It is well known that whalesharks are huge, gentle fish that eat plankton and travel the world. But little else is known about this ocean giant, though scientists and tour operators are working fast to change that. New information and discoveries are emerging constantly about Rhincodon typus. Here’s five of the most amazing new facts about Whale Sharks.
New Fact 1. Whale Sharks recover quickly from wounds and may even regrow parts of their bodies.
Whalesharks spend a lot of time at the surface, and occasionally get hit by ships. This can result in terrible injuries. If you are swimming with a whale shark at Ningaloo and see a cut, abrasion or amputation, will it recover?
It seems it will, very fast. In an extraordinary new study, researchers studied injured whale sharks in the Maldives and near Djibouti. Both natural and human-caused injuries were studied. Large cuts were 90% closed in 35 days, and over time most scars disappeared completely. The original spots and stripes even returned!
Regrowing amputated limbs is much rarer in large animals, but even that was partially achieved by one whale shark in the study. He had lost the tip of his dorsal fin, but it regenerated over 5 years.
Though whalesharks are resilient and heal well, the largest number of whale sharks in this study were injured by humans and their boats. This reinforces the importance of seeing Whale Sharks in a country where they are protected from boat strike. Australian regulations on Whale Shark encounters are strict, and our friends at Exmouth Dive & Whale Sharks are some of the best in the industry.
New Fact 2. Big ships are hurting them, but Western Australia’s tour operators are helping
Nearly one-sixth of the Whale Sharks that visit Ningaloo Reef carry serious injuries, most of them from collisions with large ships, according to a recent study by University of Western Australia.
The new study compiled photographs and information collected from Ningaloo Reef tourism operators, including Exmouth Dive & Whalesharks, and research groups, to analyse the injuries to the sharks. 39% of whalesharks had scars, but most of those were minor nicks and abrasions. Sadly, though, injuries increased over the duration of the study.
The researchers noted that the data provided by tourism operators was vital to the study.
It is hoped that the findings of the study will lead to better practices by international shipping companies.
New Fact 3. Globally endangered, but increasing at Ningaloo Reef
The IUCN lists Whale Sharks as Endangered, with a decreasing population. Major threats to whale sharks are fishing (particularly for shark fin), fisheries bycatch and shipping. Marine pollution, including oil spills, and inappropriate and unregulated tourism can also be a local threat.
But the whale shark tour industry at Exmouth, Western Australia, is world’s best practice. Whale shark numbers at Ningaloo Reef have increased, bucking the trend worldwide.
At the 5th International Whale Shark Conference in 2019 experts praised the management of the industry.
Dr Brad Norman said effective management of whale shark tourism in the region was integral in keeping populations healthy.
“The Ningaloo Reef is in the World Heritage area so it’s very well-managed and well protected and the tour operators are doing a great job,” he said.
“They encourage the tourists to keep a good distance away from the animals and to give them room and the whale sharks seem to be comfortable and they keep coming back every year.”
New Fact 4. Male Whale Sharks grow fast when young, females grow bigger but more slowly.
Research at Ningaloo Reef found that male whale sharks grow rapidly when young, then growth rate slows down as they approach average maximum size of 8.5 to 9m. Larger males do occur, but are very very old.
The drive to grow fast might be the reason why most of the whale sharks seen by people worldwide are males – predictable sources of plankton food occur closer to the coast, and the water is warmer which means less energy needed to grow. Females can stay further out in the open ocean.
Female whalesharks grow more slowly throughout life, but can grow to an average maximum of 14.5m. Very large individuals, up to 18metres long, have been recorded, and are all females.
New Fact 5. Whale Sharks give birth to live young, 300 at a time, but almost nothing is known about their breeding
Everything we know about whale shark breeding has come from one pregnant female who was caught off Taiwan. She had 304 babies inside her, all at different stages of development. 29 of them had the same father – which suggests that a female mates and stores sperm, and then fertilises the eggs when she is ready.
Mating has only been seen & recorded three times – once, recently, by a pilot working for tour boats at Ningaloo Reef. The pilot, Tiffany Klein, reported seeing a male shark acting erratically, who then approached a juvenile female, turned upside down and attempted to mate with her. She shook him off. Tiffany got photos.
No-one knows where whale sharks breed. Many females with distended bellies have been seen around the Galapagos Islands, but research so far has not been able to show that they are pregnant.
Is tourism good for whale sharks?
That depends where you go. In Western Australia, the answer seems to be yes. Visiting whale sharks with licensed tour operators means that important data is collected that contributes to scientific research, and the sharks needs are paramount.
“our results suggest that there is no evidence of long-term impacts of tourism on the whale sharks at Ningaloo.”
You can see all this for yourself on our Island Birds and Whalesharks tour in March 2022.
Read other facts about whale sharks here: https://www.wwf.org.uk/learn/fascinating-facts/whale-sharks
NOTES & REFERENCES:
IUCN Red List Whale Shark: https://www.iucnredlist.org/species/19488/2365291
Freya Womersley, James Hancock, Cameron T Perry, David Rowat, Wound-healing capabilities of whale sharks (Rhincodon typus) and implications for conservation management, Conservation Physiology, Volume 9, Issue 1, 2021, coaa120, https://doi.org/10.1093/conphys/coaa120
Lester, E., Meekan, M. G., Barnes, P., Raudino, H., Rob, D., Waples, K., & Speed, C. W. (2020). Multi-year patterns in scarring, survival and residency of whale sharks in Ningaloo Marine Park, Western Australia. Marine Ecology Progress Series, 634, 115-126. https://doi.org/10.3354/meps13173
Meekan Mark G., Taylor Brett M., Lester Emily, Ferreira Luciana C., Sequeira Ana M. M., Dove Alistair D. M., Birt Matthew J., Aspinall Alex, Brooks Kim, Thums Michele Asymptotic Growth of Whale Sharks Suggests Sex-Specific Life-History Strategies Frontiers in Marine Science VOLUME 7, 2020, PAGES 774 https://www.frontiersin.org/article/10.3389/fmars.2020.575683
Lester, Emily; Speed, Conrad; Rob, Dani; Barnes, Peter; Waples, Kelly; Raudino, Holly Using an Electronic Monitoring System and Photo Identification to Understand Effects of Tourism Encounters on Whale Sharks in Ningaloo Marine Park, Tourism in Marine Environments, Volume 14, Number 3, 2019, pp. 121-131(11) https://doi.org/10.3727/154427319X15634581669992
ABC Whale shark mating: https://www.abc.net.au/news/2019-06-12/whale-sharks-seen-mating-on-ningaloo-reef/11199336