Evaluation of alternative management strategies enables informed decisions to accelerate species recovery. For reintroductions, post-release survival to reproductive age is a key parameter influencing population growth. Here, we trial a 'stepping-stone' method to maximize the success of captive-bred animals when the availability of more suitable wild-born release candidates is limited. Our approach makes use of relatively safe and established wild populations to prepare captive-bred individuals for eventual translocation to a final release destination, thus building resilience through establishment of multiple populations over time. We developed a novel multievent model integrating encounter history and biotelemetry data to evaluate reintroduction strategies for the critically endangered Vancouver Island marmot Marmota vancouverensis. We compared post-release survival of 176 individuals (52 wild-born, 47 captive-bred marmots released directly to destinations, and 77 captive-bred marmots released with a stepping-stone approach). Survival estimates to prime breeding-age (PBA), were then used to quantify expected success of potential release strategies. Our analysis indicates that post-release survival varies by source population and release method, as well as age, season, year, and years since release. Conditional on an objective of maximizing survival to PBA, our results suggest that using wild-born marmots for translocations as often as possible, and stepping-stone captive-bred marmots prior to final release, will result in the best outcomes. There was a 0.86 probability that survival to PBA was greater for captive-bred marmots released as yearlings using a stepping-stone approach (survival to PBA mode = 0.13, 95% CRI = 0.05-0.30) than for captive-bred animals that were directly released to destination sites as one-year-olds (survival to PBA mode = 0.04, 95% CRI = 0.01-0.24). Consequently, the stepping-stone approach yields much higher population establishment or growth potential than previous release strategies that used captive-bred marmots. Optimizing the combination of release candidates, sites and timing can thereby increase the effectiveness of reintroductions.

Maximizing survival in reintroduced, captive‐bred animals requires evaluation to identify best practices. This is particularly true for critically endangered species like the Vancouver Island marmot, endemic to British Columbia, Canada. From 2003 to 2010, 301 captive‐bred marmots were implanted with transmitters and released at extinct colony locations and other potentially preferred sites to bolster wild populations and establish new colonies. We evaluated release success based on three criteria: (1) site fidelity in the first summer, (2) survival to hibernation in fall, and (3) survival through winter. We used generalized linear mixed models and information theory to estimate the influence on release success of sex, age, and release practices, as well as local and landscape‐level habitat attributes. Our results suggest that overwinter survival most limited release success in the first‐year postrelease. In all years, overwinter survival was lower for newly released captive‐bred marmots than for wild or previously released marmots. Release date best predicted overall success, and was positively related to site fidelity and survival to hibernation but negatively related to overwinter survival. Our findings suggest that focused attempts to optimize release dates are likely to maximize long‐term reintroduction success.

Through a reintroduction case study on the critically endangered Vancouver Island marmot Marmota vancouverensis, we introduced a 'stepping-stone' approach which utilizes the transition of released individuals among populations to maximize demographic growth potential (Lloyd et al., 2019). We greatly appreciate and hereby reflect on the thoughtful commentaries by Chauvenet (2019), Hayward (2019) and Th evenin (2019) to propose three key topics for future exploration.Determine if stepping-stone approach may work for any species While the stepping-stone technique showed promise with a colonial, social mammal within a meta-population structure, Chauvenet (2019) wondered what parameters might explain these positive effects to better determine the applicability for other species. We agree such information would be valuable to further marmot recovery, and we also anticipate that the explanatory mechanisms may differ in type or magnitude among species. We encourage an adaptive management approach to iteratively address sources of uncertainty for new trials. As such, ongoing learning would optimize management decisions without precluding the opportunity to test this technique for other species.The stepping-stone approach is attempting to use highly suitable release areas to allow individuals to learn or adapt before transfer to additional sites that are demographically important but have conditions which make establishment difficult. Developing key survival behaviors such as foraging, finding shelter, and avoiding predators are critical for all species regardless of taxa or life history.Hayward (2019) highlighted the challenge of recapturing released individuals at the stepping-stone site before final release at the subsequent location. We agree that potential recapture rates should be predicted and monitored due to potential variation arising through behavior, release site conditions, and tracking technology. In our study design (Lloyd et al., 2019), we addressed this issue, quantified recapture rates, and reflected upon the results to address potential applicability for other species. Specific methods and metrics of stepping-stone trials should be adapted for each species and context.Overall, we believe the stepping-stone approach may be feasible across taxa if three core conditions are present: (1) at least one wild population exists and the program goals include additional population(s); (2) multiple release site populations are available that differ in establishment suitability; (3) individuals can be recaptured at initial release sites and transferred with minimal stress to subsequent release populations.Determine if stepping-stone approach may work for any source, type, or stage of conservation translocationThe stepping-stone approach likely has primary applicability for improving the survival of na€ ıve captive-bred individuals in the wild, but it could also be useful for wild-to-wild translocations. Post-release effects afflict nearly all translocations (Armstrong et al., 2017) regardless of source. Even wildtran...

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