Biology Reference
In-Depth Information
Chapter 7
Invasion and Resistance
A
BOUT A CENTURY AGO, SUGARCANE PLANTERS
in Hawaii faced major crop losses from a
teeming rat population. Their solution seemed practical at the time: import the South Asian
common mongoose—by way of Jamaica—to eradicate the vermin. The planters unfortunately
selected the wrong control agent, with disastrous consequences. The diurnal mongooses were
exposed as abysmal predators of the nocturnal rats (which at an earlier time had also been in-
troduced into Hawaii) but avid consumers of the eggs and nestlings of native birds, many of
them rare and found nowhere else in the world. It was too late to correct the mistake; the mon-
gooses had been set free on all the main islands except Kauai. En route to that island, a wise
official is said to have dumped the mongooses overboard. Stuart Pimm, an expert on Hawaiian
extinctions, corrects the account in this way: “The mongooses intended for Kauai bit the fin-
gers of the boatman and he drowned them. That's why they never made it there.”
Hawaii's imported rats and mongooses are part of a group that ecologists term invasive
exotic species. These interlopers have the ability to outcompete native flora or fauna when
they are introduced into an ecosystem where they do not occur naturally. Every continent has
them; in North America, some of the worst invasives are plants such as purple loosestrife
from Europe and kudzu from China. In Nepal, the explosion of mile-a-minute vine from South
America threatens to drape over much of the greater one-horned rhinoceros's prime feeding
areas. Rabbits and red foxes are invasive exotic mammal species in Australia. Some species
come to or are brought to a land and have no effect on the local flora and fauna, but others
crowd out or kill off native species, not infrequently rare ones, and those obviously are the
ones of great concern. Introductions of mammals onto islands—giant ones such as Australia or
small archipelagoes such as Hawaii—have nearly always been disastrous because mammals,
as we saw in Peru and Nepal (chapters 3 and 5), are the prime ecosystem engineers every-
where.
