Giraffe Translocation Population Viability Analysis

Abstract

Most populations of giraffes have declined in recent decades, leading to the recent 24 decision to upgrade the species to vulnerable status, and some subspecies to endangered.25 1 Email: dereklee@psu.edu 2 | Lee et al. • Giraffe PVATranslocations have been used as a conservation tool to re-introduce giraffes to previously 26 occupied areas or establish new populations, but guidelines for founding populations are lacking. 27 To provide general guidelines for translocation projects regarding feasibility, we simulated 28 various scenarios of translocated giraffe populations to identify viable age and sex distributions 29 of founding populations using Population Viability Analysis (PVA) implemented in Vortex 30 software. We explored the parameter space for demography (population growth rates: λ = 1.001, 31 1.010, 1.024), and the genetic load (number of lethal equivalents: LE = 2.5, 6.29, 12.6), 32 examining how variation in founding numbers (N = 5 to 80 females) and sex ratios (M:F = 0.1 to 33 0.5) affected 100-year probability of extinction and genetic diversity. We found that even very 34 small numbers of founders (N ≤10 females) can appear to be successful in the first decades due 35 to transient positive population growth, but with moderate population growth rate and moderate 36 genetic load, long-term population viability (probability of extinction <0.01) was only achieved 37 with ≥30 females and ≥3 males released. To maintain >95% genetic diversity of the source 38 population in an isolated population, 50 females and 5 males are recommended to comprise the 39 founding population. Sensitivity analyses revealed first-year survival and reproductive rate were 40 the simulation parameters with the greatest proportional influence on probability of extinction 41 and genetic diversity. These simulations highlight important considerations for translocation 42 success, and data gaps including true genetic load in wild giraffe populations.43 viability 45 Giraffes (Giraffa camelopardalis) are endemic African ruminant ungulates, and one of only a 46 handful of extant terrestrial megaherbivores (Owen-Smith 1988). Most populations of giraffes 47 2018). Translocations have been used as conservation tools to re-introduce giraffes to previously 50 occupied areas or establish new populations (Winter et al. 2019), but quantitative guidelines for 51 establishing viable populations of translocated giraffes do not exist. 52 General guidelines for translocations suggest population modelling should be used to assist in the 53 assessment of project feasibility (IUCN 2013). Population modelling for translocation projects 54 can offer guidance on age-and sex-classes for founder populations by providing estimates of 55 population persistence, long-term viability, and genetic diversity (Seddon et al. 2007).56 Population viability analysis (PVA) is commonly used to predict the likely future status of a 57 population and thus offers a quantitative basis for evaluating alternative management strategies 58 (Boyce 1992, Morris and Doak 200...

Disproportionate admixture improves reintroduction outcomes despite the use of low‐diversity source populations: population viability analysis for a translocation of the greater stick‐nest rat

“…While scenarios with multiple source populations performed better overall, of these scenarios, those with higher founder numbers appeared to be the most successful in terms of retaining genetic diversity and minimizing inbreeding over time. The positive impact of increased founder numbers has been reported on many times in recent years (Griffith et al, 1989;Lee et al, 2020;Furlan et al, 2020;White et al, 2020a), while low founder numbers have been attributed to a number of failed reintroductions, including several translocations of woylies (brush-tailed bettong) (Bettongia penicillata) where the genetic effects of small founder numbers were further compounded by predation and drought (Fischer & Lindenmayer, 2000;Mawson, 2004;Germano & Bishop, 2009;Short, 2009). However, given the importance of conserving critical source populations, a trade-off must be reached between optimizing translocation outcomes and minimizing impacts to existing populations.…”