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Body size and oxygen stores in the blood and muscle set breath-hold limits in marine mammals, yet these characteristics are understudied in immature cetaceans. We examined body mass and hematology from birth through adulthood in beluga... more
Body size and oxygen stores in the blood and muscle set breath-hold limits in marine mammals, yet these characteristics are understudied in immature cetaceans. We examined body mass and hematology from birth through adulthood in beluga whales (Delphinapterus leucas). At birth, body mass was 8% and 6% of the maximum mass recorded for adult females and males, respectively. Body mass then increased rapidly, approaching an asymptote around 12 yr for females and 18 yr for males. Interestingly, red blood cell counts, hemoglobin content, and hematocrit levels decreased after birth; this neonatal anemia was reversed as levels increased after 2 mo postpartum. Mature levels were obtained at approximately 8, 9, and 11 mo postpartum, respectively. Neonatal mean corpuscular hemoglobin also increased with ontogeny; mature levels were achieved by approximately 13 mo after birth. In contrast, mean corpuscular volume and mean corpuscular hemoglobin concentration demonstrated a significant but subtle increase throughout ontogeny. Our results indicate that postnatal maturation was required and that maturation occurred far earlier than the age at weaning (i.e., 2-3 yr postpartum). This is atypical of marine mammals, which generally achieve mature hemoglobin levels at weaning. Hematological maturation before maternal independence undoubtedly supports the prolonged breath holds of young belugas transiting under sea ice. This assessment enhances our knowledge of cetacean physiology and provides important inputs for determining age-specific dive capacity, yielding insights into age-specific flexibility to alter underwater behaviors, as will be required for future regime shifts and disturbances.
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Research Interests: Physiology, Zoology, Behavior, Biology, Ontogeny, and 3 moreMarine Mammal Science, Fishery, and Tuna
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Muscle biochemistry of aquatic birds and mammals varies in accordance with swimming and diving performance, as well as with ontogeny. Similar to other odontocetes, the locomotor muscles (longissimus dorsi) of neonatal melon-headed whales... more
Muscle biochemistry of aquatic birds and mammals varies in accordance with swimming and diving performance, as well as with ontogeny. Similar to other odontocetes, the locomotor muscles (longissimus dorsi) of neonatal melon-headed whales (Peponocephala electra) have low myoglobin content (Mb; 1.06±0.20 g Mb/100 g wet muscle mass; mean ± SE; n=2] and low muscle nonbicarbonate buffering capacity (37.78±3.75 slykes; n=2), representing only 16% of adult Mb (6.64±0.33 g Mb/100 g wet muscle mass; n=5) and 56% of adult muscle nonbicarbonate buffering capacities (66.90±4.80 slykes; n=5). By the juvenile stage, Mb (2.75±0.80 g Mb/100 g wet muscle mass; n=3) is still only 41% of adult levels, but nonbicarbonate buffering capacity (65.61±2.62 slykes; n=3) has matured. Despite the observation that Hawaiian melon-headed whales are not deep divers or long-duration divers, their Mb rivals that found in ziphiids that forage in the bathypelagic zone and monodontids that forage under sea ice. The pelagic lifestyle of melon-headed whales likely requires sustained swimming, such that endurance training could elevate Mb in the locomotor muscle. Indeed, elevated Mb in the locomotor muscles of other pelagic odontocetes has been observed. Unlike deep-diving and Arctic-dwelling odontocetes, melon-headed whales do not achieve mature muscle characteristics before nursing. It is likely that early in life, the hydrodynamic benefits of swimming in echelon position with their mothers minimizes the endurance training of the calves that would otherwise promote rapid elevations in Mb.
Research Interests: Physiology, Zoology, Biology, Medicine, Whale, and 4 moreMedical Physiology, Myoglobin, Juvenile, and pelagic zone
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Pacific walruses may be unable to meet caloric requirements in the changing Arctic ecosystem, which could affect body condition and have population‐level consequences. Body condition has historically been monitored by measuring blubber... more
Pacific walruses may be unable to meet caloric requirements in the changing Arctic ecosystem, which could affect body condition and have population‐level consequences. Body condition has historically been monitored by measuring blubber thickness over the xiphoid process (sternum). This may be an unreliable condition index because blubber at other sites along the body may be preferentially targeted to balance energetic demands. Animals in aquaria provided an opportunity for controlled study of how blubber topography is altered by caloric intake. Morphology, body mass, blubber thickness (21 sites), and caloric intake of five mature, nonpregnant, nonlactating female walruses were measured monthly (12 month minimum). Body condition (mass × standard length−1) was described by a model that included caloric intake and a seasonal effect, and scaled positively with estimates of total blubber mass. Blubber thicknesses (1.91–10.69 cm) varied topographically and were similar to values reported for free‐ranging female walruses. Body condition was most closely related to blubber thickness measured dorsomedially in the region of the anterior insertion of the pectoral flippers (shoulders); sternum blubber thickness was a relatively poor indicator of condition. This study demonstrates the importance of validating condition metrics before using them to monitor free‐ranging populations.
