More On Infrared-triggered Camera Deer Surveys
In my August 2002 NF Ag News and Views article, I addressed the assumption that disturbance created by the infrared-triggered still camera and its associated flash has little or no effect on deer visitation to a bait station. This potentially affects the number of individuals captured on film, which in turn can affect the interpretation of a camera survey.
Another assumption we are examining involves the computation of herd composition and population estimates. In most situations, antlered bucks are the only identifiable deer managers have to work with. Generally, the total number of pictures taken of antlered bucks is divided by the number of individual antlered bucks identified, which yields the average number of pictures taken per antlered buck. It is then assumed that does and fawns have their pictures taken at the same rate. Estimates of doe and fawn numbers are calculated by dividing the total number of doe or fawn pictures by the average number of pictures taken per antlered buck. We evaluated whether antlered bucks and does are equally photogenic by comparing the number of pictures taken per identifiable buck with the number taken per marked doe during four infrared-triggered still camera surveys (Table 1).
The number of pictures taken per buck and marked doe was similar during 1999 and 2000. However, substantially fewer (34 and 44 percent) pictures were taken of does in 2001 and 2002. Population estimates extrapolated using only the number of pictures taken per identifiable buck can differ dramatically from those extrapolated using the number of pictures taken per marked doe to calculate doe and fawn estimates (Table 2).
Our preliminary data indicate that bucks and does do not necessarily have their pictures taken at the same rate, and that herd composition and population estimates extrapolated using only the number of pictures taken per identifiable buck are of questionable accuracy.