Sampling tiger ungulate prey by the distance method: lessons learned in Bardia National Park, Nepal. Wegge, P. & Storaas, T. Animal Conservation, 12:78–84, 2009. abstract bibtex Because tiger
Panthera tigris numbers are regulated by their prey base, prey abundance needs to monitored and estimated reliably. Recently, distance sampling has been adopted as the most appropriate method and is now becoming the standard monitoring protocol in all tiger range countries in south Asia. However, the accuracy of the density estimates generated by this method has not been assessed. From total counts within habitat blocks, we obtained accurate density estimates of ungulates within three main habitats in Bardia National Park, Nepal. We then applied the distance sampling method in the same habitats and compared the results. Distance sampling on foot in dense habitats (riverine forest and tallgrass floodplain) violated method assumptions, and sampling from vehicle along roads gave biased estimates. Sampling from elephant back worked well in all habitat types, but owing to their behaviour, the density of barking deer
Muntiacus muntjak was underestimated. The accuracy of the estimates varied with sampling effort; for the very abundant chital deer
Axis axis, estimates varied markedly at <200 animal observations, but converged at larger sample sizes to a similar point estimate as intensive block counts when approaching 300 observations. For the less abundant species, with <20 observations along >100 km of transect lines, the confidence intervals were quite high, and, hence, of limited value for detecting short-term populations trends. It is therefore difficult to obtain accurate density estimates of rare species by the distance method. In areas consisting of dense habitats, we recommend that the food base of tiger be estimated by distance sampling from elephant back, not on foot, directed at the main and most abundant prey species. For rare species, encounter rates obtained simultaneously may then serve as indices of relative abundances.
@ARTICLE{WeggeFebruary2009,
author = {Wegge, P. and Storaas, T.},
title = {Sampling tiger ungulate prey by the distance method: lessons learned
in {Bardia National Park, Nepal}},
journal = {Animal Conservation},
year = {2009},
volume = {12},
pages = {78--84},
abstract = {<P></P>Because tiger <I>Panthera tigris</I> numbers are regulated
by their prey base, prey abundance needs to monitored and estimated
reliably. Recently, distance sampling has been adopted as the most
appropriate method and is now becoming the standard monitoring protocol
in all tiger range countries in south Asia. However, the accuracy
of the density estimates generated by this method has not been assessed.
From total counts within habitat blocks, we obtained accurate density
estimates of ungulates within three main habitats in Bardia National
Park, Nepal. We then applied the distance sampling method in the
same habitats and compared the results. Distance sampling on foot
in dense habitats (riverine forest and tallgrass floodplain) violated
method assumptions, and sampling from vehicle along roads gave biased
estimates. Sampling from elephant back worked well in all habitat
types, but owing to their behaviour, the density of barking deer
<I>Muntiacus muntjak</I> was underestimated. The accuracy of the
estimates varied with sampling effort; for the very abundant chital
deer <I>Axis axis</I>, estimates varied markedly at <200 animal
observations, but converged at larger sample sizes to a similar point
estimate as intensive block counts when approaching 300 observations.
For the less abundant species, with <20 observations along >100 km
of transect lines, the confidence intervals were quite high, and,
hence, of limited value for detecting short-term populations trends.
It is therefore difficult to obtain accurate density estimates of
rare species by the distance method. In areas consisting of dense
habitats, we recommend that the food base of tiger be estimated by
distance sampling from elephant back, not on foot, directed at the
main and most abundant prey species. For rare species, encounter
rates obtained simultaneously may then serve as indices of relative
abundances.},
owner = {Tiago},
subdatabase = {distance},
timestamp = {2009.04.27}
}
Downloads: 0
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However, the accuracy of the density estimates generated by this method has not been assessed. From total counts within habitat blocks, we obtained accurate density estimates of ungulates within three main habitats in Bardia National Park, Nepal. We then applied the distance sampling method in the same habitats and compared the results. Distance sampling on foot in dense habitats (riverine forest and tallgrass floodplain) violated method assumptions, and sampling from vehicle along roads gave biased estimates. Sampling from elephant back worked well in all habitat types, but owing to their behaviour, the density of barking deer <I>Muntiacus muntjak</I> was underestimated. The accuracy of the estimates varied with sampling effort; for the very abundant chital deer <I>Axis axis</I>, estimates varied markedly at <200 animal observations, but converged at larger sample sizes to a similar point estimate as intensive block counts when approaching 300 observations. For the less abundant species, with <20 observations along >100 km of transect lines, the confidence intervals were quite high, and, hence, of limited value for detecting short-term populations trends. It is therefore difficult to obtain accurate density estimates of rare species by the distance method. In areas consisting of dense habitats, we recommend that the food base of tiger be estimated by distance sampling from elephant back, not on foot, directed at the main and most abundant prey species. 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However, the accuracy\r\n\tof the density estimates generated by this method has not been assessed.\r\n\tFrom total counts within habitat blocks, we obtained accurate density\r\n\testimates of ungulates within three main habitats in Bardia National\r\n\tPark, Nepal. We then applied the distance sampling method in the\r\n\tsame habitats and compared the results. Distance sampling on foot\r\n\tin dense habitats (riverine forest and tallgrass floodplain) violated\r\n\tmethod assumptions, and sampling from vehicle along roads gave biased\r\n\testimates. Sampling from elephant back worked well in all habitat\r\n\ttypes, but owing to their behaviour, the density of barking deer\r\n\t<I>Muntiacus muntjak</I> was underestimated. 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