Selection Of Release Sites Research Articles

Selection and validation of release sites for conservation translocations of temperate-zone snakes

Poor habitat quality is one of the most important reasons for reintroduction failure of reptiles; therefore, release site suitability ought to be evaluated prior to conducting conservation translocations. In temperate zone snakes, translocations have failed due to high overwinter mortality, so practitioners have recommended that release sites be located near suitable hibernacula. The presence of a Life Zone (LZ), the underground space above the groundwater table and below the frost line, may indicate the presence of suitable hibernation habitat. Identification and validation of sites with LZ, however, is challenged by the dynamic nature of groundwater and frost levels, coupled with the secretive nature of hibernating snakes. In this study, our goals were to 1) identify potential reintroduction sites for the globally imperiled Eastern Massasauga (Sistrurus catenatus) in southern Canada based on the presence of a LZ, 2) to validate the suitability of those reintroduction sites by hibernating a surrogate species (Eastern Gartersnake, Thamnophis sirtalis) in constructed hibernacula, and, 3) to determine if two separate measures of LZ were associated with the survival of individual gartersnakes to the end of hibernation. Four 1-ha study grids, each consisting of multiple groundwater and frost monitoring stations, were surveyed from 2015 to 19. Release sites were identified in each grid where a LZ of ≥ 10 cm was observed consistently for at least 2 full winters, and gartersnakes were successfully hibernated therein and at 2 reference sites over 3 winters. Overall, survival of subadult/adult snakes was very high (100 %; n = 20), regardless of site, whereas juvenile survival was lower (78 %; n = 93). A Kaplan-Meier test indicated that juvenile survival differed significantly among sites, and ranged from 60 % to 100 %. GLMM analysis indicated that mass at ingress had a significant positive effect on snake survival during hibernation. The temporary loss of a LZ did not impact snake survival. Contrary to our expectations, snake survival in hibernacula was negatively associated with both minimum LZ size and LZ frequency (i.e., the % of sampling occasions when LZ size ≥ 10 cm). Hibernating snakes can tolerate periods with a very small or non-existent LZ, but a large LZ may become unsuitable to juveniles, possibly due to a lack of moisture. Our results will guide the selection of release sites for Massasauga reintroductions, and for the development of a rigorous release site selection process for temperate zone snakes.

Lessons learned from a conservation translocation of a microendemic habitat specialist

Translocations are often characterized as “successes” or “failures”. However, this dichotomy masks the challenges of successful translocations and ignores important lessons learned in cases where a population was not established in perpetuity. We translocated 76 individuals of an imperiled endemic lizard, the Dunes Sagebrush Lizard (Sceloporus arenicolus), to a locality where it had gone extinct. Translocated lizards survived and reproduced in small numbers. Based on intensive monitoring, we were able to conclude the incipient population declined to zero individuals after 4 years. It is possible that predation, Allee effects, or stochastic factors prevented the population from sustaining itself at this historically occupied site. Valuable lessons for conservation translocations can be taken from this case. We offer novel perspectives on the IUCN Guidelines for Reintroductions and Other Conservation Translocations regarding release site selection, propagule bias, behavioral monitoring, population monitoring, and issues of land tenure. We recommend pairing knowledge of habitat requirements with quantitative analyses to select suitable release sites, translocating gravid females to jump‐start population growth, coupling delayed releases with intensive behavioral monitoring, using Poisson‐based models to determine necessary intensity of monitoring, and recognizing how issues of land tenure may present pitfalls for conservation translocations in the long term.

Climate suitability as a predictor of conservation translocation failure.

The continuing decline and loss of biodiversity has caused an increase in the use of interventionist conservation tools, such as translocation. However, many translocation attempts fail to establish viable populations, with poor release site selection often flagged as an inhibitor of success. We used species distribution models (SDMs) to predict the climate suitability of 102 release sites for amphibians, reptiles, and terrestrial insects and compared suitability predictions between successful and failed attempts. We then quantified the importance of climate suitability relative to 5 other variables frequently considered in the literature as important determinants of translocation success: number of release years, number of individuals released, life stage released, origin of the source population, and position of the release site relative to the species' range. Probability of translocation success increased as predicted climate suitability increased and this effect was the strongest among the variables we considered, accounting for 48.3% of the variation in translocation outcome. These findings should encourage greater consideration of climate suitability when selecting release sites for conservation translocations and we advocate the use of SDMs as an effective way to do this.

