Everything we know about the elusive whale shark: an interview with Sofía Green

Sofía has been lucky enough to work as a marine biologist in whale shark research for the Galapagos Whale Shark Project, with the support of Galapagos Conservation Trust, for the past eight years. For the team, every day is an adventure, as there is still so little we know about the largest fish species on Earth.

How do whale sharks shape their environment?

Whale sharks are incredible animals. They are highly migratory which means that they spend their life moving to distant parts of the ocean and cover large distances in short amounts of time. Also, they are incredible divers! A whale shark can dive to 2,000 metres and possibly even deeper.

These horizontal and vertical movements make them highly important for nutrient transport in the ocean. When moving from coastal feeding areas to open ocean/nutrient-deficient areas, they release nutrient-rich faeces which support the proliferation of phytoplankton. This is highly important as phytoplankton produces around 50% of the oxygen on Earth and helps us absorb carbon dioxide (CO₂) from the atmosphere into the ocean, essential nowadays to reduce the warming effects of CO₂ on the planet.

Through their diving activities whale sharks also support nutrient mixing, bringing up scarce nutrients such as nitrogen that have settled in deeper waters to the surface, which also supports the reproduction of phytoplankton.

Check out how whale sharks help us mitigate the impacts of climate change here.

Why is so little known about their life cycle, particularly their reproductive cycle?

Whale sharks are not easy to find. Although juveniles are found in aggregations around the world for feeding purposes, adults are seen in smaller proportions and more remote open ocean areas.

Whale sharks are generally solitary animals and the bigger they get, the further away from coastal areas they seem to venture. Tracking them in the open ocean is not an easy feat as it requires complex expeditions to reach these remote areas and a whole army of support to fund these expeditions.

Whale sharks also like to keep us guessing. Although we have been tracking adult female whale sharks, primarily from Darwin island, Galapagos for the past ten-plus years, we notice year after year that their movement patterns are not fixed. Instead of going from point A to point B, their travel routes seem to be determined by a variety of environmental factors such as food availability, sea surface temperatures and other variables that make their movements fluctuate between individuals and different years.

The females in particular are tough to find, making it so difficult to understand where they reproduce, give birth and uncover what their reproductive strategies are. In the Galapagos Islands, we have discovered a very special population of over 90% adult females, not seen at this ratio anywhere else in the world. Here we are starting to uncover their reproductive behaviour by working in collaboration with expert scientists from the Okinawa Churaumi Foundation to draw blood and take ultrasound scans from free-swimming whale sharks. Although we have not yet confirmed a pregnancy, we are learning a lot about their hormone levels and reproductive organs and hope to continue this focus of the study for the next couple of years. If you are interested in this topic, check out our recent publication.

I would love to swim with whale sharks in the wild – what are the unethical practices I need to look out for and avoid when choosing a tour company?  

This is an excellent question. Swimming with whale sharks is probably one of the most extraordinary experiences in life! Being in the presence of these spotty, gentle giants is guaranteed to take your breath away. However, it is important to do so properly to avoid affecting the whale shark’s behaviour, which can cause more harm than good.

Some people might wonder, ‘Wouldn’t it be better if we left them alone?’ Perhaps. The planet might fare better without human interference overall. However, that’s not realistic. I believe ecotourism has its benefits and experiences like these are exactly what we need to connect people to nature and inspire us to work toward conserving our planet.

Here are some tips to choose the right tour operator and ensure a responsible and ethical experience with the largest shark in the world:

1. Avoid companies that guarantee shark encounters.
   If you hope to see a whale shark in the wild, you must be prepared to miss out, as nothing is guaranteed in nature. Operators that promise encounters might use methods to lure sharks, which disrupt their natural behaviour and can have long-term consequences.
2. Look for conservation missions.
   A great way to spot responsible ecotourism partners is by checking the programmes they collaborate with. True ecotourism operators often promote shark conservation through citizen science programmes (e.g., marine count apps or photo identification efforts) or by collaborating with or donating to local scientists studying marine fauna. These operators genuinely care about the animals and support their conservation.
3. Ensure a code of conduct.
   Ethical operators have clear rules for interacting with the sharks. There should never be crowds of people surrounding a single shark. Operators should enforce minimum distance limits, prohibit touching or blocking the shark’s path and avoid any attempt to manipulate the shark’s behaviour.
4. Check for vessel speed limits.
   Vessel strikes are one of the biggest threats to whale sharks and other marine megafauna. Responsible operators enforce speed limits in sighting areas to minimise this risk.

Ecotourism is essential for shark conservation. While wildlife tourism can harm animals when done irresponsibly, it can also help save species like whale sharks from extinction. Ecotourism can challenge the demonised image of sharks perpetuated by the media, showing them as the keystone species they are. When done right, ecotourism motivates people to value and protect these incredible creatures, making it part of the solution rather than the problem.

When is the best time of year to see whale sharks in Galapagos?

Whale shark season is between June- November, during the cold season in Galapagos. To see them in the Archipelago during this time of the year, you must be an advanced scuba diver as the only way to reach Darwin island is via a weeklong dive liveaboard and the diving conditions in most places surrounding Galapagos include strong currents. If you do join one of these liveaboards, be prepared for a trip of a lifetime!

However, if you are not a diver, some sporadic sightings do occur around the central and southern islands throughout the year and some very lucky visitors have even spotted them during one of their snorkels!

What is your favourite fact about whale sharks? 

Whale sharks are ocean conservation ambassadors, often referred to as an “umbrella species.” As charismatic, impressive and beautiful animals that ocean lovers are eager to see, they are easier to protect than many of the “scarier” shark species, fish, macro marine life, and other less-recognised creatures. Because whale sharks use vast ocean areas, the more we learn about their life history, the more critical ocean habitats we identify as essential to their survival. Protecting whale sharks and these key areas doesn’t just protect this iconic species, it also helps conserve many other endangered species, commercially important fish and entire ocean ecosystems. Protect the whale shark, protect the ocean.

What is something that most people get wrong or don’t understand about whale sharks?

Whale sharks are feared by many people. Due to their enormous size and the negative image of sharks that has been perpetuated by the media, people are terrified of swimming in the ocean in general, even worse in the presence of these animals. However, whale sharks are big, friendly giants who feed primarily on zooplankton, tiny fish eggs and fish larvae. Even though their mouths could probably fit a human inside, their throat is approximately the size of a baseball, making it impossible for a whale shark to swallow us, even if they wanted to.