Fear and concealment predict group size of a common ungulate

<p>Animals commonly form groups with conspecifics. Hypotheses on the drivers of group size often (but not always) pertain to fear of predation and food availability or quality. However, for a more complete understanding of group forming, multiple, possibly interacting mechanisms should be considered. We used camera traps, detectability estimates from distance sampling, and hierarchical Bayesian modelling to index group size and test multiple additive and interacting group-formation hypotheses in white-tailed deer (Odocoileus virginianus), within Indiana, USA. We found a strong relationship between our index of group size and the following: (1) three-way interaction of spatiotemporal pulses in fear from natural predation risk and anthropogenic development; and (2) two-way interaction between the cover type in which a camera was placed (open area [defined as areas lacking vegetative cover] or concealment [defined as areas containing vegetive cover]) and the amount of concealment within the larger landscape. Specifically, we documented the largest groups in areas near anthropogenic development, in areas with high predator use intensity, and during times of day when predators were active. Additionally, we found larger groups in locations within concealment when the area of concealment in the surrounding landscape was small, and larger groups within open areas when the area of concealment in the surrounding landscape was large. Our methods can aid future behavioral and ecological studies, as we present a clear and easily replicable strategy that infers group membership from spatiotemporal proximity, corrects for differences in detectability, and enables sampling across large spatial and long temporal scales. We identified that fear of natural predators and anthropogenic disturbance interactively explained variation in group size.</p>

<p>The data set herein provides the raw data used to conduct the analysis described above. Metadata for the dataset is as follows: </p>

<p>n: the naïve indexed group size of white-tailed deer</p>

<p>conceal_8000_ST: the amount of concealment (forest or wetland) within 8 km of the camera (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>veg.x: whether the camera was located in concealment (forest or wetland) or open area (agricultural field or grassland)</p>

<p>coy_temp_ST: the coyote activity level during the time the deer group was detected (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>coy_det_per_eff_ST: the use intensity of coyotes at the camera location (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>dis_build_or_road_ST: the distance between the location of the camera and the nearest road/ building (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>For_Edge_Den_750_ST: the density of forest edges within 750 m of the camera location (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>os: the probability of deteting a deer group at each camera location</p>

<p>RMU: the Regional Management Unit the camera was deployed within</p>

<p>RMU_TL: The Regional Management Unit and sampling area the camera was placed in</p>

<p>Full_SiteID: the unique name given to each camera location</p>

<p>pref_nuet_ST: the density of preferred or nuetral twigs in the woodlot or sampling area (if the camera was placed in open area; standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>dtocover_ST: the nearest distance from the camera location to concealment (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>imp_750_ST: the average impervious surface value within 750 m from the camera location (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>humdog_det_per_eff_ST:  the use intensity of humans and dogs at the camera location (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>avoid_prop_ST: the proportion of the density of all twigs that were avoided (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>pref_nuet_prop_ST: the proportion of the density of all twigs that were preferred or nuetral (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>Avoided_ST: the density of avoided twigs in the woodlot or sampling area (if the camera was placed in open area; standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>Total_ST:  the density of all twigs in the woodlot or sampling area (if the camera was placed in open area; standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>build_buff_750_ST: the number of buildings within 750 m of the camera location (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>

<p>road_buff_750_ST: the length of roads within 750 m of the camera location (standardized, i.e., subtracted the mean and divided by the standard deviation) </p>