by John Bendon, IUCN/SSC Iguana Specialist Group.
There is an area behind the Charles Darwin Research Station that has a small dock, a walkway, a dirt road with bushes on both sides, and a boat-ramp. Here, amongst people coming and going all day, lives a colony of marine iguanas, who are living their lives alongside of humans. Comprised of single males with several females in tow, I spent many hours there observing the animals and their behaviour, and made delightful discoveries about their habits. There could be anything from seven to thirteen large males there at any time. November is a very good month to observe as the weather is fairly cool, comparatively. Their winter reminded me of May in England. The males at this time are very colourful as it is mating season. The colours vary from island to island and region to region. Here, the colours vary from red and black to red, green and black, some with stripes.
It was easy moving around in the colony as I am mostly ignored. We humans become part of their landscape and we appear to be harmless to them. You would think they would jump out of the way when you walk by, but they don’t.
King of the boat ramp © John Bendon
There appears to be a ‘king’, or boss of bosses, who is always in charge when there, strutting around and taking note, pushing forth his importance. If he is not there, another ‘boss’ takes over. When the biggest one returns, the other steps down, perhaps after a short jousting match.
Sisters and brothers © John Bendon
All the underlings in the colony cluster around each other, sometimes piles of them. In the photo below, the one on the left looks like a male to me. The head is flatter on top. I am also not sure if young males and females cluster together like this – I think they do for a while, until they are a bit older. More observation is needed, as different iguana species have different social habits. As an example, Cayman Island iguanas live solitary lives except during mating season, Rhinoceros iguanas (Cyclura cornuta) can live quite happily in crowded colonies, although with plenty of space they become more territorial. Below are the iguanas grouped together lazing around, perhaps having a family conference.
© John Bendon
Green iguanas can also live in crowds. Separate iguana species from the genus Cyclura have been known to breed in captivity and at least one island here, South Plaza, has a hybrid iguana from marine and land iguanas.
I saw some good head-butting displays one day. The iguanas go nose to nose and step backwards and forwards, doing a two step or, as they say here, the pasa-doble. Sometimes it gets very rough, but today was what I would call gentle jousting. The comical thing was this: the two bosses had hordes of females off to one side. It looked obvious which ones were with which male, but I think here on the boat ramp it is slightly more random than that. The funny bit: as the iguanas moved back and forth, doing their latin two-step, all the heads of all the females turned with them. Like watching a tennis match, heads turning one way and then the other.
Late one night, as I took a walk down to the boat ramp. This was a very public area where, during the day, many iguanas clustered; at least four bosses, though not giant-sized, and their harems. I assumed, as on the beach, that they all magically disappeared into wherever they slept at night. As I went down the wide path, trying to spot tails peeping out of the thorny bushes that grew alongside the way, I saw many females, no juveniles, all asleep by the pathway. Just there. Laid out flat, arms by their sides, fast asleep in the open. One was asleep on a lump of concrete, right by the water. Another was asleep in the middle of the walkway.
I know that it doesn’t get cold at night, in fact the temperature was 22°C that night, but to have no fear like that and to just lay out and sleep was strange, so I thought. But there you are, I was constantly being surprised by their habits, as I was by many of the animals on this unique set of islands. Here, some of the birds have changed day into night and wander around the streets and the deserted pathways. I saw pelicans, especially, doing this, and realized that it’s all to do with food. The pelicans wait for the fishermen to bring in their catches early morning, some smaller birds hang around, awake, on the branches of trees; sea lions croak in the distance. All in the dark. This is where the people are and so that must have changed their behaviour.
© John Bendon
Another day when I was there, a colleague came to find me to say he had just seen something unusual and wanted to know what it was. He took me over to the slope of the ramp, and we saw a female iguana looking at some substance on the ground. He said she had been ‘got at’ by a male and afterwards had expelled some fluid from her vent. As we looked, the female began to eat the fluid, which looked like a mixture of blood and mucus. He said he had seen this a couple of times before.
No-one seemed to know what this was and so I sent out an email to the Iguana Specialist Group, an IUCN/SSC organization, and this reached about 80 people, but no one had come across this behaviour. I had one idea about it; female iguanas sometimes make a ‘plug’ after mating, the plug being somewhere inside the vent. This stops other males servicing the female. I thought that maybe this fluid that was consumed provided material to do that in the same way that iguanas eat their own shed skin, which provides nutrients that go towards new skin.
I decided to go a little further along the bay to the next dock, where there was another group of dock iguanas. Maybe the same thing was happening there. The first thing I saw along the road was this very differently-coloured iguana on the paved road that is the long entrance to the field station, I never saw it again, although I spent the rest of the week prior to leaving, looking for it.
What I did see with this lizard was that it had eaten what looked like brown algae, for after a few minutes of watching, the lizard choked up a whole mass of undigested algae, but it was brown and not green; surely a sign that the waters at this point were getting warmer; the beach a mile to the east did not have this problem as I saw green algae all over the rocks. They stand on their haunches, bloat out their throats and shake their heads violently from side to side, and the mass gets literally ‘thrown’ up. In places where there is only brown algae, the animals starve as they cannot digest it.
The dock boss at rest © John Bendon
This dock also has a boss, a handsome character who rests in the middle of the road quite a lot and is a familiar face.
Sometimes these iguanas have to be shooed out of the way, as they seem to have no fear of vehicles.
It began to rain, something that doesn’t bother the iguanas in the least. I wandered around and found several juveniles jumping out of the water and crawling along the boardwalk.
These two dock areas represent a unique opportunity to observe group activity and these iguanas really do behave in a different way than populations living away from the public. Walking among them is almost like walking among pigeons in a town square, they just stare at you and move out of your way. What doesn’t seem to change is their mating behaviour and their general feeding habits. I never see tourists trying to feed them and they never appear to be looking to be fed either, so tourists do not impact their diet as they do in the Bahamas on the beaches, where people feed the local species with anything they have.
The next part of this account will be the diary I made at Academy Bay, charting the daily life of the inhabitants. Their lifestyle is surprisingly organized as you will see.
John is a GCT members from Bath, England. He is an illustrator/author/photographer who has worked with iguanas for over 35 years, on many iguana projects in various locations around the world.
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