Release site selection: reintroductions and the habitat concept

AbstractIdentifying release sites with good habitat quality is one of the most important steps in any reintroduction project. However, despite their wide application in legislation and research, the habitat concept and habitat-related terms remain poorly defined and subject to confusion. Reviewing a variety of definitions, we advocate for understanding habitat as an area with a species-specific set of resources and environmental conditions that enable a population to persist and reproduce. Using this understanding we investigated release site selection as well as the usage of the term habitat and other habitat-related terms in 324 reintroduction case studies and reintroduction policy documents published during January 1990–May 2016. Although the use of the habitat concept in these publications remained mostly unclear because of the lack of definitions provided, we found an overall improvement in the quality of reintroduction site assessment, and a shift towards more systematic approaches, such as habitat modelling and experimental translocation. To further improve reporting on release site selection, we recommend updating IUCN reintroduction publications and encouraging practitioners to consider the spatial and temporal heterogeneity of habitat, as well as the multiple scales at which a species selects its habitat, in the design of a release site assessment.

Effects of sediment enrichment with macroalgae, Sargassum spp., on the behavior, growth, and survival of juvenile sandfish, Holothuria scabra

To scale-up culture production of the sea cucumber Holothuria scabra using ocean grow-out systems, bottlenecks in enhancing the growth and survival of juveniles need to be addressed. As the selection of release sites is fraught with uncertainty, organic enrichment of sediment using dried Sargassum spp. to increase food abundance (i.e., microalgae and bacteria) may be a viable option to optimize ocean nursery systems. The effects of sediment enriched with dried Sargassum spp. on the diel burying behavior, growth, and survival of juvenile (>3 g) sandfish were investigated in the field for 60 days using sea pens (2.25 m2) with a stocking biomass of 66 g m−2, and in glass tanks (0.045 m2) with the same stocking biomass (∼3 g individual tank-1) in the laboratory for 30 days. Enrichment with Sargassum markedly changed sediment characteristics. Although diurnal burying behavior did not vary significantly between treatments, a greater percentage of juveniles in enriched pens and tanks remained buried during the daytime compared to unenriched pens. Without protection from predators in the wild, all juveniles from enriched pens survived compared to those from unenriched pens (85 ± 10%) after 7 days. After 30 days, absolute growth rates (AGR) of juveniles in enriched pens (0.51 ± 0.06 g day-1) and tanks (0.82 ± 0.27 g day-1) were significantly higher compared to unenriched pens (0.13 ± 0.04 g day-1) and tanks (0.49 ± 0.19 g day-1). Results showed that mean sediment chlorophyll-a content of ∼4 μg g-1 in sea pens enriched with Sargassum spp. could hasten the growth of ∼3 g juveniles to >20 g in 30 days. This study demonstrated that the organic enrichment of sediment is a viable option to optimize the growth of sandfish in an advanced ocean nursery system that may significantly improve survival prior to release for grow-out.

Predicting Optimal Release Sites for Rehabilitated Monkeys: a Vervet Monkey (Chlorocebus aethiops) Case Study

Primate rehabilitation is challenging but has become crucial as many species are threatened with extinction. Vervet monkeys (Chlorocebus aethiops) are a widespread primate species in Africa. Despite the release of comparatively large numbers of rehabilitated monkeys, the success rate is poor, with low survival. This is partly due to choosing substandard release sites. Here we use an environmental envelope model that combines species-specific environmental and spatial data (including environmental conditions such as temperature and rainfall, access to permanent water, and proximity to anthropogenic influence) to predict the best areas for release of rehabilitated vervet monkeys in KwaZulu-Natal, South Africa. Approximately 80% of the land in KwaZulu-Natal qualifies as general habitat. However, only 6225 km2 (6.7%) is classed as habitat desirable for release, as human occupation and limited water access render other areas unsuitable. Unsurprisingly, ideal release land is limited and may prove difficult to access. However, there are accessible land areas that may be viable despite human impact. This uncertainty highlights the need for site visits early in the selection process. Our model provides easily read maps that rehabilitators can use to assist with this process and potentially optimize release site selection. This method could be easily adapted to other primate species.

Alignment of threat, effort, and perceived success in North American conservation translocations.

