Ontogenetic changes in the thermal and buoyant properties of Atlantic Bottlenose Dolphin (Tursiops truncatus) blubber

The thermal properties of cetacean blubber are influenced by its lipid content and thickness. In Atlantic bottlenose dolphins (Tursiops truncatus), both these features vary across ontogeny and with reproductive and nutritional status and, thus, may result in ontogenetic differences in blubber’s insulative quality. Lipid and water contents, and thermal conductivity and thermal insulation values of Atlantic bottlenose dolphin blubber were measured across fetal through adult life history categories (n = 36), and in pregnant females (n=4) and emaciated animals (n = 5). The thermal conductivities of deep and superficial blubber layers were also measured. Thermal conductivity varied significantly across ontogeny. Fetal through sub-adult life history categories had significantly lower mean thermal conductivity values (0.11 to 0.13 ± 0.01 W/m°C) than adults (0.18 ± 0.02 W/m°C). The conductivity of blubber from pregnant females was similar to non-adult categories, while that of emaciated animals was significantly higher than all other categories. The conductivity of superficial blubber was 37% higher than that of deep blubber. Across life history categories, the conductivity of superficial blubber was similar, while that of deep blubber was significantly greater in emaciated animals. Thermal insulation varied significantly across life history categories. Sub-adults and pregnant females had the highest insulation while fetuses and emaciated animals had the lowest insulation across life history categories. The insulation of neonates and juveniles was similar to that of adult dolphins. Heat flux measurements at the deep blubber surface were significantly higher than that at the superficial surface and this difference in heat flux was significantly correlated with blubber thickness. This pattern was not observed in control materials, polystyrene foam and white pine wood. In nutritionally dependant life history categories, changes in blubber’s thermal insulation resulted from changes in blubber thickness (i.e. quantity) and not thermal conductivity (i.e. quality). Conversely, in nutritionally independent animals, blubber quantity remained stable while blubber quality varied. Differences in conductivity through the blubber depth support the characterization of deep blubber as more insulative and metabolically active layer of lipid deposition and mobilization. Finally, blubber’s composition and its ability to absorb heat suggest that it likely is a phase change material. Blubber is the hypertrophied hypodermis of cetaceans composed primarily of adipocytes and structural fibers. Because the density of lipid is less than that of seawater, blubber has the potential to contribute to positive buoyancy. The blubber of Atlantic bottlenose dolphins (Tursiops truncatus) varies both in thickness and lipid content across ontogeny and with reproductive and nutritional status. This variation in blubber’s quantity and quality may significantly influence its contribution to buoyancy. To measure blubber’s buoyant force, its density was measured volumetrically and its volume was calculated at two body sites (trunk and tailstock), across an ontogenetic series of bottlenose dolphins and in pregnant females and emaciated animals. Lipid and water content were measured to correlate compositional changes with differences in blubber’s buoyant force. The density of blubber from the trunk region (mean ± standard error = 1043.1 ± 13.18 kg/m3) was similar to that of the tailstock (mean = 1077.1 ± 24.17 kg/m3) and these were not significantly different than the density of seawater (1026 kg/m3). Density in these regions was also similar between life history categories. Blubber volume in the trunk and tailstock regions increased over two orders of magnitude between fetuses and adults. The buoyant force of trunk blubber was similar across categories (mean = –0.91 ± 8.85N) and was not significantly different from neutral buoyancy (0N). Trunk blubber of emaciated animals was twelve times more negatively buoyant than that of adults. The buoyant force of tailstock blubber was similar between life history categories (mean = –0.30 ± 1.83 N). For groups with a sufficient sample size for statistical analyses (fetus, neonate, and juvenile), mean total buoyant force of blubber was 0.61 ± 7.45 N and was not significantly different between these groups. Despite significant differences in lipid content and volume across life history categories, blubber’s contribution to buoyancy remained neutral. Because this body compartment is nearly 25% of total body mass, it may be essential for this tissue to be neutrally buoyant. Pregnancy and emaciation can significantly influence blubber’s contribution to buoyancy and may impose additional locomotor costs associated with overcoming a positive or negative vertical force. vii

