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Thea C. Johanos - One of the best experts on this subject based on the ideXlab platform.
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benefits derived from opportunistic survival enhancing interventions for the Hawaiian Monk Seal the silver bb paradigm
Endangered Species Research, 2014Co-Authors: Albert L. Harting, Thea C. Johanos, Charles L. LittnanAbstract:The cumulative benefits derived from historic small-scale, opportunistic interventions for the Hawaiian Monk Seal Monachus schauinslandi were assessed using multiple methods. The analysis focused on interventions undertaken to enhance survival of individual Seals by reducing or eliminating immediate mortality risks. These interventions included dehookings, disentangle- ments, removing Seals from high predation zones, medical interventions, and related activities. A total of 885 interventions occurred range-wide from 1980 to 2012. These included 645 inter - ventions classified as mitigating medium- to high-risk threats, involving 532 different Seals. In the Northwest Hawaiian Islands, where most of these interventions took place, we found a significant relationship between the number of interventions conducted annually and duration of field effort. The survival and reproduction of the intervention Seals were tracked through multiple generations, using (1) known survival and reproduction of intervention Seals, and (2) expected survival and re- production as determined using demographic rates estimated for the population at large. This analysis indicated that 17�24% of the 2012 population comprised either intervention Seals or de- scendants of intervention Seals. If Seals included in a multiyear (1984�1992) re habilitation and cap- tive care effort are also included, this proportion increases to 32%. These findings demonstrate the important link between the sustained population assessment field effort, the number of interven- tions that are enabled in association with those efforts, and the current status of the Monk Seal pop- ulation. In contrast to a metaphorical 'silver bullet' whereby a result is achieved through a single (or a few) highly impactive tools, we liken our success in applying multiple interventions to a fusil- lade of many silver BBs 1 .
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The Hawaiian Monk Seal in the northwestern Hawaiian Islands, 2004
2011Co-Authors: Thea C. Johanos, Jason D. BakerAbstract:Report detailing field studies of Hawaiian Monk Seals conducted at all of its main reproductive sites in the Northwestern Hawaiian Islands.
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Dizygotic twinning in the Hawaiian Monk Seal
Journal of Mammalogy, 2011Co-Authors: Jennifer K. Schultz, Brenda L. Becker, Thea C. Johanos, Jessica U. Lopez, Lizabeth KashinskyAbstract:Abstract Twinning is extremely rare in pinnipeds. Instances in which a female is observed simultaneously nursing 2 pups may represent alloparenting, or nonfilial nursing, a relatively common trait in pinnipeds. We explored the incidence of twinning in the Hawaiian Monk Seal (Monachus schauinslandi). We observed 7 sets of putative twins (i.e., an isolated female nursing 2 newborn pups) of 4,965 total births recorded between 1983 and 2008 (minimum twinning rate = 0.1%). Genetic specimens from the mother and both pups were available only for 5 of the 7 sets. Microsatellite genotyping revealed all of these to be dizygotic twins, with low probability of false assignment (P < 0.001). On average, Hawaiian Monk Seal twins were less likely to survive to weaning than singletons born in the same year and on the same island (P = 0.008). Those that weaned were smaller in size (i.e., axillary girths 1–4 SDs lower than singletons). In the critically endangered Hawaiian Monk Seal twinning appears to be a rare trait t...
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Translocation as a tool for conservation of the Hawaiian Monk Seal
Biological Conservation, 2011Co-Authors: Jason D. Baker, Brenda L. Becker, Thea C. Johanos, Charles L. Littnan, Tracy A. Wurth, John R. HendersonAbstract:Abstract The deteriorating demographic status of the endangered Hawaiian Monk Seal has motivated renewed and expanded proposals for conservation action, including translocation of Seals to improve survival. Over the past three decades, numerous Monk Seal translocations have been conducted with a variety of objectives, including mitigating shark predation and conspecific male aggression, reducing human–Seal interactions, and taking advantage of favorable foraging habitats to improve survival. Here, we analyze our cumulative experience with translocation of Hawaiian Monk Seals. We found a strong correlation between the time Seals remained in the vicinity of the release site and their age. Recently weaned pups (with little or no at-sea foraging experience) exhibited high fidelity to release sites commensurate with that shown by untranslocated pups to their birth location. In contrast, juvenile and adult Seals tended to stray from their release locations farther and sooner. Nevertheless, when 21 adult male Seals were moved more than 1000 km from Laysan Island in the Northwestern Hawaiian Islands (NWHI), to the main Hawaiian Islands (MHI), they subsequently dispersed among the MHI; however, only one was observed to return to the NWHI. Translocated Seals appeared to survive at rates comparable to Seals native to the release site. Outcomes suggest that in most cases the intended objectives of translocations were achieved. Except for one notable case, translocations within the MHI to arrest human–Seal interactions were mostly unsuccessful. These findings will be essential for informing successful large-scale translocation plans in the future.
