National Parks of Taiwan

A Passway for Humans or Crabs?

A Lesson in Practicing Land Crab Conservation

Article/ Ru-Ling You

Interviewee(s)/ Hsiao-Ching Kuo, Associate Technical Specialist, Kenting National Park Conservation Research Section.Wei-Mei Kuo, Associate Technical Specialist, Taijiang National Park Conservation Research Section

"Roads are for humans; all this stop-and-go driving, just for crabs, is really annoying!"

Kenting National Park Headquarters used to receive complaints like these every year, certain times of the year. It was because, during land crabs' spawning season – when they need to cross the coastal road to reach seashore for larvae release –Kenting National Park Headquarters (KNPH) would implement scheduled road traffic controls, to prevent female crabs and their unborn larvae from being killed by cars. However, this traffic control attracted complaints from road users – tourists,community residents, etc.

Why are traffic controls implemented to protect land crabs?And why did public complaints gradually disappear?

In a broad sense, “land crabs” include those crab species that live in streams, intertidal zones,and on the land, i.e..during the yearly breeding season, egg-carrying female crabs will follow the changes in the tide and moon phases to migrate to the seashore and release tens of thousands of larvae. The hatched flea-like larval plankton float in the sea. Most of them may become food for other sea creatures. The surviving larvae, after molting several times, grow into juveniles and then return to the land, thus starting a new life cycle.

Currently, human factors that affect land crabs'sur vival and reproduction include habitat degradation, roadkill, and hunting/capture. Since their habitat has been divided by the coastal road,the land crabs need to cross the road to release larvae; so a major factor that affects their lifecycles is having to face the threat of being killed by vehicles on their way to the seashore while completing a vital reproductive process. Therefore,in recent years, Taiwan's national park system has promoted conservation measures – based on land crab surveys and studies – to reduce challenges to land crabs' survival.

Triple Measures – Traffic Control, Ecological Surveys, and Environmental Education

The Kenting National Park area is blessed with many major land crab habitats. These include Back Bay, Siangjiao Bay Coastal Forest, the Gangkou River estuary, and Chufongbi. There,varied coastal and environmental features have given rise to abundant land crabs in vastly diverse forms. Supralittoral land crabs live in the landsea transition zone, which highly overlaps with human living areas, and thus their survival is directly affected by road development and tourism activities in coastal areas. During the yearly breeding season, female crabs need to cross the coastal road and release their larvae at the seashore. However, this timing coincides with the peak tourism season, when beach-bound traffic is heavy. This makes land crab deaths all the more likely.

To reduce roadkill, a few years ago, Kenting National Park Headquarters began traffic controls on a section of Provincial Highway 26. The section,about 2 kilometers long from Siangjiao Bay to Shadao Beach, had been a hotspot for crab roadkill rates. Since the times when land crabs migrate to the seashore for larval release varies from species to species, KNPH schedules the traffic controls on peak larval release days: The days of the full moon, and the two days that follow – that is, the 15th to 17th of the Lunar sixth, seventh, and eighth months, from 6:30 to 8:30pm. The intent was that,with measures such as scheduled road closures,directing vehicles to slow speeds, etc., a large number of land crabs could be assisted to safely reach the seashore and let their larvae free into the ocean. Some crabs appear during the period from 3am to sunrise, so on larvae-release nights,community members serve as traffic controllers for the second half of the night to help the land crabs get across the road.

In addition to reducing roadkill through traffic control measures, KNPH also took the opportunity to promote the concept of conservation, while also implementing ecological monitoring. Hsiaoqing Kuo explains: “There are a lot of things we didn’t know about land crabs' living habits, so the research team encountered difficulties in conducting surveys. By getting a sense of land crabs' larval release times, the team can carry out effective ecological monitoring and estimate crab population size. For example, as Discoplax hirtipes usually release their larvae on full moon days, traffic controls on those days will help the land crabs cross the road safely, and will allow research team members to observe and record crab populations.On-site volunteers also communicate conservation concepts to the public, achieving the purpose of environmental education.”

In light of the land crab roadkill situation, KNPH has also continued to discuss establishing ecological corridors with experts and scholars. Hsiao-qing Kuo points out that the functions of land crabs'ecological corridors are different from those for other animals. In addition to reconnecting parts of their habitats to reduce roadkill, it is also necessary to consider land crabs' par ticular breeding characteristics – they cross the road because they need to release their larvae. Thus, the female crabs have to be guided to cross the road while egg-carrying if reproduction is going to succeed.At the current stage, KNPH is still experimenting with different forms of corridors, and learning what factors affect land crab migration. These are the focuses for the next stage in Kenting's land crab conservation.

Perspective Dialogue 01

As Hsiao-Qing Kuo, Associate Technical Specialist, Kenting National Park Conservation Research Section, explains,traffic controls used to be implemented in a way that the road would be closed for 10 minutes, and then the inner lane would be open for 10 minutes, with a pilot vehicle arranged to help vehicles keep their speeds down. Such measures, inevitably, attracted complaints, and were viewed as an annoyance by the public. Later, Kenting National Park Headquarters (KNPH) communicated with the public, making the appeal: “Humans use the road for 365 days; let’s give way to land crabs for 18 hours”. KNPH invited the public to join the “Give the road back to crabs for a while” campaign. In addition, with awareness-raising advocacy in the media, most members of the public understood and cooperated with the measures, and tried to avoid using the road during traffic control periods.

