Growth of the Yellowstone grizzly bear population,
as indicated by the number of females observed with cubs and the number of cubs.The effective population size (Ne) is based on the breeding potential of a population, incorporating information about the sex ratio of breeding individuals.
Ne = 4NfNm / (Nf + Nm)Nf and Nm are the numbers of females and males that successfully breed.
Ne is also affected bylife history traits such as family size, maturation age, genetic relatedness among population members, gene flow, and population fluctuations.
Shaffer estimated that a total grizzly bear population of 70 to 90 individuals would have a 95% chance of surviving for 100 years. 1