Death Adders (Genus Acanthophis) are unique among the family Elapidae in that their appearance and biological habits have evolved in a manner convergent with viperid snakes.

Included is the stout body, ambush predation and use of a caudal lure (Hoser 1995).

In line with many species of snake, these snakes will defecate on a predator if grabbed.

While this fact may be used as a basis to assert that Death Adders store their feces just in case of this eventuality, there is little evidence to support this contention.

If one were to assert that this is the case for Death Adders, then the same could be said for other species of snake as well. In fact, taken to it's logical conclusion, the same could be asserted for any species of snake known to have defecated when caught.

The basis of this article is other factors of note.

In the captive situation snakes are fed, their food is digested and then after a period of time, it is passed out.

As with other animals, including for that matter humans, it becomes possible to estimate the various time frames for the various parts of the digestive process.

While food type and size will determine time it takes to digest food, there are some factors that are more-or-less constant.

For death Adders, food passes from the stomach to lower gut within a few days, or a week at most for larger items.

Within another week it is completely digested and passes as feces.

At least that's the theory.

However for Death Adders the pattern is not so clear.

In line with almost all snakes, increased activity will often precipitate defecation.

The basis of this is thought to be that movement of the body helps the feces pass. This may however only be part of the story.

A Death Adder fed ten days prior and ready to pass feces can be made to do so if it is moved around and allowed to crawl about for an extended period.

One way of doing this is to place the snake in a 'new' cage, meaning it has to move about somewhat. As it moves around, it passes it's feces.

This puts a time line on when a given Death Adder will pass feces or is ready to do so.

In my own collection the following occurred.

In early 2002 I obtained three neonate Death Adders (A. antarcticus), born on 4 February.

All were maintained on an identical feeding regime in terms of being fed at the same time and the same things.

This meant that things such as sloughing and defecation tended to run more-or-less in synchronization as well.

A common comment by keepers of large Acanthophis is that some will store their feces for long periods, including up to some months.

This hypothesis was tested by myself with surprising results.

On 2 March 2003, when the three Death Adders were just under 50 cm, they were fed rodents as food.

Ten days later, one of the three snakes was allowed to crawl about the floor of my office, before being placed in another different cage. The snake defecated.

The other two snakes apparently did not defecate from the same feed for more than another two weeks, indicating that the feces had been stored for at least two weeks.

This observed storage of feces was not noted in smaller and neonate Death Adders, all of whom would eat and pass feces to a relatively well-defined cycle.

Another point noted in terms of snakes in general is that they tend to defecate at the same time that they slough.

This trend is common, but by no means universal. By way of example, a Carpet Python (Morelia macdowelli) and a Diamond Python (Morelia spilota) both sloughed in early 2003 without defecating at the same time (+/- 48 hours at least).

To end June 2003, not one of 15 Adult Death Adders (Acanthophis spp.) in my care in 2002-2003 had ever sloughed without passing feces at the same time (+/- 1 hour).

Hence the basis of the preceding is to establish the following key points:

• Larger Death Adders store feces.
• Small and neonate Death Adders don't tend to store feces.
• Death Adders defecate when they slough.
• Death Adders defecate when moving, but not when they don't move, even if their food is completely digested and ready to be passed.

This all points to a simple question.

Why do large Death Adders store their feces?

Or perhaps I should ask, why do they seem to do this more than other Australian snakes?

The answer I believe lies in the fact that Death Adders do not as a matter of course move about. They are ambush predators.

Observations of Death Adders in captivity and in the wild, indicate that these snakes will remain in the same place for days or even weeks on end.

Snake feces are smelly and can be detected from some distance, even by humans who as a species do not have a particularly good sense of smell.

If a Death Adder were to defecate where they remain, then they'd be leaving themselves vulnerable to predation because the scent released by the feces would direct predators towards them.

In other words, Death Adders will store their feces and only pass it when they are actually mobile and able to leave it a sufficient distance away from where they next rest.

Because other Australian snakes are naturally mobile they will as a matter of course move about and defecate at the same time. Hence there has been no need to evolve the extended ability to store feces as seen in large Death Adders.

The same relative lack of ability to store feces applies to young Death Adders as well. They appear to be more mobile than adults, including in terms of active searching for food as opposed to ambush predation (as seen by myself in both captive and wild specimens) and also tend to feed at far greater frequency, hence a greater rate of food throughput as well.

This also explains why all snakes, and Death Adders in particular tend to defecate when they slough.

In the week or so prior to sloughing, most snakes have clouded eyes for most of this period.

The snakes are effectively blind and vulnerable and so as a matter of course remain hidden and inactive.

This effectively precludes any chance to defecate and avoid drawing attention from potential predators.

However as the snake moves about to slough, the opportunity to defecate a safe distance away from the next resting site arises. Hence the common defecation when sloughing.

This is often the first opportunity for some days that the snake can do so in a manner to avoid detection by predators.

Noting the pre-adaptation by Death Adders to store their feces in the wild and as a result of their 'stay-put' biology, it's not surprising that this storage of feces manifests at it's strongest in captivity.

In captivity (including in my own facility) these snakes tend to be held in small cages. The snakes are literally deprived of the ability to move away from their ambush site to defecate. Hence their tendency to store feces within their bodies as long as possible.

Eventually when it becomes impossible for the snake to store feces any longer, it is passed.

Noting that young Death Adders are similarly confined, one would assume that this ability to store feces would manifest in these snakes as well if they had it.

By and large it doesn’t until these snakes attain a larger size.

In other words mobile snakes have no need to store their feces. Less mobile and immobile species do and their ability to store feces has apparently evolved in direct proportion to their general mobility.

This may also explain why feces storage is sometimes seen in the Carpet/Diamond Pythons (Genus Morelia), which are also to a strong degree ambush predators, but to a lesser extent in more mobile species such as Water Pythons (Genus Katrinus).

Hoser, R. T. 1995. Australia’s Death Adders, Genus Acanthophis. The Reptilian 3(4):7-21 and cover, 3(5):27-34.