- 2017年12月12日16:01 来源：小站整理
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Naturalists and casual observers alike have been struck by the special relationship between
squirrels and acorns (the seeds of oak trees). Ecologists, though, cannot observe these energetic
mammals scurrying up and down oak trees and eating and burying acorns without wondering
about their complex relationship with trees. Are squirrels dispersers and planters of oak forests or
pesky seed predators? The answer is not simple. Squirrels may devour many acorns, but by storing
and failing to recover up to 74 percent of them as they do when seeds are abundant, these arboreal
rodents can also aid regeneration and dispersal of the oaks.
Their destructive powers are well documented. According to one report, squirrels destroyed
tens of thousands of fallen acorns from an oak stand on the University of Indiana campus. A
professor there estimated that each of the large white oaks had produced between two and eight
thousand acorns, but within weeks of seed maturity, hardly an intact acorn could be found among
the fallen leaves.
Deer, turkey, wild pigs, and bears also feed heavily on acorns, but do not store them, and are
therefore of no benefit to the trees. Flying squirrels, chipmunks, and mice are also unlikely to
promote tree dispersal, as they often store seeds in tree cavities and
underground burrows. Only
squirrels — whose behavior of caching (hiding) acorns below the leaf litter — often promote
successful germination of acorns, and perhaps blue jays, important long-distance dispersers, seem
to help oaks spread and reproduce.
Among squirrels, though, there is a particularly puzzling behavior pattern. Squirrels
the caps of acorns, bite through the shells to get at the nutritious inner kernels,
and then discard
them half-eaten. The ground under towering oaks is often littered with thousands of half-eaten
acorns, each one only bitten from the top. Why would any animal waste so much time and energy
and risk exposure to such predators as red-tail hawks only to leave a large part of each acorn
uneaten? While research is not conclusive at this point, one thing that is certain is that squirrels do
hide some of the uneaten portions, and these acorn halves, many of which contain the seeds, may
1. What does the passage mainly discuss?
(A) The ecology of oak trees
(B) Factors that determine the feeding habits of Squirrels
(C) Various species of animals that promote the dispersal of tree seeds
(D) The relationship between squirrels and oak trees
2. The word "they" in line 7 refers to
(A) oak forests
3.According to the passage , what do squirrels do when large quantities of acorns are available?
(A) They do not store acorns.
(B) They eat more than 74 percent of available acorns.
(C) They do not retrieve all the acorns that they have stored.
(D) They hide acorns in tree cavities.
4. The word "estimated" in line 11 is closest in meaning to
5. Why does the author mention "the University of Indiana campus" in line 10 -11?
(A) to provide evidence that intact acorns are hard to find under oak trees
(B) to indicate a place where squirrels can aid seed dispersal of oaks
(C) to argue in favor of additional studies concerning the destructive force of squirrels
(D) to support the claim that squirrels can do great damage to oak stands
6. It can be inferred from paragraph 3 that chipmunks do not aid in the dispersal of oak trees
(A) they store their acorns where they cannot germinate
(B) they consume most of their stored acorns
(C) their stored acorns are located and consumed by other species
(D) they cannot travel the long distance required for dispersal
7.According to the passage , which of the following do squirrels and blue jays have in common?
(A) They travel long distances to obtain acorns.
(B) They promote the reproduction of oak trees.
(C) They bury acorns under fallen leaves.
(D) They store large quantities of acorns.
8. The phrase "pry off" in line 21 is closest in meaning to
9. The word "littered" in line 22 is closest in meaning to
10. According to the passage , scientists cannot explain which of the following aspects of squirrel
(A) Where squirrels store their acorn caches
(B) Why squirrels prefer acorns over other seeds
(C) Why squirrels eat only a portion of each acorn they retrieve
(D) Why squirrels prefer acorns from a particular species of oak trees