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Antibiotic resistance in Galapagos Giant Tortoises

Published on July 06, 2021

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Scientists from the Charles Darwin Foundation (CDF), the Saint Louis Zoo Institute for Conservation Medicine (ICM), the Animal Health Research Center (INIA-CISA), the Complutense University, and the European University of Madrid, together with technicians from the Galapagos National Park Directorate (GNPD) showed that one of the most emblematic species on Earth, the giant tortoises of Galapagos, carry antibiotic resistance bacteria associated with human activities in the archipelago.

This research showed that a greater quantity of resistant bacteria is present in tortoises that share their habitat with human settlements (i.e., agricultural, urban, and tourist areas) than tortoises living at remote areas, such as the Alcedo Volcano on Isabela Island.

These results were verified after analyzing the fecal samples of 270 tortoises. Scientists searched for a total of 21 genes that encode resistance to eight different classes of antibiotics, commonly used in human and veterinary medicine, as well as growth promoters in farm animals.

“Antibiotic resistance is spreading around the world causing an invisible pandemic that compromises the health and treatment of humans and animals,” says Dr. Ainoa Nieto Claudín, author of the work, Ph.D. student and researcher at the CDF and ICM.

Researchers around the world are working together to better understand the origins, transmission, and impacts associated with these “superbugs,” as international health agencies have designated the study of antimicrobial resistance as one of the top priorities of political agendas.

“The Covid-19 pandemic has increased the use of antibiotics and, consequently, the emergence of resistant bacteria around the world. The animal-human interface creates the perfect scenario for resistance to enter wild species and contaminate their habitat, perpetuating the resistance transmission cycle,” adds Dr. Nieto Claudín.

Research conducted as part of the Galapagos Tortoise Movement Ecology Program (GTMEP) showed that giant tortoises are key species for the archipelago’s ecosystems. They are considered Galapagos engineers and gardeners, due to their role in the dispersal of seeds and the modification of the ecosystems. Increased tourism, habitat fragmentation, introduced species, and climate change are just a few of the many threats that Galapagos tortoises face today.

Dr. Sharon L. Deem, Director of the ICM and a co-author on the paper adds, “Galapagos tortoises are migratory species on islands like Santa Cruz, the most populated in the archipelago. Here, tortoises often leave the protection of the National Park and enter private lands during their annual migrations. Galapagos tortoises may spend more than six months a year in urban and agricultural areas, where they encounter new threats, such as impacts from cars, plastic ingestion, and exposure to resistant bacteria and pesticides.”

Wildlife such as Galapagos tortoises may act as sentinels of the health of the ecosystems where they live. Fernando Esperón, co-author of the paper and professor at the European University of Madrid explains, “It is essential to continue with studies of this caliber in emblematic species such as giant tortoises, to better understand how these resistant bacteria spread, proposing solutions to a global crisis that threatens the health of both people and animals.”

But it is not all bad news. Knowing the places where there is more antimicrobial resistance within the human-populated areas of Galapagos allows scientists to coordinate management actions with local institutions to control the use of antibiotics and raise awareness among local farmers.

Furthermore, the data produced by this study suggest that levels of antibiotic resistance found are low, when compared to other studies carried out in large continental cities. This suggests that the situation in the Galapagos could be reversible if scientists, decision-makers, and the local community join efforts to regulate and reduce the use of antibiotics in the archipelago.

Conservation of Giant Tortoises

Galapagos tortoise migration plays a fundamental role to maintain healthy tortoise populations. Understanding the ecological, social, and sanitary implications of these movements allows researchers to reduce the threats the tortoises are facing and contributes to their conservation.

The GTMEP program is a multi-institutional collaboration between the Charles Darwin Foundation, Max Planck Institute for Animal Behavior, Galapagos National Park Directorate, Saint Louis Zoo Institute for Conservation Medicine, Houston Zoo, and Galapagos Conservation Trust. Drs. Stephen Blake and Sharon Deem lead the program with the support of a local team based in Galapagos and a large number of international collaborators/partners.

How did it start?

They started the programme in 2009, with a few GPS devices, a field notebook, and a bike. They wanted to show, for the first time, whether Galapagos tortoises truly migrate; with the following questions in mind: where do the tortoises go every year? How and why do they move? And more important, how do human impacts may affect the conservation of such emblematic species?

Ten years of dedicated research and tons of data now support their theory: Galapagos tortoises can move long distances every year, and their movements vary according to islands, species, ecosystems and health condition.

What do they do?

They work in three islands (Española, Santa Cruz and Isabela) with four different tortoise species (Chelonoidis hoodensisC. porteriC. donfaustoi and C. vandenburghi). The researchers use tracking devices such as GPS and VHF to understand the movements of adult and juvenile tortoises in their natural environment. They also study the tortoise diet, the reproductive success of the nests, the survival of baby tortoises, and the impact of physical barriers (fences, roads, etc.) that tortoises may encounter along their migratory routes.

Their team includes a large number of experts; biologists, ecologists, veterinarians, sociologists, geographers and educators work together to produce cutting edge applied science and information that can be used by local institutions to maximize the conservation of these species.

In addition to ecological, reproductive and social studies, the programme has a strong research component focusing on tortoise health. They are assessing the health of giant tortoises and how the interaction with humans and domestic animals may affect their well-being.

The main goal of this project is to better understand Galapagos tortoise migrations, and the social, ecological and sanitary aspects that may affect their conservation.

The results

The researchers have movement ecology data of more than 100 tortoises from three different islands. They know, for example, that Española tortoises do not migrate, whereas tortoises from Alcedo volcano (Isabela) can migrate long distances every year. They did calculate that one tortoise can walk up to 10 km in two weeks and spread thousands of seeds during its journey. They also know that migratory animals use the same routes year by year, and that, on Santa Cruz Island and Alcedo volcano, both males and females migrate from the dry lowlands within the National Park area to the humid highlands where food is available all year round.

They now know the movements of newborn tortoises in El Chato area on Santa Cruz Island. Theur data show how baby tortoises move a relatively long distance from their nest, walking up to half a kilometer away until they find a place where they can feed and survive during the upcoming years.

They’ve learned that the incubation temperature determines tortoise sex; warmer temperatures will result in more females whereas colder temperatures will deliver more males. In Western Santa Cruz (C. porteri), most  of the males are born in colder and more humid areas where young tortoise survival is lower because of environmental conditions.


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