Cristian Rodriguez has a doctorate in fly sexual behavior. This is the level of specialization of this expert, who is currently working in the Galapagos Islands. Rodriguez is a Mexican researcher invited by the Charles Darwin Foundation (CDF) for the Invasive Philornis downsi Fly Control Project.

He works with a team of seven people at the CDF. The team is led by Paola Lahuatte and Charlotte Causton. Externally, they collaborate with the National Park and local and international academia. The researcher came to the islands for a six-month period to investigate fly brood size growth.

Rodriguez, who studied biology, had developed his career in agricultural pest control. At the height of the pandemic, the biologist was working on pest control on a blueberry production ranch when he heard about the Galapagos project. He happened upon an online forum discussing scientific papers on fly behavior with members of the CDF team in charge of the phyllos fly project.

"For me it was a surprise, I always envisioned my activities to the agricultural world. It's quite comforting to know that I can help the finches," says Rodriguez, who historically had developed projects in the agricultural trade.

Cristian Rodriguez monitors the biological cycle of the phylum fly at the Charles Darwin Foundation's scientific station. More than 1000 flies are under study. Photo: Manuel Novik

Days in the lab in Galapagos begin with meeting the insect's basic needs. "The insects dictate how our routine will begin," he says. Rodriguez begins by providing "breakfast" to the flies, checks the room temperature and monitors for mass mortality events.

For countless hours he analyzes the sexual behavior of the invasive avian vampire fly or philornis downsi, which has spread to the islands. At the CDF, located on Santa Cruz Island, Rodríguez works in a control laboratory dedicated to the analysis of the fly that threatens the existence of, among other species, the mangrove finch, one of the 17 iconic finches discovered by Charles Darwin, the English naturalist who visited the archipelago in the early years of the Ecuadorian Republic.

The vampire fly is an introduced fly, possibly from ships and airplanes, that lays its eggs in bird nests. Its larvae feed on the blood of the chicks, which usually end up dead. There are 18 endemic and native Galapagos birds affected by this pest.

The study groups are called hives. In these groups the life development of the flies is monitored. 

Rodriguez, who is a specialist in the fly's behavior, assures that it is a "romantic" fly. "It likes to mate at dusk," he says. The researcher works in a meticulous routine of studying this species. He feeds them with protein and powdered sugar, so that their diet is similar to that of the outside world and they can reproduce normally.

Flies are close to light and at a warm temperature to stimulate reproduction. Photo: Manuel Novik

He maintains a warm temperature in the laboratory. He keeps the flies close to light sources, so that at dusk they can simulate outdoor living conditions.

The scientist laughingly comments that at this level of research, the specificity of the study makes it necessary to focus on an almost unique environment. He recently received a visit from a colleague who has a PhD in fly diet. According to him, diet is a key element in simulating living conditions.

Searching for a biological enemy

The laboratory's goal is to replicate the life of flies in the outside world in order to find an "enemy" that will allow them to control the plague in a natural way. They must find another species that can reduce the fly population. According to the CDF, the level of fly propagation makes it impossible to try to eliminate them, so the only option is to control the species.

The Mexican researcher aims to find a solution to the pest that threatens the mangrove finch, one of Darwin's iconic finch species. Part of his work consists of sitting down to monitor and evaluate the behavior of groups of flies inside mesh cubicles.

The biological control project involves several strategies in its eight-plus years of development. The introduction of the wasp, repellents and attractants, and sterilization of the fly to prevent further reproduction are part of the strategies being considered.

CDF estimates that there are less than 100 mangrove finches left alive, a critical number. To protect the bird, they use short-term solutions such as fly attractants for later study in captivity in the laboratory or low-toxicity repellents at the base of nests. The institution has scientists who know how to climb and have managed to place the repellent in high trees, since the nests of these birds are usually in places that are difficult to access.

The Mangrove Finch (Camarynchus heliobates) inhabits the northern part of Isabela Island, Galapagos. Photo by Liza Diaz Lalova.

Breeding the birds in captivity was considered, but the option is too costly. The few live specimens make this type of finch one of the rarest in the islands. According to Galapagos Conservation, only 20 breeding pairs have been found in the last eight years.

However, these solutions are short-term. The spread of the fly requires the introduction of a "natural enemy" to regulate its population. Currently a potential candidate is a wasp discovered in continental Ecuador that seems to attack only flies. The solution would be somewhat paradoxical and also entails risks: bringing another species from the mainland to the islands.

According to Rodriguez, throughout history science has determined that there is an executioner for every victim. Flies are both victims and victimizers of specific species. The introduction of the wasp could be the solution, but the problem is that there is still no certainty about the implications of introducing this wasp into the environment and the alterations to the natural ecosystem in Galapagos.

Successful experiences already exist

The mangrove finch is found on Isabela Island, the largest of the archipelago, in the Caleta Negra area, in the northwestern mangroves of the island. According to María José Barragán, science director of the Charles Darwin Foundation, it is believed that the fly was introduced to the islands in the 1960s, although its impact was only seen in the 1990s.

María José Barragán, CDF's Science Director, spoke at a conservation journalism program, led by Hemisferios University, about the foundation's main advances in conservation on the islands. Photo: Manuel Novik

Barragán told in a conservation journalism conference held by the Universidad Hemisferios in Puerto Ayora that there was a past experience that gives them confidence that they can control this pest. In the early 2000s a cottony fungus critically affected 98 plant species on the islands. An Australian ladybug was introduced and was successful in controlling this pest. The wasp that was successful in controlling the flies would do so by parasitizing the eggs they leave in finch nests.

Rodriguez has different groups of flies that he calls "mother colonies". The researcher conducts tasks with the different groups, through which he has more than 1,000 flies under study. The CDF has more than 40 researchers working on specific conservation projects with different endemic, native and introduced species of the islands.

Introduced species and the natural balance

The mangrove finch lives in a reduced environment in a mangrove forest. Once at the nests, researchers use syringe sticks to inject the repellent into the nests. In some cases they inspect and remove larvae from the nestlings found. But the use of repellent must be done sparingly; if the dose is exceeded, the parents may abandon the nest. On the other hand, if not enough repellent is applied, the fly may survive and continue to parasitize the young birds. 

Researchers have developed skills to climb trees up to 20 meters high in order to place the repellents. Photos: © Juan Manuel García / FCD

Applying insecticides has been a momentary relief, but trees over 20 meters are dangerous and costly scenarios to access for scientists, who must use climbing equipment and improvised scaffolding.

The vampire fly is not the only cause of declines in endemic bird populations in Galapagos. Reduced food availability caused by environmental degradation, predation by invasive species, and introduced diseases are other reasons.

Video about the work with mangrove finches. Charles Darwin Foundation

Since 2014, CDF has been managing a bird conservation program with the cooperation of scientists around the world. The status of small landbird populations is especially critical on the four inhabited islands of Santa Cruz, San Cristóbal, Isabela and Floreana.

The mangrove finch now inhabits a reduced area of 30 hectares on Isabela Island. The International Union for Conservation of Nature (IUCN) classifies it as Critically Endangered.