Estimating Allee Dynamics before They Can Be Observed: Polar Bears as a Case Study
Figure 1
The polar bear life cycle underlying the two-sex matrix projection model with maternal care, An.
Stages 1–6 are females, stages 7–10 are males. sSf, sAf, sSm and sAm are the probabilities of subadult and adult survival from one mating season to the next for females and males, respectively; sL0 and sL1 are the probabilities of at least one member of a cub-of-the-year (COY) or yearling (yrlg) litter surviving from one mating season to the next; f is the mean number of 2-year-olds in a litter that survives to this age. A 1:1 sex ratio in dependent offspring is assumed. p(n4,n10) is the probability that an adult female that is not accompanied by dependent offspring is fertilized, given the numbers of such females (n4) and adult males (n10). q is the conditional probability, given survival, that a fertilized female will produce at least one COY that survives to the following mating season. Dashed arrows indicate transitions that are theoretically possible but infrequent, and are thus omitted from the population model for simplicity. The figure is modified from [28], [37].