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1.
Abstract: The annual reproductive cycle is described for the adult female Hawaiian monk seal ( Monachus schauinslandi ) from data collected at Laysan Island (1982–1991) and Lisianski Island (1982–1983) in the Northwestern Hawaiian Islands. Pupping, lactation, weaning, and molting were directly observed, while mating was rarely observed and was, therefore, inferred from the occurrence of mounting injuries and from adult male and female association patterns. Pooled birth rates during the study period were 0.544 for all adult-sized females and 0.675 for females parous in earlier years. For parturient females, pupping peaked in late March and early April, weaning in May, mounting injuries in May and June, and molting in July. For non-parturient females, the median mounting injury and molting dates occurred 17 and 28 days earlier, respectively. Pupping date set the timing of subsequent events in the annual cycle, but the timing of those events was adjusted by loss of the pup or poor physical condition of the female. Individual pupping patterns varied widely. The mean interval for births in consecutive years was 381 days; females that pupped in consecutive years gave birth later each season. Conversely, females who skipped a year or more gave birth earlier their next pupping season.  相似文献   

2.
Abstract: Endangered Hawaiian monk seal ( Monachs schauinslandi ) pups at all the major breeding islands in the Northwestern Hawaiian Islands have been tagged since the early 1980s. Pups were double flipper tagged as soon as possible post-weaning. With few exceptions, an extensive tag resighting effort was conducted annually at the same islands. These resighting data were used to estimate seal survival rates from the time of tagging to age one at all locations using the ratio of seals alive in the second year to number of pups tagged. These survival rates among the islands, from weaning to age one, averaged over the years of the study, ranged from 0.80 to 0.90. For young seals over age one, capture-recapture methods were used to calculate survival pooled through several years, and these rates ranged from 0.85 to 0.98. At French Frigate Shoals and Laysan Island, the higher numbers of tagged pups allowed separate estimates of male and female survival to be calculated. These rates suggested that survival of immature females was better than males. Beginning in 1989, survival of immature seals at French Frigate Shoals declined sharply.  相似文献   

3.
Ovaries from 14 female Hawaiian monk seals, O-24 yr of age, collected from the northwestern Hawaiian Islands were analyzed by gross and histological examination for the presence of corpora hemorrhagica (CH), lutea (CL), albicantia (CA), and dominant follicles. Seven seals, 5-24 yr of age, were mature females, and another seven seals, O-5 yr of age, were immature based on the presence or absence of CL and CA in the ovaries. Two 5-yr-old seals did not have CL and CA, but one J-yr-old and both 6-yr-old seals had CL or CA. In addition, the weight of the more active ovary increased at 5 yr of age, indicating that puberty in these female Hawaiian monk seals occurred about 5 yr of age. The total number of CL and CA was significantly correlated to the ovarian weight, but not age of the seals, indicating that visible CA of Hawaiian monk seals probably degenerate within a year. If an ovulation resulted in pregnancy, we assumed that the resulting CL from that pregnancy persisted throughout gestation and regressed approximately 2 yr after ovulation. However, the CL of pregnancy were not easily differentiated from cyclic CL that did not result in pregnancy. Four of seven mature seals were clearly polyestrous from the analyses of their ovaries and reproductive histories. The remaining three seals were pregnant in previous consecutive years, and we could not positively determine whether they were also polyestrous. The ovaries from Hawaiian monk seals had unusually large, rounded granular cells containing the aging pigment, lipofuscin. These cells were located between loose fibrous tissues in all regressing CL and CA but were not present in any CH.  相似文献   

4.
EFFECTS OF RESEARCH HANDLING ON THE ENDANGERED HAWAIIAN MONK SEAL   总被引:2,自引:0,他引:2  
We examined the effects of research handling on free-ranging endangered Hawaiian monk seals, Monachus schauinslandi , by analyzing differences in subsequent year survival, migration, and condition between handled seals and controls during 1983–1998. Each of 549 handled seals was matched to a control seal of the same age, sex, location, and year. Handling included instrumentation with tel metry devices ( n = 93), blood sampling ( n = 19), and tagging ( n = 437). No significant differences were found between handled seals and their controls in one-year resighting rates, observed migration rates, or condition. Resighting rates of handled and control seals were high (80%-100%). Available sample sizes were sufficient to detect reasonably small (9%-20%) differences in resighting rates had they existed among instrumented or tagged seals and controls (α= 0.05, power = 0.90). Too few seals were captured for blood sampling to detect even large differences in their resighting rates. However, blood samples were drawn from most instrumented seals, and there was no indication that this larger group suffered harmful effects. Duration of restraint during flipper tagging had no effect on subsequent probability of resighting. Our analysis suggests that conservative selection procedures and careful handling techniques have no deleterious effects on Hawaiian monk seals.  相似文献   

