Figure 2

Rate of population change versus abundance. Intrinsic rate of population change (r = log [N_t+1/N_t]) versus N_t (abundance) for the breeding female southern elephant seal population at the Macquarie Island isthmus during (A) the high-density era (1951–1960) and (B) the low-density era (1993–1999). Five population dynamics models (RW = random walk, EX = exponential growth, RL = Ricker-logisitc growth, GL = Gompertz-logistic growth and TL = θ-logistic growth; see Methods) were fitted to the relationship of r versus N_t. The sum of the Akaike Information Criterion (corrected for small sample sizes – AIC _c ) weights over the three density-dependent models considered (RL, GL and TL) show 77.4 % strength of evidence for density dependence during the high-density era (A) and 89.3 % support for the phenomenon during the low-density era (B).