Burney Leboeuf - Academia.edu (original) (raw)
Papers by Burney Leboeuf
Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated ... more Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated more frequently and for a longer period of time than rats administered an equivalent amount of testosterone propionate. Latency to first ejaculation following treatment was shortest in the testo sterone propionate treated animals. The maximal behavioral response to each steroid was similar in time to peak responses of androgen sensitive tissue as measured in a separate study.
Proceedings of the National Academy of Sciences, 2001
In phocid seals, an increase in hematocrit (Hct) accompanies diving and periods of apnea. The var... more In phocid seals, an increase in hematocrit (Hct) accompanies diving and periods of apnea. The variability of phocid Hct suggests that the total red cell mass is not always in circulation, leading researchers to speculate on the means of blood volume partitioning. The histology and disproportionate size of the phocid spleen implicates it as the likely site for RBC storage. We used magnetic resonance imaging on Northern elephant seals to demonstrate a rapid contraction of the spleen and a simultaneous filling of the hepatic sinus during forced dives ( P < 0.0001, R 2 = 0.97). The resulting images are clear evidence demonstrating a functional relationship between the spleen and hepatic sinus. The transfer of blood from the spleen to the sinus provides an explanation for the disparity between the timing of diving-induced splenic contraction (≈1–3 min) and the occurrence of peak Hct (15–25 min). Facial immersion was accompanied by an immediate and profound splenic contraction, with no...
A time-depth recorder was attached to a female Northern elephant scal at the end of her lactation... more A time-depth recorder was attached to a female Northern elephant scal at the end of her lactation fast before she entered the sea to feed. The animal dived continuously during its first 11 days at sea, the period recorded for a total of 653 dives. Mean dive time was 21 min, with the longest submersion lasting 32 min. Mean surfke interval between dives was 3 min, resulting in a total surface time of I1 %. Mean dive depth was 333 m and the deepest dive was 630 m, the deepest ever recorded for a pinniped. A depth histogram recorder attached to another female yielded a similar frequency distribution of dive depths.
Hormones and Behavior, 1970
Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated m... more Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated more frequently and for a longer period of time than rats administered an equivalent amount of testosterone propionate. Latency to first ejaculation following treatment was shortest in the testo sterone propionate treated animals. The maximal behavioral response to each steroid was similar in time to peak responses of androgen sensitive tissue as measured in a separate study. Saunders (1966) found that the substitution of a trimethylsilyl ether for the propionic acid moiety in testosterone propionate resulted in a peculiar ly long-acting androgenic compo und. He reported a maximum physiological response in the seminal vesicles, ventral prostate, and levator ani muscle of castrated rats 20-30 days after a single injection of the 17-trimethylsilyl ether of testosterone (SC-16148). The duration of the effect and the magnitude of the response were greater than those produced after administration of the same amount of testosterone propionate, which produced a maximum re sponse in 7-10 days. The purpose of this study was to determine whether SC-16148 also has a long-acting effect on the sexual response of castrated males to estrous females. METHODS Thirty male rats of the Long-Evans strain were used as experimental subjects; they were 70 days old at the beginning of the experiment. Stimulus females from the Long-Evans and Sprague-Dawley strains were brought into behavioral estrus by a single subcutaneous injection of 333 f.1g estradiol benzo ate in oil, 1 48-72 hours before testing. Each female received an injection
Hormones and Behavior, 1970
Prepuberal castration of male dogs did not significantIy reduce mounting during development nor s... more Prepuberal castration of male dogs did not significantIy reduce mounting during development nor sexual responsiveness of the adult dog to the estrous female. Castrate males mounted frequently, vigorously, and with short latency as adults but never achieved a copulatory tie with the bitch. Aggressive behavior of castrate males was indistinguishable from that of intact males during development. In competition for estrous females, adult castrate males developed a dominance hierarchy amongst themselves as did intact males. The two groups also performed similarly in competition for bones.
