Cetaceans（鯨目動(dòng)物）communicate through sound to find food and to interact socially.Their sounds vary between species and within communities.The long-finned pilot whales can mimic（模仿）artificial noise，but nobody had previously recorded them.A new study，however，found overlap in the cetacean sound book.
Pilot whales and orcas（虎鯨），the two largest species of cetaceans，are often seen in the same environments and are similar sizes，and both live in social groups with strong union，says Charlotte Cure，a researcher at CEREMA Lab in France，who was not involved in the study.Orcas compete for food with long-finned pilot whales and are potentially their predators.
Evidence from orca stomachs shows they do occasionally eat pilot whales.But pilot whales can mob（成群圍住）and chase them away，the only cetaceans seen defending themselves from the strong enemies in this way.
Mimicry could serve as additional defense； "One assumption is that if they use similar sounds，they may not be recognized as prey，" Erbe says.Pilot whales eating orcas' food remains might go unnoticed if they use orca-like calls. "This is all underwater，" she adds，"so these animals rely on sound for detecting their prey and predators."Long-finned pilot whales have shown an ability to distinguish between orca calls with different meanings；Cure suggests that instead of tricking orcas，the callers could instead be presenting a new orca sound to other group members."
Additional work would confirm whether mimicry is actually occurring.Researchers could pair their listening data with direct observations of the animals' interactions in the wild or perhaps even play orca sounds and watch the whales' reactions.
But if a future experiment used predatory sounds，it would need to be done.very carefully."A reaction to a predator can be very strong，" Cure says."In some protected areas，you are not allowed to do more than two predatory playbacks per year."
（1）Which of the following is NOT shared by the pilot whales and orcas？
C
C
A．They communicate through sound.
B．They often live in the same environments.
C．They can defend themselves through mimicry.
D．They always live together with other group members.
（2）What do we know from the fourth paragraph？
C
C
A．The pilot whales mimic the sounds to detect their prey.
B．The pilot whales only mimic one kind of the sounds of the orcas.
C．The pilot whales can pretend to be orcas to share the food remains.
D．The pilot whales can distinguish different meanings of orca calls to trick them.
（3）How do the researchers confirm whether mimicry is actually occurring？
D
D
A．By observing the whales from the distance.
B．By mimicking the sounds in the experiment.
C．By analyzing the data from the cetacean sound book.
D．By listening or playing the sounds and watching the whales' reactions.
（4）Which can be a suitable title for the text？
A
A
A．Pilot Whales：Copy Orca Calls
B．How Orcas Mimic Pilot Whale Calls
C．How Pilot Whales Defend Themselves
D．Orcas and Pilot Whales：Predators and Prey
