2016: Field Season!

Iguana refugia -- also known as a gutter.

December 1, 2015 -- I am counting down to January 2016, my first long trip to Palo Verde (nine weeks). Along with a field assistant (stay tuned for her introduction in a future post!), I'll be testing an Encounternet System on the iguanas to gather a much fuller social network based on physical proximity.

First we will test how the Encounternet system works at our actual study site. We will simulate iguanas climbing trees, disappearing into dry forest patches, or feeding on open areas. Once we have calibrated the system, a small groups of iguanas will try out the tags in real time, eventually scaling up to a full deployment on 30 animals.

This will be an important window toward understanding how non-cooperative animals negotiate their social lives and is part of the first studying considering the social network in and egg-laying, neotropical lizard.

Introvert? Extrovert? Ambivert?

 To understand the Spiny-Tailed Iguana's personality, I'm testing them in the field. One such examination is called the Open Field Test (OFT). Its origins reside with the fear perceived by some rodents when they can no longer touch their world -- when they are in the open, likely at greater risk of predation.

Theory suggests that bolder animals will explore the open area more than will shy animals. This makes some sense if you prefer to hug the sides of your world, touching physical objects. In Ctenosaura similis, an omnivore that often feeds in open areas, how useful is the OFT to measure fear -- and is there a statistical difference between bold and shy iguanas in their exploration of the OFT arena? Does Bold Pale Blue-Black-Red (PbKR) explore the arena more than shy Brown-Red-Green (BrRG)?

PbKR: Bold

BrRG, on tree roots near the pergola. A very shy iguana.

 To begin to answer that question, I constructed a 10' x 10' testing arena, seen below, and rigged a digital video camera on the station ladder to record 10 minutes of exploration per animal. I use an imaging tool to superimpose a grid on the area and score how many times an animal crosses the grid as well as other behaviors (jumping up sides of the walls, attempting to climbing the ladder, sitting, etc.

Open Field Testing arena with tripod on ladder to digitally record test.

It may be that bold and shy animals have similar levels of exploration because the OFT is not a good test of fear in this species. They may all be equally irritated from the loss of a visual field and spend energy searching for an escape route. While it would be fruitful to have personality tests that work for all taxa, this strikes me as unlikely -- especially in an animal that often feeds in an open field!

White-Orange-Green (WOG) grazing on the lab lawn (open field).

My How You Have Grown!

Black-Black-Green (KKG), fondly called Keg, was first captured 24 December 2014. He weighed 250 grams, and measured 15 cm from snout to length of his body. His full tail was 34.6 cm in length.

On 21 July 2015, I recaptured KKG. He only has 7.3 cm of original tail and 12.3 cm of regrown tail -- did he survive a predation attempt or did he injure the tail in some manner? His Snout-to-Vent length is now 20.4 cm and he has gained 350+ grams of weight. You can see how my hand is holding a much larger iguana than in December!

Keg is growing quickly. He has survived the perils of being a tiny hatchling predated on by almost every other animal. He is still living in the same general area, using the office roof for a refuge and feeding on the lawn in front of the lab. And he is interacting with iguanas larger and more experienced than himself.

How dry is it?

When I use fruit to bait the iguana traps, I may instead catch a capuchin monkey or a coati. This year the rains are very late, the soil is crunchy, and the leaves are wilted on the trees. 

Here is a begging capuchin who followed me on hopes of food. While they do raid traps, this is not typical in the station. 

http://youtu.be/b-6Sbi9Jg2E

And here is a male coati who also raided one of the traps:

http://youtu.be/O90LjkQYLeo

I won't bore you with the raccoon;  or that this post was delayed as I needed to release another monkey from another trap. When a troop is around, trapping stops. 

Below is a yearling iguana ignoring small trap while WWW goes for the big trap -- she was rebeaded and I took a blood sample for the molecular part of my dissertation:

http://youtu.be/3Wp0iNOWJj4

 

Find the Iguana: Pochote

Spiny-Tailed Iguana can climb a tree called the Pochote. The tree spikes are huge and sharp but no worries for an C. similis!

Can you find the iguana?

Now?

Spiny Pochote Tree

Here is a good description of the tree: http://guanacastecostarica-mitierra.blogspot.com/2012/05/costa-rican-forests-pochote-tree.html

Day Uno

Piercing an iguana's nuchal crest to add colored beads is a time-honored technique to mark individual animals. To use social network analysis tools, individual ID is a must. However, iguanas of all sorts are fascile in removing said beads -- so every trip begins with a few trapping days. 

It's quite interesting how willing Ctenosaura similes is to enter a trap for some fruit. In this very end of dry season (rains are late), fruit is likely an amazing food find. 

Also, iguanas are both disappearing and new ones join the group -- so in the 16 caught during my first full day, 4 are new to the study. Known animals are generally more useful for my questions about social structure and usually they are where I expect them to be -- same local area, same refuge and previous 6 months. Stability is important for this species.  

Breakfast for humans is 6:30; by 7:30 all traps are set and baited, and I wait for the iguanas to warm up enough to start their day. In the meantime there are the howler monkey and parrot seranades, the mosquito attacks, and the great pleasure of field work. But don't get me wrong: it's all for SCIENCE!

Vanity? No! Safety!

A large male caught today managed to give me a nice bite. Yes, iguanas have teeth! I was wearing gloves but he managed to grab my wrist. Lucky, Fitbit took the brunt, iguana processed in under 15 minutes, and within hour, out grazing again. A good day!

Iguana Toast Chronicles will not kill you!

FID, NO, OFT

Not diseases but in situ personality testsfor animals: Flight Initiation Distance, Novel Object, and Open Field Test.