Invasion Biology

Wednesday, January 24, 2007

YELLOW CRAZY ANTS ON CHRISTMAS ISLAND

Yellow crazy ant (Anoplolepsis gracilipes) is one of the largest and most destructive invasive ants (1). The native range of the species is not known exactly (2), “it may have been originated from Asia or Africa” (1). Yellow crazy ant invaded places such as Africa (South Africa), Asia (Malaysia) South America (Brazil) and Pacific Ocean (Hawaii). Anoplolepsis gracilipes was accidentally introduced to Christmas Island 1915 (3 ) and 1934 (3 ) and widespread to the entire island (3 ) .

Yellow crazy ant has unusually long leg and antennae. The researchers detected one super colony of Anoplolepsis gracilipes in 1989 on a high terrace above the Grotto (3 ) . The super colonies were again detected by researchers from Melbourne’ Monash University in 1997. The researchers were investigating the role of red land crab (Geocarcoidea natalis) on the Christmas Island ecosystem (4).

The Yellow crazy ant killed and displaced approximately ten(3) to twenty (3) millions of crabs on the rainforest floor. Crabs are keystone species of the rainforest. Anoplolepsis gracilipes consumed indigenous crabs and also occupied their burrows. They use formic acid to defend and to suppress their prey such as coconut crabs and reptiles (3 ).

The absences of crabs lead to the growth of seedling and spread of weeds on the Christmas Island. The population of Dendrocnide peltata began to increase and closed tracks which were used by people during their visitation on the Island (3) . At about ninety percent of the trees and shrubs were swarmed with sooty mould which resulted to the extensive canopy dieback. The population of indigenous birds, reptiles and mammals were also reduced. Studies indicated that the predation of immature Fregata andrewsi by crazy ant will result to decline of its population by eighty percent in the next thirty years (5). Anoplolepsis gracilipes is a dangerous agricultural pest (2).

The Park staff and experts struggled to find an appropriate method of baiting ants in 1999 and 2000. The amount of $1.5 from Natural Heritage trust was used to control crazy ants in 2000-2001(5). The successful eradication campaign took place in September 2002 and aerial baiting was used followed by continuous monitoring (5).

Masiya Kedibone
CSIR Pretoria
0001
Tel No: 012 8412123
Fax : 012 842 3676
E-mail :kmasiya@csir.co.za
weblog: http://kedimasiya.blogspot.com/

2 Comments:

  • Agai, you don't need the direct quote in the first paragraph!

    Your footnote formatting is a bit erratic.

    Your concluding paragraph is a bit weak. A bit about your own thoughts as to the future of this species and its continuation as a threat would've been nice.

    By Blogger NcK, at January 24, 2007 6:03 PM  

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