If you’ve spent enough time herping, you’ve probably noticed something strange once temperatures start dropping, the reptiles seem to disappear. That favorite rock pile that held three snakes all summer? Empty. The basking log that was crawling with lizards in July? Dead quiet. It’s not luck running out. It’s biology. What you’re seeing is brumation in action.

Brumation is one of the most misunderstood natural cycles in the reptile world. A lot of people casually call it “reptile hibernation,” but that’s not entirely accurate. Let’s break it down properly.

What Is Brumation?

Brumation is a seasonal period of dormancy in reptiles triggered by cooler temperatures and shorter daylight hours. Unlike mammals, reptiles are ectothermic (cold-blooded), meaning they rely on external heat sources to regulate their body temperature.

When the environment cools down:

• Their metabolism slows dramatically
• Digestion becomes inefficient
• Movement becomes minimal
• Energy conservation becomes critical

Instead of staying active and risking starvation, reptiles retreat into burrows, rock crevices, root systems, or underground dens and enter a low-energy state.

It’s not a deep, continuous sleep like mammalian hibernation. During brumation, reptiles may occasionally wake up to drink water or shift positions, but they won’t hunt or actively move around.

Why Do Reptiles Brumate?

When temperatures drop:

• Insects disappear
• Amphibian activity slows
• Prey becomes scarce
• Basking opportunities decrease

For species like the Common Garter Snake or the Eastern Box Turtle, staying active through winter would burn more calories than they could possibly replace. Brumation allows them to “pause” their energy expenditure until conditions improve.

This strategy is especially important in temperate climates where winter is harsh and long.

What Happens Inside the Body?

Brumation isn’t just behavioral, it’s physiological.

When a reptile enters brumation:

• Heart rate drops significantly
• Breathing slows
• Metabolic rate decreases
• Hormone levels shift
• Immune function adjusts

Interestingly, brumation also plays a role in reproduction. Many snake species require a cooling period to stimulate proper breeding cycles in the spring. In captive breeding programs, controlled brumation is often necessary for successful pairing. For example, species like the Ball Python may not reproduce reliably without a seasonal temperature drop.

Where Do Reptiles Go?

This is where things get fascinating, especially for those who love field herping.

Many species use communal dens called hibernacula. These are underground chambers that stay below the frost line but above freezing.

Some dens can hold:

• Dozens of snakes
• Hundreds of snakes
• Even thousands in extreme cases

A famous example is the massive snake dens in Manitoba, where Red-sided Garter Snake gather in enormous numbers before dispersing in spring. Seeing one of these emergence events is something every serious herper should experience at least once. It completely changes how you think about seasonal reptile behavior.

When Does Brumation Start?

It depends on:

• Geographic location
• Species
• Elevation
• Annual weather patterns

In northern states, brumation may begin as early as September or October. In milder southern climates, some reptiles may only slow down briefly, or not brumate at all. Desert species may even brumate in response to extreme heat and drought instead of cold.

Brumation is a reminder that reptiles operate on a completely different biological rhythm than mammals. They don’t fight the seasons, they adapt to them.