Ecology, 2001
The aim of this study was to determine the effects of maternal traits on reproductive expenditure... more The aim of this study was to determine the effects of maternal traits on reproductive expenditure and energy delivery to the offspring in a capital breeder, the northern elephant seal (Mirounga angustirostris). Changes in maternal and offspring energy reserves and milk-energy delivery were examined in relation to maternal parturition mass, body composition, and age in females and pups breeding at Añ o Nuevo State Reserve, California. Maternal body mass and composition had significant effects on maternal energy expenditure over lactation. Path analysis suggested no significant effects of maternal age on reproductive effort of parous females. The efficiency of milk production increased significantly with maternal age. Offspring metabolism was a relatively small component of maternal energy expenditure, with pups storing 84% of the energy obtained from milk. These effects are an important consequence of the phocid strategy for enabling terrestrial parturition despite marine feeding. This strategy has resulted in an abbreviated and highly efficient lactation system that is strongly impacted by body reserves, linking foraging success at sea with reproductive success on land. Maternal size, body composition, and age were important features of reproduction in northern elephant seals. These characteristics are rarely considered concurrently in life history studies.
Behaviour, 1972
The mating behavior of Northern elephant seals, Mirounga angustirostris, was studied during the I... more The mating behavior of Northern elephant seals, Mirounga angustirostris, was studied during the I968, I969 and I970 breeding seasons at Año Nuevo Island, I9 miles north of Santa Cruz, California. Copulation takes place primarily on land, from January to March; it is initiated and terminated by the male and lasts approximately 5 minutes. A few males do most of the breeding and the higher a male's rank in the social hierarchy, the more frequently he copulates. Some bulls may maintain high rank and participate in mating for 3 breeding seasons. Low ranking males are kept out of the harem so they attempt to copulate with females on the periphery or in the water with departing females. Males prevent subordinates from mounting females and disrupt copulations in progress. The higher a male's rank, the more freedom he has to copulate without interference, and the more frequently he interferes with the copulation of others. The highest ranking males interrupt their own copulations pre...
Journal of Comparative and …, 1968
Animal Behaviour, 1981
The probability of weaning a healthy pup increases with age in female northern elephant seals, Mi... more The probability of weaning a healthy pup increases with age in female northern elephant seals, Mirounga angustirostris. On Afio Nuevo Island, California, weaning success among 'prime' females, those 6 years of age or older, was more than double that of'young' females, those 3 to 5 years old. Prime females were better mothers than young females because of superior size, higher social dominance, and greater maternal experience; they were more likely to mate with high-ranking males and gave birth at an optimal time and place, circumstances that maximized the probability that their pups would survive, develop, and reproduce. The competitive advantage of prime-age mothers over younger ones was greatest when female and pup density was high. Young females improved their chances of reproducing successfully by emigrating from crowded harems and establishing new colonies.
Animal Behaviour, 1974
Threat vocalizations of adult male northern elephant seals, Mirounga angustirostris, were recorde... more Threat vocalizations of adult male northern elephant seals, Mirounga angustirostris, were recorded over a 5-year period to determine whether local dialects previously reported in this species are reliable. These results were obtained: (1) The mean pulse rate at Afio Nuevo Island, which was colonized in 1961, has increased every year from 1968 to 1972 but still remains slower than the mean pulse rate of all southern rookeries. (2) The pulse rate of individual adult males does not vary significantly for at least 3 years. (3) Forty-three per cent of the breeding males on Afio Nuevo Island are immigrants from southern populations each of which has a faster mean pulse rate than Afio Nuevo Island. (4) The pulse rate at San Miguel Island, a large rookery which receives few immigrants, did not change significantly from 1969 to 1972. A model is advanced to explain the data and account for geographical variation in learned vocalizations of species whose populations are expanding.
Canadian Journal of Zoology, 1992
The swim speed and dive pattern of an 8-year-old female northern elephant seal (Mirounga angustir... more The swim speed and dive pattern of an 8-year-old female northern elephant seal (Mirounga angustirostris) were recorded during the postlactation period at sea. A swim speeddistance meter and a time-depth recorder attached to the animal's back recorded the following synchronously and continuously for 29 days: swim speed, distance, depth, and duration of freeranging dives. Mean swim speeds calculated as a function of time and distance ranged from 0.91 to 1.66 m/s. Mean descent velocities were 27% greater than ascent velocities and velocities at depth. Minimum and maximum speeds ranged from 0.4 to 3.0 m/s for most segments of all dives. There was no surface swimming. Angles of descent were less steep (30-56") than angles of ascent (52-82"). Mean total horizontal distance traveled per dive ranged from 0.6 to 1.3 km, depending on dive type. From the above data and related information, each of four dive types, which accounted for the majority of dives in the record, were hypothesized to have one of the following principal functions: transit, foraging (pelagic and benthic), and process (serving rest, food processing, or anaerobic metabolite clearance).