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REPRODUCTIVE PATTERNS OF THE Hawaiian Monk Seal
Marine Mammal Science, 2007Co-Authors: Albert L. Harting, Jason D. Baker, Thea C. JohanosAbstract:We evaluated reproductive patterns of the Hawaiian Monk Seal (Monachus schauinslandi) using a combination of fitted age-specific reproductive curves and analysis of reproductive patterns of individual females. We review the difficulties inherent in the acquisition and modeling of reproductive data with emphasis on the significance of reproductive senescence to populations with dissimilar age/sex compositions. Validation of the fitted reproductive parameters was accomplished by Monte Carlo sampling of parameter distributions to compare the expected number of pups with the observed production. Although the fitted reproductive functions appear to provide an acceptable fit to the raw reproductive data, we found that the fitted curves did a poor job of predicting the actual pup production in individual years because of high variability among years. To further verify, and elaborate on, the patterns in the pooled (multi-Seal, and multi-year) rates, we examined attributes of the reproductive performance of individual Seals. The attributes included age of primiparity, reproductive rates computed over several age ranges, and the relationship between reproductive performance and Seal longevity. Analysis of individual Seal patterns reinforced the conclusion that reproductive senescence is operative in Monk Seal populations.
Jason D. Baker - One of the best experts on this subject based on the ideXlab platform.
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Relative influence of climate variability and direct anthropogenic impact on a sub-tropical Pacific top predator, the Hawaiian Monk Seal
Marine Ecology Progress Series, 2012Co-Authors: Jason D. Baker, Evan A. Howell, Jeffrey J. PolovinaAbstract:Abundance trends of Hawaiian Monk Seals Monachus schauinslandi at 6 subpopula- tions throughout the Northwestern Hawaiian Islands (NWHI) have fluctuated considerably during the past 5 decades. Direct human impacts have been widely accepted as the primary cause of pre- vious Monk Seal population declines and, consequently, much conservation effort has focused on minimizing these threats. Yet climate variability has been increasingly identified as a factor influ- encing Monk Seal demography. We endeavored to evaluate the relative influence of climate ver- sus direct anthropogenic impacts on historic trends in Monk Seal populations. Periods of growth and decline in Monk Seal abundance at 4 subpopulations were associated with positive and neg- ative phases, respectively, of the Pacific Decadal Oscillation (PDO). Moreover, PDO regime shifts were followed, after approximately 2 yr lags, by corresponding changes in Monk Seal abundance trajectories, especially in the absence confounding human impacts. We propose that the PDO is a proxy for varying productivity in the northern NWHI, the effects of which propagate vertically through the food web and are reflected in top predators such as the Monk Seal. Our results suggest that long-term dynamics of Monk Seal populations may have been driven as much, if not more, by climateocean variability as by direct human activity. In recent years, direct human impacts on Monk Seals have been virtually eliminated from the NWHI. As such, previous and continued detailed monitoring of Hawaiian Monk Seal demographics offer a unique opportunity to document and understand how future anticipated global climate change will affect marine ecosystems in the central North Pacific.
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The Hawaiian Monk Seal in the northwestern Hawaiian Islands, 2004
2011Co-Authors: Thea C. Johanos, Jason D. BakerAbstract:Report detailing field studies of Hawaiian Monk Seals conducted at all of its main reproductive sites in the Northwestern Hawaiian Islands.