5.
In the mid 1980s half of the entire Hawaiian monk seal species was located at French Frigate Shoals, and this colony may have reached environmental carrying capacity. Since 1989 this colony has declined by 55%, primarily from poor juvenile survival. Only 8%–25% of weaned pups have survived to age 2 during this period, compared to at least 80% between 1984 and 1987. We characterize (1) this drop in survival, (2) a strong, but variable, correlation between survival and size at weaning, (3) interisland differences in size from weaning to age 2 in 1991 through 1993, and (4) decadal-scale changes in mean measures of size at weaning. We compare observations at French Frigate Shoals with the colony at Laysan Island where abundance is well below historical levels and was therefore expected to be below carrying capacity. At Laysan Island juvenile survival has also been poor (30%-70%), and the size of weaned pups has decreased during the past decade. Our hypothesis is that poor survival may be due to reduced prey availability at both sites, but particularly at French Frigate Shoals. Evidence to support this hypothesis includes a large increase in total abundance at French Frigate Shoals; reduced size of weaned pups; decreased survival, emaciation, and slower growth rates of juvenile seals; and declining primary productivity. Regardless of cause, the immediate consequences at French Frigate Shoals and Laysan Island, and for the species overall, will likely be poor recruitment and productivity. Because the decline is still in progress, the ultimate consequences for the species' viability are of great concern in light of its already low abundance.  相似文献   

6.
We studied morphometric, hematology, and serum chemistry variables in 140 Hawaiian monk seals ( Monachus schauinslandi ) to establish normal baseline values for these variables among free-living seals. We compared seals at French Frigate Shoals (FFS), Midway Atoll (MID), and Pearl and Hermes Reef (PHR) because these subpopulations differ in their rates of population recovery. Dorsal standard length and axillary girth differed significantly between immature (1–4 yr old) and adult (≥5 yr old) seals among sex and island subgroups. Immature seals at FFS were shorter than those at MID and PHR; adult seals at FFS had smaller dorsal standard lengths and axillary girths compared to the other subpopulations. The differences in size were more pronounced among adult females. Significant differences were also found for hematology and serum chemistry variables among seals at FFS, MID, and PHR. Monk seals at FFS had an absolute lymphopenia and eosinopenia compared to those at MID and PHR, compatible with a stress response. Seals at FFS also had lower blood urea nitrogen than seals at PHR, and a lower plasma potassium than seals at MID or PHR. Monk seals had an absolute and relative eosinophilia compared to previously published values. Analysis of subpopulation differences is useful for population health assessment and for long-term monitoring of an endangered species.  相似文献   

7.
Plans to harvest deep-water corals in the remote Northwestern Hawaiian Islands, close to populations of endangered Hawaiian monk seals ( Monachus schauinslandi ), have raised concerns about the seals' use of deep-water habitats. Movements and diving patterns of seals studied at French Frigate Shoals (FFS) Atoll indicated two areas where five males out of 33 instrumented seals dove deep enough (300–500 m) to encounter commercially sought deep-water corals. Submarine surveys conducted at each location found beds of gold ( Gerurdia sp.) and pink ( Corallium sp.) precious coral suggesting an overlap between the foraging habitat of some seals and the target of the coral fishery. Areas adjacent to the coral beds that were visually censused using submersibles showed significantly fewer precious corals. Precious coral beds were not found on previous submarine surveys at other regions around FFS, supporting the notion that seals were selecting the areas with corals as forage habitat. Five male seals were fitted with back-mounted video cameras to document feeding among precious corals. None of the five seals dove deep enough to encounter precious corals (>300 m). However, three of the seals visited beds of black coral ( Cirrhipdhes sp.) at shallower depths (∼ 80 m). One seal was observed revisiting the black coral beds on three successive nights to feed on fish hiding among the coral stems.  相似文献   

8.
Mediterranean monk seals at Cap Blanc, western Sahara, pup annually throughout the year, although births are more frequent in autumn (October). Consequently, subsequent events of the cycle are not seasonal. This lack of synchronicity in reproduction can be attributed to the subtropical location of the colony and the presence of a semipermanent upwelling in the area. This contrasts with the consistency in the timing of parturition of individual females, which results in an interbirth period of one year, which varies by a maximum of only 15 d. The duration of lactation, which can last up to five months, correlates with that of the interbirth period. The interbirth and "molt-to-parturition" periods are relatively constant, and the only part of the cycle that appears to compensate for variation in lactation length is the "weaning-to-molt" period, which correlates negatively with the duration of lactation. As a result of the long lactation period, esrrus probably does not occur at the end of weaning, as it does in most other phocids.  相似文献   

9.
We surveyed pup survival in Mediterranean monk seals ( Monachus monachus ), at Cabo Blanco Peninsula (Western Sahara-Mauritania) colony from May 1993 to December 1997. This species breeds and hauls out on beaches inside two main caves. During the study period we detected a total of 93 pups that died or disappeared. The survival rate of 84 pups through the age of first moult (approximately two months) was 0.47. This value is similar to those reported for other pinnipeds breeding in caves but lower than for those breeding on open beaches. Mortality varied seasonally and appeared to increase as a result of storms, large ocean swells, and high tides. Mother-pup pair separation (and resulting pup starvation) and physical injury caused by impact against the rock walls of the cave and cliffs were established as the causes of most deaths. Beach surface area inside the caves also appeared to be a mediating factor in the effects of sea conditions. High pup mortality may be a limiting growth factor in this population, although cave dwelling protects the population from predators and human disturbance.  相似文献   

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