The first observation of the mass emergence of Panama's green iguanas reveals them to be surprisingly sociable reptiles.
Words: Gordon Burghardt
Images: Christian Ziegler
Welcome to the world
A tiny, bright-green head popped out of a hole in the ground and looked around, flicking its tongue onto almost everything it could reach before disappearing below ground. A few seconds later, another head emerged at a hole nearby, then another at a different hole again. This was the moment I'd waited weeks to see - the hatching of green iguanas in Panama.
Each day in early May, I ate breakfast at sunrise, grabbed a flask of coffee and headed down almost 200 steps from my hilltop station to Lake Gatun. I threw supplies into a small boat and motored out to the tiny islet of Slothia where I entered a small wooden hide facing a clearing. And there I stayed till sunset.
I knew that many dozens of adult female green iguanas had congregated months earlier in this clearing to lay eggs in nest burrows before swimming back to the mainland. But no one had ever seen nest emergence take place. Not before this.
Social interaction
I wondered when the little iguanas would leave their burrow. Finally, one cautiously emerged but rather than running to the safety of the perimeter shrubs, it walked over to another hole, stopped and licked the head of the lizard there and moved on.
Before long, about six iguanas emerged, interacted repeatedly, then gathered in a group and moved off together into the vegetation. My patience had been rewarded in spades - such sociality in a lizard was the last thing I'd expected to see.
When I first saw hatchling iguanas move in groups from the nest site and, a day or two after hatching, join in groups to follow leaders and synchronise their swim from the small islet to the lush main island, claims about the behavioural inferiority of reptiles were fresh in my mind.
Growing together
The sociality of the baby iguanas does not end after they leave the nest site. I found them in groups for many months. They sleep on exposed branches, often close to other hatchlings, if not piled on top of one another. Those sleeping in groups grow faster than more solitary individuals, maybe because they forage together.
Once iguanas are a year old, grouping behaviour is far less apparent. Occasionally, hatchlings are seen with yearlings. This could be how hatchlings learn about resources or it could simply give them access to iguana faeces, which they eat to obtain microbial flora that helps them digest their vegetarian diet.
All our evidence suggests that green iguanas are a complex social species. Reptiles, especially long-lived ones, are much more adept at acquiring, processing and using information than they have been credited for.
Words: Gordon Burghardt
Images: Christian Ziegler
Welcome to the world
A tiny, bright-green head popped out of a hole in the ground and looked around, flicking its tongue onto almost everything it could reach before disappearing below ground. A few seconds later, another head emerged at a hole nearby, then another at a different hole again. This was the moment I'd waited weeks to see - the hatching of green iguanas in Panama.
Each day in early May, I ate breakfast at sunrise, grabbed a flask of coffee and headed down almost 200 steps from my hilltop station to Lake Gatun. I threw supplies into a small boat and motored out to the tiny islet of Slothia where I entered a small wooden hide facing a clearing. And there I stayed till sunset.
I knew that many dozens of adult female green iguanas had congregated months earlier in this clearing to lay eggs in nest burrows before swimming back to the mainland. But no one had ever seen nest emergence take place. Not before this.
Social interaction
I wondered when the little iguanas would leave their burrow. Finally, one cautiously emerged but rather than running to the safety of the perimeter shrubs, it walked over to another hole, stopped and licked the head of the lizard there and moved on.
Before long, about six iguanas emerged, interacted repeatedly, then gathered in a group and moved off together into the vegetation. My patience had been rewarded in spades - such sociality in a lizard was the last thing I'd expected to see.
When I first saw hatchling iguanas move in groups from the nest site and, a day or two after hatching, join in groups to follow leaders and synchronise their swim from the small islet to the lush main island, claims about the behavioural inferiority of reptiles were fresh in my mind.
Growing together
The sociality of the baby iguanas does not end after they leave the nest site. I found them in groups for many months. They sleep on exposed branches, often close to other hatchlings, if not piled on top of one another. Those sleeping in groups grow faster than more solitary individuals, maybe because they forage together.
Once iguanas are a year old, grouping behaviour is far less apparent. Occasionally, hatchlings are seen with yearlings. This could be how hatchlings learn about resources or it could simply give them access to iguana faeces, which they eat to obtain microbial flora that helps them digest their vegetarian diet.
All our evidence suggests that green iguanas are a complex social species. Reptiles, especially long-lived ones, are much more adept at acquiring, processing and using information than they have been credited for.