A freshwater crab that lives in a tree!?
What is it?
When we think of freshwater biodiversity we naturally think of places such as rivers, streams, ponds and lakes. But not all freshwater animals live in these habitats. The Liberian tree-hole crab is an amazing species of freshwater crab that lives in the closed canopy rain forests of West Africa. Yep, it’s a freshwater crab that lives in a forest. Living far from permanent freshwater sources such as rivers or lakes, these crabs live in water-filled holes in trees to survive. At night they emerge from their homes in the trees and make their way down to the forest floor to forage for food, mostly small insects. Once they’re finished with their evening meal, they climb back up the tree where they spend their days.
Range and Habitat
This unique species was first documented in 1898 in Liberia (hence the name), but was not documented until 90 years later in 1988. It is one of only five species that belong to a rare group of freshwater crabs that are endemic to West Africa. Since 1988 sightings have increased but been restricted to small parts of the upper Guinea forest in western Liberia and Guinea and it is also thought their range extends to parts of Sierra Leone’s forest which lie between these two populations. The crab populations are solely restricted to rainforest in areas with rainwater filled natural holes found in suitably sized trees at a height of between 1 to 2 meters above the ground and they are known to exist in just five different locations across these regions. For an interactive map of the tree-hole crab’s range click here.
As such these tree-climbing crabs are extremely rare and can be hard to spot. The number of tree-hole crabs that still exist is uncertain due to a lack of information, however, it was estimated that before the civil war broke out in Liberia in 1989 there were between 5-10 per km² of closed-canopy rain forest. It is expected that this number has decreased since this time and the species is listed as endangered on the IUCN Red List. Current estimates put the number at fewer than 2500 mature individuals.
It is thought that the population numbers have been declining across its range due largely to habitat loss and deforestation related to years of civil war and political instability in the region. Due to the specific habitat of these cool crustaceans they are very vulnerable to habitat loss. Being a freshwater crab that relies on rainwater captured in tree holes, even the felling of a small number of appropriately hollowed trees in a particular area may threaten local populations. Other threats that these curious critters face include an increase in agriculture, mining and firewood collection, which again contribute to habitat loss. Given these threats, the tree-hole crab’s specialised habitat and small population size, it is of serious concern that this species is not found within a protected area, nor are there any conservation measures in place to protect this unique animal’s existence. Hopefully more research into this incredible creature will raise awareness of its plight and spur on effects to protect it.