Population Census of the Eastern Santa Cruz Giant Tortoise: Part 2

December 18, 2018

By Jeffreys Málaga, Galapagos National Park ranger. Leer en español.

Marking a tortoise

Marking a tortoise in the field for future identification

Although the range of the Eastern Santa Cruz giant tortoises (Chelonodis donfaustoi) falls mostly within the Galapagos National Park, they also migrate up to the areas known as El Camote and El Cascajo. While these areas have always been part of the tortoises’ range as they migrate to the highlands, the habitat has been greatly altered as the land is now part of the agricultural zone. Given that tortoises migrate to and are often seen in these areas — the second half of the census was conducted on private property in the agricultural zone.

We worked throughout the private properties using a combination of encampments and daytime visits, covering a diversity of farms and other properties. This region includes the producers of most of the vegetables consumed on Santa Cruz, cattle herds, along with a private tourist reserve, an adventure tourism site, and even a luxury hotel.

Our daily work in the farmlands differed little from our days working within the National Park. We’d wake each morning at 4:30 am, prepare our breakfast, and then start the day-long search for tortoises. We worked in an area of green and often impenetrable vegetation, where creeping vines covered shrubs and trees, many of which were invasive species, such as blackberry and guava. But with our well-sharpened machetes and high curiosity, we’d persevere in our search for every tortoise present in our search block. No obstacle would deter us.

Highlands of Eastern Santa Cruz

The highlands of Santa Cruz Island from the southeastern side

Perhaps the worst was the high abundance of invasive black ants (Solenopsis geminata), which often covered the vegetation. As we cut branches with our machetes, the ants would fall onto our bodies and immediately, as is their habit, they’d begin to bite. This only drove us to work as fast as possible while still following the established protocol to ensure data quality.

Given our lack of communication with the other groups, we’d constantly ask ourselves, sometimes seriously and sometimes in jest, how each group was doing. How many tortoises were they encountering? Just the thought of them getting more than us spurred us on to find more. Although my specialty is botany, I have always been a very curious park ranger. One day I noticed that the carapace and the feet of some of the tortoises seemed very similar to those of the San Cristóbal species (C. chathamensis) on my home island. After the census, I reread the publication describing the Eastern Santa Cruz tortoise and discovered that its ancestors were from San Cristóbal.

Tortoise in mud

A tortoise in the mud in the farmlands

Through my work, I have been fortunate to know most of the Galapagos Islands and to witness many changes in the ecosystems. This was the first time I had worked in the agricultural area of Santa Cruz and I noted marked differences between properties that adjoin the protected area with other private properties. On properties used for tourism, the owners make an obvious effort to maintain good conditions for the tortoises. However, they also keep the ponds full, which can be counterproductive as providing a permanent water source could change their behavior.

In those properties that are exclusively agricultural, on the other hand, the focus is on production. No doubt the presence of tortoises is problematic, so they have fences that make it impossible to enter. We also encountered tortoises within abandoned properties. These areas are invaded by black ants and a variety of invasive plants, especially blackberry, guava, elder, and spiderwort, thus creating an inexhaustible source of seeds that can be dispersed to protected park land. Once tortoises consume these plants with their thousands of seeds, they carry and deposit them throughout their range.

Barbed wire and tortoise with scratched shell

A barbed wire fence surrounding an agricultural property (left) and a tortoise with scratches on its carapace from pushing under a barbed wire fence (right)

When we completed the census, I was extremely curious to know how many tortoises are in the population. The field teams all gathered in El Cascajo. Local resident Novarino Castillo very graciously lent us his house to use as our operations center, to complete quarantine, and to compile all the field data. With our field forms filled out and GPS in hand, we circled around Wacho Tapia who led the expedition and, taking turns, gave him our data as he proceeded to download the information from our GPS units.

It was both exciting and satisfying to see how each group had covered their search blocks. The map slowly filled with lines, some more intricate than others, since the direction of the routes depended on the density of the vegetation. Once Wacho compiled the data from the 12 groups, we discovered that during the work within the park and then in the farmlands, we had located, measured, and marked with a microchip a total of 403 tortoises. I found it interesting that we found approximately 30% of the adult tortoises on the boundary between the agricultural zone and the National Park. This showed that due to the extreme drought in the lowlands and given the end of the nesting season, many males and females were migrating to higher elevations where food and water were more abundant.

Author in the field

The author (left) giving direction during the search for tortosies

We had once again successfully completed our mission. I look forward to similar work in the future, work that we will do responsibly and always with passion — remembering that Galapagos does not solely pertain to galapagueños, or even Ecuadorians, but to the world. Therefore, we must continue to take care of it because the world is watching.


Jeffreys Malaga Jeffreys Málaga first visited Galapagos in 1976 at age 11. He then moved to San Cristóbal when he was 15 and has lived there ever since. He participated in the Tortoise Workshop in 2012 that led to the development of the Giant Tortoise Restoration Initiative (GTRI), a collaboration between Galapagos Conservancy and the Galapagos National Park. That same year he was named “Guardaparque del Año,” or Park Warden of the Year. Jeffreys has been an instrumental member of the GTRI team with the Park from the start.

All photos © GTRI



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