The use of conservation translocations to mitigate human effects on biodiversity is increasing, but how these efforts are allocated remains unclear. Based on a comprehensive literature review and online author survey, we sought to determine the goals of translocation efforts, whether they focus on species and regions with high threat and likelihood of perceived success, and how success might be improved. We systematically searched the ISI Web of Knowledge and Academic Search Complete databases to determine the species and regions of conservation translocations and found 1863 articles on conservation translocations in the United States, Canada, Mexico, Central America, and Caribbean published from 1974 to 2013. We questioned 330 relevant authors to determine the motivation for translocations, how translocations were evaluated, and obstacles encountered. Conservation translocations in North America were geographically widespread (in 21 countries), increased in frequency over time for all animal classes (from 1 in 1974 to 84 in 2013), and included 279 different species. Reintroductions and reinforcements were more common in the United States than in Canada and Mexico, Central America, or the Caribbean, and their prevalence was correlated with the number of species at risk at national and state or provincial levels. Translocated species had a higher threat status at state and provincial levels than globally (International Union for Conservation of Nature Red List categorization), suggesting that translocations may have been motivated by regional priorities rather than global risk. Our survey of authors was consistent with these results; most translocations were requested, supported, or funded by government agencies and downlisting species at national or state or provincial levels was the main goal. Nonetheless, downlisting was the least reported measure of success, whereas survival and reproduction of translocated individuals were the most reported. Reported barriers to success included biological factors such as animal mortality and nonbiological factors, such as financial constraints, which were less often considered in the selection of release sites. Our review thus highlights discrepancies between project goals and evaluation criteria and between risk factors considered and obstacles encountered, indicating room to further optimize translocation projects.

Head-Started Kemp's Ridley Turtle (Lepidochelys kempii) Nest Recorded in Florida: Possible Implications

Abstract A head-started Kemp's ridley sea turtle (Lepidochelys kempii) was documented nesting on South Walton Beach, Florida on 25 May 2015. This record supports the possibility that exposure to Florida waters after being held in captivity through 1–3 yrs of age during the head-starting process may have influenced future nest site selection of this and perhaps other Kemp's ridley turtles. Such findings could have important ramifications for marine water experimentation and release site selection for turtles that have been reared in captivity.

Leadership and management influences the outcome of wildlife reintroduction programs: findings from the Sea Eagle Recovery Project.

Wildlife reintroductions and translocations are statistically unlikely to succeed. Nevertheless, they remain a critical part of conservation because they are the only way to actively restore a species into a habitat from which it has been extirpated. Past efforts to improve these practices have attributed the low success rate to failures in the biological knowledge (e.g., ignorance of social behavior, poor release site selection), or to the inherent challenges of reinstating a species into an area where threats have already driven it to local extinction. Such research presumes that the only way to improve reintroduction outcomes is through improved biological knowledge. This emphasis on biological solutions may have caused researchers to overlook the potential influence of other factors on reintroduction outcomes. I employed a grounded theory approach to study the leadership and management of a successful reintroduction program (the Sea Eagle Recovery Project in Scotland, UK) and identify four critical managerial elements that I theorize may have contributed to the successful outcome of this 50-year reintroduction. These elements are: 1. Leadership & Management: Small, dedicated team of accessible experts who provide strong political and scientific advocacy (“champions”) for the project. 2. Hierarchy & Autonomy: Hierarchical management structure that nevertheless permits high individual autonomy. 3. Goals & Evaluation: Formalized goal-setting and regular, critical evaluation of the project’s progress toward those goals. 4. Adaptive Public Relations: Adaptive outreach campaigns that are open, transparent, inclusive (esp. linguistically), and culturally relevant.

Raising Coyotes: Not Your Average Pup

Wildcat Creek Wildlife Center in Indiana has raised coyote pups since 1995 and the author has been the senior coyote caretaker since 2000. This paper details vaccines, antiparasitics, diet guidelines, housing, behavior, introducing non–littermates, preventing habituation, enrichment for survival, and release site selection.

A priori assessment of reintroduction strategies for a native ungulate: using HexSim to guide release site selection

Reintroduction of native species to unoccupied portions of their historical range is a common management strategy to enhance the future viability of animal populations. This approach has met with mixed success, due to unforeseen impacts caused by human or other factors. Some of these impacts could potentially be mitigated through the use of anticipatory modeling coupled with appropriate management strategies prior to release. As part of an ongoing restoration program, we evaluated a portion of the former range of the tule elk (Cervus elaphus nannodes) in the Central Valley of California for potential reintroduction of a free-ranging herd. We used a new spatially explicit population model (HexSim) to analyze four different elk release scenarios. Each scenario corresponded to a different release location, and the model was used to compare simulated elk movement and population dynamics 25 years into the future. We also used HexSim to identify likely locations of human–elk conflict. Population forecasts after the 25-year period were highest (mean female population size of 169.6 per iteration) and potentially harmful barrier interactions were lowest (mean 8.6 per iteration) at the East Bear Creek site. These results indicate the East Bear Creek site release scenario as the most likely to result in a successful elk reintroduction, producing the most elk and generating the fewest human conflicts. We found HexSim to be a useful tool for this type of reintroduction planning and believe that other reintroduction efforts could benefit from this type of anticipatory modeling.

