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The distribution and abundance of an invasive species: the common myna (Acridotheres tristis) on Atiu, Cook Islands
Biodiversity Conservation, BRB
Available Online

Mitchell. J.

2009
An invasive alien species are known to cause significant economic and environmental damage. Islands are much more vulnerable to the invasion of invasive alien species, and have higher rates of extinction. In the islands of the South Pacific, there are several species Polynesian land birds which are threatened with extinction due to invasive alien species and human interference. Without any intervention from humans, it is likely that these birds will suffer extinction in the next few decades. The island of Atiu in the Cook Islands (South Pacific) supports a range of avian fauna. In 2007 the Rimitara lorikeet (Vini kuhlii), also known locally as the ‘Kura’ was introduced to Atiu, to make a reserve population, as there were only approximatley 1000 left on the island of Rimitara, French Polynesia. There is concern for this species on Atiu due to the existence of the common myna (Acridotheres tristis). The myna is an aggressive invasive which is one of the world’s worst 100 invasive species. It was introduced to the Cook Islands by the government, with the intention to control the coconut-stick insect (Graeffea crouani), but is now a pest itself. A myna control programme on Atiu is being coordinated and controlled by Gerald McCormack (Cook Islands Natural Heritage Trust), working through George Mateariki, and using funding from various conservation organisations. Poisioning is being carried out by George in order to reduce myna numbers, and a bounty has been set on the birds or for every right foot so that the locals can help as much as possible. This investigation aimed to estimate the total population size on the island to use as a starting count to determine whether the programme is successful or not. Two methods were used which included roost counts to find an estimate of the population, and a transect method using a Distance programme to estimate the number of birds per hectare as well as the level of abundance in various habitat types. The two methods had overlapping results, giving a total estimated range of 3250 to 8460 birds on the island, although it is more likely to be at the higher end of this estimate at around 6000 to7000 birds. Further investigation will need to determine any change in the population size, any changes in habitat composition as well as the impact on the native species, especially the effect on the Kura and its population size.
Quantifying the dominance of little fire ant (wasmannia auropunctata) and its effect on crops in the Solomon islands
BRB
Available Online

Fasi, John

2009
Introduced most probably intentionally, as a biological control against nut fall bugs (Amblypelta sp) in coconut and cocoa, the Little Fire Ant (Wasmannia auropunctata) has for more than 30 years continued to spread and colonies a number of different environments in the Solomon Islands. To date, no studies have investigated the ecological impact of these ants. The impact of Little Fire Ants was measured on (1) the overall ant fauna within subsistence gardens, (2) the prevalence of additional insect pests in subsistence gardens, and (3) the significant pest Tarophagus sp. of one crop - taro and its natural predator Cyrtohinus fulvous. Ant fauna was surveyed on two study areas in garden sites of four common subsistence crops: potato, cassava, taro and yam; a total of 36 gardens per study area with three trials per garden, using baiting and hand collecting. The existence of insect pests that form a relationship with W. auropunctata was measured in the same gardens by standardized visual searches, plus some identification and collecting from randomly selected crop within the gardens. The impact of W. auropunctata on the significant taro pest Tarophagus sp. and its natural predator Cyrtohinus fulvous was measured in 56 taro gardens with half of the gardens infested with Little Fire Ants. Twenty five taro plants were randomly selected in each taro garden and sampled using standardized visual identification. Sites with W. auropunctata had significantly lower mean abundance of other ant species than gardens free of W. auropunctata. A number of hemipteran insects (most of them pests) were also observed to have developed relationships with W. auropunctata. Although there was no significant difference in the mean population density of C. fulvous per taro plant between taro plants infested and free of W. auropunctata, significantly more Tarophagus were found on taro plants in the presence of W. auropunctata than in the absence of W. auropunctata. Three conclusions are drawn here, (1) the presence of W. auropunctata leads to a reduction in the ant fauna at a site, and is likely to lead to ecological damage to other invertebrates and vertebrates, (2) the presence of W. auropunctata in the subsistence crops may have lead to the development of harmful relationships between hemipteran pests and W. auropunctata, and (3) the presence and dominance of W. auropunctata on subsistence crops may provide an environment that i allows insect pests to thrive. Little Fire Ants therefore pose an economic as well as an ecological risk in subsistence gardens in the Solomon Islands