The California ground squirrel must constantly balance the conflicting demands of self-preservation and predator assessment. Because predator assessment requires a fairly high degree of proximity and sensory contact, the ground squirrel can only safely assess predators from whom there is little to no immediate threat. For example, when avian predators, including the red-tailed hawk and golden eagle, launch sudden, unexpected aerial attacks, self-preservation must take precedence over the acquisition of knowledge. Rattlesnakes, on the other hand, pose relatively little immediate danger, and give the squirrel the greatest opportunity for predator assessment.

Predator assessment might normally be hampered by the inherent danger of the rattlesnake's lethal bite. But while squirrels constitute almost 70 percent of the rattlesnake's diet, adult ground squirrels are all but immune to rattlesnakes. Rattlesnakes hunt slowly and stalk their prey, in marked contrast to sudden avian attacks. And even though a rattlesnake's strike is fast, the ground squirrel can move much faster. More important, any danger posed by a snakebite is mitigated by proteins in the squirrel's blood that confer resistance to rattlesnake venom. Adult ground squirrels will generally survive a rattlesnake bite that could prove lethal to a grown human. Indeed, it is the squirrel pups that are most susceptible to rattlesnake bites, because their smaller bodies cannot neutralize a full bite's worth of venom.

This innate resistance allows the ground squirrel to change the dynamic of the traditional predator-prey relationship and approach the rattlesnake in an effort to acquire useful information regarding size and body temperature. Larger snakes, which deliver more venom per strike, are naturally more dangerous, as are warmer snakes, which can strike faster, from a greater distance, and with greater accuracy. Visual cues can be helpful, but the squirrel is often hampered by the surrounding vegetation and darkness of burrows. Auditory cues are generally more reliable. For this reason, the ground squirrel will engage in tail-flagging, sand-kicking, and substrate-throwing in an attempt to put the snake on the defensive, and coax the snake into rattling its tail. The sound of a particular snake's rattle "leaks" information about the snake's size and body temperature. Not only does this information allow the squirrel to accurately assess the surrounding danger to itself and its pups, but it also allows the squirrel to communicate this danger (or lack thereof) to other squirrels by additional tail-flagging.

1. Which of the following can most reasonably be concluded about adult ground squirrels on the basis of the passage?

A. They are found exclusively in California.
B. They have always been immune to rattlesnake venom.
C. They are sometimes vulnerable to a rattlesnake's venom.
D. They generally stay away from rattlesnakes in order to protect their young.
E. They have only avian and reptilian predators.


2. According to the passage, the adult ground squirrel generally does NOT engage in which of the following?

A. The self-application of snake scent
B. Acquisition of knowledge regarding a rattlesnake's size
C. Biting rattlesnakes
D. Large-scale assessment of avian predators
E. Communication with other adult ground squirrels


3. The author mentions the hunting method of rattlesnakes in order to

A. show how the rattlesnake can sneak up on a ground squirrel engaged in predator assessment.
B. give an example of an attack against which the adult ground squirrel must defend itself in order to survive.
C. explain why 70 percent of squirrels are eaten by rattlesnakes.
D. show how the rattlesnake is different from the red-tailed hawk and golden eagle.
E. provide a secondary explanation for the adult California ground squirrel's ability to safely approach the rattlesnake.


4. The passage suggests which of the following about predator-prey relationships?

A. They only allow for predator assessment when there is no danger from the predator.
B. They often do not allow for a high degree of predator assessment.
C. They are fairly traditional in their resistance to evolution.
D. They tend to minimize the predator-prey proximity.
E. They are the same regardless of the species in question.