CHANGES IN MORPHOLOGY WITH AGE IN MEDITERRANEAN MONK SEALS (MONACHUS MONACHUS)

In order to describe the pelage and external appearance of the Mediterranean monk seal ( Monachus monachus ) and prepare an age-sex classification guide, 120 seals from the Cabo Blanco Peninsula colony in the Western Sahara/Mauritania were periodically photographed between 1993 and 1996. Analysis of the pigmentation pattern, pelage color and pattern of natural markings of each seal established 48 phenetic types, which were, in turn, arranged in five groups (morphological classes) with multivariate cluster analysis (UPGMA). The variables that best define these groups are size and color. The variation related to relative size, sex and age of 26 identified seals monitored over three years showed that: (1) after each molt, external appearance varied considerably only in non-adults, while adult appearance was invariable; (2) marked sexual dimorphism exists in adults' external appearance; and (3) a remarkable similarity of adult and neonate pelage exists. With these results, we propose an age-sex classification guide to facilitate monk seal identification in the field.     

DIVING DEVELOPMENT AND BEHAVIOR OF A REHABILITATED MEDITERRANEAN MONK SEAL (MONACHUS MONACHUS)

Among the priority actions identified for saving the critically endangered Mediterranean monk seal are gaining basic biological information on movements and behavior, and rescuing and rehabilitating wounded, stranded, and orphaned pups. On 22 May 2004 a rehabilitated monk seal juvenile was fitted with a satellite tag, released in the National Marine Park of Alonnisos, Northern Sporades, Greece, and monitored for 167 d. Postrelease, the seal remained close to the islands of the park and within the 200-m isobath. Throughout the monitoring period, the seal reduced time hauled out, while 95-percentile dive duration and depth gradually increased. The overall maximum depth of 123 m recorded in this study is the greatest depth ever recorded for the species. These results confirm the effectiveness of the rehabilitation program carried out on the particular animal and provide additional support for the continuation of the rehabilitation program as a conservation measure for the species. We demonstrate that satellite tracking of rehabilitated seals is a valuable research and conservation tool, even for a species that commonly uses shoreline caves for resting, molting, and parturition.     

REPRODUCTIVE CYCLE OF THE FEMALE MEDITERRANEAN MONK SEAL IN THE WESTERN SAHARA

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.     

SURVIVAL RATES FOR THE HAWAIIAN MONK SEAL (MONACHUS SCHAUINSLANDI)

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.     

PUPPING HABITAT USE IN THE MEDITERRANEAN MONK SEAL: A LONG-TERM STUDY

The Mediterranean monk seal gives birth almost exclusively in coastal caves. Given its critical conservation status, the identification and protection of such sites is important for the survival of the species. From 1990 to 2004 we collected data on physical and environmental variables and monitored pupping events in thirty-four coastal caves in Greece. We modeled the probability of cave occupancy as a function of the properties of each cave. Model selection and model averaging enabled us to rank the variables that influenced use of potential pupping sites. Environmental variables related to cave seclusion, substrate, and degree of protection from wind and wave action were the most important among them. The relative importance and directions of these relationships confirm the long-standing assumption that Mediterranean monk seals require sheltered pupping sites, far from sources of human disturbance and thus are progressively limited to isolated parts of the country's coastline. We used cross-validation to examine the predictive ability of our analysis and quantified the sensitivity of our predictions to the degree of extrapolation. We conclude that, although more data are required, the model is capable of predicting occupancy for caves close to the middle of the environmental space examined in this study.     

EFFECTS OF RESEARCH HANDLING ON THE ENDANGERED HAWAIIAN MONK SEAL

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.     

MORPHOMETRY, HEMATOLOGY, AND SERUM CHEMISTRY IN THE HAWAIIAN MONK SEAL (MONACHUS SCHAUINSLANDI)

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.     

ANNUAL REPRODUCTIVE CYCLE OF THE FEMALE HAWAIIAN MONK SEAL (MONACHUS SCHAUINSLANDI)

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.     

