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. 

Ah....just 12 days and I'm back to Iguana Toast Land, where Ctenosaura similis roam free, and the average temp must be greater than my current 7 degrees F!

Since May, I've completed the first semester of my doctoral degree, taking courses, attending seminars, reading more papers than I'd like to count, and getting a research grant from my university. While every moment has not been 100% successful, the challenges have been rewarding in very good ways.

Still, I want to keep my research and thinking steeped in field situations. I see the sheer do-ability of lab organisms, but suspect I am better suited to the challenges of in-situ projects. For 15 years, I've had the honor observing I. iguana in a captive group, and during that time, numerous occasions to observe endangered wild iguana species. They are captivating, physically attractive, socially complex, exciting animals. In the case of C. similis, they are observable and often tolerate living among humans. I'm always thrilled I get to see this incredible animal live free, and to attempt to understand the basis of its social organization.

This trip I'll have along one of my favorite field colleagues, my husband. We will catch and process iguanas, explore Palo Verde National Park, and spend Christmas in the neotropics. He'll see my study site, the cast of iguana characters, and help open my second study population.

I'll be posting throughout the trip and beyond -- stay tuned!