C. Loren Buck

C. Loren Buck
Northern Arizona University | NAU · Department of Biological Sciences

PhD Biology

About

189
Publications
43,538
Reads
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3,928
Citations
Citations since 2017
89 Research Items
2214 Citations
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Introduction
C. Loren Buck currently works at the Department of Biological Sciences, Northern Arizona University. C. Loren does research in Chronobiology, Endocrinology and Physiology. Their current project is 'Urea nitrogen salvage and the gut microbiota in arctic ground squirrels'.
Additional affiliations
August 2015 - present
Northern Arizona University
Position
  • Professor
August 2015 - February 2019
Northern Arizona University
Position
  • Professor (Full)
July 2006 - August 2015
University of Alaska Anchorage
Position
  • Professor (Full)
Education
September 1992 - May 1998
University of Alaska Fairbanks
Field of study
  • Biology
September 1989 - May 1992
Montana State University Billings
Field of study
  • Biology and Education w/ a minor in Chemistry

Publications

Publications (189)
Article
Full-text available
Baleen tissue accumulates stress hormones (glucocorticoids, GC) as it grows, along with other adrenal, gonadal and thyroid hormones. The hormones are deposited in a linear fashion such that a single plate of baleen allows retrospective assessment and evaluation of long-term trends in the whales' physiological condition. In whale calves, a single pi...
Article
Full-text available
Quantification of contaminant concentrations in baleen whales is important for individual and population level health assessments but is difficult due to large migrations and infrequent resightings. The use of baleen allows for a multiyear retrospective analysis of contaminant concentrations without having to collect repeated samples from the same...
Article
Full-text available
Seasonally breeding mammals must make constant adjustments in behavior and physiology to manage energetic trade-offs between survival and reproduction. Despite encountering high levels of climate and resource variability across the year, specialist Abert’s squirrels (Sciurus aberti), lack the capacity to express hibernation or pronounced morphologi...
Article
Environmental pollution causes adverse health effects in many organisms and contributes to health disparities for Arctic communities that depend on subsistence foods, including the Yupik residents of Sivuqaq (St. Lawrence Island), Alaska. Sivuqaq's proximity to Russia made it a strategic location for U.S. military defense sites during the Cold War....
Article
Full-text available
Animals vary considerably in the amount of behavioral plasticity they exhibit in daily activity timing and temporal niche switching. It is not well understood how environmental factors drive changes in temporal activity or how interspecific differences in the plasticity of activity timing ultimately manifest in free-living animals. Here, we investi...
Poster
Baleen powder has been previously shown as a viable technique to study stress and reproduction in large, Mysticeti whales. Steroid hormones are deposited into the baleen’s keratin matrix in such a way that allows for multi-year study of single individuals. Several steroid hormones have been validated in bowhead whales (Balaena mysticetus), and here...
Article
Purple Martins (Progne subis) are migratory birds that breed in North America and overwinter and complete their molt in South America. Many of the breeding populations are declining. The eastern North American subspecies of Purple Martin (P. subis subis) comprises >90% of all Purple Martins. This subspecies overwinters and molts in the Amazon Basin...
Article
Many animals adjust the timing of seasonal events, such as reproduction, molt, migration, and hibernation, in response to interannual variation and directional climate-driven changes in temperature. However, the mechanisms by which temperature influences seasonal timing are relatively under-explored. Seasonal timing involves retrograde signaling in...
Article
Full-text available
The vertebrate sodium‐iodide symporter (NIS or SLC5A5) transports iodide into the thyroid follicular cells that synthesize thyroid hormone. The SLC5A protein family includes transporters of vitamins, minerals, and nutrients. Disruption of SLC5A5 function by perchlorate, a pervasive environmental contaminant, leads to human pathologies, especially h...
Article
Full-text available
The Arctic is a hemispheric sink for both legacy and current use persistent organic pollutants (POPs). Once in the Arctic, POPs biomagnify in food webs, potentially reaching concentrations in high trophic level animals that pose a health concern for people who subsist on those animals. Indigenous Peoples of the Arctic may be highly exposed to POPs...
Article
Understanding reproductive physiology in mysticetes has been slowed by the lack of repeated samples from individuals. Analysis of humpback whale baleen enables retrospective hormone analysis within individuals dating back 3-5 years before death. Using this method, we investigated differences in four steroid hormones involved in reproduction and mat...
Article
Full-text available
Synopsis Male mammals of seasonally reproducing species typically have annual testosterone (T) cycles, with T usually peaking during the breeding season, but occurrence of such cycles in male mysticete whales has been difficult to confirm. Baleen, a keratinized filter-feeding apparatus of mysticetes, incorporates hormones as it grows, such that a s...