HAWAIIAN MONK SEALS (MONACHUS SCHAUINSLANDI) FORAGING IN DEEP-WATER CORAL BEDS

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.     

FORAGING OF JUVENILE MONK SEALS AT FRENCH FRIGATE SHOALS, HAWAII

Emaciation and poor survivorship of juvenile Hawaiian monk seals at French Frigate Shoals atoll prompted a study of their foraging, using video camera technology ( crittercam ). Nine juveniles between the ages of 1 and 3 yr (six males, three females) were fitted with crittercam to identify their foraging habitat and feeding behavior. All feeding was directed at small (≤ 10 cm), cryptic, benthic prey. Older seals (ages 2 and 3), varied in their foraging intensity with most of their attention directed at shallow atoll depths (10–30 m). In contrast, the three yearlings focused all their feeding in the sand fields (50–100 m) on the atoll's outer slope. Bottom trawls were used to assess the prey abundance of the sand habitat and found 70% of the numerical catch was flounder ( Bothidae ). Extrapolating the yearlings' prey capture rate (0.13/min, derived from the crittercam video) over their total bottom time yielded an estimated 1–1.3 kg/day of flounder. The mean size of flounder (5 ± 1.7 cm) caught in the bottom trawls was close to the size at which larval flounder settle from the plankton (3 cm), suggesting that localized changes in oceanography could directly impact the seals' prey supply. Extensive use of sand communities by young seals may be the strongest link yet identified between juvenile survivorship and oceanographic dynamics.     

CONCENTRATIONS OF ESTRONE SULFATE and PROGESTERONE IN PLASMA and SALIVA, VAGINAL CYTOLOGY, and BIOELECTRIC IMPEDANCE DURING THE ESTROUS CYCLE OF THE HAWAIIAN MONK SEAL (MONACHUS SCHAUNSLAnDI)

Blood and saliva samples, vaginal swabs, and bioelectric impedance measurements were collected 1–3 times per week from a captive adult female Hawaiian monk seal ( Monacbus schauinslandi ) during the spring and summer of 1991. During 1992 saliva only was collected on average 4 times weekly. Concentrations of progesterone and estrone sulfate, and the periodic appearance of cornified epithelial cells from the vagina indicated consecutive estrous cycles ranging 35 ± 3 days in duration. Progesterone concentrations in plasma and saliva had a correlation of 0.868, while estrone sulfate had a correlation of 0.982. Bioimpedance of the whole seal body resulted in a pattern similar to the estrone sulfate concentrations, but shifted forward by 2 d. Bioimpedance of the upper vaginal tissues paralleled the estrone sulfate pattern while the bioimpedance of the lower reproductive tract fluctuated without a distinct pattern. The luteal phase ranged 17–20 d and the follicular phase was 15–18 d in length. These results indicate that: (1) the Hawaiian monk seal, in captivity, is a polyestrous seal, in contrast to other phocid seals that have been studied; (2) salivary concentrations of estrogen and progesterone may provide an accurate, less-invasive method of monitoring reproductive hormones in captive Hawaiian monk seals; and (3) vaginal cytology and bioelectric impedance reflect physiological changes associated with the estrous cycle.     

IMPROVED BODY CONDITION OF WEANED HAWAIIAN MONK SEAL PUPS ASSOCIATED WITH EL Niño EVENTS: POTENTIAL BENEFITS TO AN ENDANGERED SPECIES

Efforts to enhance recovery of endangered Hawaiian monk seals ( Monachus schauinslandi ) require an understanding of factors influencing population dynamics. This study examines relationships between body condition and survival of monk seal pups at French Frigate Shoals and Laysan Island and El Niño events. Girth measurements and mass estimates were used as indicators of pup body condition, and survival was evaluated from weaning to age 2. Linear models and logistic regression analysis were used to evaluate El Niño effects. Temporal trends in mean girth, mass, and survival were identified at both study sites. After accounting for temporal trends, girths were 3.7 cm and 2.7 cm greater during El Niño years at French Frigate Shoals and Laysan Island, respectively. Average mass estimates were significantly greater during El Niño years at French Frigate Shoals (2.6 kg increase), but were not significantly different at Laysan Island (1.8 kg increase). Weaned pups born at French Frigate Shoals during El Niño years survived significantly better, but this effect was not detected at Laysan Island. El Niño events probably affect pup condition and survival, but these parameters need to be monitored during future El Niño events to clarify these relationships.     

