Niche construction and Dreaming logic: aboriginal patch mosaic burning and varanid lizards ( Varanus gouldii ) in Australia

Abstract

Anthropogenic fire is a form of ecosystem engineering that creates greater landscape patchiness at small spatial scales: such rescaling of patch diversity through mosaic burning has been argued to be a form of niche construction, the loss of which may have precipitated the decline and extinction of many endemic species in the Western Desert of Australia. We find evidence to support this hypothesis relative to one keystone species, the sand monitor lizard (Varanus gouldii). Paradoxically, V. gouldii populations are higher where Aboriginal hunting is most intense. This effect is driven by an increase in V. gouldii densities near successional edges, which is higher in landscapes that experience extensive human burning. Over time, the positive effects of patch mosaic burning while hunting overwhelm the negative effects of predation in recently burned areas to produce overall positive impacts on lizard populations. These results offer critical insights into the maintenance of animal communities in the desert, supporting the hypothesis that the current high rate of endemic species decline among small animals may be linked to the interaction between invasive species and mid-century removal of Aboriginal niche construction through hunting and patch mosaic burning.

Invasive cane toads might initiate cascades of direct and indirect effects in a terrestrial ecosystem

“…Previous studies have used the occurrence of fresh goanna tracks and pits that goannas create whilst foraging to index goanna abundance (Paltridge 2002;Bird et al 2014;Read and Scoleri 2014). Both indices have been validated against known abundances in other varanid species (Anson et al 2014).…”

“…The reduction of vegetation coverage by fire is known to influence the abundance of sand goannas and smaller lizard species (Letnic et al 2004;Bird et al 2014). To investigate whether differences in the fire history could explain differences in the abundance of goannas, skinks and dragons we obtained data on the fire history of each active search site from the North Australian Fire Information.…”

“…5a): (1) Cane toad activity should negatively affect goannas owing to lethal ingestion; (2) the foraging activity of goannas should negatively affect the abundance of skinks and dragons (Olsson et al 2005); (3) because of selective predation pressure, goanna activity should have a stronger impact on skinks than dragons (Sutherland 2011); (4) we used distance to the nearest dam as a proxy for the impact of cane toads because the impact of cane toads on goannas was negatively correlated with distance from dams (see ''Results'' section); (5) dingo activity should negatively affect goanna activity owing to predation (Paltridge 2002); (6) habitat modification resulting from grazing by livestock can have detrimental effects on both the abundance of goannas and of smaller lizard species such as skinks and dragons (James 2003); (7) time since fire was hypothesized to positively affect populations of goannas (Bird et al 2014) and to negatively affect skinks and dragons (Letnic et al 2004).…”

Living on a flammable planet: interdisciplinary, cross-scalar and varied cultural lessons, prospects and challenges

“…Aboriginal people living in the xeric hummock grasslands of Western Australia use fire extensively at landscape scales for many reasons, including to facilitate traditional hunting practices. Burning increases foraging returns for burrowed prey, particularly varanid lizards and other herpetofauna [29,60,66]. While some spot fires are lit during the summer months, the vast majority of broadcast fires are ignited during the winter months, when fuels are dry and winds are strong and consistent.…”

“…Anthropogenic fires are kept small by actively seeking downwind firebreaks or burning patches surrounded by previous burns; individuals are motivated to do so by the threat of social sanctions via traditional punishment rituals for out-of-control burning. Anthropogenic fire increases pyrodiversity-fire-generated ecological heterogeneity and diversity [61]-and reduces both the size of, and distance between unburned patches, reducing the cost of access to post-fire refugia for animals living in the region and more than doubling the density of edge loving species such as kangaroo and monitor lizard [49,66].…”