Canadian Journal of Zoology-revue Canadienne De Zoologie, 1997
Psychopharmacology, 1969
Strychnine sulphate administered to rats during post-natal de velopment affected the rate of maze... more Strychnine sulphate administered to rats during post-natal de velopment affected the rate of maze learning in adulthood. Rats given the drug in a rich environment (drug-rich group) learned a maze at a faster rate than rats treated similarly but raised in laboratory cages (drug-caged group). The performance of rats given no drug was intermediate to that of the drug-rich and drug-caged groups.
Stable isotope analysis is useful for examining the feeding strategies of mammals. Isotopes in t... more Stable isotope analysis is useful for examining the feeding strategies of mammals.
Isotopes in the annual deposition growth layers of dentine in teeth permit assessment of ontogenetic
dietary shifts in individuals, because this metabolically inert tissue is not resorbed after
deposition. Profiles of stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) from the teeth of
northern elephant seals Mirounga angustirostris, aged between 1 and 11 yr, were described from
stranded individuals in San Benito and Magdalena Islands, Mexico, between 2000 and 2009. δ13C
and δ15N values differed with age in each sex indicating shifts in feeding habits throughout life, as
well as in their physiological condition. Although steady δ13C values within each individual suggest
fidelity to feeding grounds, differences in δ13C values between males and females were likely
a reflection of sexual segregation on the feeding areas, which begins during the juvenile stage.
Mean δ15N values of males (18.3‰) and females (18.2‰) would suggest that both groups feed at
a similar trophic level; however a combination of differences in benthic versus pelagic and longitudinal
foraging habitats would be masking real sex differences in trophic level, estimated for the
species at 4.6. δ15N and δ13C values varied markedly between individuals of the same sex, suggesting
the potential existence of diverse feeding strategies leading to a resource partitioning in
this species. The alleged fetal growth layer has a δ15N value 1.8‰ higher than the average of the
adult female stage, suggesting that the fetal layer is more likely the product of the intensive nursing
during the first month of life.
Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated ... more Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated more frequently and for a longer period of time than rats administered an equivalent amount of testosterone propionate. Latency to first ejaculation following treatment was shortest in the testo sterone propionate treated animals. The maximal behavioral response to each steroid was similar in time to peak responses of androgen sensitive tissue as measured in a separate study.
Proceedings of the National Academy of Sciences, 2001
In phocid seals, an increase in hematocrit (Hct) accompanies diving and periods of apnea. The var... more In phocid seals, an increase in hematocrit (Hct) accompanies diving and periods of apnea. The variability of phocid Hct suggests that the total red cell mass is not always in circulation, leading researchers to speculate on the means of blood volume partitioning. The histology and disproportionate size of the phocid spleen implicates it as the likely site for RBC storage. We used magnetic resonance imaging on Northern elephant seals to demonstrate a rapid contraction of the spleen and a simultaneous filling of the hepatic sinus during forced dives ( P < 0.0001, R 2 = 0.97). The resulting images are clear evidence demonstrating a functional relationship between the spleen and hepatic sinus. The transfer of blood from the spleen to the sinus provides an explanation for the disparity between the timing of diving-induced splenic contraction (≈1–3 min) and the occurrence of peak Hct (15–25 min). Facial immersion was accompanied by an immediate and profound splenic contraction, with no...
A time-depth recorder was attached to a female Northern elephant scal at the end of her lactation... more A time-depth recorder was attached to a female Northern elephant scal at the end of her lactation fast before she entered the sea to feed. The animal dived continuously during its first 11 days at sea, the period recorded for a total of 653 dives. Mean dive time was 21 min, with the longest submersion lasting 32 min. Mean surfke interval between dives was 3 min, resulting in a total surface time of I1 %. Mean dive depth was 333 m and the deepest dive was 630 m, the deepest ever recorded for a pinniped. A depth histogram recorder attached to another female yielded a similar frequency distribution of dive depths.
