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A Day in the Life of a Whale Shark Biologist

Words and images by Simon Pierce

Hey everyone! I’m Simon. I’m from New Zealand, and I’m 39 years old. I studied Australian stingrays for my PhD degree. In 2005, I moved over to Mozambique to start a research project on whale sharks. I still work mostly with whale sharks, in Mozambique and many other different countries around the world. My job title is Principal Scientist at the Marine Megafauna Foundation. Right now, I’m in my office in New Zealand. I think you’ll find this post more interesting if I pretend I’m back working on Mafia Island, Tanzania, which is where I was last doing fieldwork. Let’s go with that! Mafia is one of my favorite places to visit each year. From about November to January, the sharks are found close to shore feeding on shrimp at the surface. The shrimp are quick, so the sharks have to swim fast to catch them. The sharks’ fins are often sticking out of the water which makes them easy to see. An average-sized whale shark at Mafia is about 20 ft long; their fins are big!

I spent six weeks in Tanzania over ‘whale shark season’ with my research buddy, Dr Chris Rohner. We stay at the well-named Whale Shark Lodge, on the top of a small hill near the beach. Our days are pretty similar. Each morning we wake up at about 6 am. There are lots of birds, monkeys and lizards around to keep us company at the lodge. The dining area overlooks the bay. Sometimes we can even watch whale sharks feeding off the beach while we eat banana pancakes for our own breakfast. It’s a lovely way to start the day. Around 7 am, we get picked up at the beach by our friend Captain Liberatus. He started taking tourists out to see whale sharks off Mafia way back in 2004. He knows lots of fishermen, who go out to sea even earlier than us, so they often call him if they see sharks. If we don’t hear from them, we slowly motor around the bay in our little boat until we find a shark ourselves. Whale sharks all have a beautiful pattern of white dots and lines. Every shark has a slightly different arrangement of spots, so we take a photo of each side, just behind the gills, to see which shark it is. We’ve seen some of them over 50 times! Chris has memorized what many of the sharks look like, so he’s often able to tell me who the shark is. We’ve counted about 170 sharks at Mafia now, after starting work there in 2012. Once we’ve done that, we’ll check if it’s a male or a female. The males have a clasper on each pelvic fin and the females don’t. We don’t know why yet, but it’s mostly male sharks that we see at Mafia. About nine out of every ten sharks we’ve seen there is a male. I’d love to know where all the females are hiding! We also estimate the length of the shark. Whale sharks seem to grow very slowly, and might live for over 100 years. Later this year we’ll be using a stereo-video system, where two GoPro’s are used together to measure the length of the shark, to find out how fast they grow. Most of the whale sharks at Mafia are big kids. We haven’t seen any babies, and we haven’t seen any larger than 30 ft. Once they get to about that size they become adults. At that stage they seem to leave Mafia, and probably live away from the coast for the rest of their lives. Sometimes the sharks get hit by boats or tangled in nets, so we always check the shark’s skin and fins for signs of injury. If we see any, we’ll take a photo of those for our records too.

All of that usually only takes a minute or two. If it’s a shark we haven’t seen before, or haven’t seen that year, we’ll often take a small skin sample using a biopsy pole. My student Alex Watts is studying how whale sharks in different parts of the world are related to each other for her PhD work in the UK. Clare Prebble, who is finishing up her PhD in the UK at the moment, has been looking at the chemistry of the sharks’ skin to see what they’ve been eating, and whether they’ve traveled away from Mafia over the past few months. In other years we’ve tagged sharks to follow their movements, so we’ve got a good idea of their habits and where they like to hang out now. Though a lot of the sharks like to stay around Mafia right through the year, one of the sharks (Santa) has been to the Seychelles and back. Two sharks that we know from Mozambique have swum over a thousand miles north to Mafia as well. We usually see a few whale sharks each day. Around lunchtime, Liberatus drops us off back at the beach and we head back to the lodge. After lunch, we sort through our photos and upload them to the global whale shark database at We label the skin samples, then put a piece of each in the freezer for chemistry studies, and a bit in preservative. That keeps them in good condition since we haven’t got a laboratory at Mafia. We enter all the information we’ve gathered that day into a spreadsheet. Once that’s all done we often reward ourselves with a piece of chocolate (okay, a few pieces). Then we’ll often have some emails to reply to and scientific papers to write up for the rest of the afternoon. The sunsets are really nice at Mafia, so we normally relax around then to watch the sun go down and have dinner. If either of us have got friends visiting, we make them watch Pitch Perfect because it’s aca-awesome. Otherwise, I’m usually in bed early to get a good sleep – swimming around after whale sharks is tiring!

Being a whale shark biologist is great. We work in some beautiful places, like Mafia. We’re helping the community there to develop whale shark tourism so everyone can swim with the sharks, so it creates jobs for people and makes everyone want to keep the sharks safe. I get to work with some of my best friends, which makes it a lot of fun. Most importantly, we all love the whale sharks. They’re big, they’re gorgeous, and they’re often really friendly and curious. Sadly, in some parts of the world, including other places in Tanzania sometimes, people still hunt them. The research and conservation work we’re doing is helping to protect them from harm, so I think I’ve got the best job in the world. You can see more about our work in Tanzania in this video.

Thanks for reading!

You can check out more of Simon's research and photography on his WEBSITE

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