Sliding under the crystal-clear blue waves, camera in tow, underwater photographers can only dream about capturing what David Choy did earlier this year. In front of him, two tiger sharks (Galeocerdo cuvier) – one male, one female – began to dance, with the male chasing the female in intricate circles until they finally swam away into the gloom.
Was this a courtship ritual? Possibly.
The tiger sharks, named for their distinctive striped pattern, have a circumglobal range in tropical and warm temperate oceans and are among the largest of the sharks (measuring up to 18 feet or 5.50 meters long). Listed as Near Threatened (NT) in the IUCN Red List of Threatened Species, it is believed have had an “overall population reduction of close to 30% globally over the past three generations (53-68 years) based on actual levels of exploitation.”
These two tiger sharks were filmed at the Tubbataha Reefs Natural Park in the Sulu Sea off the Philippines. Known as the ‘Amazon of the seas,’ the Philippines is often called the “world epicenter for marine biodiversity.” The Tubbataha Reefs Natural Park is an incredible example of this with its pristine reefs and high diversity of marine life; located within the Coral Triangle, this park supports over 360 species of corals (almost 90% of all coral species in the Philippines) and almost 700 species of fish. Approximately 200 species of sharks and rays exists in the country’s waters – making it one of the highest in the world in terms of diversity – and previous surveys documented at least 20 species of shark and ray within the park alone.
Tiger sharks are hardly found anywhere else in the country, but their presence in the Tubbataha Reefs makes it possible for scientists to capture them to generate greater understanding of their kind. A team of researchers from the Large Marine Vertebrates Research Institute Philippines (LAMAVE) and the Tubbataha Management Office (TMO) have been successfully tagging these predators in the Park since 2016. LAMAVE’s Dr. Alessandro Ponzo has used an array of technology (from embedded acoustic tags to fin-mount tags) to better understand how these predators use Tubbataha as a habitat, their range, and the potential areas of concern in the protection of the species.
TUBBATAHA REEF, PHILIPPINES - APRIL 23: A bluespotted stingray (Taeniura lymma) and also a little ... [+]
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“There [has been] an increase in the number of reported sightings of tiger sharks in Tubbataha Reefs Natural Park over the last decade. Tubbataha has the highest reported sightings of the species in the Philippines and in Southeast Asia,” explained The Natural Park’s Research Officer, Ms. Retchie Pagliawan. “Research on tiger sharks is being spearheaded by our NGO partner - Large Marine Vertebrates Research Institute Philippines. They were able to attach satellite and acoustic tags to a few tiger sharks. The data revealed that the tiger sharks move more than 200 kilometers outside the Park.”
Declared a World Heritage Site in 1993, Dr. Andy Cornish, program Leader of World Wildlife Foundation (WWF) Sharks, once said Tubbataha was “one of a handful of sites in Southeast Asia where sharks are actually making a recovery.” This is because the park is incredibly well managed and enforced, not to mention it is quite isolated from populated areas. Scientists from various organizations believe this is how multiple generations of sharks have been allowed to flourish here with little outside pressures… for now.
Unfortunately, it has an incredible amount to lose from the threats currently facing our oceans and inevitably reaching this oasis: overfishing, climate change, marine litter and pollution, reckless tourism ventures, oil exploration, and more. It’s only a matter of time before some of these start to knock on the door of the National Park. How the ecosystems and animals who call it home will fare relies on both local and international actions.
Today, one can only enjoy what they see as they dive under the waves… hopefully two sharks indicating that life will go on with their captivating dance.
#News | https://sciencespies.com/news/tiger-shark-courtship-ritual-caught-on-tape/
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