Our work featured in The New York Times!
Our study on how tourists feeding turtles could be harmful was featured in an article on The New York Times, and even made the cover of the international edition. Great honor to be mentioned by this paper, and very important that the message on harmful impacts of feeding marine wildlife is spread as far as possible. Great collaboration together with nature photographer Shane Gross to get this story out.
Cover of the international weekend edition of The New York Times, 15-16 May, 2021
Screenshot of New York Times article, published May 11, 2021, written by Priyanka Runwal
Caught on film! TurtleCams show how tourists feed (and influence) turtles
Young green turtles’ behaviour is influenced by tourists feeding the animals. This was discovered by researchers of Wageningen University & Research through the use of TurtleCams: cameras mounted on the shells of green turtles in the Bahamas. This is the first time scientists use such cameras to record the interaction between tourists and animals for scientific purposes.
The green turtle is an endangered species whose population has plummeted. The animals must continuously adapt to – amongst other – habitat loss and climate change. The increasing influence of tourists pose an extra threat to the species, Fee Smulders, PhD candidate Aquatic Ecology and Water Quality Management, discovered.
New camera system
Wageningen researchers developed a new, low-cost GPS-camera system in collaboration with co-author Owen O’Shea of the Centre for Ocean Research and Education in the Bahama’s. This system allowed them to film the behaviour of five green turtles for five hours. After five hours, the adhesive with which the camera was attached dissolved, allowing the device to float to the surface. Following the GPS signal, the researchers then retrieved the cameras.
The recorded images revealed not only how the five turtles that were equipped with a camera behaved, but also showed footage of other green turtles without cameras. The footage is available online through the link of the open-access paper. Smulders: ‘Using cameras in this way allows us to narrate the wild animals’ own story, about their natural behaviour and their interaction with humans.’
New food source
Green turtles in their natural habitat are mostly vegetarians. Seagrass is their staple food. The TurtleCam footage, however, showed tourists feeding the animals bits of squid. The researchers calculated that the turtles’ seagrass consumption was reduced six-fold when tourists were in the area. In the long run, their body will evolve to accommodate such new food sources, making them dependent on fish and meat, which are not always available. This poses an additional challenge for the already endangered animals.
Aggressive
In addition to changes in their diet, the scientists also noted a change in behaviour. These naturally calm animals exhibited aggressive behaviour towards each other, in competition over food, and towards the tourists. ‘They probably confused hands and fingers with food’, Smulders thinks. The competition for food and related aggression worsened when the corona pandemic caused a sudden drop in tourism in 2020.
The TurtleCams revealed that green turtles purposely swim towards boats and humans. ‘Normally, we use special nets to catch the turtles for research purposes. Here, we could simply scoop them out of the water with our hands,’ says Smulders. ‘The animals being this tame is a threat.’ It increases the risk of injury through, for example, boat propellors, and makes them vulnerable to poachers. Although poaching is strictly prohibited, poachers still operate all over the world. ‘Sadly, we discovered our prediction was correct: a poacher recently extracted eight green sea turtles from the waters at our research location,’ Smulders states.
Global issue
Following an online search, the team discovered that tourists across the globe feed sea turtles. Not just the green sea turtle, but also two other (critically) endangered turtles, the loggerhead turtle and the hawkbill sea turtle. ‘This leads us to believe that the change in diet and behaviour of the sea turtles occurs in all their habitats, from Australia to Tenerife’, says Marjolijn Christianen, assistant professor at Wageningen University & Research.
‘Our research shows the dangers of feeding wild sea animals’, Christianen states. ‘To mitigate the damage and protect the turtles, we must communicate the consequences of this feeding activity to tourists around the world.’ The researchers published their findings in the scientific journal Global Ecology and Conservation.
Fieldtrip to Bonaire in COVID19 times
During 2020 a lot of our fieldtrips were cancelled due to travel restrictions. Therefore we had to quickly find alternatives and work together with local researchers that could maintain our ongoing experiments, for example on Bonaire. But after one year, our turtle exclosure experiment would come to an end and an intensive set of final measurements and sampling could not be arranged from a distance. After applying for special permission I finally was allowed to travel to Bonaire in October 2020, although my students were not allowed to travel with me.
