Samuel Wasser - Academia.edu (original) (raw)

Papers by Samuel Wasser

Research paper thumbnail of Biogeography and Ecology of the Rain Forests of Eastern Africa

Cambridge University Press eBooks, Jul 29, 1993

Research paper thumbnail of Genetic assignment of large seizures of elephant ivory reveals Africa’s major poaching hotspots

Research paper thumbnail of Shifts in fisher (Pekania pennanti) diet in response to climate-induced tree mortality in California assessed with DNA metabarcoding

Journal for Nature Conservation, Jun 1, 2023

Research paper thumbnail of Elephant genotypes reveal the size and connectivity of transnational ivory traffickers

Nature Human Behaviour, Feb 14, 2022

Transnational ivory traffickers continue to smuggle large shipments of elephant ivory out of Afri... more Transnational ivory traffickers continue to smuggle large shipments of elephant ivory out of Africa, yet prosecutions and convictions remain few. We identify trafficking networks on the basis of genetic matching of tusks from the same individual or close relatives in separate shipments. Analyses are drawn from 4,320 savannah (Loxodonta africana) and forest (L. cyclotis) elephant tusks, sampled from 49 large ivory seizures totalling 111 t, shipped out of Africa between 2002 and 2019. Network analyses reveal a repeating pattern wherein tusks from the same individual or close relatives are found in separate seizures that were containerized in, and transited through, common African ports. Results suggest that individual traffickers are exporting dozens of shipments, with considerable connectivity between traffickers operating in different ports. These tools provide a framework to combine evidence from multiple investigations, strengthen prosecutions and support indictment and prosecution of transnational ivory traffickers for the totality of their crimes.

Research paper thumbnail of Natural Variation in Stress Hormones, Comparisons Across Matrices, and Impacts Resulting from Induced Stress in the Bottlenose Dolphin

Advances in Experimental Medicine and Biology, 2016

Knowledge regarding stress hormones and how they vary in response to seasonality, gender, age, an... more Knowledge regarding stress hormones and how they vary in response to seasonality, gender, age, and reproductive status for any marine mammal is limited. Furthermore, stress hormones may be measured in more than one matrix (e.g., feces, blood, blubber), but the relationships between levels of a given hormone across these matrices are unknown, further complicating the interpretations of hormones measured in samples collected from wild animals. A study is underway to address these issues in a population of bottlenose dolphins trained for voluntary participation in sample collections from different matrices and across season and time of day.

Research paper thumbnail of Biogeography and Ecology of the Rain Forests of Eastern Africa. Edited

Research paper thumbnail of Shift of maternal gut microbiome of Tibetan antelope (Pantholops hodgsonii) during the perinatal period

Research paper thumbnail of Influence of season, age, sex, and time of day on the endocrine profile of the common bottlenose dolphin (Tursiops truncatus)

General and Comparative Endocrinology, Nov 1, 2021

Understanding baseline hormone levels, the magnitude of intra-individual variability, and their v... more Understanding baseline hormone levels, the magnitude of intra-individual variability, and their variation as a function of life history is difficult in toothed whales (e.g. dolphins and porpoises) because of the effects of capture stress. To determine the endocrine profile of the common bottlenose dolphin (Tursiops truncatus) as a function of season, time of day (TOD), age, sex, and reproductive status, blood corticosteroids, thyroid hormones, and catecholamines were repeatedly measured in a managed-care population exposed to ambient light and water temperatures of San Diego Bay. Additionally, fecal hormone metabolites were assessed for cortisol, aldosterone, and triiodothyronine. Samples were collected at two to four-week intervals over a period of two years, and multiple times within a day at monthly intervals over a year. Samples were collected through the voluntary participation of the dolphins in the blood draws and fecal collections in order to avoid the effects of handling stress. All serum hormones except aldosterone significantly varied with season and all serum hormones except total thyroxine significantly varied as a function of TOD. Fecal glucocorticoid metabolites significantly correlated with circulating cortisol levels, and there was a significant seasonal effect on triiodothyronine fecal metabolites. Strong seasonal effects demonstrated complex interactions with age and sex suggesting that contextual information is critical to interpreting differences in endocrine profiles. Strong circadian patterns further suggest that sampling design is important to the interpretation of blood or fecal collections, particularly since diurnal changes in some serum hormone levels are similar to the magnitude of seasonal differences. Despite potential impacts of feeding schedules on diurnal patterns, managed care populations can provide important insights into seasonal and age-related endocrine changes in toothed whales.

