Joined: 24 Oct 2006
, given: 0
Despite its 1989 designation as a threatened species under [#permalink]
24 Apr 2007, 23:33
Despite its 1989 designation as a threatened species under the federal Endangered Species Act, the desert tortoise, Gopherus agassizii, has declined in numbers by ninety percent since the 1980s. Although federal protection made it illegal to harm desert tortoises or remove them from the wild of the southwestern North American deserts, this measure has been insufficient to reverse the speciesтАЩ decline, and further intervention is required.
Recovery has been slow, partly due to the desert tortoiseтАЩs low reproductive potential. Females breed only after reaching full size at fifteen to twenty years of age, and even then may only lay eggs when adequate forage is available. Although the number of eggs in each clutch varies, and each female might lay a few clutches in one season, the average mature female produces only a few eggs annually. From these precious eggs, hatchlings emerge wearing soft shells that will harden slowly into protective armor over the next five years. The vulnerable young are entirely neglected by adult tortoises, and only five percent ultimately reach adulthood.
Predators are blamed for most tortoise deaths; ravens, specifically, are estimated to cause more than half of the juvenile tortoise deaths in the Mojave Desert. Tortoise eggs and juveniles, with their delicate shells, can fall prey to many birds, mammals, and other reptiles. For protection from predators, as well as from desert temperature extremes, tortoises of all ages burrow into the earth. However, if rabbits and rodents are scarce, larger mammalian predators may dig tortoises out of their burrows, devouring even mature tortoises despite their hardened shells.
Even with current protections from human interference, the desert tortoise faces a tough recovery, so additional measures must be taken. First, the limited habitat of desert tortoises, with soil suitable for their burrows, must be protected from development. Next, urban expansion often has the unintended effect of increasing raven populations, so aggressive measures to control the birds are necessary to increase desert tortoise hatchling survival rates. Finally, released captive tortoises typically perish, and can pass upper respiratory tract disease into the wild population with devastating consequences, so continuing education of pet tortoise owners is essential.
Question: It can be inferred from the passage that the desert tortoise mortality rate would be most likely to decrease if which of the following were true?
A. Desert tortoise burrows were cooler.
B. Male and female tortoises mated more frequently.
C. Adult tortoises provided better care for their young.
D. Forage plants were abundant in the habitat of the desert tortoise.
E. Rabbits were abundant in the habitat of the desert tortoise.
C or E?