Article
Full-text available
Hibernation involves prolonged intervals of profound metabolic suppression periodically interrupted by brief arousals to euthermy, the function of which is unknown. Annual cycles in mammals are timed by a photoperiodically-regulated thyroid-hormone-dependent mechanism in hypothalamic tanycytes, driven by thyrotropin (TSH) in the pars tuberalis (PT)...
Article
The short-beaked echidna (Tachyglossus aculeatus) is a monotreme endemic to Australia and New Guinea, and is the most widespread native mammal in Australia. Despite its abundance, there are considerable gaps in our understanding of echidna life history such as reproductive cycles in both sexes, patterns of stress physiology, and possible seasonal c...
Article
Hibernation is associated with long lifespan: on average, hibernating mammals live 15% longer than non-hibernators of equivalent mass. We investigated how survival varies with sex, season, and the deployment of biologgers in arctic ground squirrels [Urocitellus parryii (Richardson, 1825)], a widely-distributed northern hibernator. The duration of h...
Article
Full-text available
Sampling blood for endocrine analysis from some species may not be practical or ethical. Quantification of hormones extracted from nontypical sample types, such as keratinized tissues, offers a less invasive alternative to the traditional collection and analysis of blood. Here, we aimed to validate assays by using parallelism and accuracy tests for...
Article
Full-text available
In waters off Península Valdés (PV), Argentina, southern right whales (SRW, Eubalaena australis) are occasionally exposed to domoic acid (DA), a neurotoxin produced by diatoms of the genus Pseudo-nitzschia. Domoic acid toxicity in marine mammals can cause gastrointestinal and neurological clinical signs, alterations in hematologic and endocrine var...
Article
The short-beaked echidna (Tachyglossus aculeatus) is a monotreme endemic to Australia and New Guinea, and is the most widespread native mammal in Australia. Despite its abundance, there are considerable gaps in our understanding of echidna life history such as reproductive cycles in both sexes, patterns of stress physiology, and possible seasonal c...
Article
Full-text available
Baleen whales are subject to a myriad of natural and anthropogenic stressors, but understanding how these stressors affect physiology is difficult. Measurement of adrenal glucocorticoid (GC) hormones involved in the vertebrate stress response (cortisol and corticosterone) in baleen could help fill this data gap. Baleen analysis is a powerful tool,...
Article
Full-text available
Perchlorate is a water-soluble contaminant found throughout the United States and many other countries. Perchlorate competitively inhibits iodide uptake at the sodium/iodide symporter, reducing thyroid hormone synthesis, which can lead to hypothyroidism and metabolic syndromes. Chronic perchlorate exposure induces hepatic steatosis and non-alcoholi...
Article
Full-text available
Understanding calving rates of wild whale populations is critically important for management and conservation. Reproduction of humpback whales (Megaptera novaeangliae) is difficult to monitor and, even with long-term sighting studies, basic physiological information such as pregnancy rates and calving intervals remain poorly understood in many popu...
Article
Multiple factors can influence the immune response of ectothermic vertebrates, including body temperature, gonadal steroids, and seasonality, in ways that are thought to reflect trade-offs between energetic investment in immunity vs. reproduction. Hibernating tegu lizards (Salvator merianae) are a unique model to investigate how immunocompetence mi...
Article
Obtaining endocrine data from alternative sample types such as baleen and other keratinized tissues has proven a valuable tool to investigate reproductive and stress physiology via steroid hormone quantification, and metabolic stress via thyroid hormone quantification in whales and other vertebrates. These alternative sample types provide an integr...
Conference Paper
Purple Martins (Progne subis) are insectivorous birds that spend their breeding season in North America before migrating to South America, where they molt. Many individuals migrate to the Amazon basin, a region of high mercury (Hg) contamination, which raises the possibility that observed declines in Purple Martins could be linked to mercury exposu...
Poster
Full-text available
Understanding pregnancy in free-living cetaceans is exceedingly difficult and has hampered our understanding of pregnancy rates in large whales. Using baleen, it was possible to quantify progesterone levels (often termed the "pregnancy hormone") during known pregnancies in two humpback whales with sighting records. The areas of baleen with correspo...
Article
Monitoring the physiology of wild populations presents many technical challenges. Blood samples, long the gold standard of wildlife endocrinology studies, cannot always be obtained. The validation and use of non-plasma samples to obtain hormone data have greatly improved access to more integrated information about an organism’s physiological state....
Article
People with NR5A1 mutations experience testicular dysgenesis, ovotestes, or adrenal insufficiency, but we do not completely understand the origin of this phenotypic diversity. NR5A1 is expressed in gonadal soma precursor cells before expression of the sex-determining gene SRY. Many fish have two co-orthologs of NR5A1 that likely partitioned ancestr...
Article
Full-text available
Background: This study used a community-engaged approach to examine associations between environmental contaminants and health outcomes among residents of Yuma, Arizona. Our team conducted a process evaluation to assess scientific rigor and adherence to community engagement principles. Objective: Our evaluation focused on four dimensions of comm...
