Translocations as Experiments in the Ecological Resilience of an Asocial Mega-Herbivore

Species translocations are remarkable experiments in evolutionary ecology, and increasingly critical to biodiversity conservation. Elaborate socio-ecological hypotheses for translocation success, based on theoretical fitness relationships, are untested and lead to complex uncertainty rather than parsimonious solutions. We used an extraordinary 89 reintroduction and 102 restocking events releasing 682 black rhinoceros (Diceros bicornis) to 81 reserves in southern Africa (1981–2005) to test the influence of interacting socio-ecological and individual characters on post-release survival. We predicted that the socio-ecological context should feature more prominently after restocking than reintroduction because released rhinoceros interact with resident conspecifics. Instead, an interaction between release cohort size and habitat quality explained reintroduction success but only individuals' ages explained restocking outcomes. Achieving translocation success for many species may not be as complicated as theory suggests. Black rhino, and similarly asocial generalist herbivores without substantial predators, are likely to be resilient to ecological challenges and robust candidates for crisis management in a changing world

Post-release mortality in black rhinoceros (<i>Diceros bicornis</i>) after (A) reintroduction and (B) restocking.

<p>Cohort size and habitat quality (estimated carrying capacity <0.1, 0.1–0.2 or >0.2 rhino per km²) explained reintroduction mortality while age class explained deaths after restocking. Age classes conform to Hitchins' A (calf) to F (adult) aging scheme <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030664#pone.0030664-Beech1" target="_blank">[31]</a>. Numbers of rhino (i.e., n) in each category are indicated above each bar. nd = no data. The dash line across each indicates mean mortality rate for all reintroduction (A) and restocking (B) events.</p

Results summary of the 29 candidate models for reintroduction mortality risk among 89 cohorts and 414 reintroduced black rhino.

<p>Models are in descending order from most to least supported based on Akaike second-order Information Criteria (AIC_c). Leading models from previous analyses without interaction terms <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030664#pone.0030664-HoeghGuldberg1" target="_blank">[<i>9]</i></a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030664#pone.0030664-Frair1" target="_blank">[23<i> </i>]</a> are italicized. The model without fixed effects is indicated in bold type. A ‘*’ indicates an interaction term in the regression between two variables and, by implication, predictors in interactions were also present additively in models (e.g., a*b refers to model including a+b+a*b as fixed effects).</p