Learning to count: adapting population monitoring for Endangered huemul deer Hippocamelus bisulcus to meet conservation objectives

Abstract

Considerable efforts have been invested in recent years to improve methods for both data collection and analyses required for population monitoring. Where historical or current estimates of population size are not adjusted for detection probabilities they may be too inaccurate to provide meaningful estimates of trends and thus monitoring methods need to be adapted. Here, we use data from the Endangered huemul deer Hippocamelus bisulcus to outline a framework to develop accurate robust estimates of detection probabilities that can be incorporated into new surveys in a cost-effective way and applied to existing survey data sets. In particular, by retroactively estimating detection probabilities for surveys of huemul, we show that current survey methods for huemul are inadequate to determine population trends reliably. Based on these results we propose a new monitoring method for the huemul and discuss the importance of estimating accuracies of historical survey data to ensure that changes in the abundance of the species reflect real population trends and are not an artefact of variation over time in the accuracy of survey data.

Good intentions gone wrong: did conservation management threaten Endangered huemul deerHippocamelus bisulcusin the future Patagonia National Park?

“…In general Patagonian climate is temperate with an annual mean temperature of 6.5°C (Endlicher, 1991). Mean annual precipitation in Lago Cochrane National Reserve is 800 mm, the majority of which falls between June and September (Wittmer et al, 2010).…”

“…Because of the large sample of marked individuals huemul abundances in the Reserve were well known. Population estimates outside Lago Cochrane Reserve were largely based on periodic surveys in which wardens reported individuals they encountered, and were therefore less accurate (Wittmer et al, 2010).…”

Short Communications

“…1936;, as is known for other Odocoilines including Odocoileus and Rangifer. Given the above evidence, it is therefore unrealistic to classify females < 3 years old as juveniles and base calculations of intrinsic population growth rates on 'adult' female huemul (Wittmer et al 2010). Other parameters misrepresented regard claims by Garcia et al (2008) that available information indicates that females have only a fawn every second year, unless the fawn dies early on.…”

The recovery of a population of the Vulnerable tarukaHippocamelus antisensisnear La Paz, Bolivia: opportunities for conservation and education

“…As a further measure against double counting we considered the timing of observations and the distance between simultaneous observations. Direct observations made at the same time on different transects allowed us to estimate the minimum abundance of individuals in the area (modified from Povilitis, 2002;Barrio, 2007;Wittmer et al, 2010), which we used to calculate the minimum density for calibration of our indirect abundance indices. We used tracks to confirm that no other tarukas were using the area at the same time on other transects and we are confident that our abundance estimate is only for a minimum number of individuals.…”