Comparative and Cumulative Energetic Costs of Odontocete Responses to Anthropogenic Disturbance

Odontocetes respond to vessels and anthropogenic noise by modifying vocal behavior, surface active behaviors, dive patterns, swim speed, direction of travel, and activity budgets. Exposure scenarios and behavioral responses vary across odontocetes. A literature review was conducted to determine relevant sources of disturbance and associated behavioral responses for several odontocete species (bottlenose dolphin, killer whale, harbor porpoise, and beaked whales). The energetic costs of species-specific responses to anthropogenic disturbance were then estimated. The energetic impact varies across species and scenarios as well as by behavioral responses. Overall, the cumulative energetic cost of ephemeral behavioral responses (e.g., performing surface active behaviors, modifying acoustic signals) and modifying swim speeds and activity budgets likely increases daily energy expenditure by ≤4%. In contrast, the reduction in foraging activity in the presence of vessels and/or exposure to sonar has the potential to significantly reduce individuals’ daily energy acquisition. Indeed, across all odontocete species, decreased energy acquisition as a result of reduced foraging undoubtedly has a larger impact on individuals than the increased energy expenditure associated with behavioral modification. This work provides a powerful tool to investigate the biological significance of multiple behavioral responses that are likely to occur in response to anthropogenic disturbance

Growth in marine mammals : a review of growth patterns, composition and energy investment

Funded under award from Office of Naval Research: N000142012392. DPC and SA were funded under the E&P Sound and Marine Life Joint Industry Programme of the International Association of Oil and Gas Producers (IOGP; grant 00-07-23). CRM is supported by the Australian Integrated Marine Observing System (IMOS), IMOS s enabled by the National Collaborative Research Infrastructure Strategy.Growth of structural mass and energy reserves influences individual survival, reproductive success, population and species life history. Metrics of structural growth and energy storage of individuals are often used to assess population health and reproductive potential, which can inform conservation. However, the energetic costs of tissue deposition for structural growth and energy stores and their prioritization within bioenergetic budgets are poorly documented. This is particularly true across marine mammal species as resources are accumulated at sea, limiting the ability to measure energy allocation and prioritization. We reviewed the literature on marine mammal growth to summarize growth patterns, explore their tissue compositions, assess the energetic costs of depositing these tissues and explore the tradeoffs associated with growth. Generally, marine mammals exhibit logarithmic growth. This means that the energetic costs related to growth and tissue deposition are high for early postnatal animals, but small compared to the total energy budget as animals get older. Growth patterns can also change in response to resource availability, habitat and other energy demands, such that they can serve as an indicator of individual and population health. Composition of tissues remained consistent with respect to protein and water content across species; however, there was a high degree of variability in the lipid content of both muscle (0.1–74.3%) and blubber (0.4–97.9%) due to the use of lipids as energy storage. We found that relatively few well-studied species dominate the literature, leaving data gaps for entire taxa, such as beaked whales. The purpose of this review was to identify such gaps, to inform future research priorities and to improve our understanding of how marine mammals grow and the associated energetic costs.Publisher PDFPeer reviewe

Variability of Disk Emission in Pre-Main Sequence and Related Stars. II. Variability in the Gas and Dust Emission of the Herbig Fe Star SAO 206462