EDITOR'S CHOICE: Saving the hihi under climate change: a case for assisted colonization

Summary Climate change is affecting the spatio‐temporal distribution of environmental conditions, forcing species to shift their range in response. Species not capable of dispersing naturally may benefit from conservation translocations. A key aspect of translocation planning is release site selection: under the 2012 IUCN guidelines for reintroductions and other conservation translocations, selected sites are expected to match the biotic and abiotic needs of the candidate species now and in the future. Here we present a methodological framework to identify optimal translocation sites under climate change. Our method is the first to explicitly combine statistical and predictive population modelling to understand the relationship between climate, climate change and population dynamics, in order to perform robust habitat suitability analyses for conservation decision‐making. We use the hihi Notiomystis cincta, a bird endemic to New Zealand, as a case study. We focus on the population of Tiritiri Matangi Island, which has been provided with ad libitum supplementary food since 1996. This offers the unique opportunity to study the direct impact of climate and future change in climatic conditions on a population free of confounding constraints. Climate is found to drive hihi population dynamics, even though they are not limited by the availability of food. Thus, despite the current management of the species, climate change remains a major threat to its long‐term persistence. Moreover, under predicted climate change for the country, hihi suitable habitat will shift southward: the two current largest hihi populations will face unsuitable climatic conditions in the coming decades, and habitat that was not part of the species' historical range may become suitable. Synthesis and applications. Assisted colonization is increasingly being considered as an adaptation tool for species threatened by climate change. Justifying the use of this extreme conservation action, however, requires robust evidence that it is necessary and clear guidance on where to translocate individuals of threatened populations. We show how both requirements can be met using habitat suitability modelling if knowledge of the relationship between climate, climate change and the species' population dynamics is systematically used to guide the modelling process.

Predicting post-release establishment using data from multiple reintroductions

For any reintroduction it is important to maximise the probability of released individuals establishing in the target area (settling and surviving to breed). Factors influencing establishment have typically been studied at single sites, making it impossible to assess factors that vary at the site level (e.g. connectivity) or quantify unpredictable variation among sites. Using data from 14 reintroductions of the North Island robin (Petroica longipes) to native forest reserves, we show how Bayesian modelling can be used to identify general drivers of establishment and to account for site-to-site variation when making predictions for new sites. High landscape connectivity and high rat tracking rates (a density index) at reintroduction sites were key factors associated with lower individual establishment probabilities. Habitat similarity between source and release sites was also important, as robins sourced from native forest had higher establishment than those from exotic pine forest. Previous predator experience appeared to affect establishment in sites with mammalian predators, as founders sourced from sites with these predators had higher establishment than those from other sites. Our approach can be applied to a wide range of species that are being reintroduced to multiple sites, providing guidance on source and release site selection, efficacy of management interventions, and the numbers of individuals to release to achieve desired initial population sizes. The results are not only applicable to these particular species, but can be used to predict site suitability for reintroductions of species with similar dispersal behaviour or other ecological characteristics.

Experimental reseeding of juvenile spiny lobsters ( Jasus edwardsii): Comparing survival and movement of wild and naïve lobsters at multiple sites

We used mark–recapture methods to assess the relative survival of naïve and wild-caught juvenile lobsters released to coastal reef in southeast Tasmania, Australia. Naïve lobsters were captured as pueruli (first benthic post-larval stage) and reared in tanks for 12 to 18 months. Naïve and wild-caught lobsters were identified individually by an antennal tag and released by divers at 4 sites. In dive surveys performed over 3 to 5 weeks we resighted similar numbers of wild and naïve lobsters at 2 of the sites, but significantly more naïve lobsters at the remaining sites. Multistate mark–recapture models detected no difference in apparent survival between treatment groups at 3 of the sites. Lower apparent survival of naïve lobsters at the fourth site was attributed to the small size of this reef and the absence of adjacent lobster habitat. Many naïve lobsters did not recognise habitat boundaries and moved away from the release reef onto sand. Acoustic tracking revealed that selecting release sites with contiguous reef extending a minimum of 30 m in all directions should negate losses of this kind. At 3 sites apparent survival estimates were low for wild and naïve lobsters in the 24 h following release. Apparent survival was much higher when lobsters were released into seafloor cages. Acoustic tracking indicated that low apparent survival of lobsters released outside cages was due largely to emigration from our survey areas rather than losses to predation. By following simple criteria in the selection of release sites it is possible to ensure that survival rates among released naïve lobsters are equivalent to those of wild lobsters released in the same manner.

