The art of deception: Mimicry and camouflage
Camouflage and mimicry. Two key strategies built on deception, and present in a surprising number of rainforest residents. Each tactic can be simplified and distilled to one or two key ideas, but I am not going to do that. These are rich, complex and endlessly fascinating topics deserving of exploration and explanation.
Camouflage in its simplest form is crypsis. It is simply blending in to one’s environment. I say simply, but in reality, there is nothing simple about it. It involves the evolution of colours, and patterns over time. Moreover, crypsis is only effective when a suitable substrate or background is chosen. A leaf-mimicking katydid would be wholly out of place and easily picked off out in the open or on a tree trunk. Thus there must be some kind of feedback between the animal and its environment to ensure effective use of its camouflage. But that leaf-mimicking katydid of which we just spoke is more than simply colours and patterns, it is shape and form. Enter masquerade. This is a relatively new term used to describe the evolution of different shapes to approximate an environmental, non-animate object. All well and good. Show me the money (or leaf-mimicking katydid as the case may be)!
So, these animals essentially have Harry Potter’s cloak of invisibility right? Why don’t all animals employ this strategy? Well, Sani is a magical place, but it isn’t Hogwarts. Camouflage though remarkable has its limitations and drawbacks. As we just covered, camouflage is only effective when the proper background is selected. However, what if that background is either not available or sub-optimal? Well I’m glad you asked! Some insects and animals have evolved the ability to actually change colours and patterns, increasing their mobility and expanding their range. This isn’t simply the realm of the chameleons, but also amphibians and even some insects. Without delving too deeply into the biochemistry and physics of light and how it relates to specialized cells, basically, chromatophores, pigment containing cells which may also reflect light change orientation resulting in a change in appearance. Alternatively, some insects and spiders contain light-reflecting guanine crystals, whose expansion and contraction can be used to either signal, confuse or camouflage. Some organisms have built variation into their very DNA. Certain genes, ones which control colour and pattern, which can be modified without impacting the entire organism are magnets for such mutation hotspots, and even within a single brood, siblings can appear very different to one another. Whether this is true genetic variation or epigenetics (chemical modification of the DNA through the addition/subtraction of chemical groups associated with the DNA which impact gene expression, rather than the modification of the DNA base pairs (Adenine, Guanine, Cytosine, Thymine) themselves) is a question for a directed study. However, sometimes strategies fail, sometimes you have the wrong shaped screwdriver. It is still an exquisite tool, but when things go awry and need to be fixed, it’s not going to going to open up that macbook air (that for some reason uses a proprietary, special order, not commonly used pentalobed head. I mean come on Apple, seriously?!!). Others, find their way onto the menu, and if they have not yet mated, their poor genetic constitution dies with with them (is selected against), enabling more phenotypic (physiological) and hence genetically suitable individuals of the species to carry on.
And there’s more! Even when crypsis/camouflage is behaving as it should, it is still a trade off. This isn’t a blank cheque to pass unnoticed. The animal must change it’s behavior to suit its environment. If you are a moss mimic, and then you stray from the moss, you risk increased predation rates. Even though perhaps the most succulent leaves and the tastiest fruits, are elsewhere. For this reason most camouflaged creatures are active by night, when visual predation is at its nadir (while there are still some specialized visual predators, most rely on their other senses, olfaction, proprioception, acoustic, etc…). Through behavioral complementation of their physiological adaptation, they are able to minimize risk.
Camouflage is a complex world unto itself, with epizoons, symbiotic relationships between organisms, predation, parasitization, a wealth of overlapping life strategies. Books have been written and reams of information exist to explore, which I strongly encourage everyone to do, because this is just the cap of the mushroom, there’s a whole world below ground.
Before delving into the world of subterfuge and mimicry, where nothing is at it seems, it is worth exploring aposematism, or bright, contrasting warning colouration, which can often form the basis for mimicry.
Yellow and black, a strident warning to potential predators of toxicity and unpalatability. Yet how did this come to be? How do you get from palatable and vulnerable to toxic beauty?
‘De novo’ (from new) biosynthesis of toxins is a possibility, though more common, and potentially less work, is bioaccumulation or biological magnification. This strategy involves an organism usually adapted to a host plant, feeding, sequestering, concentrating, and perhaps slightly modifying biochemical constituents in the plant’s sap. These toxic compounds provide a degree of safety as animals come to learn and associate them with colors and patterns like those seen here.
Excellent strategy, no? But that’s not the entire story. This toxic lifestyle is not without its cost. Sequestration and modification of these biochemical compounds requires the right tools for the job, whether that be specialty enzymes or specific cells or organs to hold this hazardous soup and prevent poisoning oneself. This adaptation while obviously beneficial can slow growth and development, allowing faster growing competitors the opportunity to out-compete. Moreover, an organism’s evolution doesn’t happen in a vacuum. The plants meanwhile are modifying their biochemical constitution in the ‘hopes’ of ridding themselves of these essentially parasitic grazers and the predators are evolving means of detoxifying themselves and increasing their menu options.
