General Impact
High densities of the yellow crazy ant (Anoplolepis gracilipes) have the potential to devastate native 'keystone'
species, resulting in a rapid alteration of ecosystem processes and negative effects on
endemic species. The most notable example concerns the native forests of Christmas
Island, in which populations of the yellow crazy ant have exploded in recent decades (at
least 60 years after its initial introduction) (CBD 2003).Please follow this link for more details on the impacts of yellow crazy ants on biodiversity. For a summary of the general impacts of invasive ants, such as their affect on mutualistic relations, the competitive pressure they impose on native ants and the effect they may have on vulnerable ecosystems please read this document: invasive ants impacts compiled by the ISSG.
Location Specific Impacts:New South Wales (Australia) 
Reduction in native biodiversity: Species and populations in NSW that may become threatened by the presence the Anoplolepis gracilipes include ants such as Rhytidoponera spp., Pheidole spp., Paratrechina spp., eastern sedgefrog (see Litoria fallax in IUCN Red List of Threatened Species), eastern grass skink Lampropholis delicata, and a burrowing skink Ophioscincus truncates. A range of other ground-dwelling invertebrates and vertebrates may be affected in NSW (DECC, 2005).
Threat to endangered species: Species and populations in NSW that may become threatened by the presence the Anoplolepis gracilipes include ants such as Rhytidoponera spp., Pheidole spp., Paratrechina spp., eastern sedgefrog (see Litoria fallax in IUCN Red List of Threatened Species), eastern grass skink Lampropholis delicata, and a burrowing skink Ophioscincus truncates. A range of other ground-dwelling invertebrates and vertebrates may be affected in NSW (DECC, 2005). Northern Territory (Australia)
Agricultural: Dr Benjamin Hoffmann advises that pest ants, particularly the African big-headed ant and the yellow crazy ant, are a major threat to the environment and are also a serious pest of agriculture as they cause outbreaks of sap-sucking insects, which harm plants (ScienceDaily Magazine, Dec 12 2003).
Ecosystem change: Dr Benjamin Hoffmann advises that pest ants, particularly the African big-headed ant and the yellow crazy ant, can form huge colonies, totally displacing native animals and seriously disrupting ecological processes (ScienceDaily Magazine, Dec 12 2003).
Human nuisance: Pest in aboriginal settlements.
Predation: Displacement of native ants. South India (India)
Agricultural: Nesting undermines crop plants; tends scale insects.
Human nuisance: Formic acid irritates farmworkers; household pest.
Predation: Displaces native ants. Java (Indonesia)
Agricultural: Tends scale insects in plantations. Bird Is. (Seychelles)
Reduction in native biodiversity: Gerlach (2004) found the impacts of crazy ants to be less than had been reported by other authors, possibly as he distinguished between the effect of habitat and other factors. Results suggest that A. Gracilipes significantly decrease abundances of other ant species and paussine beetles, but not other invertebrates.
Threat to endangered species: In 1997 the ant spread into the island's colony of nesting sooty tern (See Sterna fuscata in the IUCN Red List of Threatened Species). "This caused the failure of tern breeding in 1999 due to the ants swarming over the ground, disturbing the chicks and causing them to shake their feet constantly. This is normally a behaviour used to dislodge ticks but the numbers of ants resulted in constant repetition of the movement, leading to excessive energy expenditure, reduced feeding, and ultimate exhaustion and death (Robert 1999b)" (Gerlach, 2004).Additionally the crazy ant has been recorded preying on blind snakes (Ramphotyphlops braminus Daudin), turtle (Eretmochelys imbricata Linnaeus) hatchlings and fairy tern (Gygis alba Sparrm) chicks that had fallen from their nests (Gerlach, 2004).
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