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Translocation as a tool for conservation of the Hawaiian Monk Seal
Biological Conservation, 2011Co-Authors: Jason D. Baker, Brenda L. Becker, Thea C. Johanos, Charles L. Littnan, Tracy A. Wurth, John R. HendersonAbstract:Abstract The deteriorating demographic status of the endangered Hawaiian Monk Seal has motivated renewed and expanded proposals for conservation action, including translocation of Seals to improve survival. Over the past three decades, numerous Monk Seal translocations have been conducted with a variety of objectives, including mitigating shark predation and conspecific male aggression, reducing human–Seal interactions, and taking advantage of favorable foraging habitats to improve survival. Here, we analyze our cumulative experience with translocation of Hawaiian Monk Seals. We found a strong correlation between the time Seals remained in the vicinity of the release site and their age. Recently weaned pups (with little or no at-sea foraging experience) exhibited high fidelity to release sites commensurate with that shown by untranslocated pups to their birth location. In contrast, juvenile and adult Seals tended to stray from their release locations farther and sooner. Nevertheless, when 21 adult male Seals were moved more than 1000 km from Laysan Island in the Northwestern Hawaiian Islands (NWHI), to the main Hawaiian Islands (MHI), they subsequently dispersed among the MHI; however, only one was observed to return to the NWHI. Translocated Seals appeared to survive at rates comparable to Seals native to the release site. Outcomes suggest that in most cases the intended objectives of translocations were achieved. Except for one notable case, translocations within the MHI to arrest human–Seal interactions were mostly unsuccessful. These findings will be essential for informing successful large-scale translocation plans in the future.
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Range-wide genetic connectivity of the Hawaiian Monk Seal and implications for translocation.
Conservation biology : the journal of the Society for Conservation Biology, 2010Co-Authors: Jennifer K. Schultz, Jason D. Baker, Albert L. Harting, Robert J. Toonen, Brian W. BowenAbstract:: The Hawaiian Monk Seal (Monachus schauinslandi) is one of the most critically endangered marine mammals. Less than 1200 individuals remain, and the species is declining at a rate of approximately 4% per year as a result of juvenile starvation, shark predation, and entanglement in marine debris. Some of these problems may be alleviated by translocation; however, if island breeding aggregates are effectively isolated subpopulations, moving individuals may disrupt local adaptations. In these circumstances, managers must balance the pragmatic need of increasing survival with theoretical concerns about genetic viability. To assess range-wide population structure of the Hawaiian Monk Seal, we examined an unprecedented, near-complete genetic inventory of the species (n =1897 Seals, sampled over 14 years) at 18 microsatellite loci. Genetic variation was not spatially partitioned (w=−0.03, p = 1.0), and a Bayesian clustering method provided evidence of one panmictic population (K =1). Pairwise FST comparisons (among 7 island aggregates over 14 annual cohorts) did not reveal temporally stable, spatial reproductive isolation. Our results coupled with long-term tag-resight data confirm Seal movement and gene flow throughout the Hawaiian Archipelago. Thus, human-mediated translocation of Seals among locations is not likely to result in genetic incompatibilities. Resumen: La foca (Monachus schauinslandi) es una de las especies de mamiferos marinos en mayor peligro critico. Existen menos de 1200 individuos, y la especie esta declinando a una tasa de ∼4% por ano como resultado de la inanicion juvenil, depredacion por tiburones y enmaranamiento en escombro marino. Algunos de esos problemas se pueden aligerar por translocacion; sin embargo, si las colonias reproductivas insulares son subpoblaciones aisladas efectivamente, el movimiento de animales puede alterar adaptaciones locales. En estas circunstancias, los manejadores deben balancear la necesidad pragmatica de incrementar la supervivencia con preocupaciones teoricas sobre la viabilidad genetica. Para evaluar la estructura de la poblacion de M. schauinslandi en toda su area de distribucion, examinamos un inventario genetico, casi completo y sin precedentes, de la especie (n =1897 focas, muestreadas a lo largo de 14 anos) en 18 loci microsatelite. La variacion genetica no estaba subdividida espacialmente (w=−0.03, p = 1.0), y un metodo de agrupamiento Bayesiano proporciono evidencia de una poblacion panmictica (K =1). Comparaciones pareadas FST (entre 7 grupos insulares en 14 cohortes anuales) no revelo aislamiento reproductivo espacial, temporalmente estable. Nuestros resultados, combinados con datos de avistamiento de marcas, confirman el movimiento de individuos y el flujo de genes en el Archipielago Hawaiano. Por lo tanto, es probable que la translocacion de focas por intervencion humana no resulte en incompatibilidades geneticas.