Achievements and lessons learned in restocking giant clams in the Philippines

For almost 20 years, the Marine Science Institute (MSI), University of the Philippines, has been culturing giant clams to restore depleted populations of these large bivalves in the Philippines, and to promote giant clam farming as a sustainable livelihood. Restocking activities were done in collaboration with local groups by providing training in the culture and ocean rearing of giant clams, and by implementing a “users pay” approach. Initially, a variety of giant clam species was used but once F1 broodstock of Tridacna gigas were reared, restocking focused on this species due to its scarcity and fast rate of growth. About 20 000 T. gigas were placed on coral reefs. In addition, >50 000 clams ( T. gigas, T. squamosa, T. derasa, T. crocea, T. maxima and Hippopus hippopus) were distributed through other means. Altogether, >40 sites throughout the Philippines received cultured giant clams. Grow-out trials to test the viability of supplying giant clams for the aquarium trade to create new sources of income were conducted successfully with a group of fishers in Bolinao, Pangasinan. However, this initiative encountered legal obstacles when the government regulatory agency prohibited the export of cultured clams, regarding this as a threat to the conservation of wild individuals. The long experience in culturing and restocking giant clams in the Philippines provides many lessons for other countries wishing to restore stocks of these large bivalves. Particular care needs to be given to selection of release sites, negotiations with participating groups to safeguard the released clams, adequate transfer of technology to collaborators, and transport of large clams from nursery areas to release sites.

Establishing a New Wild Population of Tuatara (Sphenodon guntheri)

Abstract: Translocations of reptiles and amphibians have been questioned as a conservation tool because they generally have not been successful. However, translocation is the only method by which many species can be restored to parts of their former range, which increases their conservation security. Tuatara ( Sphenodon spp.), sole surviving members of the reptilian Order Sphenodontia, are restricted to offshore islands of New Zealand. Dispersal into former habitat on the mainland or other islands, following removal of the causes of extinction, is unlikely. Captive rearing of reptile hatchlings from eggs collected in the wild to produce founders for new populations is also a conservation technique that has had mixed success. However, captive incubation and rearing are techniques that allow large numbers of tuatara to be produced to start new populations without detrimental effects on small source populations. We document the first contemporary translocation of S. guntheri, providing details on selection of release sites and founders. Release sites were chosen on a rodent‐free island that provided a variety of habitats for tuatara as well as abundant food and shelter. The release propagule comprised 18 wild‐caught adults and 50 captive‐reared juveniles. Four separate release sites were established to separate adults from juveniles during the establishment phase. Five years of monitoring indicate that at least 57% of tuatara survived translocation and that reproduction has occurred on the new island. All tuatara increased in weight and length, demonstrating that tuatara have an indeterminate growth pattern. The 56% of recaptured juveniles represented a cross section of the sizes released. We evaluated the use of head‐started juveniles as founders, based on survival and growth data. Because tuatara are long‐lived, late‐maturing reptiles with slow reproduction, establishment of a self‐sustaining population will take decades of monitoring to confirm.

BIOLOGICAL CONTROL ATTEMPTS BY INTRODUCTIONS AGAINST PEST INSECTS IN THE FIELD IN CANADA

AbstractThis is an analysis of the attempts to colonize at least 208 species of parasites and predators on about 75 species of pest insects in the field in Canada. There was colonization by about 10% of the species that were introduced in totals of under 5,000 individuals, 40% of those introduced in totals of between 5,000 and 31,200, and 78% of those introduced in totals of over 31,200. Indications exist that initial colonizations may be favoured by large releases and by selection of release sites that are semi-isolated and not ecologically complex but that colonizations are hindered when the target species differs taxonomically from the species from which introduced agents originated and when the release site lacks factors needed for introduced agents to survive or when it is subject to potentially-avoidable physical disruptions. There was no evidence that the probability of colonization was increased when the numbers of individuals released were increased by laboratory propagation. About 10% of the attempts were successful from the economic viewpoint. Successes may be overestimated if the influence of causes of coincidental, actual, or supposed changes in pest abundance are overlooked. Most of the successes were by two or more kinds of agents of which at least one attacked species additional to the target pests. Unplanned consequences of colonization have not been sufficiently harmful to warrant precautions to the extent advocated by Turnbull and Chant but are sufficiently potentially dangerous to warrant the restriction of all colonization attempts to biological control experts. It is concluded that most failures were caused by inadequate procedures, rather than by any weaknesses inherent in the method, that those inadequacies can be avoided in the future, and therefore that biological control of pest insects has much unrealized potential for use in Canada.