Evolution in action
In the shallow coral reefs of Raja Ampat, a unique evolutionary story is unfolding. This region hosts several species of the genus Hemiscyllium, commonly known as walking sharks. These sharks use their muscular pectoral and pelvic fins to "walk" across the seafloor and even over exposed coral at low tide. This group of sharks represents the most recent shark radiation on Earth, having split from their nearest ancestor only about 9 million years ago. While sharks as a group are ancient, with origins dating back more than 400 million years, walking sharks demonstrate that evolution can still produce new forms in this old lineage.
The evolution of at least nine distinct walking shark species was driven by the changing geology of the Indo-Australian Archipelago. Over millions of years, shifting tectonic plates, volcanic activity, and fluctuating sea levels created and then isolated shallow reef habitats. Shark populations became separated from one another, a process called vicariance, which led to them evolving into new, distinct species. The Raja Ampat epaulette shark, Hemiscyllium freycineti, is endemic to these waters and was the first of Indonesia's walking sharks to be scientifically described in 1824. Six of the world's known walking shark species are found in Indonesia.
A master of survival
The ability to walk is an adaptation for life in complex, shallow-water reef systems. It allows these nocturnal predators to navigate crevices and hunt for crustaceans, worms, and small fish in places other predators cannot reach. This "walking" also provides a survival advantage during low tides, when the sharks can become trapped in isolated, oxygen-poor tide pools.
To cope with these hypoxic conditions, epaulette sharks have developed a remarkable physiological response. They can slow their heart rate and breathing and selectively reduce blood flow to non-essential parts of the brain. This allows them to survive for hours in low-oxygen water that would be lethal to most other fish. This combination of unique locomotion and extreme physiological tolerance makes the walking sharks of Raja Ampat an example of speciation and adaptation. The Hemiscyllium freycineti population is classified as Near Threatened, facing risks from habitat degradation due to tourism development and climate change.