers, by 1889, a La Paz-based pearl company had come to completely dominate the world pearling industry. A 400-grain pearl, found in the shores of Mulege, now forms part of the Spanish crown jewels.

A 1903 article in The New York Times says that the Baja pearl industry had produced more than two million dollars worth of pearls in 1902, including some of the “finest jewels of this kind found anywhere in the world”. The article emphasizes that the area is “noted for its fancy pearls – that is to say, the colored and especially the black ones”. But by 1936 the natural oyster stocks had been depleted past the point of recovery. This depletion, combined with the widespread availaility of relatively inexpensive cultured and artificial pearls, led to the demise of the natural pearl industry in Baja. Today very few natural pearls are harvested in the Sea of Cortés, but several Baja California firms do cultivate pearls. So La Paz, once the center of the world’s pearling industry, is still known today as the “Pearl of the Sea of Cortés”. But remember, should you encounter one of those few remaining natural pearls while diving in the Bay of La Paz and decide to take it home, El Mechudo will make sure grabbing that pearl is the last thing you ever do!

*Much of the information on the pearl industry in La Paz presented here was researched by Tony Burton and presented in his Did You Know column for MexConnect in June 2008.  His sources include:

Anon. Important Pearl Fisheries on the Coast of California. The New York Times, June 14, 1903.

Hardy, R. W. H. 1829 Travels in the Interior of Mexico in 1825, 1826, 1827 and 1828. London: Henry Colburn & Richard Bentley. Reprinted in 1977, Texas: Rio Grande Classics.

Kunz, G. F., and Stevenson, C. H. The Book of the Pearl: Its History, Art, Science and Industry.Dover. 2001.

Mayo, C. M. Miraculous Air: Journey of a Thousand Miles through Baja California, the Other Mexico.Milkweed Editions. 2007.