Introduced Species of the
Galapagos Islands
by JUAN ORTIZ
Introduced
Species of the
Galápagos Islands
Since the discovery of the Galápagos Islands in 1535, approximately 1,639 introduced species have been recorded, including plants, invertebrates, vertebrates, fungi, viruses, and bacteria.
Among the first introduced species were the black rat (Rattus rattus) and the house mouse (Mus musculus).
The arrival of almost all non-native species is closely tied to human activity, whether intentional or accidental.
Introduced species have made their way to the islands through various means: on fruits and vegetables, boats, planes, or inside luggage.
What Are
Introduced Species?
Introduced species refer to organisms brought to the
Galápagos by humans from other parts of the world
These species were not originally found in the
archipelago and disrupt the natural ecosystem by
establishing themselves in a habitat without their native
predators or competitors.
Many of these species were accidentally introduced,
carried on cargo ships, planes, agricultural products, or
personal belongings. In other cases, they were
intentionally brought, sometimes as food sources or
ornamental plants.
Types of Introduced Species
The introduced species in the Galápagos are categorized as follows:
Naturalized species: 888 species (54.2%) –
These species have adapted and now thrive
without human intervention.
Human-dependent species: 575 species (35.1%) – These organisms survive only through human assistance or are restricted to human settlements. Like the dengue mosquito.
Coexists with introduced species: 33 species (2%) – Species that interact or cohabit with other introduced organisms without causing major issues. Like ies and some parasites.
Intercepted species: 48 species (2.9%) – These species were stopped before they were
introduced on the islands.
Historic record only: 15 species (0.9%) – These species were recorded in the past but are no longer present.
Eradicated species: 5 species (0.3%) – These
species have been successfully removed from
the ecosystem.
Status of Introduced Species
- Controlled non-native species:
These species are present but do not
severely aect the ecosystem or are
actively managed to prevent damage.
Example: Some agriculture or
ornamentation plants.
- Invasive species: 59 invasive species.
These species adapt quickly, spread
aggressively, and compete with or prey
on native organisms, causing signicant
ecological harm. There are an additional
83 species categorized as potentially
invasive species. Examples of invasive
species: Goats, blackberry plants, and
black rats.
What Do Introduced
Species Cause?
The impact of introduced species on the
Galapagos ecosystem is profound and
multifaceted.
Because many native species evolved in
isolation and without natural predators, they are
highly vulnerable to competition and predation
by introduced organisms.
Some key effects include:
- Predation and extinction of native species: Rats, cats, and
dogs prey on eggs and young animals, threatening the survival
of species like giant tortoises, land iguanas, and seabirds
- Competition for food and space: Plants like blackberry (Rubus niveus) overrun native vegetation, blocking sunlight and altering nutrient cycles. Animals such as goats consume large quantities of vegetation, depriving native herbivores of food.
- Habitat destruction: Goats and cattle graze extensively, leading to soil erosion and the loss of critical habitats for endemic plants and animals.
- Disease transmission: Introduced mosquitoes transmit
diseases such as avian malaria to birds, including Darwin’s
nches, which have no immunity.
- Ecosystem imbalance: Native species like cactus finches and tortoises depend on specific plants, and when these are displaced by invasive flora, it disrupts the food web and ecosystem functioning.
The cumulative efect of these pressures can lead to the
extinction of native species, loss of biodiversity, and the
collapse of natural ecosystems.
What Are the Most
Notorious Introduced
Species in the Galápagos?
Several introduced species have gained infamy for their destructive
effects on the islands. Among the most harmful are:
Goats (Capra aegagrus hircus):
Introduced by settlers, goats quickly spread
across islands such as Santiago and Pinta,
decimating vegetation and threatening the
survival of native herbivores, particularly
giant tortoises.
Black rats (Rattus rattus):
These rats prey on the eggs and hatchlings
of native birds and reptiles, endangering
several endemic species.
Blackberry (Rubus niveus):
This invasive plant forms dense bushes,
displacing native plants and altering
ecosystems.
House cats (Felis catus):
Feral cats prey on a wide range of native
animals, including birds and reptiles, further
disrupting the delicate ecosystem.
What Measures Have Been Taken Against Introduced Species?
Given the severity of the ecological damage caused by introduced species, multiple strategies have been implemented to control or eradicate them:
Eradication programs: Large-scale eorts, such as the removal of goats from Pinta Island, have been successful in restoring native vegetation and allowing the reintroduction of species like tortoises.
One of the most effective efforts to control invasive species was the Isabela Project, which targeted eradicating goats on several islands, including Santiago, Pinta, and Isabela.
The “Judas goat” strategy played a critical role in the project. In this approach, goats fitted with radio collars (the “Judas goat”) were released to lead hunters to hidden goat populations. This allowed conservationists to track and eradicate thousands of goats effectively. The Isabela Project became a global model for invasive species management, combining helicopter hunts with ground operations.
Quarantine protocols: Strict inspections are conducted on all goods and materials entering the islands to prevent the accidental introduction of new species.
Community education and involvement: Awareness campaigns encourage residents and tourists to avoid bringing non-native plants and animals to the islands. Local communities also participate in conservation efforts, including volunteer programs to remove invasive plants.
Ecosystem restoration: On islands like Santiago, where invasive species have been eradicated, efforts are underway to reintroduce native species and restore natural ecosystems.
Conclusion
Introduced species pose a significant threat to the biodiversity of the Galápagos Islands, driving extinctions, disrupting ecosystems, and spreading diseases. However, projects like Isabela’s goat eradication program demonstrate that conservation eorts can restore ecosystems to their natural state.
The future of the Galapagos depends on continuous monitoring, education, and cooperation. Through collective efforts, this unique environment can be protected, and the survival of its native species
will be ensured for generations to come.
References
“Introduced Species Dashboard” dataZone, Charles Darwin Foundation,
https://datazone.darwinfoundation.org/en/introduced-species. Accessed 18 October 2024.