Prioritizing among removal scenarios for the reintroduction of endangered species: insights from bearded vulture simulation modeling

Abstract

Translocations are an increasing feature of threatened species conservation plans, but the impact of removal of individuals on the source population is seldom studied. Using computational Population Dynamics P System models and the Pyrenean Bearded Vulture population as a case study we looked at: the effect on the source population of alternative strategies for removal of individual birds for use in reintroduction projects; and the trade‐offs between the various management options. According to our models (over a 30 year prediction horizon) the removal of one clutch, juvenile or non‐territorial adult each year over an 11 year period, results in an annual loss of 1.57, 3.71 and 0.97 territories, respectively. We forecast the impact of a plausible removal scenario for the Pyrenees source population (the removal of five clutches and five non‐territorial adults each year over 11 years), leading to a predicted loss of 16 breeding territories. Nevertheless, changes in demographic parameters, mainly in productivity and adult survival, could substantially affect these predicted results. With the current demographic parameters, the removal scenarios that were estimated to not affect population size after 30 years (95% CI) are limited to: (1) the removal of five clutches and five non‐territorial adults during a single year; (2) the annual removal of five non‐territorial adults during a 6 year period; and (3) the annual removal of five clutches during a 6 year period. Our results suggest that removals from the Pyrenean Bearded Vulture source population should be performed with caution due to uncertainties arising from stochastic changes in survival and productivity.

Exploratory and territorial behavior in a reintroduced population of Iberian lynx

“…The time invested and the economic costs of these projects can become limiting factors in guaranteeing the success of reintroduction and reinforcement programs 12 . Adaptive, evidence-based management is therefore required 13,14 to optimise the human and economic resources invested and to increase the probability of a successful reintroduction 15 .The endangered Iberian lynx (Lynx pardinus) is an endemic species in the Iberian Peninsula, and was widely distributed in the past 16 . During the twentieth century, its numbers declined greatly with many local extinctions and a significant reduction in its historical range 17,18 .…”

Removal modelling in ecology: A systematic review

“…Even if the original aim of this method was to deplete a species, and some of the studies included in this review use the method for this purpose [ 2 , 22 , 107 , 108 , 113 , 117 , 119 ], most of the studies included in this review were focused on understanding abundance of a particular species due to general interest (for example [ 78 , 81 – 84 , 88 , 143 ]). However, as a management tool it has been used not only to estimate abundance [ 12 , 144 ], but also, to estimate catchability [ 35 , 66 , 68 , 109 , 118 ], migration [ 13 , 43 , 71 , 85 ], habitat selection [ 64 , 77 , 96 ], endangered species [ 26 , 116 , 145 ], population dynamics [ 90 , 103 , 124 ] or translocation [ 23 ]. The potential of removal models to facilitate the estimation of population size in the source population whilst also obtaining a pool of individuals to translocate/reintroduce means that such models will remain important and will likely be further developed.…”

“…It has not been possible to determine if this increase in publications over time is a noteworthy trend or if this is confounded with the general increase in numbers of publications PLOS ONE more generally. If there is a genuine increase in use of this methodology, it is potentially an indication of the role of removal modelling in studies of reintroduction, especially when translocated individuals are removed from endangered populations [26], and the adaptations of model collection protocols to adopt a "removal" design for other data types such as occupancy and distance sampling, as will be discussed in the Adapting sampling schemes using removal theory Section f this paper.…”

Removal modelling in ecology

“…However in recent years there 57 has been a more constant stream of published papers, suggesting a resurgence of interest 58 in the method (Fig 2). This is potentially an indication of the role of removal modelling 59 in studies of reintroduction, especially when translocated individuals are removed from 60 endangered populations [26], and the adaptations of model collection protocols to adopt 61 a "removal" design for other data types such as occupancy and distance sampling, as 62 will be discussed in "Adapting sampling schemes using removal theory" Section. 66 Methodological Contributions 67 Early model developments 68 The basic principle of the removal method is that a constant sampling effort will remove 69 a constant proportion of the population present at the time of sampling.…”

“…However, there is less information regarding the 350 impact of translocations on the source or donor population [155,156]. These impacts can 351 dramatically affect community stability, which is especially important when translocated 352 individuals are from endangered populations [26]. The main components that can affect 353 the stability of a population are: resistance, that is the ability to maintain its current 354 state when subjected to a perturbation [157]; amplitude, that will determine, after some 355 alteration, if it will return to its original state [158]; elasticity is the property that will 356 determine the rate of return to its initial configuration when the perturbation exceeds 357 the resistance of a community, but not its amplitude [158].…”