Squirrels can't speak bird language, so how come they are so interested in listening to the birds chatting next door?

Nature is not a very friendly place for small animals because they have to face various unknown dangers, the most deadly of which are predators that target them.

Therefore, many small animals will make full use of various information sources in the environment (such as smell, sound, etc.) as early warning signals.

In the same ecosystem, when multiple species are prey to the same predator, one of the species will collect environmental information provided by other species to enhance its own vigilance.

For example, squirrels often have overlapping habitats with many bird species, even though squirrels cannot communicate with birds and there is no very close ecological connection between them.

But they all have a common enemy - the red-tailed hawk (Buteo jamaicensis), a ferocious bird that preys on birds, reptiles and various small mammals, including squirrels.

Squirrels generally forage for food in trees or on the forest floor. As they forage and eat, they often look up from time to time to scan their surroundings, which is their alert nature.

If squirrels sense that danger is approaching, they will immediately stop what they are doing and stay still or run away.

However, this high-frequency alert behavior not only consumes the squirrels' physical strength, but also prevents them from doing other things peacefully, such as having a good meal or finding a girlfriend.

Therefore, in order to better avoid predators, squirrels will also rely on their bird neighbors. Previous studies have shown that squirrels will listen to the alarm calls of birds to determine whether there is any danger in the surrounding environment.

A recent study published in the journal PLoS One found that squirrels not only listen to the alarm calls of birds, they even eavesdrop on the birds' "daily chats" and use the information contained in the birds' calls as safety cues.

Although it is not clear how exactly they understand bird language, the study's observations suggest that squirrels do so.

Keith Tarvin, a professor at Oberlin College in Ohio, and his colleagues went to Oberlin Park with several recordings they had made. Since the squirrels in this area are familiar with the presence of humans, they will not disturb them too much.

After making sure there were no obvious threats around, the researchers played a short clip of a red-tailed hawk's call. The results were obvious: the squirrels immediately went into alert mode, some remained motionless, while the more timid ones ran away. After the call was played, the squirrels remained highly alert and raised their heads more frequently to observe the surrounding environment.

After the squirrels calmed down, the researchers played two other recordings to them, one of which was a 3-minute "daily chat" of birds, and the other was a natural environment sound without bird calls. The environmental sound served as the control group, while the one with bird calls served as the experimental group.

The bird calls in the experimental group included American robins, chickadees and other birds that are also afraid of red-tailed hawks. If they find red-tailed hawks or other predators approaching, they will make warning calls; but when there is no danger, their calls are similar to the "daily chat" style.

The researchers observed the reactions of 54 squirrels after hearing the recordings, 28 of which were heard by recordings of birds chatting, and the other 26 squirrels were heard by natural environmental sounds.

Based on their observations, they found that no matter which recording they heard, the squirrels showed similar vigilance behaviors (vigilance behaviors were judged when the squirrels suddenly straightened their bodies, flattened them, stretched their heads, or started running, while actions such as licking their fur or scratching themselves were considered non-vigilance states).

However, compared with the squirrels that heard the sounds of the natural environment, the squirrels that heard the chattering of birds raised their heads less frequently, and as time went on, this alert behavior of raising their heads decreased significantly. Even in a relatively long period of bird calls, the squirrels did not raise their heads, which shows that they are using the chattering of birds as a safety signal.

For squirrels, "eavesdropping" on birds' chats to judge dangerous situations around them may be the result of adaptation to the environment . With these birds' tip-offs, squirrels can focus more on foraging or courtship instead of worrying about their sudden death all the time.

In addition, the participants of this study also stated that their observation experiment also had many limitations. For example, the recordings recorded the sounds of birds flapping their wings and hitting leaves in flight, so they did not know whether the squirrels only responded to the sounds of birds chatting or to other noises in the recordings.

Finally, the research team also mentioned the impact of human noise on the environment at the end of the paper. As human noise increases, it may become increasingly difficult for squirrels to hear the chattering of birds , so the squirrels will have to spend more time guarding their surroundings.