单项选择题

Allelomimetic behavior may be defined as behavior in which two or more individual animals do the same thing, with some degree of mutual simulation and coordination. It can only involve in species with sense organs that are well enough developed so that continuous sensory contact can be maintained. It is found primarily in vertebrate, in those species that are diurnal, and usually in those that spend much of their lives in the air, in open water or on open plains. In birds, allelomimetic behavior is the rule rather than the exception, though it may occasionally be limited to particular seasons of the year as it is in the redwing blackbird. Its principal function is that of providing safety from predators, partly because the flock can rely on many pairs of eyes to watch for enemies, and partly because if one bird reacts to danger, the whole flock is warned. Among mammals, allelomimetic behavior is very rare in rodents, which almost never move in flocks or herds. Even when they are artificially crowded together, they do not conform in their movements. On the other hand, such behavior is a major system among large hoofed mammals such as sheep. In the pack-hunting carnivores, allelomimetic behavior has another function that of cooperative hunting for large prey animals such as moose. Wolves also defend their dens as a group against larger predators, such as bears. Finally, allelomimetic behavior is highly developed among most primate groups, where it has the principal function of providing warning against predators, though combined defensive behavior is also seen in troops of baboons. According to the passage, what happens to the behavior of rodents when they are artificially crowded together