A 15.5cm-long tooth from a sperm whale was found in the Sisters' Islands Marine Park last month, making it the second find related to the marine mammal this year.
In July, the nine-tonne carcass of an adult female sperm whale was found floating off Jurong Island. Affectionately dubbed Jubi Lee, its skeleton is being prepared for display at the Lee Kong Chian Natural History Museum by end-February.
The tooth was found by an officer of the museum, Ms Toh Chay Hoon, who was conducting an intertidal walk for the National Parks Board (NParks) in a lagoon within the marine park on Nov 25.
The museum's head, Mr Peter Ng, said: "The find is a rallying call for marine conservation in Singapore, highlighting its importance and the work that NParks and university researchers are doing."
PARK'S SOLID CONTRIBUTION
This find highlights the important role that the marine park plays in documenting and communicating the significance of biodiversity discoveries in Singapore.
DR KARENNE TUN, deputy director of the coastal and marine division at NParks' National Biodiversity Centre
Museum scientists believe the tooth could have come from an adult male sperm whale.
"The size of the tooth suggests it was from an animal much larger than the 10.6m female sperm whale that was found dead off Jurong Island," wrote Ms Toh and Mr Marcus Chua, the museum's curator of mammals and birds, in a paper published last Friday in the Singapore Biodiversity Records.
The tooth, which weighs about 400g, is bigger and thicker than the ones found in the female, which were each about the size of a person's finger, said Mr Chua.
As sperm whales swallow their prey whole, their teeth are likely to be of limited use for feeding. Instead, male sperm whales have large teeth in their lower jaws that are thought to be for battling other males, Mr Chua said.
But signs of weathering on the tooth make it difficult to determine how long it has been exposed and how it came to Singapore.
The surface layers on the tooth seem to have been lost, Mr Chua said. "This could be due to mechanical abrasion or chemical reactions. We don't know how fast (these layers) go away, so we can't tell how long it's been out there," he said. The information available is also not enough to determine how the tooth came to be in the lagoon.
One possibility is that Singapore is on the migratory route for these marine mammals, which can grow up to 20m. While female sperm whales and calves remain in waters close to the Equator all year round, males migrate to colder waters and head back towards the Equator to breed. Another possibility is that the tooth could have been transported to Singapore with sand or other land reclamation materials.
"We will be working closely with the Lee Kong Chian Natural History Museum to share this exhibit at the Sisters' Islands Marine Park Public Gallery on St John's Island as well, for the public to gain a deeper understanding of the rich biodiversity in our waters," said Dr Karenne Tun, deputy director of the coastal and marine division at NParks' National Biodiversity Centre.
"This find highlights the important role that the marine park plays in documenting and communicating the significance of biodiversity discoveries in Singapore."
Mr Stephen Beng from the marine conservation group of the Nature Society (Singapore) said the finds show the inter-connected nature of the world's seas and oceans, and throw up a "thrilling mystery" about what could have happened to the whales along the way.
He said: "It is this connectivity we have to remain mindful of when gauging our impact on the natural world. We can make consumption choices in our daily lives which can help slow climate change and ensure the long-term sustainability of our oceans."