TDA-IME Project Final Report June, 2013 Insects and Spiders Insects are diverse and abundant in mangrove forests, where they play important ecological roles, not least as part of mangrove food chains that make mangrove plant primary production available to aquatic consumers as detritus. Herbivores such as caterpillars and beetles feed on leaves causing significant damage that also accelerates the process of converting mangrove leaves to detritus. Detritivores such as termites eat dead wood or decaying leaves. Pollinators such as bees play crucial roles and can also produce significant quantities of honey, which is an important local food source in some countries (e.g. Viet Nam). Weaver ants, Oecophylla smaragdina, construct nests by folding mangrove leaves together using sticky secretions. Oecophylla feeds on the sugary secretions of the coccid bugs, which suck plant sap and other insects and will defend their nests and thus the mangrove tree they inhabit by attacking with a sharp bite. Synchronously flashing “fireflies” (actually Pteroptyx beetles of the family Lampyridae) are associated with Sonneratia caseolaris mangrove trees in some areas in Asia and the western Pacific. In Selangor, Peninsular Malaysia and a few other locations in Indochina, including Cambodia and Thailand, the fireflies are a valuable ecotourism attraction. Conversely, mosquitos and sandflies, which can occur in abundance in mangroves, are a nuisance that may also affect human health. Conversion or degradation of mangroves may increase the risk of mosquito-borne malaria, one reason being that these practices create more standing water as potential breeding sites for mosquitos (Hong and San, 1993). Various spiders inhabit mangroves, including web-building species (Family Gasteracanthidae) and wolf and jumping spiders, which descend from the trees at low tide to forage over the mud for insects. The spider Pardosa (Family Lycosidae) is adapted to a semi-aquatic life, made possible by a body covering of hydrofuge (water-repellent) hairs. It shelters and breeds in air-filled burrows in the intertidal mud and feeds on juvenile fiddler crabs (Stafford-Deitsch, 1996). Amphibians, Reptiles, Birds and Mammals Amphibians are rarely found in brackish or salt water, but the crab-eating frog Rana cancrivora is an exception and both the adults and larvae are quite common in the mangroves of Indochina. Mangrove-associated reptiles include numerous species of snakes and lizards, crocodiles and turtles. Some snake species only enter mangroves intermittently from adjacent terrestrial habitats to forage; for example, pythons (Python molorus) and king cobras (Ophiophagus hannah). Other snakes are more specialist mangrove-dwellers, such as the cat snake Boiga dendrophila and the mangrove pit viper (Trimeresurus purpureomaculatus). Sea snakes (Hydrophidae) also utilize mangrove habitats. The primitive Laticauda colubrina breeds on land, but other sea snakes are fully aquatic. In Southeast Asia the mangrove monitor lizard (Varanus indicus) may reach up to 1 m in length. It is often caught and used as bait to trap mud crabs (Ashton, pers. obs.). The estuarine crocodile (Crocodylus. porosus) is found from India through Southeast Asia and Australia and can reach up to 8 m in length, but is now relatively rare in Indochina. Many bird species have been recorded in mangrove forests, but most are not mangrove residents. They may migrate seasonally, commute daily, or at different states of the tide, or may use mangroves selectively as feeding, nesting or refuge sites (Macintosh and Ashton, 2002). For example, 200 bird species were recorded from mangroves in Australia, but only 14 passerine species were confined to mangroves, with 11 other species being found predominantly in mangroves, but frequently also occurring elsewhere (Noske, 1996). Waders probe for buried invertebrates on the mudflats, or amongst the mangrove trees. Herons, egrets and kingfishers catch fish in the shallow waters or prey on mudskippers and crabs on 39
Transboundary Diagnostic Analysis of Indochina Mangrove Ecosystems
To see the actual publication please follow the link above