White-White-Brown Returns!

C. similis nesting mounds

It may seem odd to declare the return of a missing iguana through a photo of nesting mounds -- but our best guess is that White-White-Brown, gone since 2/5/16, was off laying her eggs. Her return and sighting today showed us a healthy-looking but thin iguana. Tag intact, attached to her body, solar battery well charged, all is good.

Female digging her nest.

WWBr looking thin yet healthy! 

WWBr

Part of calibration and deployment means attempting to understand how well tags work and endure the natural inclination of C. similis to shove themselves into small rock crevices, dead tree limbs, and all sorts of human-created refuge spots. We now have proof that nest digging does not damage a tag, and that the natural pattern of digging and resting will keep a solar battery charged. Or, at least in the case of WWBr, it works!

Of nine tagged animals, two are male. Of the seven female, two are missing with no tag radio signals. We are hopeful they, like WWBr, will return in good health, simply behaving normally.

Week Four: In which things go wrong...but also right

Yellow-Green-Yellow comes down Big Tree.

By mid-day on 5 February, we had deployed eight working tags on iguanas. A ninth tag, #3 wasn't charging correctly and had to be placed in a lower power mode.

On 10 February, tag #5 on White-White-Brown (WWBr) went Missing-in-Action, along with the lizard. We hope she is off on a great adventure and eventually returns. Her tag send no signal which may mean it is dead, or simply out of range.

White-Orange-Green, the famous WOG of this blog, decided there was little reason to come out and bask for almost a week. We watched with trepidation as her battery voltage drop. Luckily, WOG decided it was time to reappear -- and her battery is charging fine.

Every day we get up before dawn and download logs from the base stations. The logs are the physical proximity encounters between animals, all to understand their social structure. Base stations also record "pings" from tags so we know when and generally how far tag #5 was from any base station when it and WWBr went missing. Each base is managing to successfully "talk" to tags, receive log downloads, and cover a good physical area.

PBKR

 Of course after bringing tag #3 to a good charging level, and spending two days trapping an animal that interacts with the tagged group, Pale Blue-Black-Red (PBKR), our twice daily voltage checks revealed the tag was again not keeping a charge. So, back into a low power mode.

To help understand the data logs, we are processing a number of days by hand. 8 days and ~7 tags is roughly 25,000 lines of tag-to-tag pairs, by day, time, and radio signal strength. It does tell a story!

Week Three: The System is Live!

Base Station location map.

At some point, our testing had to end, parameter decisions needed to be made, and the system to move from enclosed indoor place on to live animals in their habitat.

Base Stations were located near the group of animals we planned to tag and monitor. Two weeks of calibrations, a few days for percolation of plans, and we were ready to collect real data.

Solar Encounternet tag

Next task was trapping eight iguanas -- and luck was with us! We managed a dominant and subordinate male, and six females of varying personalities. Some are bold while others much more shy. The group, tagged in less than 12 hours, went live on 5 February 2016.

Another stream of issues: would the tags stay on the iguanas? Would we see lizards itching at the tags, suggesting they were annoying and changing their behavior?

The tags are powered by solar panels with the expectation that the natural basking behavior of a Spiny-Tailed Iguana would keep them charged -- would they really work that way?

Would the iguanas visit areas near enough to base stations to ensure proximity log downloads?

Will the raw data make any sense?

Like all new endeavors, getting over one hurdle simply means time to get ready for the next mess.

To save battery power, tags enter a "sleep mode" at the end of an iguana day, and the Base Stations follow an hour latter. This is reversed in the morning. I set clocks, download logs, and check battery levels starting at 5:30 am; tags awake at 6:00 am.

For the first week, it's important to see what Bases are being used by which iguanas, and making sure all animals are downloading interaction logs. We are mostly in good shape except for one iguana who does not seem to have come out of a hide in a couple of days. Tomorrow the hunt is on!

Rusty, our dominant male, wearing his tag. 

Week Two: Tags, and Bases, and RSSI, oh my!

Base Station on 3 meter pole with Megan Heier. 

Calibration. Our dear friend Wikipedia offers this explanation: Calibration is the process of finding a relationship between two quantities that are unknown (when the measurable quantities are not given a particular value for the amount considered or found a standard for the quantity). 

I am using Encounternet radio frequency identification tags on Spiny-Tailed Iguanas. When the iguanas are within a certain physical distance of each other, the tags will log their encounters. What needs to be calibrated is the relationship between distance and Radio Signal Strength Indicators (RSSI).

If the RSSI between two tags (soon to be attached to actual iguanas) is -11, how close are they to each other? What about when they are +7 RSSI?

How close does an iguana with a tag need to be to a base station to ensure a power-efficient download of physical proximity logs? 

What height of the base station ensures the above, 3 or 1.5 meters?

When the antennas go in the same vs. opposite vs. perpendicular directions from each other, what does that do to RSSI?

Where should the base stations be mounted?

When should we log tag interactions (wake up call) and when should we stop (bedtime)?

Which iguana sub-group would be useful to test the calibration on real animals? (This is not a trivial consideration -- it would be good to have different personalities, sexes, and perhaps not too many animals that climb 20 meter trees....)

So, we've attached base stations to different height PVC poles, marched tags up and down a measuring tape in the hot sun, taking numerous pages of data. And as explained, RSSI is stronger when off the ground (lizards with jet packs, anyone?), away from concrete and piles of rebar,  and best if antennas are parallel and facing each other.

We have mostly learned how to set controls in the system software, have a good idea of which iguanas will get tags, and are almost ready for a real run.

Rusty, a large male who patrols the open area in the above photo, has more than 8 females in his territory. He also has several second-rank males that he has to address, running them off as needed. The females are bold and shy which should also help test the system and begin to answer the question, why do these non-cooperative animals have the social structure they exhibit?