Philippine Frogs

Frogs are remarkably diverse in the Philippines—80 to 90 species are now known, about 20 of which have been discovered in the just past five years. Both facts—the large numbers and the frequent discovery of new species—may initially come as a surprise, but make sense in retrospect. Frogs are quite sensitive to salt water, and most species die quickly in seawater. Although typhoons may occasionally create rafts of vegetation on which frogs can be propelled across the ocean by strong winds, most of the time they are unable to move between islands. And so we find that most of the Ice-Age islands have a unique set of frog species, just as they do with other groups of animals and plants. 
     The rapid discovery of new species is explained by two recent developments. First, the number of field biologists and field projects in the Philippines has increased rapidly inthe past ten years, so more information is available than every before, especially from the poorly know montane and mossy forests. Second, as logging roads reach every farther into previously inaccessible areas, biologists have been scrambling to get to the forest before it disappears. Ironically, biodiversity is often discovered within earshot of chain saws. 
      All frogs have much in the same body plan, but there is considerable diversity in the details of their appearance, and an even greater variation in their reproductive biology. Although many frogs lay large numbers of eggs in small ponds, as is widely known, most species do not. Some species lay their eggs only in fast-moving mountain streams, virtually gluing them to rocks; others lay them in tree hollows and at the base of leafy stems of pandans and ferns where rainwater accumulates; still others lay their eggs in wet moss, where there is no standing water at all. Although most species develop into tadpoles before they metamorphose into adults, all of the species in the genus Platymantis undergo direct development—a tiny froglet climbs out of the egg, with no tadpole stage at all. Frogs that lay eggs in tree hollows and leaf axils often skip the tadpole stage and lay only five to ten large eggs; frogs that lay eggs in large ponds can produce up to 2,000 at a time.
     Because many species of frogs live in streams and ponds for much of their lives, they are among the most sensitiveindicators of water quality and watershed condition. Of the 80 to 90 species now known, 60 to 70 percent are threatened by habitat destruction. An unexpected source of pressure on the native species has come from the recent escape of several non-native species (from North America and mainland Asia) from commercial farms on Luzon that produce frog legs for export to other Asian countries. These non-native species are aggressively colonizing central Luzon, competing with unique native species for food.

Original URL: http://archive.fieldmuseum.org/vanishing_treasures/V_Frogs.htm