Aposematism, Müllerian Mimicry, and Batesian Mimicry

Red Flags, United Fronts, and Tricksters

If you are a wild animal, you spend a lot of your time either trying to eat, or avoiding being eaten, and over time many different strategies have evolved to be the best hunter, or the most difficult prey, such as mimicry. 

While many organisms use group defense, camouflage, or behaviors (such as being nocturnal) to avoid being eaten, there are some that have evolved a brave and bold strategy: be poisonous, and make sure everyone knows it – this is called Aposematism. 

What is Aposematism? 

Aposematism is the term used for poisonous animals – be it reptiles, amphibians, insects – that have a bright coloration that works as a warning signal, or red flag, to potential predators saying, “I either taste really bad or could kill you, don’t eat me!” 

You can think about it kind of like this, if you have ever tried a food and really hated it, or maybe it even made you sick, you are pretty likely to not try that food again, right? Well the same applies for aposematism. A bird might try to eat a bright yellow butterfly, such as a Monarch, then realize how horrible it is, and they are likely to avoid all butterflies that look like that from then on. 

So here is where the interesting piece comes in, there are some animals that have evolved to have similar aposematic patterns and colors, so that once a predator learns not to eat one of them, it won’t eat any of them – it is kind of like a united front against predation and is called Müllerian mimicry. Now, there are also mimics who take advantage of these same colors, but don’t produce any nasty toxins themselves, the tricksters, and this is called Batesian mimicry. Let’s break down these biomimicry basics. 

A note before we get into it: Nature can be tricky, and most things are found more on a spectrum rather than black and white. In this case the spectrum can be referred to as Batesian-Müllerian mimicry rings, as opposed to two distinct systems, but breaking it down into distinct parts will help us understand the system better.  

What is Müllerian mimicry? 

Müllerian mimicry is when two (or more) poisonous or unpalatable (bad tasting) animals share a similar coloration and/or pattern. The idea is that these two animals form a mutualistic relationship, where they both benefit from sharing a similar look. 

If species A and B for example are Müllerian mimics, and a member of species A is eaten, or maybe just bitten into, the predator is less likely to attack either species A or species B, and vice versa. Now this only really works if the mimics are found in the same place, and predators are able to learn to avoid them. At the end of the day, it is kind of like group or herd defense, but for individuals that don’t have to live together. 

What animals use Müllerian mimicry? 

Thought there are many examples, here are a few examples of Müllerian mimicry: 

• Butterflies are a common and well studied example
  • The famous Heliconius butterflies
  • Monarchs and Viceroy butterflies
• Bees, wasps, and other hymenopterans
• Beetles, like the net-winged beetles 
• Frogs, like Peruvian Poison frogs

What is Batesian Mimicry? 

There are a few tricksters that have managed to take advantage of these colorful warning signs used by aposematic animals, without actually producing any toxin themselves. 

But why is it advantageous to mimic poisonous animals? 

Animals are always trying to avoid being eaten, but toxins are often energetically expensive to produce, so, Batesian mimics have managed to copy the look of other more dangerous animals which helps them to avoid predation, like the mullerian mimics, but without having to be poisonous. 

Now, the mimics aren’t always perfect twins, but we aren’t sure if it is because they look “close enough” for it to still fool predators, or if there are other trade-offs involved making it too difficult for them to look exactly like their poisonous almost-twin. 

Biologists will often refer to this relationship as parasitic, because the Batesian mimic is gaining from its aposematic twin, without giving anything in return. In fact, if a predator eats a Batesian mimic that is palatable, it may attack the actually dangerous species a different time. 

What animals use Batesian Mimicry? 

Here are a few interesting examples of Batesian Mimicry: 

• The Coral Snake and the False Coral Snake (here)
• Hover flies (Syrphidae) mimic bees and hornets 
• Hornets with varying aggression 
• Various other Arthropods, like Hawk Moth (sphingidae) caterpillars that resemble snakes 
• Even the cinereous mourner, a baby bird that mimics poisonous caterpillars!

Recap: What is the difference between Müllerian and Batesian mimicry? 

Müllerian mimicry is when two poisonous or unpalatable animals have similar coloration and patterns while Batesian mimicry is when a non-poisonous animal mimics the patterns or coloration of a poisonous or unpalatable animal without actually producing any toxins themselves. 

The spectrum – Batesian-Müllerian mimicry rings 

So, as mentioned previously, Müllerian vs Batesian mimicry isn’t necessarily black and white, but more of what is called a Batesian-Müllerian mimicry ring. There are a few reasons that make the relationships between these groups more of a spectrum than a “win-win” or “win-lose” etc. Some of the reasons are: 

• If a Batesian mimic is eaten, this can reduce what we call the “error-cost” that can happen when there are forgetful of naive predators, so the aposematic species doesn’t lose any individuals – known as quasi-Müllerian mimicry
• Sometimes a Müllerian mimic is less poisonous than the other, so one species is technically gaining more from the relationship, referred to as quasi-Batesian Mimicry 
• Even within one species, the level of defense produced could vary, so within a species there could be certain individuals gaining more benefits than others! 

So with this being said, just like any interesting theory in Ecology, nothing is 100 percent the rule all of the time!

Overall, we can see here that animals have evolved all kinds of ways to avoid predation. Whether they are truly poisonous or bad tasting, or are just faking it, these bright colors can help them avoid being eaten and carry on to reproduce and help their species continue for another day.