• The rare and endangered soil-dwelling purple frog (Nasikabatrachus sahyadrensis) begins its life as a tadpole in certain fast-flowing streams of the Western Ghats.
  • Scientists have now found that the speed with which water flows down these streams is one of the main factors that determine the presence and aggregation of these Tadpoles.
  • The tadpoles are rheophilic, which means they thrive in running water.
  • Apart from several other body adaptations, their specialised mouthparts, which are like suckers, help them to anchor onto rocky areas in flowing water for nearly 100 days.
  • Though found throughout the streams, the tadpoles tended to gather in large numbers only in areas with relatively higher water flow velocity.
  • They also preferred steep, rocky slopes (65°-90° incline) and a water depth of 2-3 cm.
  • The tadpoles were always active, moving even when they were attached to the rocky portions of the streams to feed on algae growing on rocks.
  • The moment they sensed danger, they ‘escaped by immediately relaxing their hold on the rock, a behaviour that let them drift some distance downstream before re-attaching themselves to the substrate. Tadpoles in earlier stages of development stayed mostly in relatively slow-flowing portions of the stream’, while older tadpoles were found in faster currents.
  • The construction of dams and check dams, and levelling and narrowing of streams to expand plantations can alter stream characteristics, in turn affecting the survival of the purple frog tadpole.
  • The damming effect can also slow down the streams feeding water to the river.