Document ID: chunk:federal_register_of_legislation:F2007B00385:body:0:p9
Version: federal_register_of_legislation:F2007B00385
Segment Type: other
Provision Reference: 
Character Range: 25051–28013

of the species
Until further information is obtained, by applying the precautionary principle to the EPBC Act criteria, all areas of primary plateau and terrace rainforest on the island should be considered as potential habitat critical to survival (Figure 1). If the shrew is found to be extant, identifying habitat requirements critical to survival is recommended.

Important populations
None known, as the species has not been recorded since 1985. Should any individuals be located, they would be regarded as constituting a component of an important population.

Part C: Known and Potential Threats

Identification of threats
Known Threats:  Not known.

Potential Threats:

Disease
The Christmas Island Shrew was considered to be probably extinct by 1908 (Andrews 1909), suggesting exposure to threats other than broadscale habitat destruction. About this time (1901 to 1904), the endemic Maclear's Rat Rattus macleari became extinct, proposed to be the result of the introduction of trypanosome-infected Black rat Rattus rattus (Pickering and Norris 1996). Isolated island species that have evolved in the absence of diseases common to continental faunas are more susceptible due to loss of population heterogeneity (Caughley and Sinclair 1994). Introduction of a new disease is the most likely cause of the initial decline.

Yellow Crazy Ant Anoplolepis gracilipes
This ant was accidentally introduced to the island between 1915 and 1934.  Crazy ants form multi-queened supercolonies, and dramatic increases in supercolony formation began in the mid to late 1990s at several widespread locations, including The Dales area. Prior to aerial baiting in September 2002, supercolonies infested over 2500ha of rainforest.

Crazy ants have the potential to alter the whole ecology of the island. For example, the Red Crab Gecaroidea natalis population has declined by at least 30% due to ant attack, resulting in dramatically altered plant community dynamics (Garnett & Crowley 2000; M. Jeffery, PAN, pers. comm.). Additionally, the ants farm scale insects, causing damage to trees resulting in dieback and canopy thinning (Garnett & Crowley 2000; M. Jeffery, PAN, pers. comm.). Flow on effects could include spread of the introduced Black Rat into areas formerly occupied by the crabs, alteration in both ground- and tree-dwelling invertebrate diversity and abundance, changes in ground layer vegetation structure, invasion of weeds and introduced Giant African Land Snail Achatina fulica in die-back affected forest, and alteration in leaf litter depth affecting soil moisture. The direct effects on the shrew are unknown, but it is likely that breeding, shelter and foraging sites would be severely effected. It is also likely the ants kill young animals in the nest, and possibly adults in severely affected areas (as recorded for a Christmas Island Pipistrelle in a harp trap in The Dales area by Lumsden et al. 1999).

A priority conservation management