Hormones and Behavior, 1970
Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated m... more Castrated rats given a single large injection of an ether of testoster one, SC-16148, copulated more frequently and for a longer period of time than rats administered an equivalent amount of testosterone propionate. Latency to first ejaculation following treatment was shortest in the testo sterone propionate treated animals. The maximal behavioral response to each steroid was similar in time to peak responses of androgen sensitive tissue as measured in a separate study. Saunders (1966) found that the substitution of a trimethylsilyl ether for the propionic acid moiety in testosterone propionate resulted in a peculiar ly long-acting androgenic compo und. He reported a maximum physiological response in the seminal vesicles, ventral prostate, and levator ani muscle of castrated rats 20-30 days after a single injection of the 17-trimethylsilyl ether of testosterone (SC-16148). The duration of the effect and the magnitude of the response were greater than those produced after administration of the same amount of testosterone propionate, which produced a maximum re sponse in 7-10 days. The purpose of this study was to determine whether SC-16148 also has a long-acting effect on the sexual response of castrated males to estrous females. METHODS Thirty male rats of the Long-Evans strain were used as experimental subjects; they were 70 days old at the beginning of the experiment. Stimulus females from the Long-Evans and Sprague-Dawley strains were brought into behavioral estrus by a single subcutaneous injection of 333 f.1g estradiol benzo ate in oil, 1 48-72 hours before testing. Each female received an injection
Hormones and Behavior, 1970
Prepuberal castration of male dogs did not significantIy reduce mounting during development nor s... more Prepuberal castration of male dogs did not significantIy reduce mounting during development nor sexual responsiveness of the adult dog to the estrous female. Castrate males mounted frequently, vigorously, and with short latency as adults but never achieved a copulatory tie with the bitch. Aggressive behavior of castrate males was indistinguishable from that of intact males during development. In competition for estrous females, adult castrate males developed a dominance hierarchy amongst themselves as did intact males. The two groups also performed similarly in competition for bones.
Ecology, 2001
The aim of this study was to determine the effects of maternal traits on reproductive expenditure... more The aim of this study was to determine the effects of maternal traits on reproductive expenditure and energy delivery to the offspring in a capital breeder, the northern elephant seal (Mirounga angustirostris). Changes in maternal and offspring energy reserves and milk-energy delivery were examined in relation to maternal parturition mass, body composition, and age in females and pups breeding at Añ o Nuevo State Reserve, California. Maternal body mass and composition had significant effects on maternal energy expenditure over lactation. Path analysis suggested no significant effects of maternal age on reproductive effort of parous females. The efficiency of milk production increased significantly with maternal age. Offspring metabolism was a relatively small component of maternal energy expenditure, with pups storing 84% of the energy obtained from milk. These effects are an important consequence of the phocid strategy for enabling terrestrial parturition despite marine feeding. This strategy has resulted in an abbreviated and highly efficient lactation system that is strongly impacted by body reserves, linking foraging success at sea with reproductive success on land. Maternal size, body composition, and age were important features of reproduction in northern elephant seals. These characteristics are rarely considered concurrently in life history studies.
Behaviour, 1972
The mating behavior of Northern elephant seals, Mirounga angustirostris, was studied during the I... more The mating behavior of Northern elephant seals, Mirounga angustirostris, was studied during the I968, I969 and I970 breeding seasons at Año Nuevo Island, I9 miles north of Santa Cruz, California. Copulation takes place primarily on land, from January to March; it is initiated and terminated by the male and lasts approximately 5 minutes. A few males do most of the breeding and the higher a male's rank in the social hierarchy, the more frequently he copulates. Some bulls may maintain high rank and participate in mating for 3 breeding seasons. Low ranking males are kept out of the harem so they attempt to copulate with females on the periphery or in the water with departing females. Males prevent subordinates from mounting females and disrupt copulations in progress. The higher a male's rank, the more freedom he has to copulate without interference, and the more frequently he interferes with the copulation of others. The highest ranking males interrupt their own copulations pre...
Journal of Comparative and …, 1968
Animal Behaviour, 1981
The probability of weaning a healthy pup increases with age in female northern elephant seals, Mi... more The probability of weaning a healthy pup increases with age in female northern elephant seals, Mirounga angustirostris. On Afio Nuevo Island, California, weaning success among 'prime' females, those 6 years of age or older, was more than double that of'young' females, those 3 to 5 years old. Prime females were better mothers than young females because of superior size, higher social dominance, and greater maternal experience; they were more likely to mate with high-ranking males and gave birth at an optimal time and place, circumstances that maximized the probability that their pups would survive, develop, and reproduce. The competitive advantage of prime-age mothers over younger ones was greatest when female and pup density was high. Young females improved their chances of reproducing successfully by emigrating from crowded harems and establishing new colonies.