We present thirteen epochs of near-infrared (0.8-5 micron) spectroscopic observations of the pre-transitional, "gapped" disk system in SAO 206462 (=HD 135344B). In all, six gas emission lines (including Br gamma, Pa beta, and the 0.8446 micron line of O I) along with continuum measurements made near the standard J, H, K, and L photometric bands were measured. A mass accretion rate of approximately 2 x 10^-8 solar masses per year was derived from the Br gamma and Pa beta lines. However, the fluxes of these lines varied by a factor of over two during the course of a few months. The continuum also varied, but by only ~30%, and even decreased at a time when the gas emission was increasing. The H I line at 1.083 microns was also found to vary in a manner inconsistent with that of either the hydrogen lines or the dust. Both the gas and dust variabilities indicate significant changes in the region of the inner gas and the inner dust belt that may be common to many young disk systems. If planets are responsible for defining the inner edge of the gap, they could interact with the material on time scales commensurate with what is observed for the variations in the dust, while other disk instabilities (thermal, magnetorotational) would operate there on longer time scales than we observe for the inner dust belt. For SAO 206462, the orbital period would likely be 1-3 years. If the changes are being induced in the disk material closer to the star than the gap, a variety of mechanisms (disk instabilities, interactions via planets) might be responsible for the changes seen. The He I feature is most likely due to a wind whose orientation changes with respect to the observer on time scales of a day or less. To further constrain the origin of the gas and dust emission will require multiple spectroscopic and interferometric observations on both shorter and longer time scales that have been sampled so far.Comment: 42 pages, 10 figure

From Tissues to Landscapes: How Thermal Physiology, Water Use, and Climate Influence Patterns of Landscape Use in Elephants

In the following chapters the interaction between large body size and climate and the resulting influence of this interaction at the level of the tissue, the whole body, and at the landscape level are investigated. In chapter one, tissue level adaptations of Asian (Elephas maximus)(Loxodonta africana)oC range of ambient temperatures were used to construct climate dependent thermal and water budgets. In chapter three, these budgets were used to construct a coupled biophysical and dynamic programming model to investigate how climate together with thermal, water, and energy demands, interact to produce landscape level patterns of habitat use. At the tissue level, the integument of elephants has a high water and low lipid content and its thermal conductivity (0.19±0.01 to 0.23±0.13 W m--10C) approaches the upper limit of previously measured mammalian values. The integument's resistance to water loss is also low and is comparable to or less than that of some amphibians. At the whole body level, low integumental resistance results in high rates of cutaneous evaporative water loss (E.m.: 0.31 and 8.9 g min-1m-2; L.a.: 0.26 and 6.5 g min-1m-2) and at temperatures between 28-30oC, elephants are fully dependent on evaporative cooling to dissipate heat produced from resting metabolism. At the landscape level, simulations under six combinations of climate and primary productivity demonstrated that under cool and moderate climates, primary productivity was the strongest determinate of home range size, however, at temperatures above 24-27oC, ambient temperature was limiting as elephants were more tightly tethered to water with less access to food. Climate appears to have a non-linear influence on landscape use because evaporative cooling increases exponentially with ambient temperature. Although the drivers of landscape use by large herbivores are complex, the results of this work demonstrate the importance of interactions between body size and climate spanning three levels of biological organization, in setting the fundamental spatial and temporal patterns of landscape use reported for elephants

Applying Principles of the PDP Towards Mentoring

In this paper, we explore how core principles of the mentoring training offered by the Institute for Scientist & Engineer Educators (ISEE) Professional Development Program (PDP) have been adopted by PDP alumni and applied in different contexts. The core themes of the mentoring work conducted by ISEE, which are Inquiry, Equity & Inclusion, and Assessment, form an extensible basis for PDP participants to use as they develop their own mentoring programs. The panel/paper is structured to briefly identify core components of mentoring in the PDP model and then discuss how former PDP participants have applied these in a variety of other venues. With the goal of broadening access & persistence in STEM, the PDP emphasized: the role of ownership and agency, the practice of explanations, the creation of opportunities for recognition, providing formative assessment, and a recognition of and introduction to STEM culture. The PDP has had a unique way of “staying with” participants and provided a framework for mentoring in other modalities including: peer-to-peer, informal, and in the development of new formal programs. These offshoots include key PDP ideas such as: providing support for belonging in STEM, placing value on teaching, promoting adaptability and cultural relevance, and a “training the trainers” modality of mentorship. The panelists will provide examples from programs for undergraduate students, graduate students, teaching professionals, and faculty. The session also provided opportunities for attendees to share their experiences and take-away lessons from the PDP model of mentoring and some of the panel feedback is included in this paper. The ISEE community has a shared vocabulary, toolset, and ethos that continues to inform alumni mentoring since the inception of the PDP

