Direct observation of 387 embryos in the early stages of development was combined with observations on breeding behaviour and reproductive biology obtained from the published literature, to estimate the timing of births, oestrus, ovulation and implantation, and to derive estimates of the duration of pregnancy, embryonic diapause and active gestation for crabeater seals (Lobodon carcinophagus). The total duration of pregnancy (conception to birth) is estimated to be 11.3 months (344 days). It is estimated that the pupping season extends from late September to early November, with peak births in mid-October. The estimated mean duration of lactation is approximately 17 days; the mean date of weaning is 31 October (14 October to 17 November); and the mean date of conception is 4 November (18 October to 21 November). Oestrus, ovulation and conception occur approximately 4 days after weaning. Estimates of times of weaning and conception were made assuming that the preimplantation period is the same in all individuals. The mean date of implantation of the embryo is 24 January+/-17 days; the duration of embryonic diapause is 2.7 months (81 days); and the duration of active gestation (implantation to parturition) is 8.8 months (264 days).

Growth in length and weight of a large sample of crabeater seals Lobodon carcinophagus collected over the period 1967-78 is reported. Growth in dorsal standard length of 1146 seals (490 males, 656 females) from 0.5 to 20 years of age was similar to the pattern seen in other phocid seals. Length was plotted against age and Gompertz curves fitted to the data. Growth rates were estimated from the derived equations: males, y=231.9-58.7 e(-0.55t); females, y=236.8-63.6 e(-0.44t). The asymptote is at approximate length 234 cm and age 10 years in both males and females. Body weights were recorded for 249 seals aged from 0.5 to 20 years, of which reliable age estimates for 230 (100 males, 130 females) were available. Rates of growth in body weight were estimated from the derived equations: males, y=200.0-94.1 e(-0.48t); females y=212.4-116.2 e(-1.40t). The best estimate of body weight from linear body measurements is obtainable from a predictive equation relating body weight, length and axillary girth, determined by maximum likelihood: W=0.000046 LG(2) (W, body weight; L, dorsal standard length; G, axillary girth). There was no significant difference between the sexes. Seasonal variations in body condition could not be determined because all animals were sampled in February and March. However, inter-year differences in recovery of body condition of adults, following the demands of breeding and moulting in the spring and summer, were observed. The data represent a unique time series covering the 1960s and 1970s. In terms of global climate change they should provide a valuable baseline for future studies.

Geographic variation was observed in skulls of several otariid species, with a general change in size corresponding with a change in latitude and primary productivity. The largest specimens were from cool temperate localities, conforming mostly to Rensch's rule. Skulls of Australian sea lions from Western Australia were generally smaller in condylobasal length, but were more robust than those from South Australia. The subantarctic fur seal did not conform to Bergmann's rule: skulls from Amsterdam Island (37degrees55'S) were largest, those from Gough Island (40degrees20'S) intermediate and those from Marion Island (46degrees55'S) the smallest. For both sexes, skulls of southern sea lions from the Falkland Islands were smaller than their equivalents from mainland South America. Similarly, skulls of South African fur seals from south-east South Africa appeared smaller than those from the west coast of South Africa and Namibia; skulls from Namibia grouped separately from those of south-east and west coast, South Africa. We postulate that the Otariidae are in the process of species divergence, much of which may be driven by local factors, particularly latitude and resources.

The age of crabeater seals Lobodon carcinophagus was first estimated from the teeth by counting layers in the dentine in transverse sections of the canine teeth. Reliable estimation of age from canine teeth in animals older than c. 10 years is not possible because of root closure at a relatively early age. The present investigation compared various methods of estimating age by examination of tooth sections from a large sample of crabeater seals from Marguerite Bay, Antarctic Peninsula. The most reliable estimations were shown to be obtained by counting layers in the cementum of the third postcanine tooth. Ages of 1233 animals (58% female, 42% male) ranged from 0.5 to 39 years. It is suggested that time- and age-specific historical material is potentially relevant for contemporary growth and life-history studies as well as for trophic relations or concentrations of pollutants in animal tissues.

