Arboreality increases reptile community resistance to disturbance from livestock grazing

Abstract

Domestic livestock grazing directly alters ground‐level habitat but its effects on arboreal habitat are poorly known. Similarly, the response to grazing of ground‐dwelling fauna has been examined, but there are few studies of arboreal fauna. Globally, grazing has been implicated in the decline of vertebrate fauna species, but some species appear resistant to the effects of grazing, either benefiting from the structural changes at ground level or avoiding them, as may be the case with arboreal species. Here, we examine arboreal and terrestrial habitat responses and reptile community responses to grazing, to determine whether arboreal reptile species are more resistant than terrestrial reptile species. We conducted arboreal and terrestrial reptile surveys on four different grazing treatments, at a 19‐year experimental grazing trial in northern Australia. To compare the grazing response of arboreal and terrestrial reptile assemblages, we used community, functional group and individual species‐level analyses. Species responses were modelled in relation to landscape‐scale and microhabitat variables. Arboreal reptile species were resistant to the impact of grazing, whereas terrestrial reptiles were negatively affected by heavy grazing. Terrestrial reptiles were positively associated with complex ground structures, which were greatly reduced in heavily grazed areas. Arboreal lizards responded positively to microhabitat features such as tree hollows. Synthesis and applications. Arboreal and terrestrial reptiles have different responses to the impact of livestock grazing. This has implications for rangeland management, particularly if management objectives include goals relating to conserving certain species or functional groups. Arboreal reptiles showed resistance in a landscape that is grazed, but where trees have not been cleared. We highlight the importance of retaining trees in rangelands for both terrestrial and arboreal microhabitats.

The impact of cattle grazing regimes on tropical savanna bird assemblages

“…Neilly et al . () found that grass cover, grass height, leaf litter and coarse woody debris were much lower in the heavy grazing treatment. There were also differences in habitat variables between the two vegetation types, for example, C. ovata and number of dead trees, were higher in box compared to ironbark.…”

“…The response of habitat variables to the grazing treatments has been previously analysed in Neilly et al . (). Neilly et al .…”

“…Overall, species that use lower habitat strata are likely to be more responsive to grazing (either positively or negatively), than those using higher level habitat strata (Neilly et al . ). Indeed, the height at which a bird species forages has been used to predict grazing response and response to woody vegetation changes (Martin & Possingham ; Tassicker et al .…”

Heavy livestock grazing negatively impacts a marsupial ecosystem engineer

“…Although microhabitat selection is often investigated as a mechanism likely driving grazing responses (e.g. Neilly et al, 2016Neilly et al, , 2017, rufous bettongs could be responding to other direct and indirect grazing impacts, as observed in other fossorial mammals in rangelands (Rosi et al, 2009;Poudel et al, 2016). High cattle densities may increase the chance of nest trampling and could be a reason for bettongs to avoid the heavy grazing treatment.…”

“…The soils are generally phosphorous deficient (4-8 ppm) and therefore are relatively infertile . Currant Bush (Carissa ovata) is patchily distributed throughout the grazing trial, however C. ovata cover, as well as tree richness and total number of trees, were higher in the box compared to the ironbark (Neilly et al, 2017). On the Wambiana grazing trial, trees are not cleared and the pasture has not been improved with fertilizer or introduced grass species.…”