Researchers show that animal speed would be the most important factor in determining the size of the eyes in mammals. What about the horse?
Twice larger than our eye, bigger even than that of the elephant and the whale, the eye of the horse is imposed by its size. What differentiates all these animals? Their speed of movement: "If you think of mammals which are fast like the cheetah or the horse, we can almost deduce that they have very big eyes" declares Chris Kirk of the University of Texas "That gives them a better Vision to avoid collision with obstacles in their environment when they move very quickly. In a comparative study of 50 species of mammals, the researcher arrives at the conclusion that the mass and speed of the animal are the preponderant factors in the size of their eyes. The fact that an animal is nocturnal, with the need to see well at night, would have little influence on the size of its eye but would rather play on its shape.
The researcher talks about the ability to avoid obstacles but seems to ignore that in the case of the horse, he naturally lives in the plain, in clear spaces. This kind of study which establishes correlations between different factors unfortunately does not explain the real causes that have pushed nature to provide such big eyes to our companions. Nobody will want it to be Lady Nature, as their gaze can be cute!
Where can this funny idea come from?
The idea that horses have the biggest eyes in the animal kingdom is explained in particular by the importance that human beings attach to the gaze. Our perception is not objective and can vary from person to person. Anthropomorphism often gets involved: we lend animals to the emotions and intentions that are ours but which often do not have any meaning reported to the world of animals in question. Thus, someone who is afraid of horses or who is not comfortable with them can overinvest their eyes and thus find that they are particularly big.
What is the horse's vision?
Horses have eyes adapted to their herbivorous lifestyle. Thanks to the lateral positioning of their eyes and their elongated pupil, horses benefit from a particularly extensive field of vision corresponding to around 340 °. Their binocular vision allows them to estimate the relative distance of objects by raising the neckline.
On each side, monocular vision allows them to quickly distinguish everything that is in motion, an essential capacity to detect the danger.
The horse also has blind areas which are just behind the rump and under its nose, when its head is raised. This explains the presence of long hairs on the chin and around the eyes, the vibes, which give them information beyond the vision.
The horse in the darkness
The horse has a good vision in the dark because, in freedom, the night pasture represents 20 to 50% of the daily pasture time. However, the horse will have a slow accommodation and will struggle during rapid variations in lighting.
It is for this reason that the horse can be reluctant when it comes to bringing it into a dark place (stable, van, or truck) or that you want to work in a place where the brightness is very variable.
Animals with the largest eyes generally concern animals that need a very developed vision. These are birds of prey such as eagles or owls, or certain species of fish and reptiles.
The horse has some anatomical particularities
The question of organ size is amazing. The mechanism of natural selection leads living organisms to adopt the expression that is most suitable for the perpetuation of the species. Also, horses have internal organs of size proportionate to their anatomy and their physiological needs. However, we can speak of two anatomical characteristics.
The horse's stomach is special insofar as it is divided into two parts: the glandular stomach and the non-glandular stomach. This allows them to effectively digest the large amount of fiber in their diet composed of grass and hay. The big intestine of horses is also special. It is suitable for microbial fermentation of vegetable fibers.
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