Deep in the ocean, sharks pursue their prey. Large species found in open-water, like the famous Great White (Carcharodon carcharias) use their strength and speed to overpower prey, much like a lion on the savanna.
Others defend themselves with claws…
Other animals join together to avoid getting eaten.
And still others hide in their homes…
Or even in plain sight.
The ocean is full of amazing examples of camouflage. Many fish blend into the background of their habitat to avoid being detected. Scientists call this crypsis. Crypsis is a great defense because if a predator cannot see or sense their prey they will not attack.
It also is an advantageous for predators, allowing them to hide from their prey until they are ready to ambush them. Many camouflaged ocean dwelling animals are both predators to smaller animals and prey to larger animals. Such ambush methods are commonly used by small sharks, like the spotted wobbegong shark (Orectolobus maculatus).
Other animals literally shine like the sun in order to blend in. Take the velvet belly lantern shark (Etmopterus spinax), one of the smallest known sharks, usually only around 18 in (45 cm) long.
Found in deep waters of the Atlantic Ocean, the velvet belly, like other lantern sharks is bioluminescent (much like fireflies). It can illuminate its belly which may seem counterproductive for something trying to blend in. But blending in doesn’t just depend on the specific environment the organism is found in, it also depends on its predators. And predators of the velvet belly lantern shark include other larger sharks that have eyes on the top of their heads. These predators can detect fish or other prey above them by looking for shadows cast when the sunlight, shining down through the ocean surface, is blocked by the body of the prey organism. This is where having a bioluminescent abdomen helps the small lantern shark blend in. Instead of casting a shadow, the velvet belly produces its own light, mimicking the sunlight filtering down and making it nearly invisible from below. And their dark backs make them blend in from above as well! Check out this video.
Camouflage is not just crypsis, but also includes mimicry which is when organisms avoid detection by disguising themselves as another organism or object. For example, some seahorses pretend to be coral.
As does the frogfish.
Whereas camouflage often requires animals to remain very still, mimicry works best if the animal can move like the organism they are copying. For example, the leafy sea dragon (Phycodurus eques) doesn’t just look like the kelp in which it lives, it also sways like kelp in the ocean current (see this video).
These animals are clearly well adapted to their specific habitats, as their patterns and markings might be quite obvious against a different background. However, some animals, like cuttlefish and the closely related octopii, can blend in across multiple habitats by literally changing their skin colors and patterns as they swim. Check out this amazing video and the NOVA documentary on cuttlefish.
Although all the examples of camouflage above were from the ocean, there are also many amazing terrestrial examples.
In the desert the earless desert lizard (Cophosaurus texanus)blends in with the light colored sand and rocks.
In the arctic tundra animals change the color of their coats to match the changing seasons. Winter brings a white coat of fur…
… and in summer a brown pelt instead.
Clearwing butterflies in the tropics have transparent wings allowing them to disappear no matter where they settle.
The blue morpho butterfly is one of the world’s largest butterflies with a dull brown color and eyespots that give it camouflage against predators when its wings are closed.
However, when they open their wings it is a bright blue. So as they fly the contrast between bright and dull colors makes it seem like they are appearing and disappearing, making them hard to follow (see this video or this one about how the blue color is formed).
Mimicry is also common across many ecosystems. It is an effective defense because even if the animal can plainly be seen, it is not recognized as food. A bird looking for insect prey will not pay attention to this dead leaf…
… which is not actually a dead leaf at all, but rather a butterfly.
Another example is this leaf insect which has one dark shade of green on top and a lighter shade below to mimic the leaves within which it lives. Its shape and markings make it look like a leaf that has been partially eaten. And it even goes so far as move like a leaf (see this video).
Vertebrates also use mimicry. Like this frog in the rainforest…
… or this chameleon, which not only can change colors (see this video) but also has lines that disrupt a predator’s search by breaking up the shape of its body.
Disruption is another form of crypsis and it describes the use of color patterns like stripes or spots that break up the outline of the body, making it look less like an animal and more like light reflecting off of surfaces. Disruption makes it harder for the predator to both see and more difficult to attack if seen.
A good example is the American bittern, a wetland bird…
No matter what ecosystem you live near, you don’t have to go far to find examples of camouflage, in fact you can find them in your own backyard or neighborhood park, if you are observant, patient, and maybe a little bit lucky.
This past week some of my colleagues and I have been working with the curious and intelligent young scholar-scientists of Rutgers-Newark’s Aim High Academy. These rising high school seniors are working side-by-side with us to discover and document urban and suburban biodiversity in the wilds of New Jersey. In fact it was their discoveries that gave me the idea to write this week’s blog on mimicry and crypsis.
Like many of us going about our everyday life, my students were surprised to find so many insects and other living things right at our feet in our lawns…
… and abandoned fields (see this post by Megan Litwhiler).
This week we found a northern walking stick insect…
… and a thorn bug…
… so tiny they appear to be a thorn on a shrub instead of an insect.
Thorn bugs are part of a family of insects known as treehopperes or Membracids and they come in some pretty wild shapes (check out this link).
We also found praying mantids…
… which also use camouflage but to catch prey rather than avoid predation. Mantids lie in wait for their prey, mimicking the plants they live in (see this video).
We also found some insects that are purposely not blending in, like the monarch butterfly which uses warning coloration to scare off predators. Such advertisements will be the topic of my next post, so please check back soon.