Also along Radhanagar beach on Havelock, it looks like it’s been hailing sand. It’s the weirdest thing, millions of sand balls, uniformly of two sizes, covering the greater part of the upper beach.
There is no mystery to what is making these of course. That much is evident as soon as you set foot on the beach scattering hundreds of Sand bubbler crabs (fam. Dotillidae) and smaller hermit crabs (fam. Paguroidea, and hence the different ball sizes). The balls are the neatly packaged refuse discarded during their feeding excursions.
“The sand bubbler crab eats the thin coating of edible particles on sand grains. Sand grains are scraped up with the downward pointing pincers and brought to the mouthparts that sift out these tiny particles. The shifted sand is then discarded in a little ball. As it processes sand, a little path is scraped out from the burrow entrance. Little balls of sifted sand is piled up on either side of this path.” (Wildfactsheets).
More wondrous even than that is the complexity of patterns that these form; a maze of profoundly intricate sculpting of epic proportions; a labyrinth to foil all the cunning of Theseus. So, how could the lowly crab be responsible? At least, that is how it seems to the casual, awe-filled spectator. The more careful observer can take time to try to understand how.
First, what becomes apparent is that the larger pattern can be reduced into individual repeating units. These are amazing in themselves, whorls and spirals and spokes, coil and corkscrew about each burrow. It is aesthetically beautiful worthy of the greatest artist. The landscape is a beachy masterpiece.
Only through art can we emerge from ourselves and know what another person sees (Marcel Proust)
And underlying each of these art installations is a deeper, phenomenological explanation.
“Sand bubbler crabs Scopimera inflata are central place foragers that spend long periods feeding on nutritionally poor surface sediment adjacent to their burrows. Individuals make series of excursions from their burrows usually moving progressively in clockwise or anticlockwise directions so that they feed on areas of “virgin” sediment on successive forages. … Foraging crabs were under intense predation pressure … Crabs can escape attacks by retreating back into their burrows but normally waited for less than a minute before recommencing to forage …” Optimal and Anti-Predator Foraging in the Sand Bubbler Crab Scopimera inflata (Decapoda: Ocypodidae) Evans, S.M. et al.. Journal of Crustacean Biology 30(2):194-199. 2010 doi: 10.1651/09-3160.1
This repetitive behaviour is the crab applying a set of conditions on its foraging along the lines of,
01 go beyond where I foraged before (if this is the first time, then it will be the closest point to my burrow)
02 forage in an arc, keeping the same distance from the burrow
03 return to burrow
04 repeat lines 01-03
And that’s how central-place foraging works, by iterating over such an algorithm. The dilemma arises when it’s costing more energy to travel away from the central-place (e.g., burrow, nest, waterhole) than can be gained from the food when you get there. In the meantime, the traces of each excursion that get left behind (e.g., sand balls, flight paths, trampled grass) accumulate into unfathomably complex patterns, seemingly unrelated to the individual events that made them.
You’ll have heard the expression, “a cake is more than just its ingredients”, often in description of a phenomenon called emergence (although you might not have realised it), where combining elements leads to an additional effect, or emergent property. Emergence, particularly in the natural sciences, has been a hot topic for the last decade or two, but Aristotle was the first to write on the general subject in his Metaphysics, two thousand years ago, “The whole is different from the sum of its parts”, the philosophy inherent in holism.
An emergent property is formally defined in one of three ways (compare each against the figure, below):
i. A property of an integrated system arising at a level of organization higher than that of the components of that system, and that may be explained by the occurrence of those components.
ii. A property of an integrated system arising at a level of organization higher than that of the components of that system, that we fail to predict, infer or extrapolate from study of the components of that system, but subsequently may be explained by the occurrence of those components.
iii. A property of an integrated system arising at a level of organization higher than that of the components of that system, that we fail to predict, infer or extrapolate from study of the components of that system, and remains unexplainable by the occurrence of those components.
These emergent properties then give rise to two distinct types of emergence:
1. Syntactic emergence. The emergence of structure and form, (e.g., spider webbuilding, and the double helix of Watson & Crick 1953).
2. Semantic emergence. The emergence of “meaning” in biological structures, (e.g., optimal self-replicating genetic code). The perception and storage of sensory cues (e.g., of the presence of prey), is also derived from semantic emergence.
A well-known example, and widely used tool in the study of emergence, is John Conway’s “Game of Life” program which allows you to look at pattern formation (self-organization) in a cellular automaton based on simple, scale-dependent rules propagate. Researchers have found that forms of this emergence equate to emergent property definitions i. and ii., “some global properties of cellular automata can be described by entropies and Lyaponov exponents”, and definition iii. where “behaviour is formally undecidable”. Importantly, it has been shown that self-organization is not purely a simulation artefact by testing models using stochastic parameters.
Much of the natural world can be explained in the same reductionist way. Famously, the very shells that hermit crabs adopt are products of a set of these variables, in this case the spirals that they generate conform to a mathematical progression that we know of as the Fibonacci series, yet the vast array of shells that we find in nature vary only in a few tweaks to the shell’s rate of growth and it’s generating curve.
And of course this is exactly what we’re seeing in the sand patterns on Radhanagar beach: a nested self-organisation akin to fractals, arising from combining simple rules and parts. Plus the industry of the humble crab.
If you would like read further about central-place foraging, emergence and spatial ecology please get yourself a copy of PIOSPHERES: water and the consequences of spatially constrained plant-herbivore interactions.
There is another piece of art involving parts and rules that is (remotely) relevant, and not just in name:
Naming of Parts by Henry Reed (1914 – 1986)
To-day we have naming of parts. Yesterday,
We had daily cleaning. And to-morrow morning,
We shall have what to do after firing. But to-day,
To-day we have naming of parts. Japonica
Glistens like coral in all of the neighboring gardens,
And to-day we have naming of parts.
This is the lower sling swivel. And this
Is the upper sling swivel, whose use you will see,
When you are given your slings. And this is the piling swivel,
Which in your case you have not got. The branches
Hold in the gardens their silent, eloquent gestures,
Which in our case we have not got.
This is the safety-catch, which is always released
With an easy flick of the thumb. And please do not let me
See anyone using his finger. You can do it quite easy
If you have any strength in your thumb. The blossoms
Are fragile and motionless, never letting anyone see
Any of them using their finger.
And this you can see is the bolt. The purpose of this
Is to open the breech, as you see. We can slide it
Rapidly backwards and forwards: we call this
Easing the spring. And rapidly backwards and forwards
The early bees are assaulting and fumbling the flowers:
They call it easing the Spring.
They call it easing the Spring: it is perfectly easy
If you have any strength in your thumb: like the bolt,
And the breech, and the cocking-piece, and the point of balance,
Which in our case we have not got; and the almond-blossom
Silent in all of the gardens and the bees going backwards and forwards,
For to-day we have naming of parts.
Other posts in this series: Passages from India.