According to available information, the list of introduced invertebrates in the Galapagos Islands totals 543 identified species. Of the eight most aggressive species, three are ants.

Some species of ants in urban environments can affect human beings by invading their homes and workplaces, where they contaminate food and cause discomfort and emotional stress. Their bites can affect human health and make them mechanical vectors for pathogens. Urban ants can damage electrical cabinets and switchboards, as well as appliances such as refrigerators, TV sets, videos, stereos, and computers.

Worldwide, more than half of the ant fauna associated with humans has been introduced mainly from tropical countries to other latitudes. These species considered to be exotic, are among the group of so-called "roving ants", which possess a number of biological and ecological characteristics that favor their spread through human trade activity.

Roving ant colonies contain multiple queens. They form unicolonial societies where there are no distinct boundaries. Their workers, small and sterile, exhibit a marked tendency to migrate and show no aggression among nests. On the other hand, they are very aggressive towards other native species which they displace.

Galapagos ecosystems are threatened by several species of this type of ant, against which control and eradication plans are held.

Big-headed ant (Pheidole megacephala)

Big-headed ants are highly invasive. They can nest in soil, rock, wood, or in urban areas. Multiple queen colonies can join to form mega-colonies, extending over large areas.

	Big-headed ants are a plague on other islands, attacking newborn animals, as this chick on Kure Atoll, Hawaii.

They get their food from sugars secreted by other insects, or from substances with sugar, fats, or proteins found in homes, and are therefore a nuisance to people.

They can also displace other insects and kill newly hatched birds.

These ants displace most native and endemic invertebrate fauna from the areas where their colonies are directly located, due to their attacks, and as such are a serious threat to biodiversity. Tests indicate reductions in vertebrate populations where these ants are extremely abundant.

They are also a threat in populated areas, both agricultural and urban.

Urban areas are private areas on populated islands where the greatest changes in the environment occur, through the construction of buildings and infrastructure, road systems, introduced species, pollution, etc. Most human activities are concentrated here, making them the collection and distribution centers, where most of the people and cargo arrive from the mainland and from other islands.

So far it has been determined that the big-headed ant is distributed in four districts of Puerto Ayora, on Santa Cruz Island, and two in Puerto Baquerizo Moreno, San Cristóbal Island.

Although these areas are not under the jurisdiction of the GNP, the vision of an "island" territorial management forces the emphasis on the importance of strategic relations between the different administrations (e.g., Municipal Governments, INGALA and DPNG) that must collaborate on the interdependent network level to find solutions to land use problems and other existing problems in the Galapagos socio-ecosystem.

The effects on plants and horticultural crops can be direct due to the consumption of seeds, or indirect by sheltering insects such as phytophages that reduce plant productivity. These mechanisms facilitate the invasion by an introduced plant species.

	» Introduced ants in Galapagos

It is also a social problem because these ants chew irrigation lines, telephone wiring, and electrical cables. They have an impact on health because they are generally in contact with waste or garbage and thus are carriers of viruses and bacteria that can cause diseases in humans or pets.

The monitoring methods used for the eradication of ants have been used in similar projects and have been very effective. These methods include trapping, attractants, and toxic baits which will be placed in sites infested by this species and then gradually in other urban and specific areas such as garbage dumps and collection centers of each inhabited island. This will enable the identification of the degree of infestation of these ants on the islands of Santa Cruz and San Cristóbal, and then implement the necessary actions to control or eradicate this aggressive species in Galapagos using toxic bait or fumigation.

The insecticide Sigue Pro® is also applied. Sigue Pro®´s insecticidal action is slow enough not to alert the ants of its danger, so it does not give the workers the opportunity to move the queens, larvae, and pupae to establish a new colony, as with the use of other chemicals.  

The acquisition of enough Sigue Pro® is considered for 2009, in order to eradicate this species from both islands. Monitoring actions must be implemented on other islands to eliminate the possibility of ants invading other areas.

Fire ant (Wasmannia auropunctata)

The little fire ant, or Wasmannia auropunctata (Roger) red ant, is one of the most aggressive species that has been introduced in the Galapagos Islands in its entire history.

This ant has been listed as one of the 100 most dangerous invasive species in the world by the Global Invasive Species Program. This species was introduced into the islands between 1910 and 1920 and first colonized Santa Cruz. It has since colonized other islands of the Galapagos.

	The little fire ant is one of the most aggressive species that has been introduced in the Galapagos Islands in its entire history.

The red ant W. auropunctata was first reported on Marchena in 1988 and poses a serious threat to fragile ecosystems such as the ones on the Galapagos, as it produces a negative impact on communities of ants and other native invertebrates. This introduced species also produces a decline in the population density of reptiles and birds and it also causes damage to plants because it has a close relationship with the cottony cushion scale Icerya purchasi, another invasive species in Galapagos.

On Marchena, since the year 2000, a fire ant eradication program has been implemented in a 26-hectare area. This island has an area of 130 km², an altitude of 340 meters, and comprises two vegetation zones, the arid area and the very dry area. For this activity a methodology that consists of two phases was developed:

In the first phase fire ants and other communities of ants were monitored, using sausage, peanut butter, cookies, and tuna fish as bait, as well as Pitfall and Berlese traps to estimate the relative abundance of the species and the distribution of the ants.

In the second phase the fire ant elimination program was implemented, using the specific insecticide bait Siegue Pro® (hydramethylnon 0.73 g/kg) that was released into the infested area after each monitoring.

In the last six monitoring efforts conducted since 2002 in the treated area, W. auropunctata was not found and the native communities had been stabilized.

The methodology used in this eradication program was effective and can be used in other areas or islands where this ant is distributed.

	Park Rangers and scientists from the Charles Darwin Foundation collected data on Marchena during the first eradication phase in the year 2000.

In the immediate future systematic monitoring should be performed to determine other areas on the island invaded by this ant.

In 2009, there are plans to conduct a monitoring patrol and try to establish this important information and thus budget the resources to perform the total eradication of introduced ants on Marchena Island.

On Isabela Island campaigns to control the presence of the fire ant (Solenopsis geminata) are carried out in the nesting sites of tortoises in "Cinco Cerros". Likewise the eradication of W. Auropunctata is to be resumed at the "San Pedro" site, where the 32-hectare invaded area was already established.

At the beginning of 2007 the presence of S. geminata was detected on Champion Islet so monitoring was immediately carried out to determine the degree of infestation of the islet.

To date, four applications of Siege Pro® have been made, which is believed to have eradicated this invertebrate. However, careful monitoring should be made to determine the effectiveness of the actions that were begun.

This program has counted on the support of:

The Charles Darwin Foundation for the Galapagos Islands (CDF) is an international nonprofit research organization dedicated to providing scientific research, technical assistance and information in order to ensure the success of conservation in Galapagos.