The Musurana (Mussurana bicolor)

Disarano arrived with us only recently and, if I’m being completely honest, I had absolutely no idea what species I was about to meet.

Based on the description we’d been given, I was expecting a North American ring-necked snake.

What arrived was... decidedly not.

Disarano is an odd-looking little chap. At around eighteen inches long, he’s incredibly slender, dressed in slate grey to almost black across the back, with deep red flanks fading into a faint collar around the back of his neck. Then there’s his belly... and I’m still not entirely sure how to describe it. If snakes entered beauty contests, he’d certainly fancy his chances.

Unfortunately, appearances weren’t the whole story.

He arrived dehydrated, carrying patches of retained shed, painfully thin and with noticeable weakness through the lower third of his body. His enclosure was in an even sorrier state than he was. A strange, bone-dry substrate, a single hide and a water bowl. That was the sum total of his world.

We were told he was around three years old and hadn’t eaten for more than three months.

So, as seems to be becoming something of a tradition around here, we were off to another flying start.

The initial examination was exactly that—an examination. Penny will probably tell you there was a very obvious look of curiosity on my face. I’d never worked with this species before. I knew next to nothing about it, let alone about the individual sitting in front of me.

And, strangely enough, that was the exciting part.

Most of the animals that come through our door have decades of husbandry information behind them. Royal pythons, bearded dragons, leopard geckos—you can fill a bookshelf with what’s been written about them. This little snake was different. Every observation suddenly mattered. Every behaviour was another tiny piece of a puzzle that, as I was about to discover, very few people have ever attempted to put together.

So, I did what I always do when I meet a species for the first time.

I started reading.

Within minutes, I’d discovered that musuranas are among South America’s most fascinating snakes. Ten minutes later, I’d realised almost nobody seems to have studied them in any meaningful detail. Two hours after that, I was buried in museum records, taxonomic revisions and obscure natural-history notes, wondering why a snake famous for hunting venomous snakes had apparently decided that the occasional frog, the odd bat—and sometimes a very confused opossum—wasn’t off the menu either.

That was the moment I realised this wasn’t going to be a normal care guide.

It was going to be an investigation.

Following the Evidence

The first thing I discovered was that even the snake's name wasn't as straightforward as I'd hoped.

Most older publications refer to the species as Clelia bicolor. More recent taxonomic work, using both morphological and molecular evidence, has transferred it into the genus Mussurana, making its currently accepted scientific name Mussurana bicolor. Fortunately for me—and unfortunately for anyone trying to search the literature—they're referring to the same animal.

That small discovery turned out to be a sign of things to come.

The deeper I searched, the more obvious it became that Mussurana bicolor isn't one of those species with decades of ecological research behind it. There are no comprehensive field studies documenting its daily routine. No radio-tracking studies mapping its movements across the landscape. No carefully measured thermal preferences. No papers explaining how often it climbs, where it shelters, how large its home range might be or even how long individuals typically live in the wild.

For a snake found across several South American countries, that's quite remarkable.

What does exist is a collection of observations. Museum specimens. Taxonomic revisions. Dietary notes. Locality records. Individual feeding observations. Small pieces of information scattered throughout the scientific literature, each telling a tiny part of the story.

Put together carefully, those fragments begin to paint a picture.

Home

Mussurana bicolor is known from Argentina, Paraguay, Bolivia, Brazil and Peru. Rather than occupying a single habitat type, it appears to favour the seasonally changing landscapes of south-central South America, particularly regions such as the Pantanal and the Gran Chaco.

These are environments defined by contrast.

Parts of the landscape can be dry for months before becoming flooded during the rainy season. Grasslands give way to woodland. Dry scrub borders wetlands. Forest edges merge into open savanna. It is a landscape that rewards flexibility, and the musurana appears perfectly at home within it.

Most published observations describe snakes active on the ground. Individuals have been encountered moving across open grassland, hunting within wetlands and travelling close to permanent water. At present there is little evidence suggesting that M. bicolor spends much time above ground, although equally there is no evidence proving that it doesn't. As with so many aspects of this species, nobody seems to have looked closely enough to know.

