On the 7th of April, I went for the Horseshoe Crab Rescue and Research Programme at Kranji Mudflats. I chose to go on this field trip as I thought that it would be a fun and unique experience that I could not find elsewhere, and it ended up exceeding my expectations!
It was a cool Thursday morning, and I woke up before the sun had risen for the first time in a very long while. Feeling very sleepy but also very excited, I made my way to Kranji Mudflats and met up with the other BFF-ers outside the gate, where we chatted (and fought off mosquitoes) while waiting for everyone to arrive. It was really nice to meet others who, despite coming from different walks of life, shared the same love for nature and biodiversity!
Eventually, we were given a briefing and led down to the mudflats by our guide, Lester from Nature Society Singapore. Although most people think of these places as wastelands, I was struck by its natural beauty, with mangrove trees growing all around, and the vast expanse of sea contrasted with the skyscrapers of Malaysia in the horizon. We trudged through the muddy substrate until we were deep enough into the mudflat, and Lester stopped to share more about horseshoe crabs before we began our survey.
According to Lester, there are four species of horseshoe crabs worldwide, and two of them are found in Singapore – the coastal horseshoe crab and the mangrove horseshoe crab. As their names suggest, the coastal horseshoe crab is more commonly found on beaches, while the mangrove horseshoe crab is usually found in mangroves. Lester explained to us the differences between these two species – while coastal horseshoe crabs can grow up to the size of your head, mangrove horseshoe crabs are smaller and usually grow up to the size of your palm. Mangrove horseshoe crabs also have shorter spines on the side of their bodies, have rounded rather than triangular tails, and are darker in colour.
Lester also shared about the behaviour of horseshoe crabs, who, as bottom feeders, feed on whatever they find on the sea bottom. They also moult as they grow, which is why we often find horseshoe crab moults along our shores. Then, Lester taught us how to differentiate male and female horseshoe crabs, which can only be done once they reach sexual maturity (horseshoe crabs which are at least 7.5 cm from tip to tip are considered adults!). Males have distinctively swollen, ‘buff’ front legs, and tend to be smaller than females. This is because when they mate, the male attaches onto the female, and since its mouth is on its bottom, it cannot eat.
After Lester’s sharing, we started our survey of the horseshoe crabs in the mudflat. We stood in a line parallel to the shore, then slowly moved down towards the water as we dug around in the mud for horseshoe crabs. The horseshoe crabs found would have their length taken and their sex identified. It was not easy to find them at first, but I eventually found a few, which was exciting! Lester shared that the population of horseshoe crabs used to be much larger, and that surveys would yield buckets upon buckets of horseshoe crabs.
Unfortunately, the horseshoe crabs here face a number of challenges, which is why they are not as plentiful today. Firstly, horseshoe crabs are not protected under the Wildlife Act, and as such, are particularly vulnerable to human threats like land reclamation and net fishing. Also, the changing, increasingly sandy substrate at Kranji Mudflats is unsuitable for horseshoe crabs, which is why they are being found in increasing numbers at Sungei Buloh Wetland Reserve instead.
Interestingly, I learnt that horseshoe crabs here are also being threatened by the invasive Charru mussels from South America. These Charru mussels are one of the many other species found on the mudflat, which include flower crabs, thunder crabs, sea anemones, drill snails and cone snails. They were first found in large numbers here in 2015 to 2016, and could have arrived in Singapore in ballast water. They are harmful to horseshoe crabs as they can prevent horseshoe crabs from burrowing into the ground, and can even latch onto them, preventing them from moving or eating properly. Thankfully, volunteers have been doing their best to manually remove these invasive mussels.
Not only did I have a lot of fun during this field trip, but I also learnt a lot about horseshoe crabs, and gained a better understanding of the need to protect these interesting creatures. Thank you Lester! According to Lester, most of the people (including him) with Nature Society Singapore are volunteers, and it struck me how much of our conservation efforts are down to volunteer efforts, and how passionate these volunteers are.
Through this field trip, I also realised how important first-hand experiences with nature and biodiversity are in developing a love for the environment. It was only after getting down and dirty in the mudflats with the horseshoe crabs that I began to understand the importance of protecting them. When people are able to appreciate the beauty of the natural world, they will be more likely to take action to protect it. As put by Baba Dioum, “In the end we will conserve only what we love, we will love only what we understand, and we will understand only what we are taught.”
Thanks for reading!
BFF Biodiversity Challenge 2022 