2017 Roatán Project Report

Monitoring the Roatán Spiny-tailed Iguana and Cultivating the Next Generation of Researchers and Managers

Report submitted by Ashley Goode and Stesha Pasachnik

Photographs by Ashley Goode unless otherwise noted.

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March 2017 workshop participants taken at Paya Bay’s Black Iguana Bar. Photo by Paya Bay staff.

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A participant marks their first Ctenosaura oedirhina of the workshop.

After assessing the background and interests of the participants, we designed the field and lecture components of the workshop to cater to them. In addition to basic iguana capture and processing, participants left having practiced blood drawing, distance sampling, behavioral ethograms, flight distance surveys, re-sighting surveys, data collection, and project planning. Each participant in August also contributed to writing an IUCN Red List update (Ctenosaura bakeri and Ctenosaura palearis), thus they will be co-authors on these publications. We also began a dietary study by creating a catalogue of local flora, and collecting and sorting scat samples from the iguanas. The floral catalogue includes plant species that were blooming or fruiting during the two workshops. These scat data will eventually be used in a short communication on diet, and all participants will be co-authors.

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A juvenile Ctenosaura oedirhina sighted during a distance sampling survey.

We believe that by training participants we help to build capacity in the region, for those just beginning their research careers and those already involved in iguana projects. For the two students who participated in August 2016, this workshop exposed them to the necessary components of field research, becoming familiar with important data collection techniques. In one participant’s post-workshop survey he said, “ …I came here without any experience or particular interest in iguanas, and I leave with a lot of knowledge (on iguanas and general stuff) and I’m actually interested in continuing working/researching about this group.” The species program manager participant gained ideas for additional research that could be incorporated into her programs, and access to experts in the field with whom she can continually reach out to for advice.

Two participants retrieve fresh palm seed samples for the diet study.
Two participants retrieve fresh palm seed samples for the diet study.

Participants in general gained a better understanding of threats to iguanas and of the technology available to track and monitor them. In order to assess the success of the workshop we used pre- and post-workshop surveys. One participant remarked in their post-workshop survey, “I really enjoyed the fact that we got to do most of the stuff we were learning through the presentations.” Another said, “…the lectures showed application of things I know ‘on paper’ but hadn’t really seen.”

One of the participants from the March 2017 workshop is now interested in working on a project focusing on the Southern Honduran Spiny-tailed Iguana (Ctenosaura praeocularis) with a student from our August 2016 workshop. The park ranger from St. Eustatius, from our March workshop, left with new ideas on how to better monitor and protect the Lesser Antillean Iguana (I. delicatissima), including parasite screening. The undergraduate student from March left with plenty of capture and tagging practice so that he will have a very productive season on his project with the Motagua Spiny-tailed Iguana (Ctenosaura palearis).

Monitoring. Natural history data was collected for the 6th and 7th year. Mark/recapture surveys were conducted at five of our study sites. Distance sampling surveys continued along previously-defined line transects. In August 2016, 99 new iguanas were captured and tagged and 20 iguanas were recaptured by workshop participants, adding to the growth and survival data for this species. Two of the recaptured iguanas were from 2010, three from 2011, and most were from 2013–2015.

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Number 57, a recapture in March that was first captured and tagged in 2010.

Analysis of the data from 2016 may not indicate actual population changes because it was collected in the week following Tropical Storm Earl. Severe weather does not often impact Roatán due to its location, however, because there was multiple days of rain and heavy cloud cover, iguanas were not as visible as they usually are during this time of the year. Density estimates from this season indicate a decrease from the previous year by ~34%, while encounter rate remained unchanged. Again, this is not likely an actual decrease, but an artifact of the post-storm collection bias.

Over the course of this study from 2010 onward, we have demonstrated an overall decline in this species. Thus, continued monitoring of demographic trends is vital to proper management of this species. In addition, maintaining a presence on the island helps to reinforce the protection of the iguanas, especially at study sites where hunting intrusion occurs. The population has been monitored using mark/recapture techniques for seven years, while distance sampling data has been collected for six years now.

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Two participants work together to measure and tag, while Ashley Goode records the data. Photo by Stesha Pasachnik.

While 2016’s distance sampling data may be an outlier because of Tropical Storm Earl, these data allow us to assess the effect of such events over time. The 20 recaptured and 99 newly-tagged iguanas provide important data points for growth, coloration, and survival analysis. Recaptured individuals during the last workshop show that some of the originally captured iguanas from 2010 are still surviving. These demographic data provide the first long-term monitoring effort for this genus and can thus be used as a model for other species within the genus.

Future Plans.  We will continue these workshops to ensure that monitoring of this species persists, while building capacity in iguana range countries. In future years, we would like to include additional smaller projects, similar to the dietary study. This will allow participants to experience managing data collection, analyzing data, and give them the opportunity to publish short articles.