Foraging behaviour in tadpoles of the bronze frog Rana temporalis: Experimental evidence for the ideal free distribution
Foraging behaviour in tadpoles of the bronze frog Rana temporalis:
Experimental evidence for the ideal free distribution
DHEERAJ K VEERANAGOUDAR, BHAGYASHRI A SHANBHAG and SRINIVAS K SAIDAPUR*
Department of Zoology, Karnatak University, Dharwad 580 003, India
*Corresponding author (Fax, 91-836-2448047; Email, saidapur@hotmail.com)
The ability of bronze frog Rana temporalis tadpoles (pure or mixed parental lines) to assess the profitability of food habitats and distribute themselves accordingly was tested experimentally using a rectangular choice tank with a non-continuous input design. Food (boiled spinach) was placed at two opposite ends of the choice tank in a desired ratio (1 : 1, 1 : 2 or 1 : 4) to create habitat A and B. The tadpoles in Gosner stage 28–33, pre-starved for
24 h, were introduced in an open ended mesh cylinder placed in the center of the choice tank, held for 4 min (for acclimation) and then released to allow free movement and habitat selection. The number of tadpoles foraging at each habitat was recorded at 10, 15, 20, 25 and 30 min time intervals. The actual suitability, Si (the food available in a habitat after colonization of tadpoles) of each habitat was obtained from the equation Si = Bi – fi (di) where Bi is basic suitability (amount of food provided at each habitat before release of tadpoles), fi is the rate of depletion of food (lowering effect) with introduction of each tadpole, and di is the density of tadpoles in habitat
i. The expected number of tadpoles at each habitat was derived from the actual suitability. With no food in the choice tank, movement of the tadpoles in the test arena was random indicating no bias towards any end of the choice tank or the procedure. In tests with a 1 : 1 food ratio, the observed ratio of tadpoles (11⋅71 : 12⋅28) was comparable with the expected 12 : 12 ratio. The observed number of tadpoles in the habitats with a 1 : 2 food ratio was 8⋅71 : 15⋅29 and 7⋅87 : 16⋅13 for pure and mixed
Experimental evidence for the ideal free distribution
DHEERAJ K VEERANAGOUDAR, BHAGYASHRI A SHANBHAG and SRINIVAS K SAIDAPUR*
Department of Zoology, Karnatak University, Dharwad 580 003, India
*Corresponding author (Fax, 91-836-2448047; Email, saidapur@hotmail.com)
The ability of bronze frog Rana temporalis tadpoles (pure or mixed parental lines) to assess the profitability of food habitats and distribute themselves accordingly was tested experimentally using a rectangular choice tank with a non-continuous input design. Food (boiled spinach) was placed at two opposite ends of the choice tank in a desired ratio (1 : 1, 1 : 2 or 1 : 4) to create habitat A and B. The tadpoles in Gosner stage 28–33, pre-starved for
24 h, were introduced in an open ended mesh cylinder placed in the center of the choice tank, held for 4 min (for acclimation) and then released to allow free movement and habitat selection. The number of tadpoles foraging at each habitat was recorded at 10, 15, 20, 25 and 30 min time intervals. The actual suitability, Si (the food available in a habitat after colonization of tadpoles) of each habitat was obtained from the equation Si = Bi – fi (di) where Bi is basic suitability (amount of food provided at each habitat before release of tadpoles), fi is the rate of depletion of food (lowering effect) with introduction of each tadpole, and di is the density of tadpoles in habitat
i. The expected number of tadpoles at each habitat was derived from the actual suitability. With no food in the choice tank, movement of the tadpoles in the test arena was random indicating no bias towards any end of the choice tank or the procedure. In tests with a 1 : 1 food ratio, the observed ratio of tadpoles (11⋅71 : 12⋅28) was comparable with the expected 12 : 12 ratio. The observed number of tadpoles in the habitats with a 1 : 2 food ratio was 8⋅71 : 15⋅29 and 7⋅87 : 16⋅13 for pure and mixed