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In this Nature League Lesson Plan, Brit explores the four main categories of communication for life on Earth, and discusses the realities of interspecies communication.

Guest starring: Adrian Adams as the bit partner, Sean Kirkpatrick as the great potoo, Jane as sweet baby Jane, and Abby Dalbey as cat snuggle videographer.

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Welcome back to Nature League!

It's a brand new month, and that means it's time for a brand new theme. This month's theme is communication.

And while this thing is really good at helping us stay in touch, life on Earth has some amazing alternatives when it comes to getting a message across. [CHEERY INTRO MUSIC]. Communication. This word can have a lot of meanings, so let's start with a basic working definition.

In the study of animal behavior, and for the purposes of this Lesson Plan, communication can be broadly defined as the passing of information from one individual to another. The “passing” bit means that a signal not only has to be sent, but also received. So, if I'm alone in here talking to no one, I'm just talking- not communicating. [BREAKER SWITCH SOUND AS LIGHTS TURN OFF].

Uh, is anyone here? So, why does life need to communicate at all? This answer is pretty straightforward- basically all pieces of survival can depend on sending and receiving messages between individuals.

Reproduction, feeding, protection, coordinating group behavior- the list goes on and on. The awesome part is the fact that all of the species on Earth communicate a little differently. I mean, even a single species can use a huge array of options.

Das ist richtig. É verdade. Hiyo ni kweli. Dayone.

Communication basically comes down to two components: sending signals, and receiving them. That part is simple. However, the complexity comes from the insane amount of signal types we find in life on Earth.

These signals can be broadly grouped into four main categories, though there are of course some lesser known ones, and probably ones we haven't even discovered yet. These main categories of signals are auditory, visual, tactile, and chemical. Let's check them out one at a time.

Auditory communication relies on signals in the form of sound. This one is really common in the Animal Kingdom, and if your sound is on, it's the one I'm using right now to communicate this information to you. Sound exists physically as a waves, and sound waves can travel in both air and water.

That means auditory communication isn't limited to life on land- in fact, some of the most famous nature sounds come from marine animals. Auditory signals in some dolphins and whales are so complex that certain species use several different languages, and even individuals in the same region might speak in what we think of as accents. [ADRIAN AS

WHALE:] Hey, you want to go disembowel the little baby seals? [BRIT AS

WHALE:] Can't you give that to me one more time? I have no idea what you're sayin'. Birds are another group of organisms that display an incredible amount of diversity and complexity when it comes to making sounds. In fact, in bird taxonomy, an entire group of birds named passerines are separated from other birds by the fact that they exhibit song behavior.

I'm a passerine, doo doo doot! These auditory examples are intraspecies- the signals are passing between individuals of the same species. But there are also interspecies auditory examples, where a signal can pass between different species.

When a rattlesnake produces its famous rattle sound, the purpose is typically to signal to another species, “Hey buddy, back up”. Sometimes the sounds one species makes can unintentionally sound like something a different species uses. For example, the great potoo sounds almost exactly like an angsty teenager yelling for his mom. [GREAT POTOO CALL].

Mom! If you're watching this episode with sound off and subtitles on, my communication mode for this Lesson Plan has switched from auditory to visual. Visual communication is all about sending and receiving messages that can be seen.

Indeed, a picture is worth a thousand words, and simple changes in something like posture can work wonders in terms of getting the point across, even without sound. In fact, humans have entire languages based on only visual signs. In most mammals, facial expressions convey a lot of visual information.

But this is just one type of visual signal. Posture can be a signal in itself, as well as the movement of non-facial body parts. Some organisms can even do something as drastic as change their coloration to get a visual signal across, like when parts of female monkeys become bright pink and red to signal that they are ready for mating.

Visual signals aren't limited to mammals, though. For example, individual crocodiles will exhibit changes in posture like lifting their snout and angling their head to communicate their intentions when interacting with other individuals. And now for tactile signals.

Tactile communication relies on signals conveyed through touch. While sound can travel in waves, and visual cues can be seen from as far away as the eyes allow, touch requires...well...touching. Because of this, tactile communication is less common in certain situations.

While less common for, say, mammals, tactile signals are commonly used by organisms like insects. Take bees, for instance. A honeybee will perform something called a waggle dance to indicate to other honeybees where they found a recent food source.

Dancing out the route to dinner might be categorized as a visual signal given between the bees; however, this movement actually happens inside the nest where it's dark. And while dancing in the dark might seem like a waste of perfectly good visual entertainment, it isn't a waste of communication. The honeybees in the nest sense the series of motion using tactile receptors.

That brings us to our last main category of signaling, which is chemical. Let's get chemical, chemical! Specifically, biologically secreted chemicals called “pheromones”.

Pheromones are released by individuals for the explicit purpose of communicating with other individuals, usually of the same species. One of the most known examples of pheromones in humans is the ability for us to “smell” out a potential mate. Someone biologically attractive was just here….

But pheromones are used for much more than reproductive attraction- these chemical signals can communicate the presence of danger, direct others to a food source, trigger a series of behavioral responses, and even act as a presence/absence indicator of certain individuals. Take a look at ants. When an individual finds a food source, they leave a pheromone trail from the food to the colony so that the rest of the ants can find their way back and forth.

A great example of chemical communication is seen in domestic animals like cats and dogs. When my sweet little baby Jane cat comes and rubs her face against mine, she's leaving behind pheromones as a sort of signal, typically called marking. If you've ever walked a dog, you've probably seen this same behavior, but in the form of urine.

Several biological fluids contain pheromones, and peeing is an easy way to leave behind a message. We've discussed the Whats and Whys of several categories of communication, but we haven't touched on the How. How do all of these signals come to exist as the primary form of communication for each species?

Like any other adaptation, the types of communication we see in life on Earth is a product of natural selection. Basically, the signals that helped individuals be successful and have more offspring wound up becoming present in populations because they were advantageous. What's cool about this is that the types of signals used by individual species are tailored to their success in the environment.

The insane amount of communication types we see is a product of what works for each individual species. Plants use chemical signals because that works for them, and was the most beneficial option back in the day. So need to evolve vocal chords!

In general, life...uh...finds a holla at each other. There's one more thing we should mention about communication- it only works if there's a language in common between the individuals sending and receiving signals. When there isn't a shared set of meanings correlated with these auditory, visual, tactile, or chemical signals, a sent message can't really be received.

This is why it's important to keep in mind that while some species can communicate with others, it's only by means of pattern recognition or the chance that both species share a similar signal. Humans can't even tell what other humans are communicating unless they're using the same patterns of signals, whether that's verbal language, written words, or shared physicality. And even then, all you have to do is watch a typical sitcom to notice how often miscommunication plays a role in social interactions. [

BRIT:] And I said, "Penguins don't eat popcorn!" [

ADRIAN:] That's the last time we invite your uncle to Thanksgiving! [LAUGH TRACK]. And just think! These miscommunications happen between two individuals of the same species using the same type of signal in the same language. So, we might never be able to truly understand what another species is saying, but we can certainly recognize that everything on Earth has a voice, in some form or another.

We'll be exploring these forms of communication throughout the month, so make sure to come back next week for a communications themed Field Trip! And to keep going on life on Earth adventures with us each week, make sure you go to and subscribe.