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Fat-level measurements used to indicate individual body condition and fitness are useful only when taken at a region along the body where fat responds to variations in caloric intake. Investigations to identify appropriate... more
Fat-level measurements used to indicate individual body condition and fitness are useful only when taken at a region along the body where fat responds to variations in caloric intake. Investigations to identify appropriate species-specific regions are limited, especially for cetaceans that have a specialized fat (blubber) that serves as an energy reserve and provides insulation. Over 18 mo, body mass of six pilot whales varied (range: 50–172 kg), and although caloric intake increased when water temperatures were lower, generally the best-fitting state-space model for length-adjusted mass was based on a single factor, caloric intake. After correcting for body length (range: 330–447 cm), the slope for blubber thickness and “blubber ring” thickness (average blubber thickness along a girth) in relation to body mass was positive and had a P value of <0.10 at six of 16 blubber measurement sites and one of five girth measurement sites, respectively. The slope for body girth (a reflection of changes in underlying blubber thickness) in relation to body mass was positive and had a lower P value (P<0.10) at three of five girth measurement sites. Results indicate that blubber from the anterior insertion of the pectoral fins to the posterior insertion of the dorsal fin is the most metabolically active region. This region includes the midflank site, a location where blubber thickness measurements have historically been taken to monitor cetacean body condition. Conversely, blubber in the peduncle region was comparatively inert. These findings must be considered when measuring blubber thickness and body width (i.e., photogrammetry) to monitor the condition of free-ranging cetaceans.
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Synopsis The demands on the locomotor muscles at birth are different for cetaceans than terrestrial mammals. Cetacean muscles do not need to support postural costs as the neonate transitions from the womb because water’s buoyant force... more
Synopsis The demands on the locomotor muscles at birth are different for cetaceans than terrestrial mammals. Cetacean muscles do not need to support postural costs as the neonate transitions from the womb because water’s buoyant force supports body weight. Rather, neonatal cetacean muscles must sustain locomotion under hypoxic conditions as the neonate accompanies its mother swimming underwater. Despite disparate demands at birth, cetaceans like terrestrial mammals require postnatal development to attain mature musculature. Neonatal cetaceans have a low proportion of muscle mass, and their locomotor muscles have lower mitochondrial density, myoglobin content (Mb), and buffering capacity than those found in the adult locomotor muscle. For example, the locomotor muscle of the neonatal bottlenose dolphin has only 10 and 65% of the Mb and buffering capacity, respectively, found in the adult locomotor muscle. The maturation period required to achieve mature Mb and buffering capacity in the locomotor muscle varies across cetacean species from 0.75 to 4 and 1.17 to 3.4 years, respectively. The truncated nursing interval of harbor porpoises and sub-ice travel of beluga whales may be drivers for faster muscle maturation in these species. Despite these postnatal changes in the locomotor muscle, ontogenetic changes in locomotor muscle fiber type seem to be rare in cetaceans. Regardless, the underdeveloped aerobic and anaerobic capacities of the locomotor muscle of immature dolphins result in diminished thrusting capability and swim performance. Size-specific stroke amplitudes (23–26% of body length) of 0–3-month-old dolphins are significantly smaller than those of &gt;10-month-olds (29–30% of body length), and 0–1-month-olds only achieve 37 and 52% of the mean and maximum swim speed of adults, respectively. Until swim performance improves with muscle maturation, young cetaceans are precluded from achieving their pod’s swim speeds, which could have demographic consequences when fleeing anthropogenic disturbances.