A Creature of the Night

One of the clearer patterns to emerge from the available literature is that Mussurana bicolor appears to be primarily nocturnal.

Almost every documented behavioural observation has occurred after dark. Individuals have been recorded actively feeding during the evening, with observations extending into the night. Whether this reflects genuine nocturnality or simply the times at which people happen to encounter the snake remains uncertain, but the evidence currently available points firmly towards a species whose world truly comes alive after sunset.

What Does It Eat?

This was where the story became considerably more interesting.

Mention musuranas to most reptile keepers and you'll usually hear the same sentence:

"They eat snakes."

They're absolutely right.

But they're also only telling part of the story.

Direct observations confirm that Mussurana bicolor actively preys upon other snakes. One particularly well documented account describes an individual capturing and constricting the water snake Helicops leopardinus before swallowing it head-first over the course of nearly forty minutes.

If that were the only record available, we'd probably describe the species simply as an ophiophagous specialist and move on.

Except that isn't the whole story.

The published literature also contains repeated records of frog predation. In fact, one dietary review identified amphibians as the most frequently recorded prey items within the material examined. Lizards also appear in dietary summaries, while mammals are represented by at least one documented bat predation event.

Suddenly the musurana looks rather different.

Instead of being a snake that occasionally eats something else, the evidence currently suggests a capable generalist predator with a particular aptitude for hunting snakes whenever the opportunity presents itself.

Exactly how often each prey type is taken remains unknown.

Built for Predation

The feeding observations themselves reveal something equally interesting.

Whether subduing frogs or snakes, Mussurana bicolor has been observed using constriction before swallowing prey head-first. It is an elegant, methodical predator rather than an explosive one.

Like all snakes, it relies heavily upon chemical information gathered by the tongue and Jacobson's organ to interpret its surroundings. Beyond that, however, surprisingly little has been published. The popular image of musuranas relentlessly tracking venomous snakes across South America is certainly an appealing one, but careful science requires us to separate what has been demonstrated from what merely seems plausible.

At present, remarkably few behavioural studies have attempted to answer those questions.

More Questions Than Answers

And perhaps that's the most fascinating thing about Mussurana bicolor.

After several hours reading the available literature, I realised I'd learnt plenty about where the species occurs and what it occasionally eats.

What I still didn't know was arguably far more important.

How warm does it choose to be?

Does it bask?

How far does it travel each night?

Does it return to the same refuges?

Does it actively follow snake scent trails?

Does it specialise on certain prey in different parts of its range?

Does it spend time climbing that simply hasn't been documented?

Nobody seems to know.

For some species, these would be surprising omissions.

For Mussurana bicolor, they're simply opportunities waiting for someone to start paying attention.

Fortunately for me...

One had just moved into the spare room.

Building a Hypothesis

Before I could observe Disarano, I had to build him a home.

Normally that's the easy part. With most reptiles there's enough published information to build an enclosure with a fair degree of confidence. You know the temperatures, the lighting, the humidity and the general environmental requirements long before the animal arrives.

This time was different.

The literature had given me enough information to make educated decisions, but not enough to be certain any of them were correct. So rather than trying to recreate a care sheet that doesn't really exist, I tried to recreate possibilities.

The published records suggested a terrestrial colubroid from the seasonally changing landscapes of South America. Activity records pointed towards a predominantly nocturnal lifestyle, so a basking area of 28–32°C combined with low-level UVB within Ferguson Zone 1 seemed like a sensible starting point rather than an unquestionable requirement. If the species was naturally active after dark, it seemed reasonable that any UV exposure in the wild would probably be incidental rather than prolonged.

The habitats occupied by Mussurana bicolor appear to range from dry savanna and Chaco scrub to seasonally flooded wetlands. Rather than trying to choose one or the other, I decided to build both. A thermal gradient was paired with a humidity gradient, allowing Disarano to make the decision instead of me.