Engaging in science practices in classrooms predicts increases in undergraduates' STEM motivation, identity, and achievement: A short‐term longitudinal study

Our short-term longitudinal study explored undergraduate students' experiences with performing authentic science practices in the classroom in relation to their science achievement and course grades. In addition, classroom experiences (felt recognition as a scientist and perceived classroom climate) and changes over a 10-week academic term in STEM (science, technology, engineering, and mathematics) identity and motivation were tested as mediators. The sample comprised 1,079 undergraduate students from introductory biology classrooms (65.4% women, 37.6% Asian, 30.2% White, 25.1% Latinx). Using structural equation modeling (SEM), our hypothesized model was confirmed while controlling for class size and GPA. Performing science practices (e.g., hypothesizing or explaining results) positively predicted students' felt recognition as a scientist; and felt recognition positively predicted perceived classroom climate. In turn, felt recognition and classroom climate predicted increases over time in students' STEM motivation (expectancy-value beliefs), STEM identity, and STEM career aspirations. Finally, these factors predicted students' course grade. Both recognition as a scientist and positive classroom climate were more strongly related to outcomes among underrepresented minority (URM) students. Findings have implications for why large-format courses that emphasize opportunities for students to learn science practices are related to positive STEM outcomes, as well as why they may prove especially helpful for URM students. Practical implications include the importance of recognition as a scientist from professors, teaching assistants, and classmates in addition to curriculum that engages students in the authentic practices of science

Recovery rates of bottlenose dolphin (\u3ci\u3eTursiops truncatus\u3c/i\u3e) carcasses estimated from stranding and survival rate data

Recovery of cetacean carcasses provides data on levels of human-caused mortality, but represents only a minimum count of impacts. Counts of stranded carcasses are negatively biased by factors that include at-sea scavenging, sinking, drift away from land, stranding in locations where detection is unlikely, and natural removal from beaches due to wave and tidal action prior to detection. We estimate the fraction of carcasses recovered for a population of coastal bottlenose dolphins (Tursiops truncatus), using abundance and survival rate data to estimate annual deaths in the population. Observed stranding numbers are compared to expected deaths to estimate the fraction of carcasses recovered. For the California coastal population of bottlenose dolphins, we estimate the fraction of carcasses recovered to be 0.25 (95% CI = 0.20– 0.33). During a 12 yr period, 327 animals (95% CI = 253–413) were expected to have died and been available for recovery, but only 83 carcasses attributed to this population were documented. Given the coastal habits of California coastal bottlenose dolphins, it is likely that carcass recovery rates of this population greatly exceed recovery rates of more pelagic dolphin species in the region

Growth in marine mammals:a review of growth patterns, composition and energy investment

Growth of structural mass and energy reserves influences individual survival, reproductive success, population and species life history. Metrics of structural growth and energy storage of individuals are often used to assess population health and reproductive potential, which can inform conservation. However, the energetic costs of tissue deposition for structural growth and energy stores and their prioritization within bioenergetic budgets are poorly documented. This is particularly true across marine mammal species as resources are accumulated at sea, limiting the ability to measure energy allocation and prioritization. We reviewed the literature on marine mammal growth to summarize growth patterns, explore their tissue compositions, assess the energetic costs of depositing these tissues and explore the tradeoffs associated with growth. Generally, marine mammals exhibit logarithmic growth. This means that the energetic costs related to growth and tissue deposition are high for early postnatal animals, but small compared to the total energy budget as animals get older. Growth patterns can also change in response to resource availability, habitat and other energy demands, such that they can serve as an indicator of individual and population health. Composition of tissues remained consistent with respect to protein and water content across species; however, there was a high degree of variability in the lipid content of both muscle (0.1–74.3%) and blubber (0.4–97.9%) due to the use of lipids as energy storage. We found that relatively few well-studied species dominate the literature, leaving data gaps for entire taxa, such as beaked whales. The purpose of this review was to identify such gaps, to inform future research priorities and to improve our understanding of how marine mammals grow and the associated energetic costs