An empty plane, an empty island! It was a different experience on Bonaire, with dive shops closed, and predominantly residents on the island. The vibrant dive community is what livens up the island and although tourists form the main income for the island, I did not miss the 3000+ tourists that arrive at the island everyday by cruiseboats.
I worked together with one student that managed to travel to Bonaire when it was still allowed, and together we performed all final measurements of the turtle exclosure experiment, took underwater videos, processed a lot of samples into the evenings and in our limited spare time went for some fun dives!
The trip was very successful, I was amazed at the impact of excluding turtles for one year on the seagrass morphology. Measurements will reveal the impact of turtle grazing on ecosystem services and recovery capacity of turtlegrass. See below an impression of our time on Bonaire
New paper on invasive seagrass flowers: male plants first to colonize new habitats?
Seagrasses are marine flowering plants that can reproduce both sexually (through flowering and subsequent seed formation) and asexually (through clonal growth). Sexual reproduction increases genetic diversity, resilience and dispersal success of seagrasses.
The invasive seagrass Halophila stipulacea originating from the Red Sea and Western Indo-Pacific, has been successfully invading the Mediterranean Sea since 1894 and the Caribbean Sea since 2002.
In this new paper, we found that so far, only male flowers have been described of the successful invasive seagrass species H. stipulacea in the Caribbean Sea. Female flowers and fruits have not been reported. This means that fragmentation and fast clonal growth may be the only factors explaining its current success. This needs to be taken into account in further studies studying H. stipulacea expansion.
In-depth monitoring of reproductive structures in invaded seagrass meadows, both in the Mediterranean and the Caribbean Sea is important to assess further invasion potential. Given past misunderstandings regarding the identification of H. stipulacea reproductive structures, we have developed a field guide with a dichotomous key, to take into the field and identify the various structures by eye. https://doi.org/10.1515/bot-2020-0046
Follow-up turtle spy cameras on the Bahamas
Next up was Eleuthera, an island in the Bahamas. Here, we wanted to deploy cameras on sea turtles to look at grazing behaviour and predator interactions. Turtle predators such as tiger sharks are more abundant in the Bahamas compared to the Dutch Caribbean, and therefore we are interested in how this impacts turtle grazing behavior. However, on Bonaire, we were unsuccessful in finding our cameratags back. So we had to search for an alternative way of retrieving our cameratags, after they are automatically released from the turtle. We decided to try out GPS trackers, bought at Spy Spot Investigations in Miami.
We had one morning in Miami in transit to Eleuthera and very very last-minute managed to buy the trackers. Then we had to reshape our cameratag-design to fit the tracker and for the device to fit on smaller turtles. We bought local simcards on Eleuthera and hoped that this method would provide us with real time locations of the package
We captured the turtles in the morning and attached the camera devices to their carapaces. The cameratag including the GPS tracker in custom-made waterproof yellow packaging is shown on the left.
The next morning, we used the app provided with the GPS tracker to locate the floating package. We saw the trajectory, and where it washed ashore. This way, by boat, we could easily retrieve the cameratag the next day. This was way easier than our previous method, and we managed to deploy and retrieve 5 more cameras during our week on Eleuthera. On the camera footage, we saw turtles grazing on seagrass in various habitats: this data is very valuable to us and will be analyzed further. Additionally, we want to try out this new method on Bonaire as well and hope to increase our sample size.
We had memorable field week filled with trial and error, long hours and nightly boat rides, but overall we are very happy with our results, thanks to this great team!
Gallery with pictures (click-through) to get an impression of our work (including a lot of seagrass work now unmentioned) this week
And then sadly it was time to leave the island again! Eleuthera was an amazing experience, the island is beautiful and it’s very nice to compare the seagrass ecosystem here to the one on Bonaire. We learned a lot and go back with lots of data to be analyzed at Wageningen University and research. Stay tuned for updates.
Underwater construction and pilot with turtle-mounted camera’s
Oct/Nov 2019: Time for one of the craziest fully packed fieldwerk trips I’ve ever been on!
