Dusty, regarding the Broad Headed snake I was able to find a number of threats besides simply collection for the pet trade. The pet trade was actually listed as a significant factor for decline in only one area, a single study site. That's still disturbing but I'm not sure if one should call it a threat to the species. Personally I would like to know if the study site represented the entire population, or if it might possibly have been just a small and easily accessable portion of a greater population. The author also says the Broad Headed snake was collected extensively throughout the 1950's to 1970's and no mention was made of any declines or extirpations during that time. Here is the text I am refering to, the link is below:

The entire range of the Broad-headed Snake occurs in an area with the highest density of human population in Australia, and accordingly has wide-scale habitat degradation (Shine & Fitzgerald 1989; Cogger et al. 1993).

Clearance of habitat has resulted in fragmentation and isolation of populations. High levels of human visitation and associated habitat disturbance threaten remaining populations (Cogger et al. 1993).

The disturbance and removal of rocks used as retreat sites has the greatest effect on snake abundance. The rocks preferred by both snakes and their gecko prey are similar in diameter, thickness and underlying substrate to the rocks preferred by 'bushrock' collectors. The amount of rock disturbance through overturning, piling up, removal or smashing has an impact on the abundance of snakes as well as on geckos preyed on by the snakes (Shine et al. 1998; Webb et al 2008 ) and spiders preyed on by the geckos (NSW NPWS 2001). Also, rock collectors may deliberately kill snakes (Cogger et al. 1993). Illegal rock removal and disturbance remains a common practice in national parks (Goldingay & Newell 2000; Shine & Fitzgerald 1989). Disturbance is most common near roads and walking tracks, and snakes are more common away from access routes (Goldingay 1998; Goldingay & Newell 2000).

Broad-headed Snakes were collected in large numbers from the 1950s to the 1970s for pets (H. Cogger in Shine et al. 1998). A mark-recapture study carried out in Morton National Park, NSW from 1992 to 2002 found that the population of snakes was stable over 1992–96 but declined dramatically in 1997, coincident with evidence of illegal collecting, possibly stimulated by a government amnesty that allowed pet owners to obtain permits for illegally held reptiles. In 1997, 85% of adult females disappeared from the population, and the data indicate that reptile collectors were causing the local extinction of Broad-headed Snakes from the study site (Webb et al. 2002c).

Bushfires may pose a threat to snake populations through altering the availability of hollows and prey, or endangering snakes when occupying hollows (NSW NPWS 2001).

The importance of tree hollows as summer habitat for snakes means that forestry activities may also threaten some populations (NSW NPWS 2001; Webb & Shine 1997a) and post-logging burning may impact upon prey populations. 'Habitat' trees left by foresters are smaller and contain fewer hollows than trees preferred by snakes (Webb & Shine 1997a).

The species requires shelter rocks that receive high levels of solar radiation. Local increases in vegetation density could result in increased shading of retreat sites, potentially rendering them thermally unsuitable. It is likely that fire deterrence since European arrival has led to an increase in vegetation density and this may have contributed to the decline of the species, however this is yet to be objectively demonstrated (Pringle et al. 2003).

The presence of beak marks on the occasional snake indicates that predatory birds may prey on the species (J.K. Webb, personal observation in Pringle et al. 2003).

Foxes and cats are potential predators of the Broad-headed Snake (NSW NPWS 2001).

http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=1182#australian_distrib

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