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Extremely low genetic diversity in the endangered Hawaiian Monk Seal (Monachus schauinslandi
2009Co-Authors: Jennifer K. Schultz, Jason D. Baker, Robert J. Toonen, W. BowenAbstract:Hunted to near extinction in the late 19th century, the endangered and endemic Hawaiian Monk Seal (Monachus schauinslandi) exhibits low variation at all molecular markers tested to date. Here we confirm extreme paucity of genetic diversity, finding polymorphisms at only 8 of 154 microsatellite loci tested (143 novel species-specific loci, 10 loci from Antarctic Seals, and 1 previously characterized locus). This screening revealed unprecedentedly low levels of allelic diversity and heterozygosity (A 5 1.1, He 5 0.026). Subsequent analyses of 2409 Hawaiian Monk Seals at the 8 polymorphic loci provide evidence for a bottleneck (P 5 0.002), but simulations indicate low genetic diversity (He, 0.09) prior to recorded human influence. There is little indication of contemporary inbreeding (FIS 5 0.018) or population structure (K 5 1 population). Minimal genetic variation did not prevent partial recovery by the late 1950s and may not be driving the current population decline to;1200 Seals. Nonetheless, genotyping nearly every individual living during the past 25 years sets a new benchmark for low genetic diversity in an endangered species. Genetic variation is the raw material of evolution and a prerequisite for adaptation via natural selection (Fisher 1930). Measures of genetic diversity are often used to estimate individual fitness and the potential for population persistence (Coltman et al. 1999; Hansson and Westerberg 2002; Reed and Frankham 2003). Genetically depauperate species may have a reduced ability to mount an effectiv
Shannon Atkinson - One of the best experts on this subject based on the ideXlab platform.
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Organochlorines in the free-ranging Hawaiian Monk Seal (Monachus schauinslandi) from French Frigate Shoals, North Pacific Ocean.
The Science of the total environment, 2004Co-Authors: Maia K Willcox, Lee Ann Woodward, Gina M Ylitalo, Jon Buzitis, Shannon AtkinsonAbstract:The Hawaiian Monk Seal (Monachus schauinslandi) is an endangered species found only in the Hawaiian Island chain. The largest subpopulation, at French Frigate Shoals, has been in decline since 1989. In order to assess organochlorine (OC) levels in the Hawaiian Monk Seals, whole blood and blubber samples were collected in 1999 from 46 free-ranging Hawaiian Monk Seals at French Frigate Shoals, and were analyzed for eight dioxin-like polychlorinated biphenyls (PCBs) as well as six other PCB congeners, DDT and DDT metabolites. Average levels of the total PCBs in blood samples from adult male, juvenile and reproductive female groups were 4800, 4000 and 3000 ng/g lipid wt., respectively, whereas 3200, 1300 and 1200 ng/g, respectively, in blubber from the three corresponding groups. p,p'-DDE was the only DDT detected in blubber samples, and no DDTs were detected in blood samples. Concentrations of the total PCBs in adult males were significantly higher than the levels measured in either reproductive females or juveniles. There were significant correlations between age and blubber p,p'-DDE, estimated mass and total blood PCBs or blubber p,p'-DDE, and body condition and total blood PCBs. Although it is clear that the Hawaiian Monk Seal has been exposed to OCs, it is unclear what biological effects, if any, these xenobiotics may have on the animals.