Observations of humpback whale song in various parts of the world have shown that the song is a complex sequence of sounds that at any time is stereotyped within a geographical stock but differs between stocks. The song changes with time at a variable rate, usually in a gradual and evolutionary fashion. This paper reports observations of song change that differ from anything previously observed. A completely new song appeared spontaneously in a small number of singers in the east Australian stock, increasing in prevalence to completely replace the original song within two years. The two songs coexisted in the population for this period but individual singers generally produced one song or the other, with few occurrences of an intermediate variety. The new song was found to be the same as that observed off Western Australia. Previous comparisons have shown the east and west coast songs to be unrelated despite a small amount of interchange between the two stocks. The rapid rise to dominance of an introduced song indicates that song change is not necessarily evolutionary, gradual, or internally driven.

Humpbacks have picked up a catchy tune sung by immigrants from a distant ocean. The song patterns of humpback whales (Megaptera novaeangliae) depend on where they live, with populations inhabiting different ocean basins normally singing quite distinct songs. Here we record a unique and radical song change in the song of humpback whales in the Pacific Ocean off the Australian east coast. Their song was replaced rapidly and completely by the song of the Australian west coast population from the Indian Ocean, apparently as a result of the introduction of only a small number of 'foreign' singers. Such a revolutionary change is unprecedented in animal cultural vocal traditions and suggests that novelty may stimulate change in humpback whale songs.

Marine Mammal ScienceVolume 15, Issue 4 p. 1370-1373 STONES IN THE STOMACHS OF SOUTHERN ELEPHANT SEALS1 M. M. Bryden, M. M. Bryden Department of Veterinary Anatomy and Pathology, University of Sydney, New South Wales 2006, Australia; e-mail: [email protected]Search for more papers by this author M. M. Bryden, M. M. Bryden Department of Veterinary Anatomy and Pathology, University of Sydney, New South Wales 2006, Australia; e-mail: [email protected]Search for more papers by this author First published: 26 August 2006 https://doi.org/10.1111/j.1748-7692.1999.tb00900.xCitations: 3 1 Dedicated to Dr. Ken Norris, outstanding scientist and valued friend. We were fortunate to have several visits by him to Australia, enabling virtually all marine mammalogists in this country to benefit from his infectious enthusiasm, energy, and insight. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume15, Issue4October 1999Pages 1370-1373 RelatedInformation

Southern elephant seals, Mirounga leonina L., do not inhabit the northwest coast of Tasmania today, but archaeological evidence indicates that they did so in prehistoric times, when they constituted an important food resource to the Aboriginal tribes of the region. Skeletal remains of at least 300 elephant seals were present in one midden alone. There is distinct sexual dimorphism in the canine teeth of elephant seals, and regular seasonal variations in the density of concentric layers of calcified dentine, as well as the pattern of these variations, provide insight into the age and reproductive history of individual animals. The sectioned canine teeth of 145 southern elephant seals (107 females, 38 males) from a Tasmanian midden were examined to provide information on the age and sex of the seals as well as aspects of their reproductive history. The age distributions differed between the sexes, and partly explain the different frequencies of males and females. All the males were young, immature individuals, none more than 6 years old, which is about the age at which a secondary growth spurt occurs in males and results in a marked sexual disparity in body size. By contrast, 47% of the females were of breeding age, 26% had given birth to pups, and several were up to 20 years of age. At least 26% of animals were estimated to be less than 3 months old, the approximate age at which they go to sea for the first time, confirming that they were born on the northwest Tasmanian coast. Animals were killed throughout the year, and there is evidence of change in reproductive pattern over time, consistent with a response to predation pressure. The evidence points to the conclusion that the population was exterminated by Aboriginal hunters, through selective exploitation of smaller animals, which included significant numbers of breeding females. Copyright © 1999 John Wiley & Sons, Ltd.

The inert marker titanium dioxide was added to the food of two male New Zealand fur seals (Arctocephalus forsteri) and three Australian sea lions (Neophoca cinerea) in Taronga Zoo, Sydney, in a series of 15 trials. The enclosures were checked constantly during daylight hours, and defaecation times and location of samples noted. Samples were collected at feeding times, at approximately 0930, 1300 and 1500 hours. During the night the animals were checked at 30-min intervals, the location of samples noted, and samples collected at the first feeding time next morning. Faecal collections were made for up to 50 h after dosing. Marker concentrations in faecal dry matter were determined and mean retention times calculated from the mean concentration-time curves. The mean time between dosing and first recovery of marker (Initial Recovery Time) was 4 h for A. forsteri and 6.5 h for N. cinerea. Mean retention time, a better index of rate of passage of digesta, was 14.6 h for A. forsteri and 14.9 h for N. cinerea. Thus, the marker concentration curves indicated a rapid rate of food transit through the gastrointestinal tract, as has been observed in several (but not all) pinniped species.

