What is a visual sampling survey for herpetofauna?
While often ignored, herpetofauna is one of the most important – and sometimes most abundant – groups of animals in a given ecosystem. Herpetofauna, usually shortened to “herps,” comes from Ancient Greek for “creeping thing” and refers to animals classed as reptiles and amphibians.
You might notice you can walk down a trail for a long time without ever spotting a herp. Even in tropical areas, where these animals can far outnumber other vertebrates, they can be tricky to find. Most herps are quite small and very well camouflaged. Even the largest snakes in the Amazon – anacondas – look just like a log when they sit still so they can hide in plain sight.
But herps are just as important to monitor as their flashier and fuzzier counterparts. Frogs, salamanders, lizards, snakes, turtles, and crocodilians play a crucial role in the balance of their local ecosystems, controlling invertebrate, fish, and small mammal populations, and serving as food for larger predators. They are also particularly sensitive to the health of their local environment, meaning their presence and diversity are an indicator of ecosystem wellness.
Even if snakes and lizards can provoke fear, it is essential to track and monitor the herp populations living in a given area to understand the health of the local ecosystem.
What to expect from a visual sampling survey?
Visual sampling surveys are considered one of the best ways to monitor populations of reptiles and amphibians in a given area. This methodology is extremely simple, requiring researchers to walk down a transect – a straight piece of trail around 1-2km long – and record every herp they see along the way.
Usually, herpetologists (scientists who study herps!) will record the species, location, and age, and sometimes will also add in physical measurements and a photo. Importantly, just like with Bird Point Counts, this methodology should be repeated several times at the same time of day along the same trail to create a clear picture of local diversity. Ideally, this survey will also be repeated throughout several years, helping us understand how diversity changes over time or over seasons.
This survey is often done during the day and during the night to capture the difference between diurnal and nocturnal species. Many herps are active at night, so usually night walks are more exciting and uncover more diverse species than daytime surveys.
The key during these surveys is to walk extremely slowly, almost in slow motion. During the night, you will use a headlamp to scan the forest for signs of life, often looking for bright spots called eyeshine, where animals’ tapetum (the back of the eye) reflects back at you. With each step, scan the forest floor, then the undergrowth, then sweep to any branches above your head. Repeat again on the other side when you take your next step. Herps can be small and well-hidden so you should take your time to look carefully.
Be patient. It can take over an hour to walk a kilometer at this pace, but it truly is the best way to spot these mysterious creatures. And you don’t have to be a trained scientist to do so! Studies show that students and tourists may be nearly as good at spotting as herpetologists (and certainly six eyes are better than two!) so keep your eyes peeled.
When you have reached the end of the transect, you will turn around and head back home. You might realize it only takes 10 minutes to walk the whole transect back! That means you were doing it right.
If you want to learn more about herps and join us on a survey, check out our tours in Ecuador!