For most big game species, the Department conducts aerial surveys primarily to estimate male to female and young to female ratios. We are still improving survey techniques that are giving us better data on population trend over time as well, but actual population estimates for each unit are difficult to accurately determine.
Jim Heffelfinger's book indeed provides an excellent overview of the approach.
In some areas with gentle terrain and little vegetation, we may use fixed-wing aircraft to fly grids across the entire unit or representative portions. Grid size is dependent on abundance of wildlife we are surveying. If the wildlife are abundant, we can fly wider grids and still obtain enough observations to get tight confidence intervals on the ratio data we collect. On the other hand, if wildlife are not abundant, then we fly tighter grids to increase the number of observations. We still try to fly grids that are sufficiently wide to avoid recounting the same group.
If the terrain is less gentle, we may use helicopters to fly grids. In steep, mountainous terrain, we will fly blocks of habitat that we may contour. In these instances, the wildlife managers select blocks that are "representative" of the wildlife habitat in their unit. We try to fly the same blocks in subsequent years to get a better idea of how wildlife are trending in that unit. Our goal is to standardize approaches to the extent possible
We use aerial surveys for bighorn sheep (helicopter blocks), deer (helicopter blocks, helicopter grids, and fixed-wing grids), javelina (helicopter blocks, helicopter grids, and fixed-wing grids), and elk (helicopter blocks, helicopter grids, and fixed-wing grids). We have been using this approach for about 5-6 years for deer and javelina, quite a number of years for bighorn sheep, and we are just beginning to do so for elk. Elk are still primarily surveyed from the ground in many units, but the aerial techniques are working well in quite a few units.
The local wildlife manager is generally involved in the survey, but some get green when flying and need to be replaced by someone less susceptible to motion sickness when flying (bouncing) along an uneven landscape and staring out the side window for a couple hours.
Buck:doe ratios for deer have been increasing in recent years, and we have changed the season dates and lengths in most units to reduce the number of deer hunters in the field at any one time. Last year statewide buck:doe ratios for mule deer were 27:100 and for white-tailed deer were 30:100.
That is the short course on Department aerial wildlife surveys.
SDHunter11 and CMC are correct in observing that survey data is not all that goes into a hunt recommendation. The observations and data that a wildlife manager collects over the course of a year plays a large role in the formulation of his final recommendation. We try to avoid going to "where all the deer are" or otherwise attempting to bias our surveys. We try to accurately survey the unit to get the best snapshot of the herd.
Brian Wakeling
Game Branch Chief