PUP PRODUCTION AND POPULATION TRENDS OF THE AUSTRALIAN FUR SEAL (ARCTOCEPHALUS PUSILLUS DORIFERUS)

We estimated the number of live Australian fur seal pups using capture-markresights, direct ground counts, or aerial photography at all breeding sites following the pupping season of November-December 2002. Pups were recorded at 17 locations; nine previously known colony sites, one newly recognized colony and seven haul-out sites where pups are occasionally born. In order of size, the colonies were Lady Julia Percy Island (5,899 pups), Seal Rocks (4,882), The Skerries (2,486), Judgment Rocks (2,427), Kanowna Island (2,301), Moriarty Rocks (1,007), Reid Rocks (384), West Moncoeur Island (257), and Tenth Island (124). The newly recognized site was Rag Island, in the Cliffy Group, where we recorded 30 pups. We also recorded pups at the following haul-out sites: Cape Bridge-water (7 pups), Bull Rock (7), Wright Rock (5), Twin Islet (1), The Friars (1), He des Phoques (1), and Montague Island (1). In total, we estimate there were 19,819 (SE = 163) live pups at the time of the counts. We discuss trends in pup numbers and derive current population estimates for the Australian fur seal.     

CLIMATE CHANGE AND RINGED SEAL (PHOCA HISPIDA) RECRUITMENT IN WESTERN HUDSON BAY

Climate warming is predicted to reduce the extent of ice cover in the Arctic and, within the Hudson Bay region, the annual ice may be significantly decreased or entirely lost in the foreseeable future. The ringed seal ( Phoca hispida ), a key species that depends on sea ice, will likely be among the first marine mammals to show the negative effects of climatic warming. We used 639 ringed seals killed by Inuit hunters from western Hudson Bay (1991–1992, 1999–2001) to assess trends in recruitment relative to snow depth, snowfall, rainfall, temperature in April and May, North Atlantic Oscillation (NAO) from the previous winter, and timing of spring break-up. Snowfall and ringed seal recruitment varied from lower than average in the 1970s, to higher in 1980s and lower in 1990s. Prior to 1990, seal recruitment appeared to be related to timing of spring ice break-up which was correlated with the NAO. However, recent 1990–2001 environmental data indicate less snowfall, lower snow depth, and warmer temperatures in April and May when pups are born and nursed. Decreased snow depth, particularly below 32 cm, corresponded with a significant decrease in ringed seal recruitment as indicated by pups born and surviving to adults that were later harvested. Earlier spring break-up of sea ice together with snow trends suggest continued low pup survival in western Hudson Bay.     

THE MAXIMUM RANGE OF VOCAL COMMUNICATION IN AIR BETWEEN A HARBOR SEAL (PHOCA VITULINA) PUP AND ITS MOTHER

Abstract: The transmission losses with distance of four pure tones (0.5, 1, 2, 4 kHz) were measured in the air 9 cm above the surface of the coastal waters in the Bay of Fundy. The study was conducted between May and July 1992, on warm days with low winds. The measured transmission losses were as much as 11 dB less than predicted by spherical spreading (6 dB/distance doubled), at 400 m (0.5 kHz). This enhanced sound transmission is probably due to the air temperature profile which increases with height above the water's surface. Such a profile causes sound waves to refract towards the water, thereby reducing spreading losses. High-frequency sound absorption negates enhanced transmission at 4 kHz, at distances over 500 m. On days with low winds and low ambient noise levels, a seal pup calling at 90 dB re 20, μPa at 0.5 kHz should be detectable by the mother up to 1 km away, and may be audibly recognizable up to 140 m away.