Novel Conditions in Conservation Translocations: A Conservative-Extrapolative Strategic Framework

James Hunter-Ayad,Andrew Digby,Ralf Ohlemüller,Scott Jarvie,Philip J Seddon,Mariano R Recio,Glen Greaves

doi:10.3389/fcosc.2021.691714

Abstract

In response to anthropogenic threats, conservation translocations are increasingly used to combat species' population and range declines. However, moving animals outside of their current distribution can mean introducing them to novel conditions, even in the case of reintroductions to formerly inhabited areas due to ecosystem changes following extirpation. This exposure to novel conditions introduces uncertainty that can undermine decision making for species conservation. Here we propose two strategies, which we define as conservative and extrapolative, for approaching and managing novelty and the resulting uncertainty in conservation translocations. Conservative strategies are characterised by the avoidance and removal of novel conditions as much as possible, whereas extrapolative strategies are more experimental, allowing exposure to novel conditions and monitoring outcomes to increase understanding of a species' ecology. As each strategy carries specific risks and opportunities, they will be applicable in different scenarios. Extrapolative strategies suit species in recovery which can afford some experimental management, or species facing novel and emerging threats which require less traditional translocations, such as assisted colonisations. We provide examples, applying our framework to two endemic New Zealand species with long histories of translocation management: tuatara (Sphenodon punctatus), a reptile and takahē (Porphyrio hochstetteri), a flightless bird.

Highlights

Anthropogenic ecosystem degradation has occurred throughout human history (Waters et al, 2016), resulting in species declines and extinctions
We identify the challenges posed by the novelty inherent in conservation translocations in relation to release-site selection and post-release habitat use, and provide a conceptual framework to explore how this novelty can be approached following either a conservative or an extrapolative strategy
We separate strategies into two broad categories based on defining novel conditions as those not represented within a species relict distribution

Summary

INTRODUCTION

Anthropogenic ecosystem degradation has occurred throughout human history (Waters et al, 2016), resulting in species declines and extinctions. This population admixture serves the purpose of avoiding inbreeding and genetic bottlenecks, but might limit the ability of takaheto adapt to conditions in any one secure site as continual translocations between secure, relict and wild sites are used to maintain genetic diversity across the global takahepopulation (Lees et al, 2014; Zavodna et al, 2015; Greaves et al, 2020) Despite this control, some local behavioural adaptations have been observed as takaheat secure sites expand their use of resources that have limited availability in the Murchison Mountains such as fallen fruits, exotic grasses, small reptiles, and the chicks of other bird species ( ducks). The primary focus is on likely predation pressure from introduced mammals and the feasibility of mitigation, ease of access and minimising excess dispersal through natural barriers

DISCUSSION

DATA AVAILABILITY STATEMENT