Thomas Mitchell and the Wellington caves: The relationship among science, religion, and aesthetics in early-nineteenth-century Australia

THOMAS MITCHELL (1792–1855), explorer and Surveyor-General in New South Wales between 1828 and 1855, was a talented and competent draughtsman who was responsible for the original sketches and even some of the lithographs he used to illustrate his two journals of exploration, published in 1838 and 1848. In this paper, I will be concerned with the 1838 journal, entitled Three Expeditions into the Interior of Eastern Australia; with descriptions of the recently explored region of Australia Felix, and of the Present Colony of New South Wales. On the whole, it is a detailed and lavishly illustrated account of the land Mitchell encountered, along with its inhabitants and natural history. My particular interest is in offering an explanation for differences between a sepia sketch depicting a cave at Wellington, NSW, that Mitchell prepared as one of the illustrations for geological material included in this journal, and the final lithograph.

Presence-absence versus abundance data for monitoring threatened species

Effective detection of population trend is crucial for managing threatened species. Little theory exists, however, to assist managers in choosing the most cost-effective monitoring techniques for diagnosing trend. We present a framework for determining the optimal monitoring strategy by simulating a manager collecting data on a declining species, the Chestnut-rumped Hylacola (Hylacola pyrrhopygia parkeri), to determine whether the species should be listed under the IUCN (World Conservation Union) Red List. We compared the efficiencies of two strategies for detecting trend, abundance, and presence-absence surveys, underfinancial constraints. One might expect the abundance surveys to be superior under all circumstances because more information is collected at each site. Nevertheless, the presence-absence data can be collected at more sites because the surveyor is not obliged to spend a fixed amount of time at each site. The optimal strategy for monitoring was very dependent on the budget available. Under some circumstances, presence-absence surveys outperformed abundance surveys for diagnosing the IUCN Red List categories cost-effectively. Abundance surveys were best if the species was expected to be recorded more than 16 times/year; otherwise, presence-absence surveys were best. The relationship between the strategies we investigated is likely to be relevant for many comparisons of presence-absence or abundance data. Managers of any cryptic or low-density species who hope to maximize their success of estimating trend should find an application for our results.