Comparing radio-tracking and visual detection methods to quantify group size measures

Abstract

Abstract1. Average values of animal group sizes are prone to be overestimated in traditional field studies because small groups and singletons are easier to overlook than large ones. This kind of bias also applies for the method of locating groups by tracking previously radio-collared individuals in the wild. If the researcher randomly chooses a collared animal to locate a group to visit, a large group has higher probability to be selected than a small one, simply because it has more members.2. The question arises whether location of groups by means of finding collared animals has smaller or greater bias than searching for groups by visual observation. If the bias is smaller or same, this method can be recommended for finding groups. However, such a comparison cannot be made by speculation, only by empirical investigation.3. The present study compares the two methods empirically, by statistically comparing group size measures (mean, median, quantiles, frequency distribution, and ‘typical group size’) between two data sets. These data sets comprise of Rocky Mountain mule deer group size values collected in the same area during the same period of time, referring either to groups located by the traditional ‘search and observe method’ or located by tracking formerly collared individuals.4. All group size measures are statistically similar in the two samples, thus we conclude that the two methods yielded similar biases. Although the true group size measures are not known, we presume that both methods have overestimated them. We propose that these results do not necessary apply to other species, thus cannot be generalized. The reason for this is that bias may depend on factors specific to the species: bias of visual observation may depend on how well the species conceals itself in the existing habitat, and the bias associated with finding groups using collared animals is likely dependent on group size distribution and also on the proportion of collared animals in the population.

Infectious Disease and Grouping Patterns in Mule Deer

“…We compared the mean, median, quartiles and frequency distribution of group size in these 2 parts to look at the representation of small groups and determine viability of calculating TGS. As all comparisons lead to the same conclusion that the group size distribution is the same in the 2 parts (data not shown) [ 51 ], we proceeded with the calculations using all records (n = 2656 group). Group size distribution of our sample is not normally distributed.…”

Use of environmental sites by mule deer: a proxy for relative risk of chronic wasting disease exposure and transmission

“…Found mule deer carcasses from other ongoing studies involving radio-collared deer (Silbernagel et al 2011, Reiczigel et al 2015, Mej ıa Salazar et al 2016, Mej ıa-Salazar et al 2017a). Available all year, but mainly in early gestation and rut (Appendix S1: Fig.…”