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Gross Anatomy of the Digestive Tract of the Hawaiian Monk Seal, Monachus schauinslandi1
2001Co-Authors: Gwen D. Goodman-lowe, Shannon Atkinson, James R. CarpenterAbstract:Abstract: The digestive tract of a female juvenile Hawaiian Monk Seal was dis-sected and described. Intestine lengths were measured for a total of 19 Seals ranging in age from 1 day old to over 10 yr old. Small intestine (SI) lengths were measured for 10 Seals and ranged from 7.1 to 16.2 m; mean SI to stan-dard ventral length (SVL) ratio was 7.1 ± 0.9 m. Large intestine (LI) lengths were measured for 11 Seals and ranged from 0.4 to 1.2 m; mean LI: SVL was 0.5 ± 0.1 m. Total intestine (TI) lengths were measured for 18 Seals and ranged from 7.5 to 18.4 m; total intestine length to SL ratio was 7.9 ± 1.3 m. SI and LI lengths both exhibited a linear relationship relative to SVL, whereas stomach weight: SVL showed an exponential relationship. TI: SVL was signifi-cantly smaller than ratios determined for harbor, harp, and northern elephant Seals, but was not significantly different from those of crabeater, leopard, and Ross Seals. No correlation was seen between gut length and body length for seven species of Seals, including the Hawaiian Monk Seal. THE Hawaiian Monk Seal, Monachus schauinslandi, has a population currently esti-mated at 1300 individuals with a decline cur-rently occurring at French Frigate Shoals (FFS) (National Marine Fisheries Service [NMFS], unpubl. data), where one of the largest subpopulations exists. The decline at FFS is likely due, in part, to the starvation of juvenile Seals (Gilmartin 1993). Because the assimilation of ingested prey is affected by digestive tract morphology in species that have been studied (Lawson et al. 1997), it is essential to understand all aspects of th
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Assimilation efficiency of prey in the Hawaiian Monk Seal (Monachus schauinslandi)
Canadian Journal of Zoology, 1999Co-Authors: Gwen D. Goodman-lowe, James R. Carpenter, Shannon AtkinsonAbstract:Assimilation efficiency, digestive efficiency, metabolizable energy, and nitrogen retention in three captive adult male Hawaiian Monk Seals (Monachus schauinslandi) were measured with the indigestible marker chromic oxide for four experimental diets: a control diet of herring (Clupea harengus) and three test diets consisting of flagtail (Kuhlia sandvicensis), squid (Loligo sp.), and lobster (Panulirus marginatus), each of which was used in combination with herring. The addition of all three test prey to herring decreased the digestibility of gross energy by a mean of 3.58 ± 3.89%. Assimilation efficiency of gross energy was 96.1 ± 4.0% for herring, 73.8 ± 6.8% for flagtail, and 94.1 ± 5.7% for squid, but could not be determined for lobster. Digestive efficiency and metabolizable energy of the diets examined were high (4602.2 ± 247.1 and 4062.5 ± 178.4 kcal/d, respectively; 1 kcal = 4.18 kJ) and were positively correlated with the amount of gross energy ingested. Nitrogen retention was highest for the squi...
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Nutrient, fatty acid, amino acid and mineral analysis of natural prey of the Hawaiian Monk Seal, Monachus schauinslandi.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 1999Co-Authors: Gwen D. Goodman-lowe, Shannon Atkinson, J.r Carpenter, H AkoAbstract:Proximate nutrients, gross energy content, mineral, amino acid and fatty acid composition were determined for teleost, cephalopod and crustacean prey of the Hawaiian Monk Seal. Crude protein was highest in the octopus, Octopus cyanea (80.0%), crude fat was highest in the Muraenid teleost, Gymnothorax eurostus (14.1%), whereas crude ash was highest in the lobster, Panulirus marginatus (11.6%). Gross energies ranged from 4.0! 0.01 kcal g ! 1 in the Labrid teleost Bodianus bilulunatus to 6.0! 0.12 kcal g ! 1 in the moray eel, Gymnothorax undulatus. Essential amino acids occurred in lower concentrations as a percentage of the total amino acids (35.8! 2.6%) than non-essential amino acids (64.2! 2.6%), but the ratio of individual amino acids to total amino acid concentrations were similar to those required by some monogastric terrestrial species and fingerling salmon. The fatty acid concentrations varied widely among species (range=1.2‐16.5 mg 100 mg ! 1 ); however, the teleosts had higher total fatty acids than the non-teleosts. This study indicates that, from a nutritional standpoint, some prey may be more beneficial to the Hawaiian Monk Seal; however, these prey are not necessarily the most abundant or available to some populations of the Monk Seal. © 1999 Elsevier Science Inc. All rights reserved.
