Poisonous South American cane toads were introduced into Australia in 1935 in an attempt to control a beetle that was eating sugar cane crops. However, the toads did not control the beetles and, instead, they caused an environmental disaster. Today, the toad population is estimated to be greater than 200 million. As the invasive toads spread westward across northern Australia, many native species were negatively affected. For example, in the years since the toads’ introduction, scientists have observed that the entire population of the northern quoll, a small squirrel-sized carnivore, has declined more than 75%. The decline is due to the fact that the quolls mistake the poisonous toads for something that they can safely eat. When they eat the toads, they die from the poison that the toads produce. The northern quolls may soon become extinct if something cannot be done to save them. Recently, some quolls were found to have a genetic trait that makes them uninterested in preying on the toads. Scientists have now discovered that these quolls with “toad-smart genes” can pass them on to their offspring. The scientists plan to release quolls that avoid eating the toads into native populations, hoping that they will breed and produce offspring that also avoid eating the toads, thus saving the species from extinction. Select the two best answers on how the northern quoll extinction would affect the other organisms in the ecosystems where they once lived.
