EPOW Ecology Picture of the Week -- The Games That Pythons Play

Explanation: Watch your step! That's no rock. It's an Indian python, also called an Indian rock python.

This week we are in Keoladeo Ghana National Park, more popularly called Bharatpur Bird Sanctuary, in central India on the Deccan Plateau. Indian pythons thrive here in the arid environment. These massive snakes -- the ones in this week's photos are about 4 m (12 feet) long -- are generally harmless, actually, but they feed on all manner of small and large birds, mammals, amphibians, and other reptiles. Once, from elephant-back in the grasslands of Dudhwa National Park in northern India, I observed a huge Indian python swallowing a hog deer! Other reported prey includes gazelle, jackal, porcupine, rats, and even a leopard!

Indian pythons -- subspecies Python molurus molurus -- are the most common type of python in the Indian subcontinent. This subspecies is told by the lack of an extra suborbital scale (this feature can be seen in this week's main photo). Occurring in northern West Bengal in northeast India, and in Myanmar eastward, is the subspecies Python molurus bivitatus, or the Burmese python, which is found in more aquatic environments such as marshlands and tal (lake) areas. The Burmese python subspecies has an extra suborbital scale which is wider than tall. The reticulated python, Python reticulatus, is told from both subspecies of Python molurus by the present of pits on the 3rd and 4th lip shields, and a greater number (297) of body scales.

So ... what are the "games that pythons play?"

Take a look at the following photos I snapped in Keoladeo Ghana National Park. It shows a colony of Indian pythons -- at least 6 in all, actually -- inhabiting a large burrow complex that was initially dug by an Indian porcupine. (Click on images for larger versions.)

Two huge pythons snuggling in the warm sunshine
near the burrow entrance.

Like other boas, pythons kill their prey by
constriction, and can swallow prey far larger
than their own body diameter.

Click for the full-frame photo that shows one of
several entrances to the burrow system on the
bottom right, partly covered by dry grass.

Pythons often take over other species' burrows; this behavior constitutes an important "key ecological function" of wildlife ... the primary burrow excavator (in this case, the porcupine) provides an essential habitat element, the burrow, for obligate secondary burrow users (the pythons).

The burrow system is extensive, with several entrances
and likely a deep and complex tunnel system. Porcupines
inhabit the burrows, but I suspect that perhaps jackals might
also have had a hand (paw) into digging some of this, as well.

In this case, the burrow apparently was still occupied by the porcupine! So why haven't the pythons eaten their host?

The answer is not obvious. Here are two possibilities.

(1) Perhaps the relationship between porcupine and snake is a one-sided commensal relationship where one member (the snake) benefits and the other member (the porcupine) receives neither harm nor benefit. (2) Or perhaps the relationship is more mutualistic, where the porcupine is protected from other predators by the presence of the snakes, and is thus allowed to continue its burrowing activity that also benefits the snakes. Either of these scenarios is possible for the stable "economy" to develop and be maintained as what has been called in the ecological literature an evolutionarily stable strategy (ESS).

So let's conjure up a bit of game theory and formalize these scenarios a tad more.

A game is a depiction of whether and how each player might benefit or lose from some behavior. In the following tables, the two players are the porcupine and the python. Each can either receive some benefit (+), remain neutral (0), suffer a detriment (-) by their interactions. I have assigned an arbitrary number of game points (100) to show outcomes.

Take a look at this first game, which corresponds to the first scenario above, in which the python benefits (+) but the porcupine receives neither help nor harm (0):

Game A
Python

+ 0 -

Porcupine +

0 100

-

The second scenario, in which both species benefit, can be depicted by this game layout:

Game B
Python

+ 0 -

Porcupine + 100

0

-

And to generalize this relationship:

Game C
Species 2

+ 0 -

Species 1 + a b c

0 d e f

- g h i

Now, you see that evolutionarily stable strategies might arise when there is mutualistic advantage to both species (a) or at least when there is a commensal relationship with advantage given to one species (b, d).

Further, there may be neutral selection for outcomes with no interaction, that is, neither advantage or disadvantage, to both species (e). Neutral selection means that there would be no adaptive advantage or disadvantage of the situation to either species, so no "push" to evolve behaviors favoring or avoiding such a situation. (Such is likely not the case with our pythons and porcupine.)

Other outcomes (c, g) denote harm to one species and benefit to the other, such as occurs with predation or parasitism. To attain some stability in such situations would require some checks and balances so the predator doesn't consume all the prey or so that the parasite does not kill all its hosts.

And the other remaining outcomes pertain to unilateral disadvantage (f, h) or mutual disadvantage (i), neither situation of which would evolve stable strategies and wouldn't last for long.

So ... what is going on in the snake pit in India? Which game are pythons playing?

EPOW - Ecology Picture of the Week