In Peru, conservationists and archaeologists unite to save a threatened gecko

LIMA — For more than two decades, José Pérez Zúñiga, a researcher at Cayetano Heredia University in Lima, has set out at night to search by the light of a flashlight through the pre-Inca ruins of the city for hidden treasure — not ancient artifacts of gold, but a tiny gecko with gold-flecked eyes.

“When I first started my research, my interests were scientific, and my goal was just to study this species, but today, my focus is on its conservation,” he says of his work with the critically endangered Lima leaf-toed gecko (Phyllodactylus sentosus).

Endemic to the valley of Lima and occurring almost entirely in a handful of archaeological sites scattered across the Peruvian capital, the lizard is threatened by urbanization, invasive species and inbreeding. However, local archaeologists and conservationists have been working together to bring the rare reptile back from the brink of extinction.

Displaced from the desert

The Lima leaf-toed gecko has a beige body striped and blotched in yellow and brown, and measures just 10 centimeters (4 inches) from head to tail. Each of its long toes tapers into a leaf-shaped adhesive pad. Unlike other geckos, though, it struggles to climb vertical surfaces; for much of its history, it had no need to.

The gecko’s natural habitat was once a barren area of the Peruvian coastal desert, flanked by the Rímac and Chillón rivers. Here, it thrived for eons, hiding beneath boulders during the day and darting across the sands at night to hunt insects and spiders. But with the first mass influx of humans, the lizard’s luck finally began running out.

The Lima civilization arose in the Peruvian desert nearly two millennia ago and began to alter the landscape to feed its growing population, redirecting the rivers to irrigate crops. “There was a decline in gecko population around this time due to habitat loss,” says Alejandra Arana, a researcher at the National University of San Marcos who has studied the species’ genomic history and co-authored a recent study on the subject. “It later recovered in numbers, but genetic diversity was lost, and the species entered a genetic bottleneck.”

After five centuries, the Lima culture collapsed due to war and environmental factors, but the civilizations that followed, such as the Wari and the Inca, would reduce the gecko’s habitat even further. Yet it was the arrival of the Spanish conquistadors in 1526 and the conquest of Peru that saw the reptile face its greatest reckoning.

Accompanying the invaders were invasive species. Domestic cats and dogs, brown rats and house mice introduced by the colonists to the new capital soon became prolific predators of the gecko, which became easy prey due to their poor climbing skills. “The only natural predators are barn owls, scorpions and a larger species of lizard,” says Pérez Zúñiga, also a co-author of the study. “So when they [cats and rats] first appeared, the species couldn’t cope.”

But predators weren’t the only threat. The city grew, and its urban sprawl devoured the desert. When the gecko was finally described by science in the 1970s, it was thought to have vanished everywhere except for several archaeological sites where it clung to survival. “It’s almost ironic that, nowadays, the remnants of these pre-Incan cultures are the last refuges for this species,” Arana says.

A refuge among ruins

After their collapse, the Lima left not only their bones and artifacts but more than 400 enigmatic adobe and clay pyramids known as huaca, scattered across what would become the capital city that bears their name. “For the Lima, the huacas were centers that combined religion, ceremony, and politics,” says archaeologist Pedro Espinoza Pajuelo, director of the Complejo San Mateo Salado archaeological site in the north of the city. “But today, these are important sites not just for the country’s heritage and archaeology but also for biodiversity. Actually, these are some of the last green areas in the city.”

The geckos have found fragments of their former desert habitat in 12 of the huacas, with suitable microclimates, abundant insect prey and labyrinthine hideaways among the nooks and crannies of the structures. Nevertheless, for these reptilian refugees, the sites are, at times, less than ideal sanctuaries.

Rats and stray cats sneak into the sites to prey on the lizards, taking a heavy toll on their already fragile populations. “A single cat or rat can do a lot of damage. Even in the largest huacas, populations barely exceed 500 individuals, so for such an endangered species, each loss is significant,” Pérez Zúñiga says.

Still, a more pernicious threat comes from urbanization. Surrounded on all sides by urban sprawl, each huaca has become an island for the geckos it supports, which are cut adrift from each other by the city. Already suffering from a lack of genetic diversity, this isolation complicates matters further; populations have begun to show signs of severe genetic inbreeding, increasing their likelihood of disease and extinction within the next decade.

Gecko guardians

During the late 1990s, when Pérez Zúñiga first began visiting the huacas to monitor and study the Lima leaf-toed gecko, he saw that archaeological excavations and the restoration of the structures had inadvertently disturbed the lizards. “Some restoration practices, like covering crevices with plaster, were preventing the geckos from escaping predators, and debris that served as hiding spots and nest sites were being removed,” he tells Mongabay.