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Initial defecation time and rate of passage of digesta in adult Hawaiian Monk Seals, Monachus
1997Co-Authors: Gwen D. Goodman-lowe, Shannon Atkinson, James R. CarpenterAbstract:In an effort to gain a better understanding of the digestive physiology of the Hawaiian Monk Seal, Monachus schauinslandi, we measured initial defecation time and rate of passage of digesta using chromic oxide (Cr,O,) and frozen corn kernels as markers. Initial defecation time ranged from 9,5 to 19 h (mean 14 + 4,8 h), which was a longer period of time than that reported for any other pinniped. The rate of passage of digesta measured using a single-pulse dose of Cr,O, was approximately 39 h for two of the three Seals, which is also longer than that reported for other pinnipeds. Possible reasons for these longer rates include morphological and physiological differences, age of the Seals, and feeding regime.. Percent Cr,O, recovery was low (52.7-74.8%), reflecting the difficulty in collecting liquid stools. Levels of protein and ash (dry matter basis) were 21.70 and 34.79%, respectively, which reflects the high protein and mineral contents of the herring diet. This study yielded essential base-line data that will provide further insight into the digestive physiology of the Hawaiian Monk Seal.
William G. Gilmartin - One of the best experts on this subject based on the ideXlab platform.
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Recovery of the Hawaiian Monk Seal (Monachus schauinslandi): A Review of Conservation Efforts, 1972 to 2010, and Thoughts for the Future
Aquatic Mammals, 2011Co-Authors: Lloyd F. Lowry, William G. Gilmartin, George A. Antonelis, David W. Laist, Hawaiian MonkAbstract:The Hawaiian Monk Seal is one of the world’s rarest marine mammal species and is listed as depleted, endangered, and critically endangered based on national and international criteria. Although its precarious status was already recognized by the 1950s, it was not until the 1970s that direct protection was afforded to Monk Seals by U.S. legislation. Many important actions were taken to try and recover the population during the following four decades, including developing a population monitoring program; controlling impacts of military facilities in the Northwestern Hawaiian Islands (NWHI); managing fisheries to reduce their impacts; removing marine debris; and responding to other issues, including die-offs, inadequate nutrition, aggression by male Seals, and shark predation. Recently, Monk Seals have reoccupied the main Hawaiian Islands (MHI). While this may be good news for their recovery, the MHI are well-populated by humans and significant management issues have appeared as Seal numbers have increased. In spite of all that has been done, Hawaiian Monk Seals are likely to go extinct unless current conditions change. At this time, the most crucial needs for the recovery are (1) maintaining an adequate research and management program throughout the Hawaiian Archipelago; (2) continuing to minimize all sources of mortality; (3) promoting an increase in the number of Monk Seals in the MHI; (4) considering bold actions that could create more favorable conditions for Seals in the NWHI; (5) ensuring that bureaucratic requirements and processes do not impede recovery actions; and (6) designing, funding, and implementing a set of actions that will stop the Hawaiian Monk Seal’s decline toward extinction and recover the population sufficiently so that it can be removed from the Endangered Species Act’s list of endangered species.
