Numerical competence in peafowl: small quantity discrimination.

The ability to discriminate numbers is widespread across taxonomically diverse animals. Some animals may have evolved enhanced numerical abilities to cope with specific social or ecological challenges. Peafowl (Pavo cristatus) are one example in which enhanced numerical abilities could be useful because peacocks have colorful trains that exhibit many eyespot feathers and females may evaluate the number of eyespot feathers to assess their mates. We therefore tested the numerical discrimination abilities of captive peafowl using a custom touchscreen apparatus. Peafowl were presented with two squares that contained a different number of circles (one to eight) and they received a reward for pecking on the square that contained more circles. To examine whether quantity factors aside from numerosity were influencing their performance, we varied the size, density or surface area of the circles. We found that the peafowl's performance was largely driven by numerosity rather than the other quantity factors. The peafowl generally performed at levels above chance regardless of the size, density or surface area of the circles. Their performance was also consistent with the Weber-Fechner Law, in which numerical discrimination is related to the ratio between numbers rather than the absolute difference. The results suggest that peafowl can discriminate among numbers and they could potentially use that ability during courtship or other contexts.