Night Patrol - Costa Rica

Out of the many tasks and responsibilities we have as field biologists in Playa Grande, the most important job is night patrol. Without night patrol, we would be hard-pressed to actually see a turtle laying her eggs. Although it is possible to find a turtle on the beach during daylight hours, the most opportune time is at night. Sea turtles typically arrive on the beach near the nights high tide. As the tide cycles change with each passing day, so too does our patrol times. Some nights we are on the early shift from 7 pm to midnight, but as the tide comes in later and later we have swing shifts. These shifts start an hour later and last an hour longer until we start late shifts from 11 pm to 5 am. The purpose of this scheduling is to provide the best beach coverage for 3 hours before and after high tide.

Always patrolling in teams of 2 or 3 people, depending on the number of biologists and volunteers we have available, we walk sections of the beach in search of turtles. The 3 sections of beach that we walk include North and South of Playa Grande and Playa Ventanas. We do not always have the staff to patrol Playa Ventanas, however most nests laid there are relatively safe and are accounted for by the Morning Walk team. Each section covers approximately 1.5 kilometers, with Playa Ventanas being the longest. We aim to cover this distance in 20 minutes with a 20-minute break at the end of each sweep. Usually completing 6-8 sweeps per patrol, we walk around 9-12 kilometers each night. That distance is shortened significantly if a turtle comes up the beach.

When we encounter a turtle, the first step is determining what stage she is at in the nesting process. All species follow the same basic routine which consists of emerging, body pitting, digging an egg chamber, laying eggs, covering the nest, and returning to the sea. Leatherbacks (Dermochelys coriacea) are different in that they undergo an addition stage called camouflaging. This is simply making additional body pits, or largely disturbed areas of sand, which conceal the true location of their clutch of eggs. After we have determined what the turtle is doing, we begin preparations for a host of tasks. Priorities include getting an egg count or catching the eggs in a bag for relocation, inserting a thermocouple into the clutch of eggs for temperature monitoring, and getting ID numbers from the turtle. Turtles are tagged with PIT tags, which is the same method I have used before on Boreal Toads. It is a little computer chip that gets inserted into the shoulder and provides a unique ID number when scanned. These individual turtles can be tracked as they arrive multiple times throughout the season. Some have been encountered on nesting beaches for multiple seasons. We also measure the carapace (shell) length and width for each turtle and report any scars/wounds they may have acquired. Most of this work is done during the egg laying process when the turtle is in a sort of trance and seems relatively unaware of their surroundings. There are additional data collection tasks that we see to, however they are part of ongoing research projects and vary from season to season.

After the excitement of a nesting turtle we continue sweeping the beach looking for others. It makes for a busy night when we have multiple turtles, yet this is a rare occurrence. Sea turtles are not as abundant as they use to be. Due to drastically declining populations of the Eastern Pacific Leatherbacks, we are fortunate to see multiple turtles each week. In fact, we are fortunate to be able to see them at all.