Substrate followed exactly the same philosophy.

There is currently very little published information describing shelter selection or burrowing behaviour in this species, but many terrestrial snakes exploit loose soils, leaf litter and underground refuges when given the opportunity. Instead of assuming he would never burrow simply because nobody had documented it, I provided a deep, well-draining substrate capable of retaining moisture below the surface while remaining relatively dry above it.

The enclosure gradually filled itself with possibilities rather than certainties.

Multiple hides.

A generously sized water bowl.

Leaf litter.

Dried grasses.

Rockwork.

Artificial burrows.

Climbing opportunities.

Areas of open ground.

Shaded retreats.

None of them were there because I knew he would use them.

They were there because I wanted to discover whether he would.

That, after all, was the whole point of this exercise.

The enclosure wasn't built to prove I was right.

It was built to give Disarano every opportunity to prove me wrong.

First Observations

It didn't take long before Disarano made his first significant behavioural decision.

He disappeared.

To be fair, I probably would have done the same.

Having just been transported into an unfamiliar environment after what had clearly been a less-than-ideal few months, immediately seeking shelter seemed entirely sensible. I resisted the temptation to start lifting hides or checking where he'd gone. The whole point was to observe his choices, not influence them.

So, I sat on the opposite side of the room and waited.

A few minutes later, a cautious little head appeared.

From that point on, curiosity seemed to outweigh caution.

His enclosure wasn't enormous—measuring 24 × 18 × 18 inches—but it wasn't intended to be. At around eighteen inches in length, it allowed him to fully stretch out while avoiding the feeling of being marooned in a vast empty space. More importantly, every part of the enclosure was connected by cover. If he wanted to move, he could do so while remaining concealed for much of the journey.

And move he did.

Over the next few minutes, he systematically investigated almost every inch of his new surroundings.

Rapid tongue flicks accompanied almost every movement as he sampled the environment chemically. Every hide was inspected. Every corner investigated. He pushed beneath the leaf litter, tested the substrate by digging, explored the artificial burrows, climbed over the rockwork and made use of the available branches before continuing on to the next feature.

There didn't appear to be any obvious pattern to the route he chose. Rather than travelling directly from one refuge to another, he seemed intent on gathering information. Every new texture, every scent and every potential refuge appeared worthy of inspection.

Then, just as suddenly as he'd appeared...

He vanished.

By this point it was getting late, and I decided to do something that, in my opinion, is often the hardest part of behavioural observation.

Nothing.

No further disturbance.

No checking under hides.

No late-night "just one quick look."

I simply switched the lights off, left him to settle into his new home and called it a night myself.

Because if this article was going to become an investigation rather than just another care guide, the first rule was simple:

The animal had to be allowed to make the first move.

The First Feed

The following morning, Disarano had vanished.

Judging by the state of the enclosure, he'd had a productive night.

The substrate had somehow found its way into the water bowl, fresh burrows had appeared where there hadn't been any the previous evening and the carefully arranged leaves and dried grasses now had that unmistakable "someone's been stomping around in here" look that reptile keepers know all too well.

Unable to resist any longer, I quietly lifted one of the hides.

There he was.

Looking every bit as innocent as a snake can while sitting in the middle of what looked suspiciously like the aftermath of an all-night renovation project.

He'd also left me two presents.

One was a healthy pile of faeces.

The other was a perfect, one-piece shed.

Now that caught my attention.

The shed had almost escaped my notice because he'd somehow managed to weave it around almost every blade of dried grass in the enclosure. It looked remarkably similar to the way corn snakes often thread their sheds through branches and vegetation, leaving me wondering whether this was simply coincidence or a deliberate use of the available structure to help remove the old skin.

An empty bowel.

A fresh shed.

For me, that usually means one thing.

Time to eat.

I defrosted a small mouse weighing approximately ten grams, quietly cursing the fact that I didn't have a bat, an opossum or a conveniently sized snake available for comparison.

