This article was co-authored by Dylan Kelly
Counting trees may not seem like something you might do on an Eastern Indigo Snake project. Yet the vegetation measurements Dylan Kelly performs as part of The Orianne Society’s monitoring program for Indigo Snakes in the Altamaha River Drainage of southern Georgia will play an important role in our efforts to understand why this species occurs where it does, and how its populations change over time.
Why would we be measuring vegetation on a project that monitors Indigo Snakes? Vegetation plays a critical role in wildlife ecology. Obviously vegetation provides important food for many species, but the cover and structure that vegetation provides can be just as critical. Vegetation is important for Indigo Snakes in several ways. During the heat of the summer, vegetation provides shaded microhabitats that the Indigo Snakes can use to control their body temperature. For example, shaded habitats such as floodplain forests, creek edges, and cypress domes provide an ambient thermal environment that allows Indigo Snakes to be surface active without having to thermoregulate. Having a lush, nutritious ground cover is important for the Indigo Snake because it provides forage for Gopher Tortoises whose burrows the Indigo Snake relies on for overwintering sites.
However, the lack of vegetation can be just as important. Gopher Tortoises and their ground cover food source need open habitats with plenty of opportunities to warm up from the sun. Indigo Snakes also use these open patches for basking during sunny winter days. Many sandhills in southern Georgia have lost the open structure of their forests, which they would have had historically because of regular fire intervals from fire suppression or forestry practices. This has reduced the suitability of those sandhills for Gopher Tortoises and Indigo Snakes.
Our monitoring program is designed to not just estimate trends in Indigo Snake occupancy over time but determine what factors influence where Indigo Snakes occur. As we wrap up our third field season we will conduct an in-depth analysis of our data and look at how characteristics of our monitoring sites and the landscape surrounding them influence Indigo Snake occupancy (stay tuned for future newsletter articles highlighting our results!).
One set of factors that could potentially influence Indigo Snake occupancy is the structure of the vegetation, particularly vegetation that influences the openness of the habitat and availability of basking sites during the cool winter months. We suspected that Indigo Snake occupancy would be positively associated with open forests with low shrub cover and set out to collect the data that would allow us to test this hypothesis.
That’s where Dylan comes in. Dylan’s job is to collect vegetation data at 13-30 randomly selected points at each of our 40 monitoring sites. The measurements he takes are all related to vegetation structure. Canopy cover is measured using a spherical crown densitometer, a convex mirror with a series of dots arranged in a grid-like pattern. The observer holds the mirror in front of them and counts the number of dots that are covered by tree leaves and branches. This number is then converted to percent canopy cover. Dylan also uses a technique called the point-quarter method to measure tree density and basal area. At each point, Dylan measures the distance from the point to the nearest tree in each ordinal direction (NE, SE, SW, NW) and records its diameter at a specific height. A series of equations are used to calculate the number of trees per hectare and the basal area (square meters) per hectare, both of which reflect different pieces of information about the canopy structure. To wrap it up, Dylan visually estimates the amount of shrub cover around each point.
Although it may not seem glamorous, the data Dylan collects will form an important part of our monitoring project. Plus, the job is not without its perks. While taking his measurements on The Orianne Indigo Snake Preserve, Dylan captured the first hatchling Indigo Snake ever documented on the Preserve. “I have had the pleasure of seeing many animals I had never seen before in the wild,” Dylan told me. Bobcat and turkey tracks and the chorus of multiple frog and toad species are just some of the things that Dylan has seen while on vegetation duty.
Another highlight was the three-foot alligator he caught to show to a group of students that had come down to the preserve with The Orianne Society’s CEO, Dr. Chris Jenkins. He is waiting for the day when one of these highlights is an Eastern Diamondback Rattlesnake or a big bull Indigo Snake. “Any chance I have to be out in nature is a chance I eagerly jump at, and I feel honored to be able to contribute to the important work being done by The Orianne Society to protect the amazing Indigo Snake.”