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Mammals balance heat dissipation with heat production to maintain core body temperatures independent of their environment. Thermal balance is undoubtedly most challenging for mammals born in polar regions because small body size... more
Mammals balance heat dissipation with heat production to maintain core body temperatures independent of their environment. Thermal balance is undoubtedly most challenging for mammals born in polar regions because small body size theoretically results in high surface-area-to-volume ratios (SA:V), which facilitate heat loss (HL). Thus, we examined the ontogeny of thermoregulatory characteristics of an ice-breeding seal (Weddell seal Leptonychotes weddelli). Morphology, blubber thickness, rectal temperature (T(r)), muscle temperature (T(m)), and skin temperatures on the trunk (T(s)) and flipper (T(f)) in 3-5-wk-old pups, yearlings, and adults were measured. Adults maintained the thickest blubber layers, while yearlings had the thinnest; T(r) and T(m) fell within a narrow range, yet T(r) and T(m) decreased significantly with body length. All seals maintained skin temperatures lower than T(r), our index of core body temperature. The T(s)&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s were positively correlated with environmental temperatures; conversely, T(f)&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s were not. Although pups had the greatest proportion of blubber, their greater SA:V and limited ability to minimize body-to-environment temperature gradients led to the greatest calculated mass-specific HL. This implies that pups relied on elevated metabolic heat production to counter HL. Heat production in pups and yearlings may have been aided by nonshivering thermogenesis in the skeletal muscle via the enhanced muscle mitochondrial densities that have been observed in these segments of this population.
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Research Interests: Aging, Biology, Medicine, Swimming, Biological Sciences, and 15 moreOntogeny, Swimming speed, Female, Animals, Male, Body Size, Bottlenose dolphin, Experimental, First Year, Post Partum, Experimental Biology, Biomechanical Phenomena, Swimming performance, Body length, and Medical and Health Sciences
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Habitat use and activity patterns of Pacific walruses (Odobenus rosmarus divergens) have changed with climate-induced reductions in sea ice. Increases in the time active in water could result in negative energy balance, precluding females... more
Habitat use and activity patterns of Pacific walruses (Odobenus rosmarus divergens) have changed with climate-induced reductions in sea ice. Increases in the time active in water could result in negative energy balance, precluding females from sustaining lactation, which could impact population demographics. Little is known about lactation costs in walruses. We examined the energetics of 0-2-yr-old walrus calves by using Bayesian hierarchical models based on longitudinal husbandry records of growth (n = 6 females and 7 males) and caloric intake (n = 5 females and 6 males) as a proxy for maternal lactation costs. Males and females had similar growth patterns; mean mass increased from 68 kg at birth to 301 kg by 2 yr. Females had a 2,000 kcal kg(-1) higher mass storage (growth) cost than males; females typically synthesize and deposit greater amounts of adipose, which is more energy dense than lean tissue. In contrast, males had higher metabolic (basal and activity) costs, ranging from 600 to 1,800 kcal d(-1) greater than similarly sized females; males are typically leaner, and muscle is more metabolically active than adipose. Yet total daily energy requirements (storage plus metabolic components) were similar across sexes, summing to approximately 190,000 kcal over the first month postpartum. Based on these estimates and assuming that 8,103 kcal is recovered from 1 kg of mass loss in adult female walruses, suckling calves could deplete 23 kg of their mother&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s body mass over the first month after parturition if none of the lactation costs is met through ingested prey.
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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... more
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 ear...
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Synopsis The demands on the locomotor muscles at birth are different for cetaceans than terrestrial mammals. Cetacean muscles do not need to support postural costs as the neonate transitions from the womb because water’s buoyant force... more
Synopsis The demands on the locomotor muscles at birth are different for cetaceans than terrestrial mammals. Cetacean muscles do not need to support postural costs as the neonate transitions from the womb because water’s buoyant force supports body weight. Rather, neonatal cetacean muscles must sustain locomotion under hypoxic conditions as the neonate accompanies its mother swimming underwater. Despite disparate demands at birth, cetaceans like terrestrial mammals require postnatal development to attain mature musculature. Neonatal cetaceans have a low proportion of muscle mass, and their locomotor muscles have lower mitochondrial density, myoglobin content (Mb), and buffering capacity than those found in the adult locomotor muscle. For example, the locomotor muscle of the neonatal bottlenose dolphin has only 10 and 65% of the Mb and buffering capacity, respectively, found in the adult locomotor muscle. The maturation period required to achieve mature Mb and buffering capacity in t...