Research paper thumbnail of Faecal sampling using detection dogs to study reproduction and health in North Atlantic right whales (Eubalaena glacialis)

The journal of cetacean research and management, Mar 8, 2023

Research paper thumbnail of Polycyclic aromatic hydrocarbons in caribou, moose, and wolf scat samples from three areas of the Alberta oil sands

Environmental Pollution, Nov 1, 2015

Research paper thumbnail of The socioecology of interspecific associations among the monkeys of the Mwanihana rain forest, Tanzania: a biogeographic perspective

Cambridge University Press eBooks, Jul 29, 1993

Research paper thumbnail of Fecal stress, nutrition and reproductive hormones for monitoring environmental impacts on tigers (Panthera tigris)

Conservation Physiology, 2020

Research paper thumbnail of Who are the elephants living in the hybridization zone? How genetics may guide conservation to better protect endangered elephants

Global Ecology and Conservation, Dec 1, 2021

Research paper thumbnail of Biogeography and Ecology of the Rain Forests of Eastern Africa

Journal of Animal Ecology, Mar 1, 1995

Research paper thumbnail of Social Behavior of Female Vertebrates

Research paper thumbnail of Introduction to the biogeography and ecology of the rain forests of eastern Africa

Cambridge University Press eBooks, Jul 29, 1993

Research paper thumbnail of Assessing Connectivity of Wildlife Populations in Tanzania: Too Little, Too Late, or Just in Time?

Research paper thumbnail of Fecal DNA technology as a conservation tool

Research paper thumbnail of 14-Carbon demonstrates that some illegal ivory is being taken from government stockpiles

Proceedings of the National Academy of Sciences

The 14-carbon in animal tissues records the time that the tissues are formed; since the 1960s, us... more The 14-carbon in animal tissues records the time that the tissues are formed; since the 1960s, using the “bomb curve” for 14 C, the age of animal death can be determined accurately. Using animal tissue samples of known collection and formation dates for calibration, we determine the age of ivory samples from four ivory seizures made by law enforcement agencies between 2017 and 2019. The 14 C measurements from these seizures show that most ivory in the illegal wildlife trade is from animals from recent poaching activities. However, one seizure has a large fraction of ivory that is more than 30 y old, consistent with markings on the tusks indicating they were derived from a government stockpile.

Research paper thumbnail of Psychosocial stress as a cause of infertility

Fertility and Sterility, 1993

An adaptive model for the evolution of reproductive failure predicted psychosocial stress to incr... more An adaptive model for the evolution of reproductive failure predicted psychosocial stress to increase as anatomic causes of infertility decrease. The nonanatomic infertility group in our study reported greater psychosocial stress than intermediate (P < 0.008) or anatomic groups (P < 0.0005). Controls, women with nonanatomic etiologies who were not attempting pregnancy, also reported higher psychosocial stress than the anatomic group (P < 0.007). Results are consistent with the hypothesis that psychosocial distress contributes significantly to the etiology of some forms of infertility.

Research paper thumbnail of Biogeography and Ecology of the Rain Forests of Eastern Africa

Cambridge University Press eBooks, Jul 29, 1993

Research paper thumbnail of Genetic assignment of large seizures of elephant ivory reveals Africa’s major poaching hotspots

Research paper thumbnail of Shifts in fisher (Pekania pennanti) diet in response to climate-induced tree mortality in California assessed with DNA metabarcoding

Journal for Nature Conservation, Jun 1, 2023

Research paper thumbnail of Elephant genotypes reveal the size and connectivity of transnational ivory traffickers

Nature Human Behaviour, Feb 14, 2022

Transnational ivory traffickers continue to smuggle large shipments of elephant ivory out of Afri... more Transnational ivory traffickers continue to smuggle large shipments of elephant ivory out of Africa, yet prosecutions and convictions remain few. We identify trafficking networks on the basis of genetic matching of tusks from the same individual or close relatives in separate shipments. Analyses are drawn from 4,320 savannah (Loxodonta africana) and forest (L. cyclotis) elephant tusks, sampled from 49 large ivory seizures totalling 111 t, shipped out of Africa between 2002 and 2019. Network analyses reveal a repeating pattern wherein tusks from the same individual or close relatives are found in separate seizures that were containerized in, and transited through, common African ports. Results suggest that individual traffickers are exporting dozens of shipments, with considerable connectivity between traffickers operating in different ports. These tools provide a framework to combine evidence from multiple investigations, strengthen prosecutions and support indictment and prosecution of transnational ivory traffickers for the totality of their crimes.

Research paper thumbnail of Natural Variation in Stress Hormones, Comparisons Across Matrices, and Impacts Resulting from Induced Stress in the Bottlenose Dolphin

Advances in Experimental Medicine and Biology, 2016

Knowledge regarding stress hormones and how they vary in response to seasonality, gender, age, an... more Knowledge regarding stress hormones and how they vary in response to seasonality, gender, age, and reproductive status for any marine mammal is limited. Furthermore, stress hormones may be measured in more than one matrix (e.g., feces, blood, blubber), but the relationships between levels of a given hormone across these matrices are unknown, further complicating the interpretations of hormones measured in samples collected from wild animals. A study is underway to address these issues in a population of bottlenose dolphins trained for voluntary participation in sample collections from different matrices and across season and time of day.