Chapter
Conservation physiology tools can be difficult to employ in the wild. Here we discuss developments in conservation physiology research of large whales, a taxonomic group that is famously difficult to study with traditional tools. We focus on the North Atlantic right whale ( Eubalaena glacialis ) and southern right whale ( Eubalaena australis ), two...
Article
Social interactions can shape daily activity patterns, and this is an area of growing research interest. The propensity for individuals to be active at certain times of day may structure interactions with competitors and potential mates, influencing fitness outcomes. Aspects of daily activity such as timing of activity onset and offset exhibit with...
Article
The dynamic relationship between glucocorticoids and behavior are not well understood in wild mammals. We investigated how weather, body condition, and reproduction interact to affect cortisol levels and activity patterns in a free-living population of arctic ground squirrels (Urocitellus parryii). As a proxy for foraging and escape behaviors, coll...
Article
Physiological measurements are informative in assessing the relative importance of stressors that potentially impact the health of wildlife. Kelp Gulls, Larus dominicanus (KG), resident to the region of Península Valdés, Argentina, have developed a unique behavior of landing on the backs of southern right whale adults and calves, Eubalaena australi...
Article
Full-text available
Many juvenile Kemp's ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) turtles strand during fall on the beaches of Cape Cod (MA, USA), with total stranding numbers sometimes exceeding 300 turtles per year. Once rehabilitated, turtles must be released at beaches with appropriate water temperatures, often requiring transportation to sout...
Article
In his book,aptly named Extreme Conservation: Life at the Edges of the World, the author tells an engaging story of his investigations of the biology and behavior of wild herbivores adapted to some of the most extremeandthreatenedhabitatsonEarth.Thestory plays out in the high north of Alaska and Wrangel Island and the high altitudes of the Tibetan...
Article
Synthetic torpor is an induced state of deep metabolic depression (MD) in an organism that does not naturally employ regulated MD. If applied to spaceflight crewmembers, this metabolic state may theoretically mitigate numerous biological and logistical challenges of human spaceflight. These benefits have been the focus of numerous recent articles w...
Article
Full-text available
Polychlorinated biphenyls (PCBs) are a group of synthetic, lipophilic organochlorines that were banned due to their impacts on human and wildlife health and environmental persistence. Although banned, the continued release from pre-banned products allows them to persist at toxic levels in the environment. This is especially the case in lipid rich f...
Article
The Arctic is subject to long-range atmospheric deposition of globally-distilled semi-volatile organic compounds (SVOCs) that bioaccumulate and biomagnify in lipid-rich food webs. In addition, locally contaminated sites may also contribute SVOCs to the arctic environment. Specifically, Alaska has hundreds of formerly used defense (FUD) sites, many...
Poster
Located west of the Alaska mainland in the Bering Sea, St. Lawrence Island is home to approximately 1,600 Siberian Yupik residents. The island also contains two formerly used defense sites (FUDS), one of which is located at Northeast Cape. Previous research reported local environments at the Northeast Cape FUDS having elevated concentrations of org...
Article
Life history transitions and hormones are known to interact and influence many aspects of animal physiology and behavior. The South-American tegu lizard (Salvator merianae) exhibits a profound seasonal shift in metabolism and body temperature, characterized by high daily activity during warmer months, including reproductive endothermy in spring, an...
Preprint
BACKGROUND The Northern Arizona University (NAU) Center for Health Equity Research (CHER) is conducting community-engaged health research “environmental toxicant scans” in the Yuma County (Yuma, Somerton, San Luis) regions in collaboration with community health stakeholders including the Yuma Regional Medical Center (YRMC), the Regional Center for...
Article
Full-text available
Background The Northern Arizona University (NAU) Center for Health Equity Research (CHER) is conducting community-engaged health research involving “environmental scans” in Yuma County in collaboration with community health stakeholders, including the Yuma Regional Medical Center (YRMC), Regional Center for Border Health, Inc. (RCBH), Campesinos Si...
Article
Full-text available
While most studies of the impacts of climate change have investigated shifts in the spatial distribution of organisms, temporal shifts in the time of activity is another important adjustment made by animals in a changing world. Due to the importance of light and temperature cycles in shaping activity patterns, studies of activity patterns of organi...
Article
Climate is changing globally and its impacts can arise at different levels of biological organization; yet, cross-level consequences of climate change are still poorly understood. Designing effective environmental management and adaptation plans requires implementation of mechanistic models that span the biological hierarchy. Because biological sys...
Article
Full-text available
Synopsis The regulation of daily and circannual activity patterns is an important mechanism by which animals may balance energetic requirements associated with both abiotic and biotic variables. Using collar-mounted accelerometers, we assess the relative importance of reproductive stage and environmental conditions on the overall dynamic body accel...
