Horseshoe Crab Rescue & Research Programme

Exposing oneself completely under the blazing sun at noon might not be a good idea, but this is what 17 NUS Bachelor of Environmental Studies students, along with other nature lovers, were doing on last Sunday at Mandai mudflats. We bore an important mission in rescuing and counting horseshoe crabs, an endangered species in Singapore that are still in a worrying declining trend. There are only four species of horseshoe crab around the globe currently. Two of them, coastal horseshoe crab (Tachypleus gigas) and mangrove horseshoe crab (Carcinoscorpius rotundicauda) can be found in Singapore, with the former being likely globally endangered, despite the fact that both species are still categorised as “Data Deficient” in the IUCN Red List (Cartwright-Taylor et al., 2011; The IUCN Red List of Threatened Species, 2018). 



After a short introduction on the species and safety briefing, volunteers headed down to the muddy areas and “enjoyed” the hand mud spa as they pressed their palms into the mudflat, feeling for solid and spiky objects that were the carapace of a horseshoe crab. Eyesight could only help in balancing and navigating the way since horseshoe crabs can submerge up to 3cm beneath the surface, not to mention the overgrown algae and different types of marine debris (mostly plastic) glutting the mudflats which could obstruct the search. Nonetheless, there were considerable sightings of horseshoe crabs, and the size of each encounter was measured and recorded for further data analysis and species monitoring.



No one came back with clean hands or shoes at the end of the searching session. We were just like overgrown kids having playtime on mud; our pants would be a good testing material in a laundry detergent advertisement. Nevertheless, the experience was extremely fulfilling and exposed our volunteers to the importance of fieldwork and conservation.



Below are words from our BES volunteers:

“The horseshoe crab rescue & research program organized by BES and NSS was very different from other intertidal surveys that I’ve been for. When we arrived at the Mandai Mudflats, I didn’t expect the area to be so small as we were told that this is one of the most heavily populated locations (in the ENTIRE WORLD) for mangrove horseshoe crabs! Having had prior encounters with coastal horseshoe crabs, I was confused when we walked across the mudflats, and did not spot any mangrove horseshoe crabs. Later did we learnt that they were covered by the mud and seagrass, so we had to sink our fingertips into the ground to search for them. I had a lot of fun trying to find them and measuring them, knowing that I am contributing to data and research that all goes towards horseshoe crab conservation!”

– Inez, Y1 NVB



“This was my very first horseshoe crab rescue program, and I thoroughly enjoyed it. When I slowly removed my first horseshoe crab from the mud, I was filled with childlike excitement.

I guess, we don’t usually get these experiences in normal curriculum thus it was very enjoyable for me! The horseshoe crabs are quite fragile, so we had to gently pry them out from the mud as we could risk damaging their carapace or tail. At the same time, we learnt about an invasive species of mussels that was extremely prevalent in the mudflats – something that could cause harm to the local ecosystem. The NSS guides were also very friendly and helpful – shoutout to Patricia! I highly recommend everyone (doesn’t matter what age you are) to try this out at least once, as it is a great learning experience in both fieldwork and conservation in Singapore.”

– Elysia, Y3 NVB



Cartwright-Taylor, L., Yap, V. B., Hsu, C. C., & Lou, S. T. (2011). Distribution and abundance of horseshoe crabs Tachypleus gigas and Carcinoscorpius rotundicauda around the main island of Singapore. Aquatic Biology, 13, 127-136. doi: 10.3354/ab00346

The IUCN Red List of Threatened Species. (2018). Carcinoscorpius rotundicauda. Retrieved from Accessed on 6 February, 2018.

The IUCN Red List of Threatened Species. (2018). Tachypleus gigas. Retrieved from Accessed on 6 February, 2018.

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