Segui questo link per vedere altri tipi di pubblicazioni sul tema: Southern fur seals Ecology South Africa.
Articoli di riviste sul tema "Southern fur seals Ecology South Africa"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-30 articoli di riviste per l'attività di ricerca sul tema "Southern fur seals Ecology South Africa".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi gli articoli di riviste di molte aree scientifiche e compila una bibliografia corretta.
1
Brunner, S., P. D. Shaughnessy e M. M. Bryden. "Geographic variation in skull characters of fur seals and sea lions (family Otariidae)". Australian Journal of Zoology 50, n. 4 (2002): 415. http://dx.doi.org/10.1071/zo01056.
Testo completoAbstract (sommario):
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 (37�55´S) were largest, those from Gough Island (40�20´S) intermediate and those from Marion Island (46�55´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.
2
Kirkman, S. P., D. P. Costa, A. L. Harrison, P. G. H. Kotze, W. H. Oosthuizen, M. Weise, J. A. Botha e J. P. Y. Arnould. "Dive behaviour and foraging effort of female Cape fur seals Arctocephalus pusillus pusillus". Royal Society Open Science 6, n. 10 (ottobre 2019): 191369. http://dx.doi.org/10.1098/rsos.191369.
Testo completoAbstract (sommario):
While marine top predators can play a critical role in ecosystem structure and dynamics through their effects on prey populations, how the predators function in this role is often not well understood. In the Benguela region of southern Africa, the Cape fur seal ( Arctocephalus pusillus pusillus ) population constitutes the largest marine top predator biomass, but little is known of its foraging ecology other than its diet and some preliminary dive records. Dive information was obtained from 32 adult females instrumented with dive recorders at the Kleinsee colony (29°34.17′ S, 16°59.80′ E) in South Africa during 2006–2008. Most dives were in the depth range of epipelagic prey species (less than 50 m deep) and at night, reflecting the reliance of Cape fur seals on small, vertically migrating, schooling prey. However, most females also performed benthic dives, and benthic diving was prevalent in some individuals. Benthic diving was significantly associated with the frequency with which females exceeded their aerobic dive limit. The greater putative costs of benthic diving highlight the potential detrimental effects to Cape fur seals of well-documented changes in the availability of epipelagic prey species in the Benguela.
3
Brunner, S. "Cranial morphometrics of the southern fur seals Arctocephalus forsteri and A. pusillus (Carnivora : Otariidae)". Australian Journal of Zoology 46, n. 1 (1998): 67. http://dx.doi.org/10.1071/zo97020.
Testo completoAbstract (sommario):
The identification and classification of unknown specimens of Arctocephalus from regions of Australasia has proven difficult. Skulls from the New Zealand fur seal (Arctocephalus forsteri) and the Australian fur seal (A. pusillus doriferus), and data from specimens of the South African fur seal (A. p. pusillus), were examined. A visual method was devised to identify and separate A. p. doriferus from A. forsteri for both sexes and for most physiological age-groups. A statistical method for morphometric separation of these species was applied to adult specimens. Characteristics of males and females for both species fell into two broad categories: sexually dimorphic – mainly those characters that increase the ability of males to hold and defend territories; and non-dimorphic – those of functional importance. Studies of geographical variation showed that adult male A. forsteri from Australia were generally larger than those from Macquarie Island and New Zealand. Characteristics of A. p. doriferus were generally larger than those of A. p. pusillus. Nine specimens of New Zealand fur seals were morphologically different from the typical A. forsteri, which indicates the presence of extreme outliers or hybrids in the sample.
4
Botha, JA, SP Kirkman, JPY Arnould, AT Lombard, GJG Hofmeyr, MA Meÿer, PGH Kotze e PA Pistorius. "Geographic variation in at-sea movements, habitat use and diving behaviour of female Cape fur seals". Marine Ecology Progress Series 649 (10 settembre 2020): 201–18. http://dx.doi.org/10.3354/meps13446.
