The Asian House Gecko, Friend or Foe?

Since the establishment of the Asian house gecko, Hemidactylus frenatus,  in Australia 50 years ago there has been discussion regarding the potential impacts of this invasive species.  Australia is a centre of gecko origin and diversity so there is concern to what degree the Hemidactylus frenatus poses a threat Australia’s diversity and ecology. 

Some have argued that because Hemidactylus frenatus spread rapidly they can invade in natural habitats and are a strong competitor and may out-compete Australian geckos (Hoskin, 2010)

However a recent study has concluded that where they do invade it is in association with humanity, areas with lights and buildings; in human modified habitats and has no significant invasion into bush land where the Australian native geckos occupy habitats (Vanderduys E.P, Kutt A.S, 2013).

During a study conducted between 1997 and 2012 on the effects of fire, grazing and weeds on native reptiles across Queensland and the northern territory over 11 000 geckos were recorded, only 13 of which were Asian House geckos, and all from the same site in a Cape York community near homes. A site just 1km from the community was monitored recording no Asian house geckos.  This  revealed that while the invaders were found to be abundant in the community for over 30 years they had not managed to spread a kilometer.  From this evidence it has been concluded that the Asian house gecko were unlikely to become an environmental pest and aren’t likely to spread beyond areas of human influence (Vanderduys E.P, Kutt A.S, 2013).

 

Referenences:

Hoskin, C.J 2010, ‘The Invasion and Potential Impact of the Asian House Gecko (Hemidartylus frenatus) in Australia’, Austral Ecology, vol.36, no.3, pp. 240-251.

Vanderduys, E.P, Kutt, A.S 2013, ‘Is the Asian House Gecko Hemidartylus frenatus, really a threat to Australia’s biodiversity?’ Australian Journal of Zoology, vol.60, no.6, pp. 361-367.

 

Wild Boars!

Photo by Ashley Barbagello Veiwed on 08/04/2014

Feral pigs (Sus scrofa) are descendants of various sub-species of the domestic pig derived from stock that were let loose or escaped. They occupy a vast range of vegetation from subalpine grasslands to monsoonal floodplains. Their largest concentrations are on the larger drainage basins, and swamp areas of the coast and inland. (Bengsen, et al, 2014)

Feral Pigs, are an ecological, economic and social pest. Their impact on the environment is extensive.  By grazing and rooting they damage pastures, digging up large areas of native vegetation and spread weeds, cause soil erosion, degrade waterholes and wetlands. This digging behaviour can severely disrupt the composition of the soils microorganisms and consequently nutrient cycling. This can also disrupt the regeneration of plants, change the composition of the plant community and allow water erosion to occur in drainage areas where the soil is disrupted. (Bengsen et al 2014)

  Environmental damage is largely through modification of natural habitat, but predation and competition with native animals has also been reported. Feral pigs can also carry disease and parasites that affect stock and people. Through predation of stock, consumption and damage of crops feral pigs cost the agricultural industry alone an estimated $100 million per annum (Lopez et al, 2014).

Photo by Ashley Barbagello. Viewed 08/04/2014

Several methods are practiced to control feral pigs. One effective way to keep pigs out is exclusion fencing; fencing off small high value areas such as cropping or lambing paddocks. However this method is highly costly on time and maintenance and ineffective on large scale areas as well as only relocates the problem rather than contribute to control it.

 Other methods include government trapping programs and recreational hunting via shooting or dogging. It is estimated that hunters kill 15-20% of the feral pig population in accessible areas.  Currently, the most cost effective and efficient control is the use of aerial baiting with 1080 (sodium monofluroacetate) (Barrious-Garcia, Ballari, 2012).  The effectiveness of the baits depend on a few variables as not all pigs within an area will take the baits depending on alternative food availability, pig density within the area and density of baits. One study found that success rates vary form 58% to 99.4% (Hone, 2002). None of these methods have been proven to be stand alone solutions for the complete eradication of the feral pig.

References:

Bengsen A.J, Gentle M.N, Mitchel, J.L, Pearson H.E, Saunders G.R 2014, Impacts and management of wild pigs Sus scrofa, In Australia, Mammal Review, Vol.44, no.2, pp.135-147.

Barrious-Garcia M.N, Ballar, S.A 2012, Impact of wild boar (Sus scrofa) on its introduced and native range: a review, Biological Invasion, vol.14, no.11, pp.2283-2300.

Hone, J 2002, Feral Pigs in Namadgi National Park, Australia; Dynamics, impacts and management, Biological Conservation, Vol. 105, no. 2, pp.231-242.

Lopez J, Hurwood D, Dryde B, Fuller S 2010, Feral Pig Populations are structured at fine spatial scales in Tropical Queensland, Australia, National Parks, vol.9, no. 3.