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The data were collected to describe how the physiology that supports diving of beluga whales matures after birth. Specifically, body mass, hemoglobin content (blood oxygen store) and myoglobin content (muscle oxygen store) were measured... more
The data were collected to describe how the physiology that supports diving of beluga whales matures after birth. Specifically, body mass, hemoglobin content (blood oxygen store) and myoglobin content (muscle oxygen store) were measured for belugas at birth through adulthood. The goal of this investigation was to quantify age-specific morphological parameters (body mass) and physiological parameters [oxygen stores in the blood (hemoglobin) and muscle (myoglobin)] to support the determination of age-specific aerobic dive limits (cADL). cADLs define age-specific abilities for transiting under sea-ice and diving to depth for prolonged durations to support foraging activities. Long-term, longitudinal measurements of body mass and hematology (red blood cell number, hemoglobin, hematocrit, mean corpuscular volume, mean cell hemoglobin, and mean cell hemoglobin content) from birth through adulthood in belugas housed at John G. Shedd Aquarium provided historical records of these parameters....
ABSTRACTMarine mammals endure extended breath-holds while performing active behaviors, which has fascinated scientists for over a century. It is now known that these animals have large onboard oxygen stores and utilize oxygen-conserving... more
ABSTRACTMarine mammals endure extended breath-holds while performing active behaviors, which has fascinated scientists for over a century. It is now known that these animals have large onboard oxygen stores and utilize oxygen-conserving mechanisms to prolong aerobically supported dives to great depths, while typically avoiding (or tolerating) hypoxia, hypercarbia, acidosis and decompression sickness (DCS). Over the last few decades, research has revealed that diving physiology is underdeveloped at birth. Here, I review the postnatal development of the body's oxygen stores, cardiorespiratory system and other attributes of diving physiology for pinnipeds and cetaceans to assess how physiological immaturity makes young marine mammals vulnerable to disturbance. Generally, the duration required for body oxygen stores to mature varies across species in accordance with the maternal dependency period, which can be over 2 years long in some species. However, some Arctic and deep-diving s...
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Fat-level measurements used to indicate individual body condition and fitness are useful only when taken at a region along the body where fat responds to variations in caloric intake. Investigations to identify appropriate... more
Fat-level measurements used to indicate individual body condition and fitness are useful only when taken at a region along the body where fat responds to variations in caloric intake. Investigations to identify appropriate species-specific regions are limited, especially for cetaceans that have a specialized fat (blubber) that serves as an energy reserve and provides insulation. Over 18 mo, body mass of six pilot whales varied (range: 50–172 kg), and although caloric intake increased when water temperatures were lower, generally the best-fitting state-space model for length-adjusted mass was based on a single factor, caloric intake. After correcting for body length (range: 330–447 cm), the slope for blubber thickness and “blubber ring” thickness (average blubber thickness along a girth) in relation to body mass was positive and had a P value of <0.10 at six of 16 blubber measurement sites and one of five girth measurement sites, respectively. The slope for body girth (a reflection of changes in underlying blubber thickness) in relation to body mass was positive and had a lower P value (P<0.10) at three of five girth measurement sites. Results indicate that blubber from the anterior insertion of the pectoral fins to the posterior insertion of the dorsal fin is the most metabolically active region. This region includes the midflank site, a location where blubber thickness measurements have historically been taken to monitor cetacean body condition. Conversely, blubber in the peduncle region was comparatively inert. These findings must be considered when measuring blubber thickness and body width (i.e., photogrammetry) to monitor the condition of free-ranging cetaceans.
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Muscle biochemistry of aquatic birds and mammals varies in accordance with swimming and diving performance, as well as with ontogeny. Similar to other odontocetes, the locomotor muscles (longissimus dorsi) of neonatal melon-headed whales... more
Muscle biochemistry of aquatic birds and mammals varies in accordance with swimming and diving performance, as well as with ontogeny. Similar to other odontocetes, the locomotor muscles (longissimus dorsi) of neonatal melon-headed whales (Peponocephala electra) have low myoglobin content (Mb; 1.06±0.20 g Mb/100 g wet muscle mass; mean ± SE; n=2] and low muscle nonbicarbonate buffering capacity (37.78±3.75 slykes; n=2), representing only 16% of adult Mb (6.64±0.33 g Mb/100 g wet muscle mass; n=5) and 56% of adult muscle nonbicarbonate buffering capacities (66.90±4.80 slykes; n=5). By the juvenile stage, Mb (2.75±0.80 g Mb/100 g wet muscle mass; n=3) is still only 41% of adult levels, but nonbicarbonate buffering capacity (65.61±2.62 slykes; n=3) has matured. Despite the observation that Hawaiian melon-headed whales are not deep divers or long-duration divers, their Mb rivals that found in ziphiids that forage in the bathypelagic zone and monodontids that forage under sea ice. The pelagic lifestyle of melon-headed whales likely requires sustained swimming, such that endurance training could elevate Mb in the locomotor muscle. Indeed, elevated Mb in the locomotor muscles of other pelagic odontocetes has been observed. Unlike deep-diving and Arctic-dwelling odontocetes, melon-headed whales do not achieve mature muscle characteristics before nursing. It is likely that early in life, the hydrodynamic benefits of swimming in echelon position with their mothers minimizes the endurance training of the calves that would otherwise promote rapid elevations in Mb.