To find a solution, Pérez Zúñiga and his colleagues discussed with the archaeologists how they could work together to improve gecko conservation in the huacas; this developed into a full-fledged conservation program, the Gecko de Lima project. Since then, changes in the management of the sites have reduced the numbers of predators by nonlethal capture, and have maintained areas of habitat for the gecko, which endeared itself to archaeologists when it was found to feed on insects such as beetles that damage the structures. “Both the huacas and the gecko are the patrimony of Peru, so we’re working together to protect both of them,” Espinoza Pajuelo says.

Over the years, discoveries of remnant populations of Lima leaf-toed geckos outside the huacas in the hills surrounding the city have increased the species’ known range. One hilltop, Cerro La Milla, where a substantial population of lizards has been found, is surrounded by one of Lima’s most dangerous slums. “It can be quite dangerous work to monitor the species there,” says Rosa Maria Urbano Cueva, a biologist and environmental educator with the Gecko de Lima project.

With every new population of the gecko discovered, the need for conservation becomes more urgent, experts say. In 2019, several local universities and Parque las Leyendas Zoo, which has a huaca within the grounds, focused on building a captive insurance population. So far, results have been mixed. “We’ve had breeding in captivity, but hatchling survival has been too low to call it a success, but we’ll keep trying,” Pérez Zúñiga says.

The conservation program is currently planning other options, including the translocation of geckos between the huacas to boost genetic diversity. “At the moment, we’re mapping the populations and studying the genetics of each population to determine how we can improve gene flow, and we’re looking for areas of the historic range where populations could be safely reintroduced,” Pérez Zúñiga says.

The Limeño lizard

In one of Latin America’s largest cities, getting the public to care about the plight of a little brown lizard was never going to be easy, but the Gecko de Lima conservationists hit another obstacle. “There’s a common belief in our country that geckos are venomous, like snakes. People are scared of them and sometimes kill them even though they are actually harmless,” Urbano Cueva says.

To change these perceptions, the team has posted information about the species at the archaeological sites and given talks to visitors at the huacas, the zoo, local schools and online. An illustrated children’s book about the gecko is also planned for release next year, to be distributed in schools.

“Many Limeños [residents of Lima] know about endangered species from the Andes, like the spectacled bear and the condor, but most people don’t know that the gecko exists. So this is something we’re actively trying to change with the next generation,” Urbano Cueva says.

The project’s work in raising public awareness of the species’ conservation is essential, according to Chris Woolley, a gecko researcher at the University of Wellington in New Zealand.

“Urbanisation can be a major threat to lizards, and I think very often cities are undervalued for the opportunities they offer for conservation,” Woolley tells Mongabay by email. “It’s easy for people to believe that conservation is something that happens in remote locations. This is an excellent example that reminds us that we share cities with a huge variety of wildlife and that our actions in the places we live determine their future. The Lima leaf-toed gecko is a great ambassador for urban conservation.”

Though the gecko may lack the size and charisma of other threatened species, Urbano Cueva says the reptile has something else going in its favor: its location. “People from the capital can be very proud, and the gecko is only found here; it’s a true Limeño. So we hope that the more people learn about this species, the more they’ll support its conservation.”

Citations:

Arana, A., Esteves, J., Ramírez, R., Galetti Jr., P. M., Pérez Z., J., & Ramirez, J. L. (2023). Population genomics reveals how 5 ka of human occupancy led the Lima leaf-toed gecko (Phyllodactylus sentosus) to the brink of extinction. Scientific Reports, 13(1), 18465. doi:10.1038/s41598-023-45715-x

Valdez, F., Iannacone, J., Luna, A., & Cossios, E. D. (2020). Population size and dynamics of the Lima leaf-toed gecko, Phyllodactylus sentosus, in one of its last refuges. Journal of Herpetology, 54(2), 155-160. doi:10.1670/17-079

Venegas, P. J., Pradel, R., Ortiz, H., & Ríos, L. (2017). Geographic range extension for the critically endangered leaf-toed gecko Phyllodactylus sentosus Dixon and Huey, 1970 and notes on its natural history and conservation status. Herpetology Notes, 10, 499-505. Retrieved from https://www.biotaxa.org/hn/article/view/24545

Sánchez, V. M., Manrique, M. Z., & Elías, R. P. (2022). Artificial incubation of eggs of Lima gecko (Phyllodactylus sentosus) (Reptilia, Geckonidae) kept in captivity. Revista de Investigaciones Veterinarias del Perú, 33(3), e22896. doi:10.15381/rivep.v33i3.22896

Banner image: The Lima leaf-toed gecko is a critically endangered species endemic to the valley of Lima and now found almost entirely in archeological sites known as huacas. Image by Jose Perez Zuñiga.

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