Iguanas are reptiles found primarily in tropical and subtropical regions. Most of them never have to survive cold winters, but some do. When talking about iguanas, most people think of green iguanas that are native to Central and South America. The truth is, there are over 35 recognized species of iguanas out there, some of which are native to North America. These lizards have to survive cold winters, so how do they do it? Do they hibernate or migrate?
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Do Iguanas Hibernate?
Iguanas do not hibernate. Most iguanas live in tropical climates with warm temperatures all year round. Iguanas native to North America don’t hibernate either. As cold-blooded animals, they might go into brumation when the temperatures drop below certain thresholds. Iguanas living in Florida may also brumate in the cold season, but generally for days rather than months.
Iguanas are a family of lizards, including the green iguana, but also a variety of other iguanas native to the Americas.
Most of them are native to Central and South America and live in warm climate areas. These iguana species never hibernate in the wild – they don’t have to, considering their habitat’s climate. However, some iguanas that don’t hibernate in their native habitat show surprising signs of adaptation and have the capacity to go into dormancy in temperate climates.
For instance, iguana species introduced to Florida slow down their metabolisms and go into a dormant state once the temperatures drop below 45°F.
When the temperatures rise again and warm up the iguanas, they become active again. However, unlike reptiles that are native to temperate climates, most iguanas in Florida can’t survive long periods of low temperatures.
Do Iguanas Migrate?
Iguanas do not migrate to survive cold weather. However, seasonal migration is observed in most female iguanas who leave their home ranges for nesting purposes. Once their eggs are laid, they return to their home territory.
The breeding and seasonal migration patterns of iguanas vary from one species to another. The table below shows the migrating behavior in some of the most common iguana species:
| Iguana species | Native habitat | Nesting migration patterns |
|---|---|---|
| Green iguana | Mexico, Paraguay, Brazil | Long-distance migration |
| Cuban rock iguana | Cuba | Short-distance migration |
| Desert iguana | Mexico, California, Arizona | Short-distance migration |
| Spiny-tailed iguana | Mexico, Nicaragua, Panama | Mid-distance migration |
| Chuckwallas | North America | Non-migratory |
Not all iguanas have similar migration patterns. Green iguanas travel the farthest, sometimes up to two miles away from their home range. Cuban rock and desert iguanas display a short-distance migration pattern, usually remaining within 500 feet from their den or burrow.
Chuckwalla is a species of iguana native to North America. These lizards don’t migrate at all, laying their eggs in a different burrow but within their home range. The juveniles will disperse from this territory once they hatch.
The main difference between chuckwallas and other iguanas is that chuckwalla females incubate the eggs until they hatch. In other iguana species, the females lay the eggs and sometimes protect the nest for a few days before abandoning it.
In all iguana species, the offspring are on their own from the moment they hatch. There is no parental involvement, but adult iguanas are not territorial against juveniles.
Do Iguanas Brumate?
Most iguana species do not brumate in their natural habitat. However, iguanas living in temperate climates – whether native or introduced – brumate in winter. In addition to brumation, some species also estivate if the summers are very hot.
Chuckwallas and desert iguanas are two species that brumate in their native habitat.
Desert iguanas are endemic to Northern Mexico and the United States. Unlike green iguanas, which are mainly arboreal, desert iguanas are terrestrial and capable of withstanding a wide range of temperatures. They are most active at 104°F and take shelter in burrows at night.
This species is diurnal, spending most of the day foraging and basking in the sun. If the temperatures rise above 115°F, the lizards will seek shelter under shrubs or rocks until the air is cool enough for them to come out.
Desert iguanas start to prepare for winter in early fall and generally go into brumation in October. They remain inactive throughout the winter and will come only out again when the temperatures rise in spring.
Like desert iguanas, chuckwallas are diurnal lizards active from dawn to dusk. These lizards have large home ranges (up to four miles) but generally forage close to their burrows.
Chuckwallas are most active from mid-March to late August, although they could estivate in summer if the temperatures get too hot. Estivation is similar to brumation in that the lizards can slow down their heart and breathing rate and remain hidden in burrows for days. Chuckwallas generally brumate from November to March.
