Chicks can do simple sums soon after they hatch, according to a study by scientists in Italy.
Researchers observed what they called "impressive arithmetic" in newly hatched chicks, none of which had been trained or had any previous experience of problem solving.
The study is the first to find evidence for basic mathematical skills in young animals that have not been taught first.
Rosa Rugani at the University of Trento demonstrated chicks' ability to add and subtract by moving identical objects behind two screens as the animals looked on. According to Rugani, the chicks had to perform simple arithmetic to work out which screen obscured the larger number of objects.
The chicks were reared with five plastic containers of the kind found inside Kinder chocolate eggs. This meant the chicks bonded with the capsules, much as they do with their mother, making them want to be near the containers as they grew up.
In a series of simple maths tests, Rugani's team attached a fishing line to each of the plastic capsules and used it to move them behind two screens that the chick could see from behind a clear plastic door. When all of the containers had been hidden, the chick was set free to investigate.
Rugani's team found that when the chicks went in search of the capsules, they peered first behind the screen that concealed the larger number of containers.
In a more difficult test, the researchers moved the containers back and forth behind the two screens while the chicks watched. When they were released into the enclosure, the chicks still made for the screen obscuring the most containers, suggesting they had been able to keep track of the number of capsules behind each by adding and subtracting them as they moved.
The study is published in the journal Proceedings of the Royal Society B.