The development of mimicry has got to be one of the most fascinating topics in evolutionary biology. The complex interrelationship between species which has come to be reflected in each players’ very DNA and further enhanced by behavioural adaptation which has come to echo that of their model organism, oftentimes with stunning and frightful accuracy. Co-evolution, the so-called evolutionary arms race of one-upsmanship between models and mimics. This is natural history drama sewn into the fabric of this tremendous ecosystem, with new threads being woven daily.
Let’s follow one such thread. It leads up and into the rainforest mid-story, and to a small colony of ants. Unassuming, if slightly oddly shaped, the turtle or gliding ants (Cephalotes sp.). Of course these ants have their own rich biological history and heritage. But the thread we are following leads further. In fact, it twines itself around these ants, strangling them. It has become inextricably linked. It is the story of Aphantochilus rogersi, the gliding ant-mimicking crab spider. Perhaps one of the very finest of mimics, it’s likeness is awe-inspiring. Most mimics have evolved this habitus, this way of life of mimicry, as a means of protection through verisimilitude with a toxic, or aggressive model. Defensive mimicry in other words. This is not that! Aphantochilus is not content to simply take advantage of the ‘herd immunity’ provided by a semblance to the gliding ant, it also preys on its model. This is offensive mimicry, is less common, and more complex. Feeding on its model requires constant proximity to the source, the nest. This puts Aphantochilus at greater risk. However, its deception is not just chitin-deep, it has changed its behaviour as well. How it feeds. Most crab spiders will grab prey, usually pollinators (since most are ambush predators around flowers and nectar sources). Aphantochilus must grab one ant out of a colony of thousands, without drawing attention to itself, without raising an alarm. It does so by grabbing ants after they have left the nest and they are more isolated and vulnerable. After delivering the fatal bite, they hold their ant prey close. They are feeding, but they also appear as two ants engaged in trophollaxis (food/biochemical liquid exchange) or else an ant carrying a dead companion.
The former example highlights what’s known as Batesian mimicry. This is the appearance of one organism to another, more toxic, less palatable, perhaps more dangerous species, in order to garner protection through confusion/conflation with the model. The mimic is often harmless and would otherwise be quite edible. This is the form that has entered the sphere of public consciousness and is used to wow and bedazzle.
Slightly less known is Mullerian mimicry. This mimicry results in convergence of physiology between one or more organisms, each one toxic or otherwise undesirable. The larger the population with the same or similar traits, the faster the message can be perpetuated, thus reducing incidental/accidental mortalities by would-be predators.
What a wonderful world we live in of never-ending surprises! Join us next week where we explore the the downtrodden, the undervalued, the workaday cockroaches, just trying to get by in this hostile world. I will show you beauty, fantasy, and complexity where many see only revulsion.
A final note:
Whenever I point out to the guides or guests here at Sani Lodge an instance of mimicry, or post an image online, there is an initial “Wow” of amazement, followed by fascination. However, I often feel that this is a message delivered in a vacuum, with no broader, penetrating message. It is very easy to treat the similarity between model and mimic with levity, and on the same level as those magic eye, and Facebook feed photos illustrating “hidden objects” which ‘pop’ into view when viewed in the proper way. Mimicry isn’t simply a trick (though confusion and deception is the endgame), it is an important life strategy. It is the result of thousands and millions of years of random mutation, edging towards refinement of incremental, fitness enhancing physiological, biochemical and behavioral traits. It is a system in flux, and is happening now even as I write this.
Hand in hand with the dismissive way mimicry can be viewed, is also the manner in which these mimics are found. I am often told, “You are so lucky. What a lucky find”. And while “luck” or being at the right place at the right time is certainly an aspect of this, finding mimicry in one’s environment is more a question of perception and of seeing what is in fact all around us. In an earlier Facebook post (What, you’re not following us on Facebook?! Enrich your every day and start here), I mentioned search image and how encountering an object primes and develops a search image, such that what once might have been invisible (simply because one didn’t know what one was looking for, and had no visual reference), suddenly becomes apparent. But there is more. It is not simply observation, not just experience and knowledge, but also analysis and an extension of the scientific methodology, since I can also point to various mimics that I have never seen or heard of, simply based on small differences in shape, form, movement, habitus, and environment.
In brief, mimicry is one of the most fascinating aspects of evolutionary biology and understanding its mechanism is key to understanding the underlying principles governing evolution. Meanwhile, the search for mimics is an application of knowledge, it is pinging memory cells, and applying reasoning and analysis. Blown out of proportion, am I giving myself way too much credit here for simply spotting a spider amongst ants? Maybe, however one can envisage a scenario, one which isn’t immediately obvious (this isn’t the bursting of bombs or exploding volcano), maybe it’s simply a few hotter days in the year, and a little less glacier on the mountain. Easily dismissed. But by always questioning, always experimenting, never simply accepting, maybe a deeper conclusion can be arrived at, one which reaches beyond the pale of a few less skiing days, and is an important, immediate, and global concern that affects us all. Science is one of humanity’s greatest tools. It isn’t just carried out in the lab, it is a methodology, a way of thinking that can be applied to all problems and all aspects of ones life.
Author: Paul Bertner
Paul is internationally known for his macro portraits of reptiles, amphibians and insects. His photos have found a global audience in the BBC, the Discovery channel, Scientific American and other news outlets. His residency at Sani Lodge means travelers with Destination Ecuador will have unique and exclusive opportunities to work with Paul on their photography skills.