Citizen Scientist Participation, Turning Passive into Active

Taijiang National Park, which borders the ocean,is also faced with a land crab roadkill problem.Menghuan Lake, located in the Chengxi Village on the south bank of the Zengwen River, and a half-kilometer radius of coastal forest around it are the zones with the highest supralittoral land crab species diversity in the Park. This is also the habitat with the largest Cardisoma carnifex crab population in Taiwan. However, again, as the land crabs' make their way to the seashore to release their larvae, they need to cross the access road in the Qingcaolun to go down to the sea. There, they are further obstructed by vertical coastal levee structures, which means they have to spend more time on the access road, increasing the roadkill risks even more. In order to solve this problem,Taijiang National Park Headquarters (TNPH) based on the results of ecological surveys completed in 2021, has submitted suggestions to the competent authorities to improve the levee structures. Wei-Mei Kuo, Associate Technical Specialist, Taijiang National Park Conservation Research Section,observes: “A modified slope design will be friendlier to land crabs. Future levee construction projects will also take land crabs' ecosystems into consideration."

Of course, land crabs do not limit their ocean migrations to National Park areas. That’s why TNPH also entrusted a research team to investigate roadkills in Anping District, on the outer edge of the Park. The investigation showed that the spot with the highest roadkill rate was on Anbei Road;the hypothesis was that land crabs were being attracted to streetlights or store lights, and lost their way. After discussing improvement measures with government agencies, hoods have been installed on the streetlights at the curb parking spaces of Anping District's Minquan Road (Section 4), the levee on the south bank of the Yanshu River and Zhouping Road. Hopefully, this way, land crabs will not lose their way and be killed on the road.

In contrast with Kenting's Provincial Highway 26, which sees significant tourist traffic, the embankment road in Qingcaolun is a flood control road that few tourists visit. Weekday traffic is low;although there are roadkill accidents, the situation is not serious. Currently, the greatest threat to land crabs' survival in Taijiang National Park still comes from human crab hunting. As a major habitat for land crabs, the windbreak of the Chengxi Village has attracted many people who poach crabs.Particularly during the breeding season, land crabs will appear en masse at certain times, making them highly vulnerable to poaching by hunters. Large land crabs such as Cardiosoma carnifex have slow growth rates, so their populations are significantly affected by excessive hunting.

There are many human activities in Taijiang National Park, such as tourism/recreation and economic/industrial activities that impact ecosystems. As a result, securing community support and assistance is the key for land crab conservation. That’s why, in 2022, TNPH entrusted Wetlands Taiwan to implement the Project for Citizen Scientists'Participation in Land Crab Conservation in Taijiang National Park's Qingcaolun Area. The project provided training for residents of communities near Qingcaolun. Through conservation action such as ecological monitoring/surveys, traffic control,crab protection advocacy, night patrols, and more,poaching by humans has been greatly reduced.

To reduce challenges to land crab survival takes immense effort from many people. From National Park Headquarters, to research teams, crabprotection volunteers, community residents, to every member of the public who cooperates with traffic controls, all are indispensable supporters of crab protection. If we may wish to pay more attention to the small and tough life on the way to the coast during the yearly breeding season of land crabs, and we can also contribute to protect the land crabs.

Perspective Dialogue 02

The crab poaching crisis has been mitigated since Taijiang National Park Headquarter and other government agencies employed strict remedial measures. Wei-mei Kuo says that according to feedback from crab-protection volunteers,the fishing tackle shops that used to sell land crabs as bait have stopped. Some community members proactively conduct crab habitat patrols outside the project's scheduled monitoring times, incorporating crab-protection activity into their daily routines. “In addition to local community residents, some people even come from all over Tainan to support this project. They had been unaware of how this place is endowed with precious ecological resources. Once they learned the facts, they have continued to pay attention to conservation issues, and have even spontaneously committed themselves to future conservation. This is just the kind of effect we hoped to trigger through the project."

What can I do to protect land crabs?

1. Do not catch, raise, or eat any kind of land crabs; do not drive into any land crab habitat such as coastal beaches, etc.

2. When you spot people catching land crabs within Taijiang National Park, notify the Seventh Division of Seventh Special Police Corps, National Police Agency, Ministry of Interior, at (06) 284-2300.

3. Avoid traveling on coastal roads during periods when land crabs need to migrate to seashore for larvae release. If you are required to go there, slow down. If you meet egg-carrying land crabs on their way to the sea to release larvae, get out of your car and help the land crabs cross the road safely before you start off again.

4. If you’re doing land crab ecological observation, do not excessively disturb the crabs.

5. Do not use land crabs as bait when doing recreational fishing in permitted zones.

6. Do your part to help out in beach cleaning activities in coastal areas.