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Tree-climbing/
Vinegar crabs
Episesarma
spp.
Family Grapsidae
Size: 4-5
cm
Members of this wide ranging genus are usually burrowing crabs, digging
holes at the base of trees and mud lobster
mounds.
They are primarily leaf-eaters and are known as pests of mangrove
plantations for their habit of attacking propagules. They will also
scavenge meat like many other crabs. The Teochew are known to pickle
this crab in black sauce with vinegar, and take it with porridge.
The Thais like it salted, with the roe or simply fried whole. |
Episesarma climbing on
Avicennia tree; note the squarish
carapace and splayed legs
Tree-climbing or Vinegar crabs
(Episesarma spp.) sold with
eggs (gravid) at Chatuchat market
in Bangkok, Thailand |
They emerge at dusk
to being feeding on the forest floor and have been observed climbing up
trees to heights of more than six metres.
Episesarma
hides on the
reverse side of tree trunk
from a predator |
Tree-climbing
crabs can be seen more easily in the day from the boardwalk at Sungei
Buloh Nature Park during high tide.
At this time, however, they climb only high enough to clear the water
level and remain motionless on tree-trunks, leaves or boardwalk legs. |
Night low tide
Day high tide |
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This is probably a predator-avoidance behaviour, especially with the
many predatory species of fish and crabs that hunt with the incoming
tide. Out of the water, they remain motionless to avoid other predators
like kingfishers, monitor
lizards and otters. |
| Of
the three species found in Singapore, the Violet vinegar crab (E.
versicolor) is one of the most common species, with a distinctive
violet palm and the fingers white-tipped. It prefers the seaward part
of the mangroves. |
E. versicolor
E. chengtongense
E. singaporense |
E. chengtongense |
The Pink-fingered vinegar crab (E. chentongense), which has
a violet palm with pink and white finger tips, is more common in the
seaward areas. |
Like the other two species,
the Singapore vinegar crab (E. singaporense) was originally described
from Singapore and has entirely red claws. It is common in or near mud lobster
mounds.
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