By comparison, green and spiny-tailed iguanas go into a dormant state when the temperatures drop below 45°F. However, they can’t survive such cold weather for more than a few days.
How Do Iguanas Survive Winter?
As you have noticed, not all iguanas brumate. Most species live in tropical or subtropical climate areas where the temperatures remain warm all year round.
These iguanas can survive short periods of exposure to cold temperatures, but it is not a true brumation as observed in chuckwallas or desert iguanas. Instead, it is more of a cold shock that “freezes” the lizard’s vital functions for short periods of time.
This behavior has been observed in invasive iguanas living in Florida.
No iguana species is endemic to Florida. However, the state has a thriving population of green iguanas, black spiny-tailed iguanas, and Mexican spiny-tailed iguanas.
All these species have been introduced to Florida accidentally, either with cargo transports from the regions they are native to or the result of exotic pet abandonment.
Florida has mostly mild temperatures throughout the year, a characteristic that allowed these invasive iguana species to reproduce and establish themselves in the area. However, these iguanas are still not adapted to surviving long periods of cold temperatures.
They are arboreal and have no protection from cold weather. Some green iguanas may hide in burrows, but cold weather often catches them dwelling on tree branches. This is an indicator that green iguanas don’t have a seasonal “detector” that enables them to prepare for brumation.
On colder winter days, it is common to observe frozen iguanas falling from the trees. They are not dead (unless the impact with the ground kills them), but are in a state of thermic shock that blocks their vital functions. While these iguanas become active again when the temperature warms up, they can only survive short dormancy periods of a few hours up to a few days.
By comparison, desert iguanas and chuckwallas are adapted to living in temperate climates and can brumate for months. Here’s how they do it.
Terrestrial Behavior
Unlike iguanas native to South America, desert iguanas and chuckwallas are not arboreal creatures. They are land-dwelling lizards that sleep in underground burrows that can be up to six feet deep.
These lizards generally dig the burrows themselves, although they can also take advantage of dens or burrows dug by other animals.
Desert iguanas and chuckwallas use the burrows all year long. These lizards live in deserts. In these areas, nighttime temperatures can often drop under 50°F, even during summer. Sometimes, the nights can get as cold as 25°F. However, burrows are slightly warmer, helping iguanas to prevent constant cold shocks.
When daytime temperatures constantly remain under 50°F (generally between October and November), iguanas retreat to their burrows and go into brumation.
Brumation
Brumation is a state of dormancy similar to hibernation but specific to cold-blooded animals.
Iguanas start to prepare for brumation in the fall. Like most reptiles, they are not concerned about food in this period but spend as much time as possible basking in the sun, warming up their bodies before the winter arrives. Some iguanas may keep foraging while others stop feeding completely during this time.
When the temperatures drop to about 50°F, iguanas retreat to their burrows. However, they could still emerge for short periods, especially on sunny days.
As the temperatures drop under 45°F, they slow down all their body functions, including the heart rate and breathing. They can live under frosted ground for months, and usually reemerge in early spring.
When the weather warms up again, iguanas emerge from their burrows and spend time basking in the sun to warm their bodies. Once they become warm enough, they will start foraging. Iguanas are primarily herbivorous, but they can also feed on insects and other small animals, especially in spring when brumation is over.
Where Do Iguanas Go In The Winter?
Iguanas do not go anywhere in winter. They are territorial animals and do not migrate to warmer climates. Only female and juvenile iguanas travel over longer distances, the former for nesting purposes and the latter to find and establish a territory.
Once they establish a territory, they spend their winters in underground burrows (if living in a temperate climate area).
However, most iguanas live in warm climates where they don’t brumate. Some species may estivate when the temperatures become too hot.
Conclusion
Like all cold-blooded creatures, iguanas do not hibernate. They don’t migrate either, except for the impregnated females that travel to a nesting spot. Iguana species endemic to North America brumate in winter, in a process similar to that of alligators. Tropical iguanas living in Florida or other non-tropical climates can survive cold shocks (and short periods of dormancy), but they are not able to brumate for several months. Thus, if you have pet iguanas, you should keep the terrarium temperatures warm all year round.