Research Interests: Physiology, Zoology, Biology, Medicine, Whale, and 4 moreMedical Physiology, Myoglobin, Juvenile, and pelagic zone
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Body size and oxygen stores in the blood and muscle set breath-hold limits in marine mammals, yet these characteristics are understudied in immature cetaceans. We examined body mass and hematology from birth through adulthood in beluga... more
Body size and oxygen stores in the blood and muscle set breath-hold limits in marine mammals, yet these characteristics are understudied in immature cetaceans. We examined body mass and hematology from birth through adulthood in beluga whales (Delphinapterus leucas). At birth, body mass was 8% and 6% of the maximum mass recorded for adult females and males, respectively. Body mass then increased rapidly, approaching an asymptote around 12 yr for females and 18 yr for males. Interestingly, red blood cell counts, hemoglobin content, and hematocrit levels decreased after birth; this neonatal anemia was reversed as levels increased after 2 mo postpartum. Mature levels were obtained at approximately 8, 9, and 11 mo postpartum, respectively. Neonatal mean corpuscular hemoglobin also increased with ontogeny; mature levels were achieved by approximately 13 mo after birth. In contrast, mean corpuscular volume and mean corpuscular hemoglobin concentration demonstrated a significant but subtle...
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ABSTRACTThe length of time required for postnatal maturation of the locomotor muscle (longissimus dorsi) biochemistry [myoglobin (Mb) content and buffering capacity] in marine mammals typically varies with nursing duration, but it can be... more
ABSTRACTThe length of time required for postnatal maturation of the locomotor muscle (longissimus dorsi) biochemistry [myoglobin (Mb) content and buffering capacity] in marine mammals typically varies with nursing duration, but it can be accelerated by species-specific behavioral demands, such as deep-diving and sub-ice transit. We examined how the swimming demands of a pelagic lifestyle influence postnatal maturation of Mb and buffering capacity in spinner dolphins (Stenella longirostris longirostris). Mb content of newborn (1.16±0.07 g Mb per 100 g wet muscle mass, n=6) and juvenile (2.77±0.22 g per 100 g, n=4) spinner dolphins were only 19% and 46% of adult levels (6.00±0.74 g per 100 g, n=6), respectively. At birth, buffering capacity was 52.70±4.48 slykes (n=6) and increased to 78.53±1.91 slykes (n=6) once a body length of 141 cm was achieved, representing 1.6- to 2.0-year-old dolphins. Based on the age of weaning (1.3–1.6 years post-partum), muscle maturation occurred just aft...
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Little is known about the postnatal development of the physiological characteristics that support breath-hold in cetaceans, despite their need to swim and dive at birth. Arctic species have the additional demand of avoiding entrapment... more
Little is known about the postnatal development of the physiological characteristics that support breath-hold in cetaceans, despite their need to swim and dive at birth. Arctic species have the additional demand of avoiding entrapment while navigating under sea ice, where breathing holes are patchily distributed and ephemeral. This is the first investigation of the ontogeny of the biochemistry of the locomotor muscle in a year-round Arctic-dwelling cetacean (beluga whale, Delphinapterus leucas). Compared with what we know about other cetaceans, belugas are born with high myoglobin content (1.56±0.02 g 100 g(-1) wet muscle mass, N=2) that matures rapidly. Myoglobin increased by 452% during the first year after birth and achieved adult levels (6.91±0.35 g 100 g(-1) wet muscle mass, N=9) by 14 months postpartum. Buffering capacity was 48.88±0.69 slykes (N=2) at birth; adult levels (84.31±1.38 slykes, N=9) were also achieved by 14 months postpartum. As the oxygen stores matured, calcula...