pelf-ism is contagious

Apart from the terrapin-related research and conservation work that we do at the Wetlands Institute, we do other research work too. For example, one of the earliest projects that we were all involved in was the horseshoe crab spawning census that was conducted in May and June.

A census was conducted 2 days before the new moon and full moon, on the new moon and full moon, and 2 days after the new moon and full moon. During the spawning census, an intern walks some totally random number of steps on the beach for 1 km, and then count the number of male and female horseshoe crabs (Limulus polyphemus) that are found in the quadrant. Another intern records the number of horseshoe crabs in a data sheet.

The female horseshoe crab is bigger than the male, and she is usually partially submerged in the sand and the males would be “hooked” onto her. We have seen as many as 10 males to a female! Apart from the obvious difference in size, the male horseshoe crab is also characterized by the presence of a pair of boxing-gloves look-a-like legs.

Besides counting the number of horseshoe crabs in the quadrant, two other interns are responsible for counting all the male and female horseshoe crabs in the same 1 km length of the beach.

Despite what you might think about horseshoe crabs, they are pretty harmless. Some people eat them, though they haven’t much meat to begin with. And whatever you do, NEVER EVER pick a horseshoe crab up by its tail. I guess it’s akin to me picking you up by your THUMB. And, legend has it that whoever kisses a LIVE horseshoe crab will have 7 years of good luck!

More pictures taken during the horseshoe crab spawning census here.

Apart from going on a road patrol 5 times a day and performing eggectomies on roadkills, researchers at the Wetlands Institute conduct other terrapin-related studies too. For example, a visiting scientist from the Swarthmore College deploys crab traps in Mulford Creek, just behind the Wetlands Institute in a mark-and-recapture study.

In the mark-and-recapture study, the visiting scientist deploys his commercial crab traps in the creek during the first high tide of the day. The fish bait will attract crabs and well, diamondback terrapins! He then checks the traps again during the second high tide (which is usually in the evening) and he empties the traps and brings the terrapins back to the institute.

Depending on the number of terrapins that the 15 crab traps are able to trap, back in the lab, we will have a micro-chipping party We will fill up a mark-and-recapture data sheet for each terrapin, and we will then measure and weigh it. If the terrapin does not have a microchip (and most terrapins don’t), we will microchip it (but since micro-chipping is an entirely different business, I will blog about it next).

Terrapins that have been processed will be kept overnight, and they will all be released the next morning, when he checks the crab traps during the first high tide.

When we go on a road patrol, we would usually see only adult female terrapins because only females come out to lay eggs. But with the traps, we are able to trap juvenile terrapins as well as male terrapins. It is hoped that the data collected from the mark-and-recapture study is sufficient to estimate the population size of the terrapins in the area.

Female diamondback terrapins that are spotted during road patrols are processed on the spot.

She will be checked for a microchip, and if she has one, we will try to remove it. Used microchips will not be re-used but they make very good educational materials. We keep them in small vials and pass them around during talks so that the audience have an idea how big the microchips are (the size of a grain of rice).

Whenever possible, we will also measure her carapace length (shell), carapace width, plastron length (underside) and height, but usually the carapace is very badly smashed that the only measurement we could take is the plastron length.

We then check for the presence of eggs in her oviduct. Some female terrapins are run over by cars after they have laid their eggs, but there are also many that are killed before they could lay their eggs. In cases where the eggs are not crushed (and strewn all over the road), we will put her in a box and bring her back to the lab at the Wetlands Institute.

Back in the lab, we perform a little surgery to remove the eggs in her oviduct, and the procedure is called oophorectomy, or simply known as “eggectomy” at the Wetlands Institute

The flap of skin right above the leg is cut open to expose the oviduct. In some severe cases, the carapace/plastron would be so badly damaged that the oviduct is visible without having to cut it open.

The terrapin carcass is then tilted to one side so that the oviduct and the eggs would slide down. It is always easier to let gravity assist in the removal of the eggs because we do not want to squash them by inserting our fingers into the cavity and grabbing the eggs. The eggs can be easily dented if we weren’t careful with them.

On average, a female terrapin lays between 8 and 12 eggs in a clutch, and we normally salvage that amount of eggs from the roadkills, but of course, there were instances where only 1 egg was found.

And sometimes, only undeveloped eggs are found in the oviduct!

Salvaged eggs are cleaned with distilled water and wiped dry before they are placed into containers containing 3 L of vermiculite and 300 mL of distilled water. The containers are then placed into incubators set at high temperatures so that more female terrapins are produced to replace the ones run over by cars.

More pictures taken during eggectomies (Warning: DO NOT click if you are not comfortable seeing VERY GORY pictures.).