Animal Behaviour, 1974
Threat vocalizations of adult male northern elephant seals, Mirounga angustirostris, were recorde... more Threat vocalizations of adult male northern elephant seals, Mirounga angustirostris, were recorded over a 5-year period to determine whether local dialects previously reported in this species are reliable. These results were obtained: (1) The mean pulse rate at Afio Nuevo Island, which was colonized in 1961, has increased every year from 1968 to 1972 but still remains slower than the mean pulse rate of all southern rookeries. (2) The pulse rate of individual adult males does not vary significantly for at least 3 years. (3) Forty-three per cent of the breeding males on Afio Nuevo Island are immigrants from southern populations each of which has a faster mean pulse rate than Afio Nuevo Island. (4) The pulse rate at San Miguel Island, a large rookery which receives few immigrants, did not change significantly from 1969 to 1972. A model is advanced to explain the data and account for geographical variation in learned vocalizations of species whose populations are expanding.
Canadian Journal of Zoology, 1992
The swim speed and dive pattern of an 8-year-old female northern elephant seal (Mirounga angustir... more The swim speed and dive pattern of an 8-year-old female northern elephant seal (Mirounga angustirostris) were recorded during the postlactation period at sea. A swim speeddistance meter and a time-depth recorder attached to the animal's back recorded the following synchronously and continuously for 29 days: swim speed, distance, depth, and duration of freeranging dives. Mean swim speeds calculated as a function of time and distance ranged from 0.91 to 1.66 m/s. Mean descent velocities were 27% greater than ascent velocities and velocities at depth. Minimum and maximum speeds ranged from 0.4 to 3.0 m/s for most segments of all dives. There was no surface swimming. Angles of descent were less steep (30-56") than angles of ascent (52-82"). Mean total horizontal distance traveled per dive ranged from 0.6 to 1.3 km, depending on dive type. From the above data and related information, each of four dive types, which accounted for the majority of dives in the record, were hypothesized to have one of the following principal functions: transit, foraging (pelagic and benthic), and process (serving rest, food processing, or anaerobic metabolite clearance).
Canadian Journal of Zoology-revue Canadienne De Zoologie, 1997
Psychopharmacology, 1969
Strychnine sulphate administered to rats during post-natal de velopment affected the rate of maze... more Strychnine sulphate administered to rats during post-natal de velopment affected the rate of maze learning in adulthood. Rats given the drug in a rich environment (drug-rich group) learned a maze at a faster rate than rats treated similarly but raised in laboratory cages (drug-caged group). The performance of rats given no drug was intermediate to that of the drug-rich and drug-caged groups.
Stable isotope analysis is useful for examining the feeding strategies of mammals. Isotopes in t... more Stable isotope analysis is useful for examining the feeding strategies of mammals.
Isotopes in the annual deposition growth layers of dentine in teeth permit assessment of ontogenetic
dietary shifts in individuals, because this metabolically inert tissue is not resorbed after
deposition. Profiles of stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) from the teeth of
northern elephant seals Mirounga angustirostris, aged between 1 and 11 yr, were described from
stranded individuals in San Benito and Magdalena Islands, Mexico, between 2000 and 2009. δ13C
and δ15N values differed with age in each sex indicating shifts in feeding habits throughout life, as
well as in their physiological condition. Although steady δ13C values within each individual suggest
fidelity to feeding grounds, differences in δ13C values between males and females were likely
a reflection of sexual segregation on the feeding areas, which begins during the juvenile stage.
Mean δ15N values of males (18.3‰) and females (18.2‰) would suggest that both groups feed at
a similar trophic level; however a combination of differences in benthic versus pelagic and longitudinal
foraging habitats would be masking real sex differences in trophic level, estimated for the
species at 4.6. δ15N and δ13C values varied markedly between individuals of the same sex, suggesting
the potential existence of diverse feeding strategies leading to a resource partitioning in
this species. The alleged fetal growth layer has a δ15N value 1.8‰ higher than the average of the
adult female stage, suggesting that the fetal layer is more likely the product of the intensive nursing
during the first month of life.