Causes of reproductive failure in North Atlantic right whales: new avenues of research (original) (raw)
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Determination of pregnancy status from blubber samples in minke whales (Balaenoptera acutorostrata)
Marine Mammal …, 2002
Measurement of progesterone concentration in blubber was developed as a method to detect pregnancy in minke whales. Progesterone was extracted and quantified from blubber samples of minke whale carcasses by radioimmunoassay. Results showed a highly significant difference (almost 60-fold) between blubber progesterone concentrations of anatomically determined pregnant females versus non-pregnant female or male carcasses. The results of the study suggest that the blubber progesterone concentrations might be used to determine pregnancy status in free-ranging whales.
Sperm whales of the Southeast Pacific. Part VII. Reproduction and growth in the female
Latin American Journal of Aquatic Mammals, 2013
This report on the reproduction and growth of the female sperm whale Physeter catodon 2 is Part VII of our work on this whale in the Southeast Pacific. There were 1105 female sperm whales in our sample collected from two whaling stations in Chile and two in Peru. Since have shown that they belonged to a single stock, we have worked them together. A second Graafian follicle develops more than the others in each ovary so to improve the possibility of fertilization in case the first ovum fails to be impregnated. We consider the size of the Graafian follicle at, or near, ovulation to be around 100mm, larger than what has been found in sperm whales from other seas. The corpus luteum of pregnancy is significantly larger than the corpus luteum of ovulation. The corpus albicans reduces in size throughout the life of the whale and probably does not disappear. There is a highly significant correlation between the total number of corpora and age: therefore we use the number of corpora as an indication of age. The corpora atretica are more frequent in older female sperm whales reflecting less fertility in this group. The sexual cycle in sperm whales of the Southeast Pacific has been revised to last 4yrs. Sexual maturity in female sperm whales is attained at 8.2m long and 6.5yrs of age, being both values lower than in sperm whales from other seas. The female sperm whale is born at 3.90m. The incidence of twins, 0.91%, is higher than in other seas. Fertility is low in very young whales (1-2 ovarian corpora) and it is at its lowest in the older group (over 12 corpora). The highest fertility is when females have 3-10 ovarian corpora and they are 15 to 35yrs old. The proportion of active females in pre oestrus during the months of pairing is significantly higher than during the other months. Accessory ovulations during oestrus are represented by the small groups of lactating-and-recently ovulated and lactating-and-pregnant whales. Unsuccessful ovulations are more frequent in late lactation and late resting periods, being post-partum ovulation rare. Female sperm whales in the Southeast Pacific may ovulate up to four and possibly five times during an oestrus. Physical maturity is attained at 11.2m long and 33.5yrs old. Fusion of the vertebrae begins at both ends of the vertebral column and finishes between the posterior thoracic and the lumbar vertebrae. Female sperm whales of the Southeast Pacific may live, at least, up to 50yrs of age. The age at recruitment between 1959 and 1962 was 20-21yrs of age when they had accumulated 4-5 corpora in their ovaries.
A central theme in ecology is the search for pattern in the response of a species to changing environmental conditions. Natural resource management and endangered species conservation require an understanding of density-dependent and density-independent factors that regulate populations. Marine mammal populations are expected to express density dependence in the same way as terrestrial mammals, but logistical difficulties in data acquisition for many large whale species have hindered attempts to identify population-regulation mechanisms. We explored relationships between body condition (inferred from patterns in blubber thickness) and per capita prey abundance, and between pregnancy rate and body condition in North Atlantic fin whales as environmental conditions and population size varied between 1967 and 2010. Blubber thickness in both males and females declined at low per capita prey availability, and in breeding-age females, pregnancy rate declined at low blubber thickness, demonstrating a density-dependent response of pregnancy to prey limitation mediated through body condition. To the best of our knowledge, this is the first time a quantitative relationship among per capita prey abundance, body condition, and pregnancy rate has been documented for whales. As longlived predators, marine mammals can act as indicators of the state of marine ecosystems. Improving our understanding of the relationships that link prey, body condition, and population parameters such as pregnancy rate and survival will become increasingly useful as these systems are affected by natural and anthropogenic change. Quantifying linkages among prey, fitness and vital rates will improve our ability to predict population consequences of subtle, sublethal impacts of ocean noise and other anthropogenic stressors.
