Galápagos, Ecuador · Global Whale Shark Program

Galapagos Whale Shark Project

Almost all the whale sharks passing Darwin Island are large adult females, a demographic rarely seen anywhere else.

Led by Galapagos Whale Shark Project, with MMF

736individual whale sharks identified passing Darwin Island

Over 95%are adult females, typically 10–14 m (33–46 ft) long

100+whale sharks satellite tagged since the project began

60,000 km²of new marine protection in the Hermandad reserve, declared in 2022

The Galapagos Whale Shark Project studies whale sharks (Rhincodon typus) in the Galápagos archipelago. MMF is a collaborating partner, with Dr. Simon Pierce, Dr. Chris Rohner, and Dr. Clare Prebble on the research team, and our involvement is focused on Darwin, the northernmost island. We also take part in silky shark research in the Galápagos, and contributed to a completed yellowfin tuna study there.

The project’s research spans population ecology, tracking, and health assessment, with the aim of understanding and protecting the whale sharks of the Eastern Pacific.

What the project has done

Identified 736 individual whale sharks, almost all of them large adult females, a demographic rarely seen anywhere else.
Satellite tagged more than 100 whale sharks, tracking their movements across the Eastern Tropical Pacific.
Helped secure the Reserva Marina Hermandad, a 60,000 km² (23,000 square miles) expansion of Ecuador’s marine protection declared in 2022.
Carried out the first study of reproductive biology in free-swimming whale sharks, using underwater ultrasound and blood sampling.
Contributed Galápagos tracking data to a global analysis of collision risk between whale sharks and shipping, published in 2022.

Darwin's Arch at sunrise from the air, with Darwin Island behind, northern Galápagos

Support our whale shark research

Each shark identified and each tag that transmits data adds to what we know about whale shark movements. Your gift supports MMF's whale shark research, from photo-identification and satellite tracking to health assessments of wild sharks.

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Our work on whale sharks in the Galápagos

Research at Darwin Island

Darwin, the northernmost island in the Galápagos, is a global hotspot for adult whale sharks, almost all of them female. It therefore offers a unique opportunity to study their movement ecology and reproduction, and it is where MMF’s work with the Galapagos Whale Shark Project is focused. (Photo: Jonathan Green.)

The research team in an inflatable boat in front of Darwin's Arch

Population ecology

Photo-identification from each shark’s unique spot pattern, carried out during dedicated research trips and bolstered by contributions from dive guides and visiting divers, has documented 736 individual whale sharks transiting past Darwin Island, mainly during the cool season from July to early December. Over 95% are adult females, typically 10–14 m (33–46 ft) long; in contrast, almost every other known whale shark aggregation is dominated by small juvenile males. Few individuals are resighted in later years, and each shark remains for only about two days, which suggests that Darwin is a waypoint on a migration rather than a place where the sharks reside.

A large whale shark swims over the reef with divers behind it

Satellite tracking

More than 100 whale sharks have been satellite tagged since the project began. Tracking has shown that sharks tagged in July move west into the open Pacific, whereas those tagged in September and October turn toward the South American coast, and many converge off northern Peru and southern Ecuador in December and January, pointing to an important feeding area far beyond Ecuadorian waters. Individual tracks have extended up to 2,747 km (1,707 miles) from Darwin.

A diver alongside a whale shark's dorsal fin, surrounded by fish

Protecting a moving target

One shark traveled to within 80 km (50 miles) of the Cocos Island marine protected area, off Costa Rica, before turning east to Malpelo, off Colombia, precisely the kind of evidence that underpins the Cocos–Galapagos Swimway and the wider Eastern Tropical Pacific marine corridor agreed by Ecuador, Costa Rica, Panama, and Colombia. The sharks also follow the fronts where cool upwelling meets warm tropical water; as a result, protecting them means protecting moving oceanographic features, not just fixed places.

A whale shark and a diver in open blue water

Reproductive and health assessment

Large female whale sharks are rarely seen in coastal waters, but they regularly pass offshore islands such as Darwin, providing a rare opportunity to study their reproductive ecology. Working with a team from the Okinawa Churaumi Aquarium, the project team used an ultrasound system in a pressure-proof underwater housing to scan free-swimming whale sharks, and drew blood from them to measure their reproductive hormones; to the authors’ knowledge, this was the first time either had been achieved with free-swimming adult sharks or rays. The scans found developing follicles (structures containing immature eggs) in two females of 11–12 m (36–39 ft), and together with the hormone results this indicated that these animals were mature, without the need to examine a dead shark. Equally important, the scans found no sign of embryos or egg cases, which challenges the long-standing assumption that the swollen abdomens seen on large Galápagos females indicate pregnancy. Almost everything known about whale shark reproduction still comes from a single pregnant female caught off Taiwan in 1995, so where these females go to give birth remains one of the major open questions about the species.

A diver on an underwater scooter works beneath a whale shark

The first ultrasound scans of wild whale sharks

The team conducted underwater ultrasound scans, collected blood samples, and attached satellite transmitters to large female whale sharks to investigate their reproduction and movements.