Interactions of target population size, population parameters, and programmanagement on viability of captive populations

When established conservation programs expand and evolve, management practi ces may become inconsistent with program goals. In the past decade, the Ame rican Zoo and Aquarium Association expanded species conservation programs b y increasing the number of Species Survival Plans (SSP) and establishing mo re than 300 new Population Management Plan (PMP) programs. However, limited space in captive breeding facilities forces a competition among SSPs and l ess intensively managed PMPs. Regional Collection Plans establish prioritie s and allocate space accordingly by setting target population size for each species; species of high conservation priority (SSPs) are allocated space at the expense of lower priority species (PMPs). Because population size an d genetic composition interact to impact population viability, target popul ation size is a significant factor to a population's prospects for long-ter m survival. We examined four population parameters (current population size , target population size, current gene diversity, and mean generation time) for 46 mammalian SSPs and 17 PMPs. Relative to SSPs, PMPs combine smaller current and target population sizes, lower levels of current gene diversity , and shorter mean generation times than SSPs. Thus, the average PMP popula tion can expect to lose gene diversity more rapidly than the average SSP po pulation. PMPs are projected to lose 10% or more of their founding gene div ersity, within only 2 years. In contrast, the average SSP population is pro jected to lose 10% in 40 years. Populations with small current or target po pulation sizes require intensive management to avoid extinction. More inten sive genetic management of populations typically designated as PMPs, throug h recruitment of potential founders and equalization of founder representat ion, could increase gene diversity and improve viability. Less rigorous pop ulation management should be reserved for populations whose long-term survi val is either secure or that can be readily replenished from the wild. Beca use PMP populations need intense genetic management similar to that current ly in effect for SSPs, there should be neither a management-level distincti on between programs nor an arbitrary difference in space allocated to progr ams. (C) 2001 Wiley-Liss, Inc.