Research paper thumbnail of Biogeography and Ecology of the Rain Forests of Eastern Africa. Edited

Research paper thumbnail of Shift of maternal gut microbiome of Tibetan antelope (Pantholops hodgsonii) during the perinatal period

Research paper thumbnail of Influence of season, age, sex, and time of day on the endocrine profile of the common bottlenose dolphin (Tursiops truncatus)

General and Comparative Endocrinology, Nov 1, 2021

Understanding baseline hormone levels, the magnitude of intra-individual variability, and their v... more Understanding baseline hormone levels, the magnitude of intra-individual variability, and their variation as a function of life history is difficult in toothed whales (e.g. dolphins and porpoises) because of the effects of capture stress. To determine the endocrine profile of the common bottlenose dolphin (Tursiops truncatus) as a function of season, time of day (TOD), age, sex, and reproductive status, blood corticosteroids, thyroid hormones, and catecholamines were repeatedly measured in a managed-care population exposed to ambient light and water temperatures of San Diego Bay. Additionally, fecal hormone metabolites were assessed for cortisol, aldosterone, and triiodothyronine. Samples were collected at two to four-week intervals over a period of two years, and multiple times within a day at monthly intervals over a year. Samples were collected through the voluntary participation of the dolphins in the blood draws and fecal collections in order to avoid the effects of handling stress. All serum hormones except aldosterone significantly varied with season and all serum hormones except total thyroxine significantly varied as a function of TOD. Fecal glucocorticoid metabolites significantly correlated with circulating cortisol levels, and there was a significant seasonal effect on triiodothyronine fecal metabolites. Strong seasonal effects demonstrated complex interactions with age and sex suggesting that contextual information is critical to interpreting differences in endocrine profiles. Strong circadian patterns further suggest that sampling design is important to the interpretation of blood or fecal collections, particularly since diurnal changes in some serum hormone levels are similar to the magnitude of seasonal differences. Despite potential impacts of feeding schedules on diurnal patterns, managed care populations can provide important insights into seasonal and age-related endocrine changes in toothed whales.

Research paper thumbnail of Faecal sampling using detection dogs to study reproduction and health in North Atlantic right whales (Eubalaena glacialis)

The journal of cetacean research and management, Mar 8, 2023

Research paper thumbnail of Polycyclic aromatic hydrocarbons in caribou, moose, and wolf scat samples from three areas of the Alberta oil sands

Environmental Pollution, Nov 1, 2015

Research paper thumbnail of The socioecology of interspecific associations among the monkeys of the Mwanihana rain forest, Tanzania: a biogeographic perspective

Cambridge University Press eBooks, Jul 29, 1993

Research paper thumbnail of Fecal stress, nutrition and reproductive hormones for monitoring environmental impacts on tigers (Panthera tigris)

Conservation Physiology, 2020

Research paper thumbnail of Who are the elephants living in the hybridization zone? How genetics may guide conservation to better protect endangered elephants

Global Ecology and Conservation, Dec 1, 2021

Research paper thumbnail of Biogeography and Ecology of the Rain Forests of Eastern Africa

Journal of Animal Ecology, Mar 1, 1995

Research paper thumbnail of Social Behavior of Female Vertebrates

Research paper thumbnail of Introduction to the biogeography and ecology of the rain forests of eastern Africa

Cambridge University Press eBooks, Jul 29, 1993

Research paper thumbnail of Assessing Connectivity of Wildlife Populations in Tanzania: Too Little, Too Late, or Just in Time?

Research paper thumbnail of Fecal DNA technology as a conservation tool

Research paper thumbnail of 14-Carbon demonstrates that some illegal ivory is being taken from government stockpiles

Proceedings of the National Academy of Sciences

The 14-carbon in animal tissues records the time that the tissues are formed; since the 1960s, us... more The 14-carbon in animal tissues records the time that the tissues are formed; since the 1960s, using the “bomb curve” for 14 C, the age of animal death can be determined accurately. Using animal tissue samples of known collection and formation dates for calibration, we determine the age of ivory samples from four ivory seizures made by law enforcement agencies between 2017 and 2019. The 14 C measurements from these seizures show that most ivory in the illegal wildlife trade is from animals from recent poaching activities. However, one seizure has a large fraction of ivory that is more than 30 y old, consistent with markings on the tusks indicating they were derived from a government stockpile.

Research paper thumbnail of Psychosocial stress as a cause of infertility

Fertility and Sterility, 1993

An adaptive model for the evolution of reproductive failure predicted psychosocial stress to incr... more An adaptive model for the evolution of reproductive failure predicted psychosocial stress to increase as anatomic causes of infertility decrease. The nonanatomic infertility group in our study reported greater psychosocial stress than intermediate (P < 0.008) or anatomic groups (P < 0.0005). Controls, women with nonanatomic etiologies who were not attempting pregnancy, also reported higher psychosocial stress than the anatomic group (P < 0.007). Results are consistent with the hypothesis that psychosocial distress contributes significantly to the etiology of some forms of infertility.