Animal studies are very interesting. in nature documentaries, we often come across attacks from predators. Lionesses hunting gazelles or sharks attacking huge schools of fish.
In both cases, the threatened animals coordinate their movements and stay united as a collective. They all flee in the same direction, but how do they do it?
Until now, previous animal studies showed that social animals need to follow visual cues to guide their collective movement and avoid predators. However, the design of these cues was unknown.
Recently, the journal Proceedings of the Royal Society B published an article on an investigation led by researchers from the Estación Biológica de Doñana-CSIC.
The researchers explained that some animals avoid their predators by using the stripes on their bodies to indicate to the rest of the group in which direction to flee.
Animals that use this technic include; most flocks of birds, groups of mammals and schools of fish.
To carry out the animal studies, the researchers analyzed about 800 species. They divided them into four groups
- Mammals: mainly ruminants such as gazelles, zebras or giraffes
- waders (marsh), geese such as ducks and geese
- coral reef fish
“Each type of animal has a different signalling pattern: stripes, … and using the comparative method we analyze what they have in common.“ The researcher and former director of the EBD-CSIC, Juan José Negro, explained in statements to Efe.
Animal studies revealed a pattern of communication
The analysis from these animal studies were very promising. They found that lateral body bands are more frequent in social species and are less present is in solitary species.
Similarly, in species less vulnerable to predation such as geese or swans. Being large, these animals do not have predators such as ducks small ones that are targeted by hawks.
According to researchers, these body patterns are a communication mechanism that helps individuals form compact groups.
Moreover, it takes the same direction without causing chain collisions, and to confuse predators with the movement of the bands.
“We believe that the stripes are like arrows that indicate the direction of movement and that serves so that when one of them has to pull the others -because he has detected a predator or because he has decided to go in one direction- the others follow him”, he explained.
And it is that, in social groups, survival is based on the unity of the group: “When a gazelle separates itself from the rest or isolates itself, it is dead. That is why the visual signals are not oriented in any way. But show where the group should move, where it has to go to flee”.
Exceptions with stripes
However, there are exceptions because not all social species have stripes, nor do solitary species lack them.
“We know that there are very gregarious species that do not have stripes like the common starling. For example, which is grouped in thousands and even in groups of a million individuals. And they do not have stripes. Some researchers have proposed that these birds – which form very compact flocks – use the beams of light between individuals as signals”.
The animal studies also revealed that striped animals such as skunks or wasps, have these signs for the opposite. “They pretend to be very visible to predators, which is known as aposematism to be associated with danger and avoid attacks.” Says the biologist.
The study also determined that the stripes are usually achromatic, located on the scale from white to black, and without colours because this allows “this mechanism to be used even by species that do not see in colour.”
Employing dark stripes on a light background allows species with monochromatic or dichromatic vision to take advantage of this “simple and universal mechanism” that allows all species to use it even in variable light conditions such as sunrise or sunset, when the colours, the investigation concludes. animal studies