The Secret Sex Lives of Snakes
How Australian Snakes Reproduce and Why It Matters in Urban Areas
By Chris Williams, Urban Reptile Removal
When people think about snakes, reproduction is rarely the first thing that comes to mind. Yet every year across Australia, snakes are quietly mating, laying eggs, or giving birth — often right under our noses.
Understanding how snakes reproduce helps explain seasonal behaviour, why certain times of year bring more sightings, and why some snakes turn up in unexpected places like gardens, sheds, roof spaces and retaining walls.
Australian snakes have some of the most fascinating reproductive strategies in the animal world, and they are far more varied than most people realise.
Not All Snakes Reproduce the Same Way
One common assumption is that all snakes lay eggs. In reality, Australian snakes use two main reproductive strategies:
Egg-laying (oviparity)
Live-bearing (viviparity or ovoviviparity)
Many familiar species, including pythons and tree snakes, lay eggs. Others, such as red-bellied black snakes, tiger snakes and brown snakes, give birth to live young.
Both methods are successful, and neither is “more advanced” than the other. Each strategy has evolved because it works well in certain environments.
Why Some Snakes Lay Eggs
Egg-laying snakes usually deposit their eggs in warm, sheltered locations where temperature and moisture are relatively stable. These sites might include:
Rotting vegetation
Burrows made by other animals
Loose soil under logs or rocks
Warm, protected areas in urban environments
Snake eggs are covered in leathery shells, not hard shells like bird eggs. These shells allow oxygen, carbon dioxide and water vapour to pass through. This means the surrounding soil moisture plays a major role in whether embryos survive.
If the soil becomes too dry early in development, the embryos may die. If drying occurs later, some embryos can hatch early — emerging smaller but with extra yolk reserves to help them survive.
This flexibility gives young snakes a better chance in unpredictable conditions.
Communal Nesting: Strength in Numbers
In some species, multiple females may lay their eggs in the same nesting site. These communal nests can contain dozens or even hundreds of eggs.
This behaviour isn’t social bonding — it’s practical. Good nesting sites are rare, and once one is found, many females may use it year after year.
Communal nesting is occasionally discovered during construction or landscaping, which is why snake eggs sometimes appear suddenly in disturbed soil.
Pythons: The Exception to the Rule
Most egg-laying snakes leave their eggs after laying them. Pythons are different.
Female pythons remain with their eggs throughout the entire incubation period. They coil tightly around the clutch, protecting it from predators and helping regulate temperature and humidity.
In cooler climates, female pythons can even produce small amounts of body heat by shivering their muscles — an unusual trait for reptiles. This helps keep the eggs at the right temperature for development.
This intense parental investment comes at a cost. Female pythons often lose significant body weight during brooding and may take years to recover before breeding again.
Live-Bearing Snakes: Keeping the Young Inside
Live-bearing snakes take a different approach. Instead of laying eggs, the embryos develop inside the female’s body until birth.
This strategy is especially common in cooler climates, where external egg incubation would be risky. By retaining developing young internally, the female can regulate temperature by basking or sheltering as needed.
In Australia, live-bearing has evolved multiple times across different snake groups, including venomous elapids such as:
Eastern brown snakes
Tiger snakes
Mulga snakes
Red-bellied black snakes
This method allows young to be born fully formed and ready to move immediately.
Timing Is Everything
Snake reproduction is closely tied to temperature.
Because snakes are ectothermic, their reproductive cycles depend on seasonal warmth. In temperate regions like southern and eastern Australia:
Mating usually occurs in spring
Eggs are laid in late spring or early summer
Live young are born in late summer or autumn
In warmer northern regions, breeding seasons may be longer or less predictable.
This seasonal pattern explains why snake activity often increases during spring and summer — it’s the time when snakes are most active, mobile and visible.
Why Females Do All the Parenting
In snakes, all parental care is provided by females.
This isn’t because males are incapable — it’s because mating typically occurs weeks or months before egg-laying or birth. By the time the eggs are laid or young are developing, the male is long gone.
Natural selection hasn’t favoured male parental behaviour simply because males are never present at the critical time.
Egg-Laying vs Live-Bearing: Neither Is Better
It’s tempting to think of live-bearing as “more advanced,” but evolution doesn’t work that way.
Egg-laying snakes often:
Recover faster after reproduction
Breed more frequently
Produce larger clutches
Live-bearing snakes often:
Protect developing young from cold conditions
Give birth to more developed offspring
Succeed in cooler or unpredictable environments
Both strategies are highly effective in the right conditions.
Why This Matters in Urban Snake Encounters
Understanding snake reproduction helps explain several common urban scenarios:
Increased sightings in spring and summer
Pregnant females basking more often
Snakes using gardens, compost, mulch and retaining walls
Occasional discovery of eggs during landscaping or building work
A pregnant or egg-laying snake is not aggressive — it is simply trying to regulate temperature and avoid disturbance.
This is why calm, professional snake removal is essential during breeding seasons.
A Remarkable Historical Footnote
One of the earliest scientific observations of live-bearing in Australian snakes came from a young naturalist visiting Hobart in 1836. After killing a snake he believed to be harmless, a small live snake emerged from its body.
The observer was Charles Darwin.
Had events unfolded differently, the history of biology itself might have changed.
Final Thoughts
Australian snakes have evolved an extraordinary range of reproductive strategies, each finely tuned to climate, habitat and survival.
Whether laying eggs in hidden nests or giving birth to live young, snakes reproduce quietly, efficiently and largely out of sight — even in the middle of our cities and suburbs.
Understanding this biology helps reduce fear, explains seasonal patterns, and reminds us that snakes are not intruders, but long-term residents adapting to a changing landscape.
If you encounter a snake during breeding season, the safest approach is always to give it space and contact a licensed professional.
Source note:
The information in this article is drawn from Australian Snakes: A Natural History by Professor Rick Shine.