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low genetic variability in the Hawaiian Monk Seal
Conservation Biology, 1997Co-Authors: William G. Gilmartin, Maria B. Kretzmann, Axel Meyer, Gerard P Zegers, Steven R Fain, Bruce F Taylor, Daniel P CostaAbstract:The Hawaiian Monk Seal ( Monachus schauinslandi) is a critically endangered species that has failed to recover from human exploitation despite decades of protection and ongoing management efforts designed to increase population growth. The Seals breed at five principal locations in the northwestern Hawaiian islands, and inter-island migration is limited. Genetic variation in this species is expected to be low due to a recent population bottleneck and probable inbreeding within small subpopulations. To test the hypothesis that small population size and strong site fidelity has led to low within-island genetic variability and significant between-island differentiation, we used two independent approaches to quantify genetic variation both within and among the principal subpopulations. Mitochondrial control region and tRNA gene sequences (359 base pairs) were obtained from 50 Seals and revealed very low genetic diversity (0.6% variable sites), with no evidence of subpopulation differentiation. Multilocus DNA fingerprints from 22 individuals also indicated low genetic variation in at least some subpopulations (band-sharing values for “unrelated” Seals from the same island ranged from 49 to 73%). This method also provided preliminary evidence of population subdivision ( F′st estimates of 0.20 and 0.13 for two adjacent island pairs). Translocations of Seals among islands may therefore have the potential to relieve local inbreeding and possibly to reduce the total amount of variation preserved in the population. Genetic variation is only one of many factors that determine the ability of an endangered species to recover. Maintenance of existing genetic diversity, however, remains an important priority for conservation programs because of the possibility of increased disease resistance in more variable populations and the chance that inbreeding depression may only be manifest under adverse environmental conditions. La foca hawaiana es una especie en peligro de extincion cuya poblacion nunca se ha restablecido completamente de su explotacion humana a pesar de decadas de proteccion y los sucesivos programas de gestion disenados para aumentar el crecimiento de la poblacion. La crianza de las focas occure en cinco islas del archipielago hawaiano, y la migracion entre las islas es limitada. Se esperaba que la variacion en esta especie fuera baja debido a un reciente cuello de botella y al entrecruzamiento probable entre las subpoblaciones pequenas. Para probar la hipotesis de que el tamano pequeno de la poblacion y el fuerte arraigo a su lugar natal ha ocasionado baja variabilidad genetica dentro de las islas, y una diferenciacion significativa entre las islas, usamos dos metodos independientes para medir la variabilidad genetica dentro de y entre las subpoblaciones principales. Se obtuvieron secuencias de la region de control del ADN mitocondrial (359 pares de bases) de 50 focas, las cuales revelaron una diversidad genetica muy baja (0.6% posiciones variables), sin evidencia de una diferenciacion subpoblacional. “Huellas digitales” de ADN de 22 individuos tambien mostraron baja variabilidad genetica, por lo menos en ciertas subpoblaciones ( la proporcion de fragmentos compartidos por focas “sin parentesco” de la misma isla vario entre el 49 y el 73%). Este metodo tambien mostro evidencia preliminar de la subdivision poblacional (estimaciones del F′st de 0.20 y 0.13 para dos pares de islas adyacentes). Por lo tanto, intercambios de focas entre las islas podrian tener la capacidad de aliviar el entrecruzamiento local, o posiblemente tambien de disminuir la variabilidad total que se mantiene en la poblacion. La variabilidad genetica es un solo factor entre los muchos que determinan la habilidad de recuperacion de una especie en peligro de extincion. Sin embargo, el mantenimiento de la diversidad genetica existente deberia seguir siendo prioritario en los programas de conservacion, debido a la posibilidad de una mayor resistencia a enfermedades en poblaciones geneticamente mas variables, y a la posibilidad de que los efectos negativos del entrecruzamiento quizas solo se manifiesten en condiciones ambientales adversas.
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STATUS OF THE Hawaiian Monk Seal (MONACHUS SCHAUINSLANDI) POPULATION
Canadian Journal of Zoology, 1995Co-Authors: William G. Gilmartin, L. L. EberhardtAbstract:Restoration of the Hawaiian Monk Seal (Monachus schauinslandi) population to its former abundance poses a number of problems in managing a complex system. Sharp differences in history and current trend exist among the six major pupping sites. A severely unbalanced adult sex ratio has resulted in deaths from "mobbing" of estrus females at two sites. Some unknown factor apparently severely reduced the numbers of females at three of the sites and thus produced the observed excess of males. Sex ratios subsequently decreased, but losses of adult females continue at two sites. A simple model indicates that sex ratios at the two sites where mobbing is a problem would require more than 10 years to approach an equilibrium value. Data on trends from counts are compared with estimates from reproduction and survival rates and agree closely except at one site (Kure Atoll), where introductions of young females have been made.