The spatial distribution of leopard seals along the fast-ice edge in the austral spring and summer of 1992 and 1993 in Prydz Bay, Antarctica, was determined by aerial surveys. Fewer individuals were observed within the area, and the seals observed were larger, in 1992 than in 1993. Comparison of the distributions and relative sizes of the seals suggests that there may be an age-related difference in spatial behavior. The greater degree of separation among older seals may be due to intraspecific aggression increasing with age, a hypothesis supported by the high incidence of intraspecific scarring noted on leopard seals in this region. The seals' haul-out behavior was negatively related to wind-chill index.

The duration and timing of coastal residence of individually identified southern right whales at a principal aggregation area on the southern Australian coast differed markedly between females with calves and unaccompanied whales. The mean residence period of females that calved within the aggregation area was 70.9 days, with mean residence mid‐points of 20 August in 1993 and 22 August in 1994. In contrast, unaccompanied adults remained resident for an average of only 20.4 days with mean residence mid‐points of 27 July and 11 August in 1993 and 1994, respectively. Whales have been sighted at this aggregation area from mid May to late October (approx. 160 days), although the effective calving season (95‐100% of calves born) lasted only 88 days in 1993 and 96 days in 1994. The mean birth date based on first sighting with neonatal calf, and corrected for sightability bias, was 15 July in 1993 and 17 July in 1994, with 100% of calves born before 31 August 1993 and 23 September 1994.The time between birth and dispersal from the aggregation area, at or just prior to the commencement of the southward migration, was highly variable. Calves bom before the mean calving date averaged 80 days within the aggregation area, twice as long as those born after the mean (40 days). The large number of calves estimated to be less than 14 days old at first sighting, combined with the sighting of 26 pregnant females prior to parturition, suggests the majority of births occurred within, or very near to, the aggregation area.

AbstractTwo groups of underwater vocalizations were identified in a three‐year study of two captive leopard seals, Hydurga leptonyx (one female and one male at Taronga Zoo, Sydney). This was supplemented by recordings over three months from a male at Marineland, New Zealand. The sexual state of the seals at Taronga was deduced from serum hormonal concentrations: the female was considered to be in estrus at specific times during the breeding season. The seal at Marineland, New Zealand was assumed to be sexually mature on the basis of size and age. Of 12 different underwater sound types recorded, six were produced by the seals at Taronga Zoo during agonistic interactions (local calls) and were heard through most of the year. The other six sound types were produced by lone seals. These broadcast calls were produced by the female only when sexually receptive, and by the mature male during December and January, months believed to be the breeding season of wild leopard seals. We propose that underwater acoustic behavior is important in the mating system of this species, and that broadcast calls are used by mature females to advertise their sexual receptivity, and possibly by mature males in search of mates.

The behaviour of leopard seals, Hydrurga leptonyx, feeding on Adélie penguins, Pygoscelis adeliae, was investigated between November 1993 and January 1994 in Prydz Bay, Antarctica. The seals were distributed along the fast-ice edge in locations where departing penguins congregated. Five different hunting techniques were observed, four of which were used through most of the summer. Individual leopard seals favoured specific hunting techniques. Hitherto, penguin hunting was believed to be carried out primarily by a few male seals; in this study, however, the predation observed involved many different individuals of both sexes. It is estimated that six leopard seals feeding in this area over a period of 120 days would consume 2.7% of the adult penguin population.

We present a new sound type recorded from bottlenose dolphins, Tursiops truncatus, in eastern Australian waters: low-frequency, narrow-band (LFN) harmonic sounds (defined as less than 2 kHz). Most of these sounds were of frequencies less than 1 kHz and were recorded commonly from socializing dolphins. These sounds differ significantly from narrow-band whistles, which are higher in frequency and longer in duration. The absence of these sounds in most studies of the acoustic behavior of bottlenose dolphins may reflect geographic differences in repertoires or result from insufficient sampling. Alternatively, these sounds may have been ignored where the focus of research was on other sound types.

