Land crabs threatened by traffic and development
Land crab in the Cayman Islands (photo courtesy DoE)
(CNS): A new scoping study by the Department of Environment Terrestrial Research Unit found that almost 3,000 black land crabs were killed on the Queen’s Highway in East End during the two month peak migration season last summer. Writing in the DoE magazine, Flicker, graduate research student Kinsey Tedford, said there is much local anecdotal knowledge about the Gecarcinus ruricola, but almost no scientific data. With increasing indications that the crab is under threat, Tedford and Dr David Bass began their research during the 2017 season to understand the migration.
The clearest findings were the threats posed by cars and development to the species and its continued survival. In June a total of 1,328 crabs were killed crossing the highway between North Side and East End and another 1,612 in July. The research also revealed that the crabs are confined to areas along the highway with little or no development.
“The crabs seemed to prefer the undeveloped areas providing them with the necessary resources and suitable habitat,” Tedford wrote. “The loss of a forested habitat and the resources it contains is a considerable issue on the island as tourist-related development and urbanization continues. Habitat loss along the coastal side is a particular threat because it hinders the seaward migration of berried females to release larvae, as well as re-emerging megalops (juvenile crabs) moving inland.”
The researcher found that heavy rainfall and the cycles of the moon are important triggers for the migration season. Female crabs head from their inland locations to the sea to lay their eggs during the first new moon following heavy rains. But with so much road kill and less habitat, the data raises questions about the sustainability of the local crab population, which remains a popular food source.
The cultural tradition of crab hunting is already becoming far less common due to the threats to the habitat and population, and the research data is now needed to help the DoE in conservation plans and the possible introduction of sustainable harvest levels.
“As keystone species and migratory animals, land crabs have multiple roles spanning the eco-systems they cross,” said Tedford. “In the ocean, many animals feed on the crab’s larvae as they drift through the currents among seagrass beds, coral reefs, and mangrove wetlands. Land crabs also play important roles in forested coastal habitats by serving as ‘gardeners’ dispersing seeds throughout the forests and ultimately influencing the species composition of coastal plant communities.”
This first step towards a more scientific understanding of the population of land crabs will help conservationists manage what is emerging as a threatened species. But Tedford points out that this crab will need more than just habitat protection, though that will still be important to its survival as well as other endemic species that live in the same areas, such as the Grand Cayman racer snake and the Grand Cayman Bluethroated Anole.
But the threat from traffic during the crabs migration will, Tedford wrote, require other protections, such as warning signs with flashing lights in the areas where the crabs are migrating in the greatest numbers.
The next step in the research will be to look at the catch numbers. Telford said it will be important that local crabbers, are involved in providing input on potential sustainable harvest rates and future management decisions.
Email Jane.Haakonsson@gov.ky for a copy of Flicker #37
Access old issues of Flicker on the DoE website
Category: Land Habitat, Science & Nature
We were on Grand Cayman in May of 2015. Coming back one evening from Rum Point to our condo in the East End we encountered a crab migration. We had no idea that would be going on, or that it was even a thing that happened. The carnage was appalling. Driving extremely slowly, we tried very very hard not to run over the live ones. Next day? Nothing. Had we known this was the night, we would simply have adjusted our schedule. Is there a way to predict when the migration will happen? Is it possible to make some sort of publicity to warn people to stay off the roads that night?
Can someone pick up my garbage?
Did they witness 1300 crabs being smooshed with their camera or own eyes or did they walk down the road and count the leftovers to arrive at that total? I personally think they are a few thousand off; just saying. Perhaps the DoE can put out notices and warnings when these happenings occur like they do when it’s conch season so that people avoid driving those routes and those that live there can pretend it’s the apocalypse and stay inside their mansions living on rations till the plague of shanks passes? Maybe DART can build a tunnel?
Sadly crab killing is a popular sport here on the East End. You can see cars swerving to kill the crabs as they cross the road rather than try to avoid them. Like some sort of video game. Those are living creatures people. They have lives, they feel pain. Stop treating them like some kind of bonus points. Bloody sickos.
Put tunnels under road….
We could help the poor crabs by putting some concrete tunnels under the roads where they migrate, even put food in the tunnels to help attract them so they can make a safe passage, the road is the last place they want to be but it’s their only option right now
Ditch that dumb idea of warning lights and crossing areas, and simply install several large culverts and under-road concrete pipes for the crabs to cross under the road on their march to the sea. K.I.S.S. Keep It Simple Scientists! LOL.
Cars are not the only problem…
I saw a snake today writhing in unadulterated pain and agony as a car ran on just a part of it. The hot sun was scorching its poor little body by the side of the road. Can’t people just ride a bicycle? If you are in the Eastern districts take a bus and try to save the environment. We only have one. People from all over the planet come to see our chickens and iguanas. They love to feed them and their kids just love to see the vibrant colors. Frogs make the first sounds when rain is about to fall. I can remember how the swamps were full of their wondrous song as rain was coming. Can you remember that? The cycle of life in Cayman is ever coming and going. Including us.
Lots of Rental cars saturating EE.
The problem is not Barbara, its cars. We need to start a petition to stop cars from using the roads during crab season. Everybody needs to take the bus.We have too many cars on this road. Look how much we could save on road works? We could then use that money to build better schools or sports facilities? What do you all think?
Meanwhile Barbara Connolly and the PPM are in the process of destroying some of the last natural habitat that the black land crabs have left in South Sound. Please leave Smiths Cove alone!!
We have already lost red shanks and soldiers. When are we going to learn. It would be soneasy to put pipes index the roads and have crab proof very short fences to stop them all being killed on their migration routes. We should be embarrassed at what we have done and do all possible to prevent further unnecessary destruction to what is left.