Alexandra and NPS volunteers stand by a NPS sign reporting the number of sea turtle nests found in the park
While onsite, I was fortunate to visit the park with a group of NPS volunteers. Volunteers learned how to identify and track sea turtle nesting activity across different types of beach habitat. Photo credit: NPS

After spending the week on-site at Buck Island Reef National Monument (BUIS), my time as a SIP Fellow is almost over! Before I go, I’d like to finish sharing the results from the primary objective of my project: Conduct a baseline assessment of the critically endangered hawksbill turtle nesting aggregation at BUIS.

Before I “geek out” about the results from my summer spent wrangling data, let me explain how I addressed this objective. In a nutshell, I evaluated whether abundance (annual counts of females and nests) and reproductive parameters have changed over the last 31 years (1988-2019). Reproductive parameters included hatch success (proportion of eggs that hatched per nest), emergence success (proportion of hatchlings that reached the beach surface per nest), clutch size (# eggs per nest), hatchling production (# individuals produced per nest), and average female body size (length of the carapace or “shell”). Assessing temporal trends in these parameters provides important information about the status of the female aggregation and nest success in the park.

A woman crouches behind a nesting turtle to collect data
A NPS intern collects data from a hawksbill nesting at Buck Island Reef National Monument. All research is conducted under proper permits to the National Park Service. Photo credit: A. Gulick

Prior to the establishment of the Buck Island Sea Turtle Research Program in 1988, almost all hawksbill nests documented in the park during the early ‘80s were either predated by invasive mammals (rats and mongoose) or poached by humans. Since the program’s inception, nesting hawksbills have made a dramatic recovery at BUIS – going from 12 females documented in 1988, to 60-80 individuals at present. That may not seem like a lot to some, but for an animal that takes 30 years to reach maturity, that’s a major comeback! Although this is a significant conservation achievement for the park, project results indicate that female abundance has stabilized over the last 13 years, and with this trend comes questions about what’s next for the park’s sea turtle management plan. Results from my project suggest a couple of things that may be contributing to this trend: 1) Hawksbills have increased nesting activity beyond the park boundary (discussed in my previous post); and 2) Female recruitment and reproductive productivity may be declining.

A photo of an aluminum tag in the flipper of a hawksbill turtle
Females are assigned a unique ID via the application of Inconel flipper tags. NPS at BUIS is able to assess female recruitment to the nesting population by the number of “new-nesters” or un-tagged females they encounter each season. Photo credit: A. Gulick

The impacts of climate change — including warming seas, sea-level rise, increased storm frequency — pose a significant threat to the persistence of sea turtle populations worldwide, and have been linked to decreases in turtle productivity (e.g. growth rates) and loss of quality nesting and foraging habitats. Therefore, it was no surprise to find that average female body size and clutch size (# eggs per nest) for BUIS hawksbills has significantly declined over the last few decades. Smaller turtles produce fewer eggs per nest, which could eventually affect the number of hatchlings contributed to the population, particularly as female abundance stabilizes and fewer first-time nesters are documented (aka fewer females recruit to the population and/or take longer to reach maturity). Fortunately, there was no temporal trend in hatch success, emergence success, or hatchling production throughout the duration of the project — but the combination of smaller clutches and other impending threats (e.g. nest erosion by frequent storms, female-biased clutches) could change that.

Hawksbills use their rear flippers to dig a nest chamber, and lay ~150 eggs. Nesting typically occurs at night as a predator avoidance tactic, so the NPS team conducts nocturnal beach patrols every night (12 hrs per night) for 12 weeks during the peak nesting period. Photo credit: NPS

What do these results mean for hawksbill conservation at BUIS? First off, changes in female abundance and decreased body size suggest that the productivity of the population may be declining, thus reinforcing the need for continued monitoring. The next step for NPS managers is to diagnose the factor(s) behind the trends reported from my project, so appropriate management action can be implemented. This can be accomplished by evaluating if population demographics are changing, including growth rates, survivorship, clutch frequency (# nests per female during a single breeding season), and reproductive output. Sounds like a great project for the next SIP fellow!

So to close my final post, I’d like to express a huge thank you to NPS at BUIS for this fantastic opportunity to gain essential skills for pursuing a career as a federal marine ecologist, and contribute to the management of sea turtles in the park. I am also grateful to the SIP and ESA coordinators for offering such incredible opportunities for aspiring scientists and resource managers.

Want to hear more about my results, and other SIP projects from this summer? Come see my virtual presentation on August 2nd, between 2:30-4:45. You can register for the webinar here.

If you have any questions about my project or would like to learn more about what I do as a marine ecologist, please contact me (, follow along on Twitter, or visit my personal website (see Curriculum Vitae).