Nature Society horseshoe crab survey

Keeping tabs on coastal scavengers
Nature Society survey finds all stages of horseshoe crab along the shores
Jose Hong Straits Times 31 Mar 12;

HORSESHOE crabs are not the prettiest of creatures. With a spiky carapace and a long pointed tail, it is easy to see why they are sometimes viewed with fear.

Yet, they are harmless scavengers, and play an essential role in their ecosystem.

Two Saturdays ago, the Nature Society (Singapore) or NSS deployed 160 volunteers along 10 of Singapore's coasts to conduct the Horseshoe Crab Population and Distribution Survey 2012.

The first survey was done in 2009 to record the population density of horseshoe crabs around Singapore's coastline.

There are two species of horseshoe crabs in Singapore.

The mangrove horseshoe crab can be commonly seen on certain shores while the coastal horseshoe crab, suspected to be more mobile in behaviour, is much less frequently encountered on the coast.

And as the NSS discovered through earlier casual surveys, there is something big about these arthropods here.

According to Mr Goh Ter Yang, outreach officer of the NSS, Singapore's north-western shores are 'the only place in the world where there is a known permanently high population density of horseshoe crabs'.

In other places like the American eastern seaboard, huge numbers periodically appear at the beaches, but for the rest of the year, disappear from the shoreline.

Dr Hsu Chia Chi, a member of the NSS executive committee who is spearheading this survey, said the NSS 'has found all stages of horseshoe crab present' along these shores, ranging from eggs to juveniles and adults.

The NSS is halfway through collecting and analysing the results of the survey.

According to preliminary calculations, the horseshoe crab population on Singapore's north-western shores stands at a rough estimate of 200,000.

Various migratory bird species have also been observed coming here to feed, marking this stretch of coast as an important refuelling site for them.

Through studies like this, Dr Hsu hopes to get the Government to recognise the north-western shores of Singapore as a wetland reserve under the Ramsar Convention, an international treaty under which governments pledge to maintain wetlands of global importance.

This is key to the conservation of the horseshoe crab, given that the loss of habitat is the single most important factor in their demise, he said.

The Government can continue developing the land beyond the shore 'so long as it protects the mudflat which nobody uses', he said.

Furthermore, the results of this survey have an international significance. According to researchers, horseshoe crabs worldwide are under myriad threats - from being hunted for food to rampant habitat destruction - and their numbers are declining significantly.

Still, three out of four horseshoe crab species are categorised as 'Data Deficient' on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, a data list used to identify threatened animals worldwide.

Dr Hsu hopes to change that. Along with various other surveys from across the globe, the results of this survey will be collated and sent to the IUCN.

With all this information, he expects the IUCN to finally be able to give horseshoe crabs the status they deserve.

Dr Hsu believes the survey also serves as a good outreach programme to take participants out of their comfort zone.

But the NSS is still facing a shortage of volunteers 'who are willing to be trained and who will come down on a long-term and regular basis', said the general practitioner.

Such a manpower shortage was the reason no surveys were conducted between 2009 and now.

Still, as things stand, Dr Hsu is upbeat about conservation in Singapore.

'Generally, the public is much more aware of nature, conservation and of environmental biodiversity, and the Government has become more proactive,' he said.

Background story

200,000: The estimated population of the horseshoe crab on Singapore's north-western shores, according to preliminary calculations following this year's survey

SINGAPORE: 'The only place in the world where there is a known permanently high population density of horseshoe crabs.'

Mr Goh Ter Yang, outreach officer of the Nature Society (Singapore), referring to the country's north-western shores