2014 Preliminary Field Report
Natural history, demography, range, and threats of the Oaxaca Spiny-tailed Iguana (Ctenosaura oaxacana)
Report submitted by Jeffrey P. Corneil, Dr. Victor Hugo Reynoso Rosales, and Dr. Chad E. Montgomery
Photos by Jeffrey Corneil unless otherwise noted.
In the primary field season, Jeffrey Corneil (JPC) traveled with Victor Reynoso (VHR) to the coast of Oaxaca, México, for an introduction to the range and habitat of Ctenosaura oaxacana. The two researchers began in and around Puerto Escondido and surveyed towards the east, ultimately stopping at the montaine border of the state of Chiapas. The primary objective in the field while VHR was present was to establish two to three study sites. These sites would be revisited on a regular basis while at the same time surveying localities along the coast for the presence or absence of the species. After two weeks of searching, JPC and VHR settled on three study sites, Niltepec to the east, Juan Diego to the west, and a main site in the center of the two in Paja Blanca. VHR returned to México City and JPC began to collect data on the populations.
Over the course of the time spent in the field we captured 140 individuals (1 male:0.86 females; 44 females, 51 males, 45 unidentified), which is not statistically different from 1:1 (p=0.718), but we will reexamine after the second field season. The average snout-to-vent length (SVL) was 119.27 mm (110.19 mm in females and 128.77 mm in males). The average mass was 61.33 g (47.03 g in females and 69.39 g in males). Males are larger than females. There is a no difference in the relationship of mass and SVL between males and females.
A total of 566 macrohabitat points were collected. The points consisted of 139 capture points, 193 tracking points, and 234 random points. There were zero capture points or tracking points located in wet forest habitat. However, 47 of the randomly taken points were in wet forest. More tracking (94.8%) and capture (89.2%) points came from dry forest habitat than available at random (71.4%), while no capture points came from wet forest, which was the second-most common habitat available (20.1% random).
Microhabitat variables were collected at points of capture, at track locations, and at random points. An analysis of microhabitat using principle component analysis (PCA) and analysis of variance (ANOVA) indicates that the iguanas were captured in, or tracked to, points closer to rock, more rock, less vegetative ground cover, lower canopy density, a shorter canopy, and sparser trees. These characteristics are all representative of sparser/drier habitat types, whereas the alternative would be a more wet dense forest with a higher canopy and more ground cover. There is no significant difference between captures and tracks, indicating no bias in captures.
In the Paja Blanca study site, we tagged a total of 13 individuals (seven female and six male) with radio-transmitters. The 13 individuals were tracked on a recurring basis, yet never twice on the same day. The home ranges appear to be very small with the animals utilizing a few tree hollows. The data for this portion of the study is currently being analyzed and results will be provided upon completion. We also plan to conduct tracking in at least one additional population during the second field season to see if this small home range is common throughout the range of the species.
Movement rates have been calculated as minimum straight-line distance of four to five meters per hour. As with the home range, the movement rates from the individuals will be compared to the individuals from a second study site after data is collected during the second field season.
VHR and JPC were involved in education and outreach activities while both were in the field. When VHR was present, he and JPC gave talks to several local communities about their interest in C. oaxacana and what we plan to gain by studying this species in and around their towns. We met with government officials in many municipalities throughout the coast to discuss the status of the species in their localities and the potential for studies to be conducted. Generally, the stakeholders were receptive to the topic. However, the typical response was some surprise regarding the importance of the species, which is known more commonly to be an uncommon meal. In almost all cases, government officials were not aware of C. oaxacana being a species of iguana and therefore a relative of C. pectinata, which is known as Iguana Negra or Black Iguana.
JPC spoke to five community gatherings about the status of the species and the potential for the communities to benefit from living sustainably with the species on their land. Coastal Oaxacans are very proud of their land and are equally proud to have an endemic species of iguana. We found that, similar to government officials, townspeople were surprised about the uniqueness of the animal, but were interested in becoming involved once they realized this. JPC worked with professors from the local preparatory school to bring students into the field for experience working on an ecology and conservation project. The students in most cases became very interested, and three of the students are going to present at scientific herpetological conferences in México regarding the work they have been involved in.
The next step in outreach is for JPC to seek donations from major paint companies in México to implement a house-painting project publicizing and emphasizing the uniqueness of the endemic iguana species in the Paja Blanca area. This project will involve students from the preparatory school as well as members of the local community in an effort to increase the connectedness of the community to the species. Interested students will submit logos that promote the species as a unique part of coastal Oaxaca. From the submissions, a group of professors, local government, and researchers will select a logo to be painted on buildings in Paja Blanca. Nearly all buildings in the community are unpainted and the color of concrete. Homeowners will be given the opportunity to have their house painted with one side of the house showing the selected logo. These homeowners will be asked to sign an agreement not to hunt or eat the endemic species. We hope this will promote a community appreciation for the species and their habitat, which will have wider-reaching benefits to species that share habitat with C. oaxacana. This project will also have an effect on the desired ecotourism in the community by providing a more aesthetically pleasing town to visitors.