SOCIOLOGY:

Social animals must maintain social cohesion. This requires effective processing of social information.

Vision appears to be a common method of processing such information. Individual visual recognition is an advanced processing method, but it is not clear how extensive this ability extends through the animal world.

Individual visual recognition has been claimed for many social critters; however, the tests are often not rigorous. For example, pattern recognition may be at play, instead of true individual recognition.

A rigorous test of individual recognition would involve both familiar and unfamiliar individuals living within a group. Marjorie Coulon (Université Paris) and coworkers' studies of dairy cattle have shown that they do exhibit individual visual recognition.

Why dairy cattle?

Dairy cattle are an ideal mammalian species in which to probe the question of individual visual recognition capacity, for several reasons.

• There are numerous individuals living within each group. This enables a reasonable number of subjects to be tested.

• Both within and among breeds, there is a great variety of morphologies, coat patterns, and coat color. This allows for at least the possibility of easy visual recognition.

• There is evidence that cattle can visually discriminate between cattle and other domestic species, and visually recognize other cattle. However, direct behavioral evidence of the latter is lacking.

This study aimed to conclusively demonstrate, through direct behavioral evidence, whether or not cattle can visually recognize other cattle, among familiar and unfamiliar individuals.

The cattle.

Eight cattle were studied. They were all born on an experimental farm in France.

When they were six months old, they were grouped together with 16 heifers of similar age. All of the subjects were extensively trained in the recognition procedure, described next, for several months prior to the study.

The recognition procedure.

Each subject was shown 80 large color prints. Twenty were of four familiar same-breed heifers, 20 were of four unfamiliar same-breed heifers, and 40 were of eight unfamilar different-breed heifers.

Different view angles were represented in each print. In each group of 20 prints, there were 10 different views of one individual, and 10 different views of three other individuals.

In the training stage, the subjects could see two of the prints from the gate of their pens. They then walked towards one of the prints.

In order to access a food reward, they had to walk towards the print of the heifer who they would be later chosen to identify in future experiments. A successful training session required eight correct choices per session, ten trials per session, in two consecutive sessions.

Recognition results.

The scientists found that cattle can more quickly recognize familiar (group mates) rather than unfamiliar cattle. They also found that cattle have even more difficulty recognizing unfamiliar cattle with a different coat pattern than their own.

The view angle of the prints did not hinder the cattle's ability to recognize the target individual. This means that cattle are easily able to recognize known individuals, regardless of orientation.

Both the cattle's success rates and eagerness to complete the task strongly suggest that the cattle were recognizing the prints as representations of cattle. Domestic dairy cattle clearly recognize one another, most easily when they are familiar with each other, which likely aids social cohesion in the group.

for more information:
Trape, S. Coulon, M.; Deputte, B. L.; Heyman, Y.; Baudoin, C. Individual recognition in domestic cattle (Bos taurus): Evidence from 2D-images of heads from different breeds. PLoS ONE 2009, 4, e4441.