Crows are highly intelligent, social birds found on every continent other than South America and Antarctica.<\/p>\n
In a new study, researchers from the Institute of Neurobiology at Germany\u2019s University of T\u00fcbingen have found that crows are able to learn to produce a specific number of calls, showing advance planning.<\/p>\n
How many calls they will make can be predicted from the first vocalization in a sequence, a press release from University of T\u00fcbingen said.<\/p>\n
\u201cProducing a specific number of vocalizations with purpose requires a sophisticated combination of numerical abilities and vocal control,\u201d the researchers wrote in the study. \u201cWe 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.\u201d<\/p>\n
Carrion crows are known for their impressive learning ability, which includes being able to count.<\/p>\n
\u201cIn addition, they have very good vocal control. They can control precisely whether they want to emit a call or not,\u201d said Andreas Nieder, a professor of animal physiology at University of T\u00fcbingen, in the press release.<\/p>\n
The research team conducted behavioral experiments to see if three carrion crows could combine their ability to count with vocal control.<\/p>\n
The corvids were given the task of producing from one to four calls that appropriately corresponded with specific sounds or an array of Arabic numerals, followed by pecking an enter key.<\/p>\n
\u201cAll three birds succeeded in this. They were able to count their calls in sequence,\u201d Nieder said in the press release.<\/p>\n
The crows displayed a relatively long response time between when they were presented with the stimulus and their first call, which became longer as more calls were added. The delay\u2019s length was not affected by the type of stimulus.<\/p>\n
\u201cThis indicates that, from the information presented to them, the crows form an abstract numerical concept which they use to plan their vocalizations before emitting the calls,\u201d Nieder explained. \u201cUsing the acoustic properties of the first call in a numerical sequence we could predict how many calls the crow would make.\u201d<\/p>\n
Some errors were detected in the birds\u2019 calls.<\/p>\n
\u201cCounting errors, such as one call too many or one too few, arose through the bird losing track of the calls already made or still to be produced,\u201d Nieder said. \u201cWe are also able to read out these types of errors from the acoustic properties of the individual calls.\u201d<\/p>\n
Being able to produce a deliberately chosen number of calls requires a sophisticated combination of vocal control and numerical competence.<\/p>\n
\u201cOur results show that humans are not the only ones who can do this. In principle it also opens up sophisticated communication to the crows,\u201d Nieder said.<\/p>\n
The study, \u201cCrows \u2018count\u2019 the number of self-generated vocalizations,\u201d was published in the journal Science.<\/p>\n