Indian Peafowls can recognize numbers and have ability to count from 1 to 5

A research group led by Remi Sakamoto (an undergraduate student at the time of the research) and Associate Professor Tadatoshi Ogura from the School of Veterinary Medicine at Kitasato University, in joint research with Hirosaki City Yayoi Zoo Park in Aomori Prefecture, clarified that Indian peafowls can discriminate between numbers and make comparisons based on magnitude relationships. Their findings were published in Animal Behaviour.

Indian peafowls possess brightly colored eyespot patterns. Charles Darwin proposed the hypothesis that this seemingly useless feature is the result of sexual selection. Several research groups have been investigating this, but no clear conclusion has been reached. Some studies show that a higher number of eyespots increases reproductive success, while others show no relationship between eyespot numbers and female mate selection.

As a premise for these discussions, peafowls should have the ability to count, but until now, no research has confirmed whether peafowls can count. Therefore, the research group conducted experiments to investigate whether Indian peafowls possess the ability to count.

Therefore, the research group conducted experiments to investigate whether Indian peafowls possess the ability to count.

Six Indian peafowls kept at Hirosaki City Yayoi Zoo Park were given necessary training for the experiment. Thereafter, two white panels measuring 9 centimeters square were presented side by side (black dots were printed on the panels, with the two panels having different numbers of dots). For each individual, it was predetermined whether pecking the panel with more dots or fewer dots was correct, and pecking the correct panel resulted in cabbage being given. Pecking the incorrect panel only resulted in the panel being hidden, with no cabbage given. After training with panels where dots were arranged horizontally for each combination of "1 vs 2," "2 vs 3," and "1 vs 3," the correct response rate was examined using panels with dots in random locations, and the peafowls were able to select the correct answer at a significantly higher rate.

However, when the number of dots increases without changing dot size, the area occupied by black on the panel increases, so the possibility that they were selecting based on "darkness" rather than number could not be ruled out. Therefore, the same experiment was conducted using two panels in which dot size was adjusted so that the area occupied by black was the same. In this experiment as well, they were able to select the correct answer based on the number of dots, revealing that peafowls can count.

In the next experiment, the researchers investigated whether peafowls are able to make judgments based on relative magnitude relationships rather than mere numbers. In this experiment, correct responses were trained using combinations of "2 vs 3," "1 vs 3," and "2 vs 4." Subsequently, combinations of "4 vs 5," "2 vs 4," and "3 vs 5" were mixed in at random timings among these panels. Despite the peafowls having never seen these combinations before, they selected the correct panels at a significant rate. This result revealed that peafowls can discriminate between the number of dots on panels based on relative magnitude relationships.

In other words, it was clarified that Indian peafowls can count numbers at least within the range of 1 to 5 and can make judgments based on relative magnitude relationships. This research clarified the numerical cognition ability of peafowls and provided new clues to solving the mystery continuing from Darwin's time regarding the development of morphological features of Indian peafowls. Going forward, it is expected that clarifying differences in cognitive abilities between males and females, as well as discrimination of larger numbers, will help approach this long-standing mystery.

Journal Information
Publication: Animal Behaviour
Title: Indian peafowls can count numbers: experimental evidence of numerical cognition in peafowls
DOI: 10.1016/j.anbehav.2025.123348