Can translocations to islands reduce extinction risk for reptiles? Case studies from New Zealand

Towns, David R.; Miller, Kimberly A.; Nelson, Nicola J.; Chapple, David G.

doi:10.1016/j.biocon.2016.04.024

Cited by 23 publications

(13 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Translocated populations start at small population sizes, and often share demographic, environmental and genetic risks associated with relict populations (Taylor, Jamieson & Armstrong, 2005;Jamieson et al, 2008;Towns et al, 2016). Models that predict translocation impacts on source and founder populations are therefore necessary to ensure that harvesting for release does not jeopardize either population (Dimond & Armstrong, 2007;Chauvenet et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Balancing act: modelling sustainable release numbers for translocations

Easton

Bishop

Whigham

2019

Animal Conservation

View full text Add to dashboard Cite

Translocated populations often share demographic, environmental and genetic risks associated with relict populations. Models that predict translocation impacts on source and founder populations are therefore necessary to ensure that harvesting for release does not jeopardize either population. However, current models generally focus on maximizing the long‐term demographic viability and retention of allelic diversity in the founder population only. We therefore risk estimating a release number that is considered ‘appropriate' for maintaining viability and allelic diversity in the founder population but is in fact detrimental to the source. Our objectives were to determine a sustainable number of individuals for release that maximized the viability and allelic diversity of source and founder populations. We developed a spatially explicit individual‐based model that simulated hypothetical translocation scenarios for the threatened New Zealand frog, Leiopelma pakeka, which was restricted to Te Hoiere/Maud Island and has been heavily targeted for translocations. Source and translocated populations were simulated over 200 generations, representing 200 years across various initial population sizes from 20 to 300 frogs. To account for the potential loss of allelic diversity from the source population via harvesting, along with genetic drift and founder events typically associated with translocations, an additional set of simulations determined the probability of retaining a single diploid locus within populations with rare and common alleles. Our results showed that at least 120 frogs were required for populations to remain viable and maximize allelic retention in the long‐term, regardless of allelic diversity. However, harvesting more than 150 frogs led to ongoing or the onset of declines in the viability and allelic retention of source populations. We recommend that future translocations of L. pakeka harvest no more than 140 frogs from each of the sub‐populations on Te Hoiere/Maud Island. We also recommend the described approach to simulate hypothetical translocation scenarios for other managed species.

show abstract

Section: Introductionmentioning

confidence: 99%

Balancing act: modelling sustainable release numbers for translocations

Easton

Bishop

Whigham

2019

Animal Conservation

View full text Add to dashboard Cite

show abstract

“…Thus, not only did larger individuals experience higher survivorship, but they likely also have greater reproductive output. This could potentially increase the overall likelihood of translocation success (Towns et al , ).…”

Section: Discussionmentioning

confidence: 99%

“…Nonetheless, the success rate of translocations for captive‐reared lizards has rarely been monitored and evaluated (e.g. Towns et al , ). As such, our case study provides valuable information that can inform future translocation efforts.…”

Section: Discussionmentioning

confidence: 99%

“…New Zealand is a world leader in conservation management of species threatened by introduced predators (Armstrong & McClean, ; Romijn & Hartley, ; Towns et al , ). Management has focused on eradicating mammalian predators from islands before translocating native species to these island refugia, either to reinforce existing populations or to found new populations (Towns et al, ,b, Hitchmough et al , ). Translocated individuals may be bred in captivity (Seddon et al, ; Maran et al , ) and are often ‘head‐started' prior to their release (Connolly & Cree, ; Jarvie et al , ).…”

Section: Introductionmentioning

confidence: 99%

“…Conservation attempts have involved translocating lizards to offshore islands or mainland refugia, and in New Zealand, captive management is increasingly being used to found populations for translocation to new sites. However, the success of such translocations has generally been undetermined or assessed over relatively short timescales; longer term monitoring (>4 years) is required to direct future translocation efforts (Romijn & Hartley, ; Towns et al , ). We investigated the success of a translocation of a population of captive‐reared Suter's skinks on an offshore island of New Zealand as well as the factors likely to predict success.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Predictors of translocation success of captive‐reared lizards: implications for their captive management

Hare

Schumann

Hoskins

et al. 2019

Animal Conservation

View full text Add to dashboard Cite

Islands are biodiversity hotspots, but their native inhabitants are vulnerable to predation from exotic predators. Conservation of island endemics has often involved translocating captive‐reared populations to predator‐free refugia. However, the long‐term success of these translocations has rarely been assessed. We investigated the traits that maximize post‐translocation survival in a cohort of captive‐reared Suter's skinks Oligosoma suteri and compared traits normally associated with survival and persistence of lizards (body condition, speed and overall size) to that of wild‐born skinks 6 years after release onto a predator‐free island in the north‐east of New Zealand. Our models showed that larger lizards, and lizards with lower body condition, had improved survival. While sprint speed of captive‐reared lizards did not differ significantly to that of wild skinks, diving ability of captive‐reared skinks was poor, with only female captive‐reared lizards diving during trials. Our results indicate that the traits associated with higher survival after release are not necessarily obvious and may be influenced by adaptation to captive conditions. Long‐term monitoring post‐translocation is therefore vital to determine the success of the translocation.

show abstract