Article
Sodium perchlorate induces non-alcoholic fatty liver disease in developing stickleback through the accumulation of lipids in hepatocytes.
Article
Thyroid hormones (TH) are key regulators of metabolism that could play an important role in altering physiology and energy allocation across life-history stages. Here, we examine seasonal TH dynamics from 345 plasma samples collected from 134 free-living arctic ground squirrels (Urocitellus parryii (Richardson, 1825)) across three consecutive years...
Article
Full-text available
Muscular dystrophy with myositis (mdm) mice carry a deletion in the N2A region of the gene for the muscle protein titin (TTN), shiver at low frequency, fail to maintain body temperatures (Tb) at ambient temperatures (Ta) <34°C, and have reduced body mass and active muscle stiffness in vivo compared with wild-type (WT) siblings. Impaired shivering t...
Article
In many passerine birds, testosterone stimulates song and aggression but inhibits paternal care, but few studies have explored whether such effects can be reversed with testosterone blockers. We explored the effect of testosterone blockers on song, aggression and paternal care of Lapland longspurs (Calcarius lapponicus), an arctic passerine with a...
Article
Fecal hormone analysis shows high potential for noninvasive assessment of population-level patterns in stress and reproduction of marine mammals. However, the marine environment presents unique challenges for fecal sample collection. Data are still lacking on collection methodology and assay validations for most species, particularly for those myst...
Article
Full-text available
Sea turtle rehabilitation clinics and aquaria frequently transport stranded sea turtles long distances out of water, e.g. for release at sites with appropriate water temperatures. Endangered Kemp’s ridley turtles (Lepidochelys kempii) are known to exhibit an adrenal stress response during such transports. In an opportunistic study of turtles transp...
Article
Full-text available
Synopsis: The term "stress" is used to capture important phenomena at multiple levels of biological organization, but finding a general and rigorous definition of the concept has proven challenging. Current models in the behavioral literature emphasize the cognitive aspects of stress, which is said to occur when threats to the organism are perceiv...
Preprint
Full-text available
Abstract: We present data from the early 1990s on the effect of androgen blockers on song, aggression and paternal care of Lapland longspurs (Calcarius lapponicus) at Toolik Field Station, Alaska. During this time period, effects of climate change were still minimal at this site, and renesting in this species was rare. Twenty-one "blocker males" re...
Article
The tegu lizard Salvator merianae is a large, widely distributed teiid lizard endemic to South America that exhibits annual cycles of high activity during the spring and summer, and hibernation during winter. This pattern of activity and hibernation is accompanied by profound seasonal changes in physiology and behavior, including endothermy during...
Article
Full-text available
Male baleen whales have long been suspected to have annual cycles in testosterone, but due to difficulty in collecting endocrine samples, little direct evidence exists to confirm this hypothesis. Potential influences of stress or adrenal stress hormones (cortisol, corticosterone) on male reproduction have also been difficult to study. Baleen has re...
Article
Perfluoroalkyl substances (PFASs) are known to accumulate in traditional food animals of the Arctic, and arctic indigenous peoples may be exposed via consumption of subsistence-harvested animals. PFASs are suspected of disrupting thyroid hormone homeostasis in humans. The aim of this study is to assess the relationship between serum PFASs and thyro...
Article
Full-text available
Dormice born late in the year start to prepare for winter sooner than mice born earlier in the year.
Article
Full-text available
Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants. Arctic indigenous peoples are exposed to PBDEs through a traditional diet high in marine mammals. PBDEs disrupt thyroid homeostasis. The aim of this study was to assess the relationship between serum PBDEs and thyroid function in a remote population of St. Lawrence Isla...
Article
Background: Many Alaska Native communities rely on a traditional marine diet that contains persistent organic pollutants (POPs). The indoor environment is also a source of POPs. Polybrominated diphenyl ethers (PBDEs) and perfluoroalkyl substances (PFASs) are present both in the traditional diet and the home indoor environment. Objectives: We ass...
Article
Full-text available
The Earth's climate is changing at an unprecedented rate and, as ecologists, we are challenged with the difficult task of predicting how individuals and populations will respond to climate-induced changes to local and global ecosystems. Although we are beginning to understand some of the responses to changing seasonality, the physiological mechanis...
Article
People living a subsistence lifestyle in the Arctic are highly exposed to persistent organic pollutants, including polychlorinated biphenyls (PCBs). Formerly Used Defense (FUD) sites are point sources of PCB pollution; the Arctic contains thousands of FUD sites, many co-located with indigenous villages. We investigated PCB profiles and biological e...
Article
Full-text available
Sexual selection favours the expression of traits in one sex that attract members of the opposite sex for mating. The nature of sexually selected traits such as vocalization, colour and ornamentation, their fitness benefits as well as their costs have received ample attention in field and laboratory studies. However, sexually selected traits may no...