Physical communication tends to happen between animals of the same species and family groups as generally, it requires one animal (the sender) getting very close to another (the receiver), which can be quite a risk to take.
Primates like chimps have strong family structures, and these hierarchies inform who grooms whom. Generally the more important an individual, the more grooming they receive; it also reinforces this pecking order to other members of the troop and is a type of visual communication in this way too.
A particularly impressive example of physical communication is seen in honey bees (Apis mellifera). Known as the ‘Waggle Dance’, the bees use a series of movements to share information about where food can be found with other bees.
The dance explains how far away from the hive the food is (the length of the wiggle), what direction it can be found in (the angle of the wiggle), and how much food is there (the intensity of the wiggle)! From this information, the other worker bees can determine where the food is and how many of them are needed to bring it back. While this would be hard enough to decode on its own, the most impressive part of the waggle dance is that it all happens in the dark, deep in the hive! The bees ‘watching’ the dance are actually sensing the vibrations in the honeycomb beneath them and getting all this information that way.
Even more subtle than the waggle dance are the ways in which some shoaling fish or flocking birds are able to communicate and move around in their synchronised manner.
Fish have special organs running down either side of their body which allow them to sense changes in the pressure of the water around them. If two fish are swimming next to each other and the first fish turns left, the second fish can feel this change and instinctively knows which was to move, without having to see. In this way, it is possible for huge groups of fish to shoal, or move together as a group.
Some birds, like Starlings, display similar flocking behaviour, with huge groups managing to turn quickly in unison. We call this a murmuration.
Although we know why birds flock like this (safety in numbers, energy efficiency whilst flying etc.) scientists are still working to understand exactly how this information is passed from bird to bird so quickly.
Glossary
Murmuration – used to describe the movement of a flock of birds, like starlings.