Pregnancy rate and biomarker validations from the blubber of eastern North Pacific blue whales
Marine Mammal Science, 2019
Hormonal biomarkers are useful indicators of mammalian reproductive and metabolic states. The present study validated and applied the use of progesterone and cortisol blubber assays for studies of blue whales from the Gulf of California, Mexico. In a validation study for pregnancy detection, blubber progesterone concentrations were correlated with pregnancy status for four female blue whales: three resighted with a calf the year following sampling and the fourth stranded with a fetus. The progesterone concentrations were significantly higher than those measured in juvenile whales (n = 3). In the application study, blubber samples from blue whales (51 noncalf females, 2 female calves, 48 noncalf males, and 1 male calf) with known sighting histories were analyzed. Putative pregnant females had elevated progesterone concentrations. Cortisol concentrations did not differ between male and female blue whales, or among females in different reproductive classes. After correcting for uncertain ages, hence maturity status, the pregnancy rate of noncalf females was 33.4% (95% CI 32.2%-34.3%). Although interpretation of hormone biomarkers must consider all physiological states that may influence progesterone concentrations, these results demonstrate the utility of pairing hormone biomarkers with sighting histories to help assess environmental or anthropogenic impacts on reproduction in blue whales.
Marine Mammal Science, 2009
Reduced reproductive success has contributed to lack of recovery of the endangered western North Atlantic right whale (Eubalaena glacialis). Here we examined the specific life history period from just before birth through the first year to estimate calf and perinatal losses between 1989 and 2003. The lower bound estimate (17 mortalities from 208 calving events) included documented calf mortalities and presumed deaths from serious injury or disappearance from the sighting record. The upper bound estimated potential calf losses from females with delayed first parturition (>10 yr) and shortened (2 yr) or lengthened (≥4 yr) calving intervals, if the female migrated to the calving ground during these intervals. Because cows were sighted in the calving ground predominantly in years when they were available to calve, adult females sighted there in a possible calving year without a calf were assumed to have experienced a perinatal loss. Twenty-eight potential perinatal losses were detected, bringing the upper bound of calf and perinatal mortality to 45 (3.0 calves/yr). The high frequency of lengthened calving intervals in E. glacialis suggests that abortion and neonatal losses are contributing to lower reproductive success compared to Southern Hemisphere right whales (Eubalaena australis).
Assessing reproductive status of right whales (Eubalaena glacialis) using fecal hormone metabolites
General and Comparative Endocrinology, 2005
Long-term studies of the endangered North Atlantic right whale, Eubalaena glacialis, have revealed declining reproductive parameters over the past two decades, threatening recovery of this small population if current trends continue. Little is known about right whale reproductive physiology, and investigating this reproductive decline has been limited by a lack of non-lethal methods for assessing reproductive status (e.g., sexual maturation, ovarian activity, pregnancy, lactation, and reproductive senescence) in freeswimming whales. This paper describes validation of existing radioimmunoassay techniques to study reproduction in right whales by measuring estrogens, progestins, androgens, and their related metabolites in fecal samples. Over the past decade fecal steroid hormone assays have been used to assess reproductive status and function in a wide range of terrestrial wildlife species, but this is the first application of this methodology in wild cetaceans. Analysis of fecal hormone metabolite levels in combination with life history data from photographically identified whales shows that this non-invasive method can be used to determine gender, detect pregnancy and lactation, and to assess age at sexual maturity in right whales and potentially other endangered whale populations.
Endocrinological Observations of Female Minke Whales (Balaenoptera Acutorostrata)
Marine Mammal Science, 1996
Minke whales (Balaenoptera acutorostrata) are widely distributed in almost all oceans. Some investigators have described the female reproductive cycle of minke whales (IWC 1979, Best 1982, Kato and Miyashita 1991) and assumed that they have evolved a reproductive cycle of about one year in contrast to the usual two-year cycle in baleen whales with a gestation period of about one year and lactation lasting about half a year. Information on the reproductive cycle and the morphology of reproductive tract and on serum concentrations of steroid hormones in minke whales has been reported from samples obtained iii the Japanese antarctic research program (Kato and Miyashita 1991, Yoshioka and Aida 1991). However, no information is available concerning the composition of steroid hormones in follicular fluid and follicular oocytes in the minke whale. The objective of this study was to provide such information. Minke whales were sampled in the Antarctic Ocean (64 136 15 3 from February to March 1993 for the Japanese whale research program under Special Permit in the Antarctic (JARPA) organized by the Institute of Cetacean Research, Tokyo, Japan. Three pairs of ovaries (immature, early, and late pregnant; stages of early and late pregnancy distinguished by fetal length) were collected as fast as possible after death (within 2.5 h) and stored at-20°C. Blood samples from 31 female minke whales (immature and mature) were collected from the tip of the upper jaw, and the serum, collected after centrifugation at 3,000 rpm at 4°C for 10 min, was stored in glass tubes at-80°C. All samples were transported at-20°C to our laboratory, where the ovaries were thawed at 4°C overnight. Their weight and size and number of follicles, corpora lutea (CL), and corpora albicantia (CA) were recorded after thawing. All follicles and CL were removed from the ovaries, their diameters (follicle: means of three perpendicular measurements; CL: means of two perpendicular measurements) measured using sliding calipers, and the CL were weighed. Follicles were divided into three categories based on their diameters: small (~5 Help Volumes Main Menu Help Volumes Main Menu Help Volumes Main Menu Help Volumes Main Menu