Abstract
Population dynamics is a central component of demography and critical for meta-population management, especially of endangered species. We employed complete individual life records to construct census data for a reintroduced black rhinoceros population over 22 years from its founding and investigated that population’s dynamics to inform black rhinoceros meta-population management practice and, more generally, megaherbivore ecology. Akaike’s information criterion applied to scalar models of population growth based on the generalized logistic unambiguously selected an exponential growth model (r = 0.102 ± 0.017), indicating a highly successful reintroduction, but yielding no evidence of density dependence. This result is consistent with, but does not confirm, the threshold model of density dependence that has influenced black rhinoceros meta-population management. Our analysis did support previous work contending that the generalized logistic is unreliable when fit to data that do not sample the entire range of possible population sizes. A stage-based matrix model of the exponential population dynamics exhibited mild transient behaviour. We found no evidence of environmental stochasticity, consistent with our previous studies of this population that found no influence of rainfall on demographic parameters. Process noise derived from demographic stochasticity, principally reflected in annual sex-specific recruitment numbers that differed from deterministic predictions of the matrix model. Demographically driven process noise should be assumed to be a component of megaherbivore population dynamics, as these populations are typically relatively small, and should be considered in managed removals and introductions. We suggest that an extended period of exponential growth is common for megaherbivore populations growing from small size and that an increase in age at first reproduction with increasing population size, manifest in the study population, may provide a warning of density feedback prior to detectable slowing of population growth rate for megaherbivores.
