Scholars among Mice

Can rodents count? Researchers from Novosibirsk State University and the Laboratory of Behavioral Ecology of Animal Communities at the Institute of Systematics and Ecology of Animals (ISEA), SB RAS, conducted experiments to find out if mice have any abilities to count. The results were reported at the international conference Teriofauna of Russia and neighboring areas hosted by MSU in February, 2016.

The issue in question puzzles scientists all over the world, who study abilities of different species to count and use a variety of approaches. While counting, a human operates with digits, which are abstract symbols. We can add and subtract, multiply and divide them by associating a digit with the number. So far, we can conclude that among animals only chimpanzees have some abilities approaching those of humans. Humans can analyze sets of objects in different ways. When we compare them, it’s not always necessary to count accurately. It will be enough to distinguish between a large and a small set to a certain point. For instance, we can make difference between two and three objects even without trying to count. However, if we compare eight and nine objects, we’ll have to count.

“Our mice discriminate between sets with only one unit added. They can identify if the number of elements is eight or nine. We call such a skill ‘protocounting’ or preliminary counting,” says Sofia Panteleeva, PhD in biology, a research associate at the Laboratory and an instructor at NSU.

The Laboratory is headed by Prof. Zhanna I. Reznikova, ScD, and researchers conduct experiments with different animal. For this report, they experimented with Apodemus agrarius, field mice inhabiting areas around Akademgorodok. Biologists say that these mice tend to stay close to people – they can be found near countryside cottages, in backhouses, haystacks, – but they don’t become housemates with people.

The experimental setting included two similar boxes with a paper shutter as a door. The shutters had geometrical figures on them, different in number – five and ten respectively. One of the boxes contained a nut. When a mouse came, it smelled the nut and found it. The experiment was conducted three times at a row and then the mouse had a test with the boxes without the nut. Biologists wanted to make sure that the mouse ‘understood’ that the food was always located behind the shutter with ten figures instead of five. All the stages of the experiment were repeated with the training and the test, filmed and carefully analyzed.

Throughout the experiments every mouse faced the choice 20-30 times. The tests were conducted with about fifty mice. A mouse passed the exam if it had 85% or more correct attempts of choosing ‘tens’. In this case we can conclude that the animal makes difference between the sets presented. The researchers varied the form and the size of the figures (squares, triangles, circles), took different numbers of them, for example, two and three; five and six; eight and nine; five and ten again. Then the animals had a retraining with a nut in the box with fewer figures. According to the experimental results, researchers concluded that mice can distinguish not only between five and ten figures, but also between sets with as little as one-element difference. Thus, mice tend to be able to demonstrate some ‘protocounting’ skills.

“Apodemus agrarius mice are really amazing. They are quick learners. I remember one particular mouse which excelled in understanding rules for the ‘game’,” says Sofia Panteleeva. “This mouse remembered where to look for the nut and made not a single mistake during the ‘exam’.” A prominent expert on animal behavior Inga Poletaeva, when she acquainted herself with the results of Siberian scientists from Akademgorodok, called these rodents ‘scholars in the rodent world’.

In their notes for the report at the conference, the researchers pointed out that such abilities for ‘protocounting’ had been fixed as demonstrated by chimpanzees, ants and chickens. However, rodents’ abilities in this area had not been described yet.

The Laboratory is now experimenting with Asian hamsters (Phodopus) and voles (Microtinae).

“We haven’t discovered their abilities similar to those of Apodemus agrarius yet,” says Sofia Panteleeva. “But their might show their worth with time.”

Photos provided by Sofia Panteleeva

Text prepared by Dina Golubeva