Eight Little Piggies Read Online Free PDF Page B

is a good idea in principle—better a natural predator than a chemical poison. But predators, particularly when introduced from alien places and ecosystems, may engender greater problems than the creature that inspired their introduction. How can you know that the new predator will eat only your problem animal? Suppose it prefers other creatures that are benign or useful? Suppose, in particular, that it attacks endemic species (often so vulnerable for lack of evolved defenses in the absence of native predators)?
    Biological control should therefore be attempted only with the utmost caution. But, speaking of folk songs and citing a more recent composition than the old lady and the fly, “When will they ever learn?” In my personal pantheon of animals to hate and fear, no creature ranks higher than Euglandina , the “killer” or “cannibal” snail of Florida. Euglandina eats other snails—with utmost efficiency and voraciousness. It senses slime trails, locks onto them, and follows the path to a quarry then quickly devoured.
    Euglandina has therefore developed a worldwide reputation as a potential agent of biological control for other snails. Yet, despite a few equivocal successes, most attempts have failed, often with disastrous and unintended side-effects, as Euglandina leaves the intended enemy alone and turns its attention to a harmless victim.
    Forgive my prejudices, but I know what Euglandina can do in the most personal way (biologists can get quite emotional about the subjects of their own research). I spent the first big chunk of my career, including my Ph.D. dissertation, working on a remarkable Bermudian land snail named Poecilozonites . (This Darwin’s finch among mollusks is the only large land snail that reached Bermuda. It radiated into a score of species in a great range of sizes and shapes. The fossil record is particularly rich, but at least three species survived and were thriving in Bermuda when I began my research in 1963.) Euglandina had been introduced in 1958 to control Otala , an imported edible snail that escaped from a garden and spread throughout the island as an agricultural pest (same story as Achatina and Partula on Moorea). I don’t think that Euglandina has even dented Otala , but it devastated the native Poecilozonites . I used to find them by thousands throughout the island. When I returned in 1973 to locate some populations for a student who wanted to investigate their genetics, I could not find a single animal alive. (Last year, I relocated one species, the smallest and most cryptic, but the large Poecilozonites bermudensis , major subject of my research, is probably extinct.)
    Thus, I feel the pain of Jim Murray, Bryan Clarke, and Mike Johnson. They had published papers on Moorean Partula since the mid-1960s. They never expected that their last pair of articles would be a wake.
    Euglandina was introduced to Moorea on March 16, 1977, with the official advice and approval of the Service de l’Economie Rurale and the Division de Recherche Agronomique —despite easily available knowledge of its failures and devastations elsewhere. * Euglandina ignored Achatina and began a blitzkrieg, against Partula —more thorough, rapid, and efficient than anything that Hitler’s armies ever accomplished. When my colleagues wrote their first article about this disaster in 1984 (see bibliography), Euglandina had already wiped out one of the seven Partula species on Moorea, and was spreading across the island at a rate of 1.2 km per year. Moorea is about 12 km across at the widest, and you quickly run out of island at that rate. My colleagues made the grim prediction that Partula would be completely gone by 1986.
    One hates to be right about certain things. In 1988, Jim, Bryan, and Mike published another note with a brief and final title: “The extinction of Partula on Moorea.” Partula is gone. My colleagues managed to collect six of the seven species before the end, and they have established