It was time to find out whether the literature reflected reality.

Thankfully, it did.

The strike was clean, immediate and surprisingly emphatic.

What surprised me wasn't the speed—plenty of snakes strike quickly—but the intensity. There was a level of alertness and commitment that immediately stood out, even when compared with many of the colubrids I've worked with previously.

As soon as he made contact, he threw three tight coils around the mouse before applying what appeared to be a firm, but relatively brief, constriction.

Then...

He let go.

For a split second I genuinely thought he'd lost interest.

Instead of immediately beginning to swallow, he started tongue-flicking rapidly around the prey item. My hand almost reached for the mouse to offer it again before I stopped myself.

Fortunately, I did.

A few moments later, he calmly relocated the head and began swallowing in the way snakes have perfected over millions of years—with remarkable efficiency and considerably more patience than the person watching him.

It was my first reminder that unfamiliar species often behave in unfamiliar ways.

Sometimes the hardest part of behavioural observation isn't watching the animal.

It's stopping yourself from interrupting it.

Two Months On

Two months later, Disarano's enclosure remains largely unchanged.

The thermal gradient is still there. The humidity gradient remains. Low-level UVB is provided throughout the day and, as far as possible, I continue to offer a varied diet that reflects at least some of the prey items reported in the literature.

To my delight, frog legs have become something of a delicacy.

Day-old quail aren't far behind.

Rodents are still accepted readily, but providing dietary variety has become just as interesting for me as it has for him.

Perhaps more importantly, his feeding behaviour has remained remarkably consistent.

Every meal follows almost exactly the same sequence.

A rapid, accurate strike.

Several tight coils.

A firm but relatively brief constriction.

Release.

A period of rapid tongue-flicking around the prey item.

Relocation of the head.

Then, finally, swallowing.

Having now watched this sequence repeated on numerous occasions, it no longer feels like an isolated observation. Whether this represents a characteristic feeding strategy of Mussurana bicolor or simply the habits of one individual remains impossible to say, but the consistency has certainly caught my attention.

Outside feeding, another pattern has emerged.

Despite providing branches, elevated hides and several opportunities to climb, Disarano spends remarkably little time off the ground. Almost all of his activity occurs at, or just below, ground level. He regularly moves beneath the leaf litter, makes frequent use of the artificial burrows and often disappears into the deeper substrate for extended periods.

If I were forced to describe his lifestyle in a single sentence, I wouldn't call him an arboreal snake.

I probably wouldn't even describe him as simply terrestrial.

"Almost fossorial" feels far closer to the truth.

Activity is equally predictable.

It is exceptionally rare to see him moving while the enclosure is brightly lit. Most evenings he waits patiently beneath cover until the lights begin to dim and temperatures start to fall. Only then does he emerge to explore, investigate and hunt.

Whether this reflects a true circadian rhythm or simply a response to captive conditions remains unknown.

What is clear is that, given the choice, Disarano consistently chooses darkness over daylight.

And, perhaps more importantly, every one of those choices has been his—not mine.

That, more than anything else, has been the greatest lesson this little snake has taught me.

Sometimes the most valuable thing a keeper can do isn't provide the "perfect" enclosure.

It's provide enough opportunities for the animal to tell you what perfect looks like.

When Disarano arrived, I thought I was rescuing a snake. Looking back, he probably rescued something in me instead.

Over the last couple of months he has reminded me that the best husbandry doesn't begin with confidence—it begins with curiosity.

We spend far too much time in this hobby trying to prove we're right. Nature has never cared whether we're right. She simply waits for us to pay attention.

Perhaps that's the greatest lesson this little South American snake has taught me.

Every enclosure is an experiment.

Every behaviour is data.

Every animal still has something left to teach us and Disarano’s is still doing that day by day.

Everything you've just read about Disarano's behaviour describes one musurana. It should not be assumed that every Mussurana bicolor will behave in the same way. The purpose of these observations is not to define the species, but to contribute another small piece to a natural history that is still being written.