Without speech, animals have evolved a huge variety of ways to let each other know what they’re thinking
Follow the leader
Ants leave helpful trails for their comrades
Pheromones are scented chemicals excreted or secreted by animals to change the physiology or behaviour of others, and they’re extremely useful. If an ant is being attacked, it can release a pheromone that raises the alarm and provokes an aggressive response from the rest of the colony. Perhaps the best-known use of pheromones in social insects is the creation of trails leading to food.
When a scout searches for food, it lays down a trail of volatile pheromones so it can find its way back to the nest and let the colony know what it’s found. If a good source is discovered others set off to find it, using the trail as a guide and releasing their own pheromones. The shortest route to the food becomes reinforced as it takes less time for ants to complete the journey, while meandering trails or those not leading to food soon evaporate.
Ants will abandon weak trails or their own new routes if they come across a strong- smelling trail, helping ants to collect food quickly and efficiently. When the source starts to run out, ants return without releasing pheromones so the trail can fade away.
Something in the air
Potential mates send secret messages
For most animals, three goals dictate their every move: eating, avoiding being killed, and producing offspring. Finding mates is a competitive business, so those looking for love need to make themselves as attractive as possible. Features like manes, flamboyant feathers and bright colours are obvious, but there’s a lot going on that we can’t see.
Sex pheromones are chemicals that are released specifically to signal an individual’s availability, attract members
of the opposite sex and encourage reproduction. Male cockroaches use their pheromones to establish hierarchies, and the scent of the dominant individual attracts the most females.
Male mammals can be seen sniffing females during breeding season, as their scent conveys information about their health, age and, perhaps most importantly, whether they’re in oestrus. Like this reindeer, males of many species open their mouths and curl back their lips; this lets the pheromones reach the vomeronasal organ, an organ on the roof of the mouth that can pick up on chemical signals. The scent of a receptive female induces changes in the male’s body so he’s ready to mate if he gets the chance.
Love letters in lights
Fireflies have real chemistry
On summer evenings, woods and fields across the world are brilliantly illuminated with the blinking glow of fireflies. These nocturnal beetles – yes beetles, not flies – emerge as the Sun starts to go down and set off chemical reactions in their abdomens. These reactions produce coloured lights, turning the fireflies into tiny torches.
The lights attract other fireflies, helping them to locate mates. To avoid confusion, each species and subspecies has its own unique combination of light colour and flash sequence. Males have even been seen synchronising their flashes – this could be a team effort to attract females, or an attempt to stop an individual getting an advantage by flashing first.