284 Monitoring Threatened Species and Ecological Communities
(‘oases’), but failed to find any evidence. It showed instead that populations of S.
youngsoni at the nine study sites f luctuated out of synch with each other, and
responded differently to rainfall, spinifex cover and numbers of mulgaras.
Observation errors differed little across the nine sites for both species,
suggesting that their trapability remained similar across time and space. By
contrast, process errors, P, showed much variation (e.g. D. blythi, P = 0.41, with
credible intervals of 0.12–0.68; S. youngsoni, P = 0.53, with credible intervals of
0.12–0.99 for one site with the longest time series), ref lecting the effects of
demographic ‘noise’ and environmental drivers.
Discussion
Large rainfall events in arid areas usually stimulate pulses of primary productivity,
and conventional wisdom holds that these pulses then prompt increases in a wide
array of consumer organisms (Letnic and Dickman 2010). A synchronous response
was indeed observed in D. blythi across nine widely separated sites. Although this
pattern was largely predictable, inspection of Fig. 21.1 provides little indication of a
consistent trend over time, despite 27 years of intensive sampling. In marked
contrast, populations of S. youngsoni f luctuated asynchronously and showed no
consistent relationship with respect to any potential environmental drivers that
Fig. 21.3. Lesser hairy-footed dunnart Sminthopsis youngsoni in the Simpson Desert. Photo: B. Tamayo/
Desert Ecology Research Group, University of Sydney.