Amazing stuff!
"Carrion crows are known as “feathered apes” for a number of good reasons. And scientists just discovered another: They can count out loud, researchers reported yesterday in Science. The work suggests that the birds understand numbers and counting in the same way humans do, making them the only other species known to have this ability.
One hallmark of human language is our ability to associate and utter a sound, such as a word, with something we see or hear. We might say “three” if we see three apples, for example. Could crows do this as well? To find out, a team worked with three carrion crows trained to produce one to four calls (a kraak) when they saw an Arabic numeral on a screen or heard a short noise. In thousands of trials, the birds usually made the correct number of kraaks required by the visual cue, but often took longer to respond to cues requiring three or four calls. ..."
From the editor's summary and abstract:
"Editor’s summary
Numerical ability has been increasingly identified in nonhuman animals. Animals as diverse as birds and bees have been shown to be able to “count, ” and they can discriminate among different numbers of objects or between greater or fewer objects. Liao et al. tested whether crows, which are known for both their numerical skills and high level of cognition, could use vocalizations to count out loud, a skill that is challenging even for young humans. The crows flexibly produced between one and four vocalizations for corresponding cues associated with numerical values. Furthermore, they used different calls for different numbers. ...
Abstract
Producing a specific number of vocalizations with purpose requires a sophisticated combination of numerical abilities and vocal control. Whether this capacity exists in animals other than humans is yet unknown. We show that crows can flexibly produce variable numbers of one to four vocalizations in response to arbitrary cues associated with numerical values. The acoustic features of the first vocalization of a sequence were predictive of the total number of vocalizations, indicating a planning process. Moreover, the acoustic features of vocal units predicted their order in the sequence and could be used to read out counting errors during vocal production."
Crows “count” the number of self-generated vocalizations (no public access)
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