Firstly, I went to Bonaire with 4 students, where we worked really hard to set up a new turtle exclosure experiment, a fish exclosure experiment and a bioturbation experiment. We had a great team and worked for long days and spend many hours underwater.
For our experiments, we’re investigating top down and bottom up impacts of nutrients and fish and turtle grazing on native and invasive seagrass growth and ecosystem services. The students got introduced to scientific diving and quickly developed their underwater construction skills.
We took seagrass samples, processed them and I tried to transfer all my knowledge of relevant seagrass research methods. We also built baited remote underwater video stations to investigate shark presence, behavior and diversity on Bonaire.
Then it was time for the second stage of our trip: to see if we could fit these camera tags on green turtles foraging in Lac Bay, Bonaire, to find out more about their grazing preferences and behavior within the bay. Marjolijn arrived from the Netherlands to help, and we were good to go!
The next day we fitted our first turtle with a cameratag, in collaboration with sea turtle conservation Bonaire. The method seemed succesfull and the camera stayed on nicely and the turtle seemed not to mind by observation after release. Tags were programmed to release after 20 hours.
However, finding back the cameratags proved to be incredibly difficult. Our retrieval equipment did not work as expected, and several times our boat broke down. After searching for days we only found back 1 of our tags, and then it was time to go to our next destination…
Eleuthera on the Bahamas! Here we would work together with CORE institute (clickthrough link through photo) on seagrass experiments and shark-turtle-seagrass interactions, together with Owen and Enrique, more of that soon.
Twitter updates from our current fieldtrip
By clicking on the images you get directed to some of our fieldwork pictures and updates
KNAW Ecology grant 2019
We’re super happy that the KNAW (Royal Netherlands Academy of Arts and Sciences) Ecology fund was awarded for our project. Now I can extend my fieldwork to go to the Bahamas, and other islands in the Caribbean. We will use this grant to answer questions concerning the impact of tropicalization on marine plant-herbivore interactions. Thank you KNAW! (for more info: https://www.knaw.nl/nl/prijzen/toekenningen-fondsen-knaw/toekenningen-knaw-fonds-ecologie-2019)
Video about our seagrass work online
Marjolijn and I assembled footage of our seagrass fieldwork in the Caribbean, and Marjolijn edited the images to display on the website of our department Aquatic Ecology of Wageningen university. See below!
Bonaire fieldtrip January 2019
This year kicked off with a 5 week fieldwork trip to Bonaire.
Already 8 months had passed since we started our fish exclusion experiment that’s part of a region wide experimental network. The 8mo sampling moment included taking pictures of the experimental plots, assessing shoot densitities and productivity in each of the 50 plots and burying a total of 100 teabags to measure decomposition rates in the sediment. We spend a lot of time underwater and in the ‘lab’(=our apartment) and concluded the work in one week with the three of us: Olivier our field assistant, Julia Msc student of Utrecht and me.
Next up was maintenance and monitoring of our turtle exclosures, and the start of a few pilot studies, including an aquarium or mesocosm experiment.
Another large part of this field trip was conducting the seagrass monitoring of Lac Bay.
Eight times we went out with the boat and in total visited 49 GPS points in the Bay, that are revisited once every two years. We assessed seagrass presence in different parts of the bay, and we use this data to follow the expansion of the invasive seagrass throughout the bay.
Last but not least, we had a visit of my chairgroup Aquatic Ecology and Water Quality Management of Wageningen University & Research. The group had a full program for five consecutive days. They visited the key ecosystems on the island and addressed several issues. We talked among others about the impact of overgrazing by goats and donkeys on erosion and subsequent coral degradation, the impact of increasing tourist pressure on marine ecosystems, mangrove expansion into Lac Bay and pollution in coastal waters by sewage/landfills/plastic. We used the broad knowledge of the group to brainstorm and discuss several key problems and possible solutions. This week inspired me to think in long-term concepts concerning research and nature conservation on Bonaire, and to broaden my scope to various issues. I particularly enjoyed conducting research on the reef (for the first time since 2015) and on land and combining those activities. Once again I was reminded of the importance of research communication and our obligation to do so.
Thanks to Stinapa for supporting us throughout this fieldtrip with logistics (boat use) and knowledge, they are of great help for researchers on Bonaire.
