AbstractOur aim was to develop a method for estimating the annual number of female elephant seals pupping in a colony from a single count. This is difficult because breeding females are not synchronous so there is no time when the entire population is present. We applied models that describe arrival and departure behavior to account for those missed in any one count and calculated correction factors that yield total population from any single count throughout a season. At seven colonies in California for which we had multiple female counts per year, we found consistent timing in arrival and departure both within and between sites for as long as 50 years. This meant that the optimal correction factor, the date when the maximum number of females was onshore, was consistent. At Point Reyes, a female count on 27 or 28 Jan can be multiplied by 1.15 to yield the total female population; at Año Nuevo Island, the correction was 1.17 on 25-26 Jan; and at Año Nuevo Mainland, 1.13 on 28-30 Jan. Correction factors at Channel Island colonies and King Range were also 1.13. Across the colonies studied, the factor 1.15 multiplied by a female count between 26 and 30 Jan was close to optimal, and this provides a method for estimating the female population size at colonies not yet studied. Our method can produce population estimates with minimum expenditure of time and resources and will facilitate monitoring of the elephant seal population size over its entire range.
Impact of new ICRU Report 90 recommendations on calculated correction factors for reference dosimetry
