Question

introduced Prey Species! Cane toads (Bufo marinus) were introduced to Australia in 1935 in a failed attempt to control an insect pest. Since then, the toads have spread across northeastern Australia, with a population of over 200 million today. Cane toads have glands that produce a toxin that is poisonous to snakes and other potential predators. In this exercise, you will graph and inter- pret data from a two-part experiment conducted to determine whether native Australian predators have developed resistance to the cane toad toxin. How the Experiment Was Done In part 1, researchers collected 12 red-bellied black snakes (Pseudechis porphyriacus) from areas where cane toads had existed for 40-60 years and another 12 from areas free of cane toads. They recorded the percentage of snakes from each area that ate either a freshly killed native frog (Limnodynastes peronil, a species the snakes commonly eat) or a freshly killed cane toad from which the toxin gland had been removed (making the toad nonpoisonous). In part 2, researchers collected snakes from areas where cane toads had been present for 5-60 years. To assess how cane toad toxin affected the physiological activity of these snakes, they injected small amounts of the toxin into the snakes' stomachs and measured the snakes' swimming speed in a small pool.

Answer 1

Affect of Toad Poison on Swimming speed of Snakes ercent Reduction in SnakeSwimming Speed 10 20 30 40 50 60 Number of Years Cane Toads Had Been Present in the Area 70

Dependent Variables: Swimming speed of Snake

Independent variable: Number of snakes collected from different area

No the Cane toad poison doesn’t show selective effect on snakes swimming speed, because the swimming speed has reduced consistently as the number of years snakes are exposed to toad poison has increased.