Green is the New Dry....

In the sense that since arrival, and many days beforehand, there has been no rain. Palo Verde looks like my Colorado home in the summer: green but on the edge of yellowing out from lack of rain and copious sunshine.

New ~2 year old C. similis.

Still green enough to eat!

This trip is short and simple -- trap iguanas, collect blood, collect parasites, and try out network analysis data collection protocol. Trapping comes first as the animals must be known as individuals to create the network.

I've spotted most of my known animals -- always a fear that they have absconded in my absence and a huge relief to see that was a false worry! However, there are a number of new animals that must be added to the network.

I won't join the marked animals until I live at least another year!

Lack of rain is detrimental to Palo Verde -- but behaviorally, iguanas are doing much the same as they also do -- up and active when the sun is out, and siesta during cloud cover. At least some things are predictable!

Summer 2014: Green Season

Traps bring out defensive behaviors in C. similis.

Count them -- seven days until I hit ground: Palo Verde National Park, Organization for Tropical Studies' Research Station. Iguanas and, I'm told, a few mosquitoes. It's Green Season, not a vacation. #100dayssummerscience finally back to lizard behavior!

This trip will ground-truth a network data collection protocol, sweeping through the site, building up interactions, understanding the connections iguanas have to each other. It will be good to see known and new iguanas -- the study animals, their haunts and preferential associations.

I'll be joined by a colleague who is interested in C. similis parasites -- internal and external. We'll be collecting various samples and profiling occurrences in this population.

But first, packing, and the usual last-minute insanity that structures all field work!

Resistible Trampa! or, Love is in the Air....

How do I catch iguanas? With a good old humane wire trap. Each day after breakfast, I 'steal' fruit from the morning's platter -- pineapple, or papaya, or bananas, or watermelon -- they are all good for enticing a black iguana into a trap. But it's not fool-proof. Sometimes there is simply too much activity near the trap, or the commotion has sprung the trap empty.

Female coming down Big Tree captures male's attention.

 Other times the lovely female nearby is far more interesting than fruit. The next few photos show a smaller male (eventually caught, beaded, and PIT tagged) showing his beauty to a not-completely convinced female, WOG. Interestingly, he displayed as if ready for battle -- lateral compression, elevated on his legs, colors very pastel. Can't you see how big and beautiful I am?!!

She soon gave the male a low-key whip with her tail. Not the tail strike that could communicate "Not even if you were the only male on a deserted island," but one that suggested, "Not yet -- try me again in a few weeks." It is, after all, only the beginnings of mating season. Courtship has its purposes!

Male displays and approaches female.

First female leaves but second female comes down and the male is all eyes.

 The male gets another try with a second female who comes down Big Tree.

His display is acrobatic!

He even gets a leg on her body....but she soon gives him a "no-go" tail whip.

This is MY space -- or perhaps I don't care much about it....

Patterns of Interactions

Each time I'm at Palo Verde, I watch the spatial pattern of animals, where they are physically located, and the places they use in their day. I observe the animals and their interaction (and try to understand why).                                                                                                                                                        

Kaplan

Animals may move for their own reasons; sometimes we may contribute to the relocation. Blue-Yellow-Brown (Kaplan) most often used a roof hide on the dining hall end of a building. But a roof leak necessitated repairs and he since moved to the opposite end of the building. Not a huge change by any means. Charcoal made the same shift and Miami uses a roof refuge very near Kaplan. They all stick their heads out in the morning and watch as we go into breakfast.

Two iguanas on branches

 In Big Tree, most of the iguanas are the same individuals observed in May. Physical movements from one refuge to another seem to be in terms of >100 m, most often >20 m.

Ctenosaura similis is described as a territorial species -- but rarely does an author define the meaning of territorial behavior. Sometimes we call the males 'resource polygynists' which tries to indicate that the males guard resources females find important. I have yet to see this in operation. (I can wholly see males guarding females from other males during breeding season -- but if they are guarding female resources at other times during the year, it's subtle beyond my means!)

Maher and Lott (1995) propose this definition of territoriality: a fixed space from which an individual or group of of mutually tolerant individuals actively excludes competitors from a specific resource or resources (1). Sounds good -- but I want to understand and better define the temporal patterns of territoriality. How often is an iguana actively excluding others from that important resource? How much time is spent on the exclusion behavior? If duration and frequency is minor compared to other activities of daily life, is territoriality an important illuminator or descriptor of Ctenosaura similis behavior? At present, I'm not convinced territoriality is the indisputable epicenter from which C. similis behavior springs.


(1) Maher, C.R and D. F. Lott. 1995. Definitions of territoriality used in the study of variation in vertebrate spacing systems. Animal Behavior, 49, 1581-1597.

My, How You Have Grown!

Am I really bigger?!

Have I really been gone from Palo Verde National Park for 6 months? In my absence, the OTS station was abuzz with changes, for humans and iguanas alike.

Pale Blue-Black-Red (Pb-K-R) has more than doubled in weight. If not for the beads, I wouldn't have recognized him! He also moved from the lab near Green-Green-Green to the Big Tree area near to White-Orange-Green.

Many other iguanas are larger, growing throughout the green (rainy) season. Adults look good and plump. This is day 2.5, and we are still rounding up the lizards (thank you, humane traps and bananas), but 19 of 53 are present and we expect to approach near 100% recapture by trip's end. We've also caught 3 new lizards.

For humans, buildings have received a fresh coat of paint, outdoor showers have been added, and the entire laundry area is shaded for staff, a great improvement. Faces are familiar and food is still good! Dry and cracked in May, the wetlands are full of water with incredible numbers of birds and and a few visible crocodiles.

Six of the 60,000,000 Black-Bellied Whistling Ducks at Palo Verde!

Am I Adapted to My Environment?

Am I Adapted to My Environment? Yup -- or you wouldn't be here!

When I think of environment, I often think of food, shelter, and weather, and oh yeah, behavior. Isn't behavior in service to the needs of foraging, avoiding predators, thermoregulation cycles? Well, yes, or at least, perhaps. But how is your behavior adapted to your environment? Doesn't your environment include conspecifics? In what ways do spend your time so that you learn and survive?

Behavior, especially interdependencies between individual animals, can have as much effect as good forage, appropriate refugia, and preferred optimum temperature zones. Individual behavior, then, should be adapted to the social structure in which an animal lives. Even in a non-cooperative animal like Ctenosaura similis, an understanding of which same-species animals might be a danger, or useful, or neutral might well tip the balance between surviving and thriving, between some offspring, and overall better fitness.

So, yes, you are adapted to your world!

Dynamic Networks

Today, this iguana fondly known as Blocky, is here, tomorrow he will be over there, the next day somewhere else...and so on. As for all the iguanas, the network structure I'll build through physical proximity will suggest a static set of interdependencies, when in fact relationships may change seasonally (wet/dry, breeding/nonbreeding) or at other temporal scales.

Territoriality itself could change. C. similis is a central-place territorial holder focused on a refuge. At that location, an iguana may chase off conspecifics while when foraging at a different location, appears to give no thought to the refuge presently undefended or the iguanas now tolerated.

Humans are also central-place territory holders -- we want to sit in 'our' seat in a classroom, feel possessive of it, but never give a thought to who occupies it next once the class is over. Our possession, like the iguana, is contextual.