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Composition of the Hawaiian Monk Seal Population at Kure Atoll, 1990
1993Co-Authors: Richard A. Van Toorenburg, William G. Gilmartin, John R. HendersonAbstract:Population recovery-related management actions have been taken to rebuild the endangered Hawaiian Monk Seal (Monachus schauinslandi Matschie) colony at Kure Atoll in the Northwestern Hawaiian Islands since 1981. In 1990, composition of the Kure population was determined by a combi- nation of methods to identify all Seals using the atoll. The resident 1990 popula- tion included 75 Seals, and an increasing trend in the mean annual beach count of Seals over the last decade is apparent. Two major changes have occurred in the population since 1985. A shift in the adult sex ratio (males/females), from 2.7 : 1 to 0.8 : 1, has developed and appears to be due to both adult male losses and increased recruitment of females. Also, the declining trend in births apparent between 1981 and 1986 has been reversed. These findings suggest cause for optimism for the continued growth of this population. THE ENDANGERED Hawaiian Monk Seal (Mo-
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SURVIVAL RATES FOR THE Hawaiian Monk Seal (MONACHUS SCHAUINSLANDI)
Marine Mammal Science, 1993Co-Authors: William G. Gilmartin, Thea C. Johanos, L. L. EberhardtAbstract:Endangered Hawaiian Monk Seal (Monachus schauinslandi) pups at all the major breeding islands in the Northwestern Hawaiian Islands have been tagged since the early 1980s. Pups were double flipper tagged as soon as possible postweaning. With few exceptions, an extensive tag resighting effort was conducted annually at the same islands. These resighting data were used to estimate Seal survival rates from the time of tagging to age one at all locations using the ratio of Seals alive in the second year to number of pups tagged. These survival rates among the islands, from weaning to age one, averaged over the years of the study, ranged from 0.80 to 0.90. For young Seals over age one, capture-recapture methods were used to caldate survival pooIed through several years, and these rates ranged from 0.85 to 0.98. At French Frigate Shoals and Laysan Island, the higher numbers of tagged pups allowed separate estimates of male and female sumival to be calculated. These rates suggested that survival of immature females was better than males. Beginning in 1989, survival of immature Seals at French Frigate Shoals decined sharply.
L. L. Eberhardt - One of the best experts on this subject based on the ideXlab platform.
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STATUS OF THE Hawaiian Monk Seal (MONACHUS SCHAUINSLANDI) POPULATION
Canadian Journal of Zoology, 1995Co-Authors: William G. Gilmartin, L. L. EberhardtAbstract:Restoration of the Hawaiian Monk Seal (Monachus schauinslandi) population to its former abundance poses a number of problems in managing a complex system. Sharp differences in history and current trend exist among the six major pupping sites. A severely unbalanced adult sex ratio has resulted in deaths from "mobbing" of estrus females at two sites. Some unknown factor apparently severely reduced the numbers of females at three of the sites and thus produced the observed excess of males. Sex ratios subsequently decreased, but losses of adult females continue at two sites. A simple model indicates that sex ratios at the two sites where mobbing is a problem would require more than 10 years to approach an equilibrium value. Data on trends from counts are compared with estimates from reproduction and survival rates and agree closely except at one site (Kure Atoll), where introductions of young females have been made.
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SURVIVAL RATES FOR THE Hawaiian Monk Seal (MONACHUS SCHAUINSLANDI)
Marine Mammal Science, 1993Co-Authors: William G. Gilmartin, Thea C. Johanos, L. L. EberhardtAbstract:Endangered Hawaiian Monk Seal (Monachus schauinslandi) pups at all the major breeding islands in the Northwestern Hawaiian Islands have been tagged since the early 1980s. Pups were double flipper tagged as soon as possible postweaning. With few exceptions, an extensive tag resighting effort was conducted annually at the same islands. These resighting data were used to estimate Seal survival rates from the time of tagging to age one at all locations using the ratio of Seals alive in the second year to number of pups tagged. These survival rates among the islands, from weaning to age one, averaged over the years of the study, ranged from 0.80 to 0.90. For young Seals over age one, capture-recapture methods were used to caldate survival pooIed through several years, and these rates ranged from 0.85 to 0.98. At French Frigate Shoals and Laysan Island, the higher numbers of tagged pups allowed separate estimates of male and female sumival to be calculated. These rates suggested that survival of immature females was better than males. Beginning in 1989, survival of immature Seals at French Frigate Shoals decined sharply.
