New study reveals the global biology of whale sharks
A new study explores how citizen science has contributed to our understanding of the basic biology and ecology of the whale shark on a global scale.
The publication: 'Undersea Constellations: The Global Biology of an Endangered Marine Megavertebrate Further Informed through Citizen Science', led by Dr Brad Norman, was a collaborative effort of 38 scientists, including LAMAVE Executive Directors Dr Alessandro Ponzo and Gonzalo Araujo, as well as David David and Elson Aca from WWF-Philippines.
What is Citizen Science and how can it help us study whale sharks?
Citizen science is the collection and analysis of data relating to the natural world by members of the general public, typically as part of a collaborative project with professional scientists. In this case the study was centred around an online library called Wildbook for Whale Sharks, which encourages scientists and the public to upload photographs of whale shark encounters.
Using a whale shark's unique spot pattern (see photo) scientists can identify individual sharks and even track their movements, when the same shark is photographed in different locations.
What does the study tell us about whale sharks around the world?
The library received almost 30,000 whale shark encounter reports from 1992 to 2014. Analysis of the photographs revealed that the photos were of 6,091 individual whale sharks submitted from 54 countries. 66% of the reports were identified as juvenile males, which are known to aggregate, generally in groups at specific locations throughout tropical and warm temperate waters, to feed. The submitted photographs allowed Brad and the team to identify 20 whale shark hotspots (where more than 100 encounters were reported). The top four were: Western Australia, Mexico, Philippines and Mozambique.
Female whale sharks were less frequently encountered, however amazingly 99% of sexed individuals from the Galapagos were female. They were also estimated to be the biggest sized whale sharks and it has been suggested that they may even be pregnant. The smallest whale shark recorded in the database is a newly born (neonate) from the Philippines and measures just 46cm in length.
Currently the Philippines is the third largest known population of whale sharks according to Wildbook for Whale Sharks, and is the largest known population in South East Asia. This is largely down to the research effort of LAMAVE and WWF-Philippines; LAMAVE researchers are currently monitoring four main whale shark aggregation sites in the Philippines.
The study confirms that at least some whale sharks undertake longitudinal movements, highlighting how photo-ID can be an inexpensive scientific technique to track whale shark movements. Individual sharks were photo-matched between Australia and Indonesia (2,700 km), Belize, Honduras, Mexico and USA, and Taiwan and the Philippines. The whale shark in Taiwan was photographed by Dr Hua Hsun Hsu from the George Chen Shark Research Centre at the National Taiwan Ocean University in May 2012, and later encountered by LAMAVE researchers in Southern Leyte, Philippines in April 2013. This represented the first international match through photo-ID in South-East Asia with a minimum distance covered of 1,600 km; you can read more about it in our scientific publication.
The study concludes that there are three main research priorities: to define regional migration routes, to understand the timings of movements and to identify critical breeding and pupping locations.
How can you help?
Become a citizen scientist! You can contribute to the global knowledge on whale sharks by uploading photographs of your encounters to whaleshark.org