Existing population models for humpback whales assume that all individuals within a population under take the annual migration from feeding areas in high latitudes to breeding areas in tropical waters. An excess of males was recorded in the commercial whaling catches near breeding areas in the southern hemisphere, but no account of this was taken in developing population models, because it was believed that this bias was a result of whalers selecting against females with young calves. Here we demonstrate that the sex ratio of migrating humpback whales near a breeding area is highly skewed towards males. A biopsy study carried out in 1992 throughout the northward and southward migrations revealed a sex ratio of 2.4 males:1 female in the population of humpback whales migrating along the east Australian coast (n = 180). A reanalysis of the catches made during commercial whaling in this and other areas of the southern hemisphere gave a sex ratio of the same order. The most plausible explanation, supported by some evidence, is that some females remain in the feeding areas throughout winter. The results reported here show that existing management models require major revision to take account of these findings.

AbstractThe response of migrating humpback whales to biopsy sampling was investigated off North Stradbroke Island, South East Queensland. Whales were allocated a behavioral category prior to biopsy sampling according to the general behavior of their pod. Behavioral reactions were recorded after each attempt. Sex was determined using a molecular genetic technique.Detectable reactions occurred in 41.6% of successful biopsy attempts, a significantly lower response rate than that reported by two studies carried out on the feeding and breeding grounds of the North Atlantic. There was no difference in the response rate of whales on their northward or southward migration. Pod size was not an important factor in predicting the response of an individual. Females responded to biopsy sampling at a significantly higher rate than males.Our results indicate that a substantial difference in response rate can occur between studies. Factors such as the type of boat used and the prior exposure of whales to human impact may be of importance. Our study suggests that female humpback whales may be particularly responsive to human disturbances. Overall, however, biopsy sampling has minimal impact on humpback whales.

The inert markers chromium‐EDTA (liquid phase marker) and ytterbium nitrate (solid phase marker) were added to the food of three southern elephant seals in Taronga Zoo, Sydney, in a series of nine trials. The enclosures were checked at 15 to 30 minute intervals for up to 60 hours after dosing, and all faeces voided on land were collected (91 samples). Marker concentrations in faecal dry matter were determined and mean retention times calculated from the concentration‐time curves.The faeces were soft to semiliquid, with mean water content of 58% (range 24–80%). The marker concentration curves indicated a rapid rate of food transit through the gastro‐intestinal tract in elephant seals compared with other carnivores. The mean time between dosing and first recovery of marker (Initial Recovery Time) was nine hours. This was significantly longer than the figure of 4.8 hours for northern elephant seals reported previously, and possible reasons for the differences are discussed. Mean Retention Time, a better index of rate of passage of ingesta, was 13 hours for the three southern elephant seals. This compares with times of 22 hours for the dog, 15 hours for the raccoon, and 13 hours for the cat, all carnivores with much shorter gastrointestinal tracts, both absolutely and relative to body size, than the southern elephant seal.It is suggested that the very long small intestine may be an adaptation to foraging at depth, combined with long periods of submergence and the need to ingest large amounts of food when the animal is at sea continuously for weeks or months.

The development of pineal function in northern elephant seals was examined in an attempt to understand the physiological basis for previously observed high daytime levels of melatonin in neonatal southern elephant seals. Pineal glands from four northern elephant seal pups, estimated age less than 1 week, weighted 3.0 +/- 0.80 g, which was significantly less than that previously found in southern elephant seals (4.6 +/- 0.35 g). Midday concentrations of plasma melatonin in pups averaged more than 3000 pmol/l in the first 5 days post-partum, but declined rapidly to less than 400 pmol/l after day 9. Daytime melatonin levels in northern elephant seals tended to be lower than in southern elephant seals, although they were very high compared with other species. A circadian cycle of plasma melatonin concentration was observed in newborn northern elephant seals, with levels of 3000-5000 pmol/l during the day, rising to more than 10,000 pmol/l late in the dark phase. Soon after weaning at 4 weeks of age, daytime and night-time levels were in the range 60-100 pmol/l and 100-400 pmol/l, respectively. When approximately 10 weeks old, most samples were in the range 100-400 pmol/l with no discernible difference between day and night levels. The results do not support the hypothesis that the pineal gland is involved in thermogenesis in new-born southern elephant seals. Instead, the very active pineal gland may contribute to energy conservation, by lowering body temperature, particularly at night. As physical insulation is acquired by the deposition of blubber, the mechanism is not required and melatonin falls to adult levels.