Testo completoAbstract (sommario):
Knowledge of animal foraging behaviour has implications for management and conservation. While Cape fur seals Arctocephalus pusillus pusillus comprise a major proportion of the southern African marine predator biomass, little is known about their at-sea movements. We investigated foraging distribution, habitat use and diving behaviour for 35 adult female Cape fur seals from 3 breeding colonies experiencing contrasting oceanographic regimes. Animals from Black Rocks, the smallest and eastern-most colony, undertook shorter foraging trips and utilised shallower waters over the shelf. In comparison, animals from the larger west coast colonies, at Kleinsee and False Bay, travelled further and utilised deeper shelf and shelf-slope waters. However, across colonies, females typically preferred depths of <500 m and slopes of <5°. Kleinsee and False Bay seals selected sea surface temperatures within the range typically preferred by pelagic prey species such as round herring, sardine and anchovy (14-19°C). Black Rocks individuals showed bimodal preferences for colder (16°C) and warmer waters (>22°C). Dive behaviour was similar between Kleinsee and False Bay individuals (unavailable from Black Rocks), with both pelagic and benthic foraging evident. Diel patterns were apparent at both sites, as dive depth and benthic diving increased significantly during daylight hours, likely reflecting vertical movements of prey species. We provide the first assessment of Cape fur seal movement behaviour for the South African component of the population. Observed geographic differences likely reflect the availability of suitable habitat but may also indicate differences in foraging strategies and density-dependent effects throughout the range of this species.
5
WICKENS, P. A. "Fur seals and lobster fishing in South Africa". Aquatic Conservation: Marine and Freshwater Ecosystems 6, n. 3 (settembre 1996): 179–86. http://dx.doi.org/10.1002/(sici)1099-0755(199609)6:3<179::aid-aqc184>3.0.co;2-n.
Testo completo
6
Harcourt, Robert. "Individual variation in predation on fur seals by southern sea lions (Otaria byronia) in Peru". Canadian Journal of Zoology 71, n. 9 (1 settembre 1993): 1908–11. http://dx.doi.org/10.1139/z93-273.
Testo completoAbstract (sommario):
Southern sea lions (Otaria byronia) were observed to prey on juvenile and adult female South American fur seals (Arctocephalus australis) at Punta San Juan, Peru (15°22′S, 75°12′W) between October 1987 and December 1988. Over the course of the study there were 165 attacks on fur seals with 33 seals killed. While both adult male and subadult male sea lions captured and killed fur seals, adult female and juvenile sea lions never acted aggressively towards fur seals. Adult males attacked fur seals on 82.4% of the occasions when they were present at the rookery, subadults on 52% of occasions. Distinctive pelage characteristics allowed some of the male sea lions to be individually identified, and differences in hunting success were observed between adults and subadults, and between five identifiable adults who hunted on at least five occasions. Motivation for attacks differed for subadults and adults, with subadult males using captured fur seals as female sea lion substitutes, guarding them from others and copulating with them, whilst adult sea lions hunted fur seals as food. However, only a small proportion of adult sea lions hunted fur seals, and with differing rates of success.
7
Shaughnessy, Peter D., Catherine M. Kemper, David Stemmer e Jane McKenzie. "Records of vagrant fur seals (family Otariidae) in South Australia". Australian Mammalogy 36, n. 2 (2014): 154. http://dx.doi.org/10.1071/am13038.
Testo completoAbstract (sommario):
Two fur seal species breed on the southern coast of Australia: the Australian fur seal (Arctocephalus pusillus doriferus) and the New Zealand fur seal (A. forsteri). Two other species are vagrants: the subantarctic fur seal (A. tropicalis) and the Antarctic fur seal (A. gazella). We document records of vagrant fur seals in South Australia from 1982 to 2012 based primarily on records from the South Australian Museum. There were 86 subantarctic fur seals: 49 specimens and 37 sightings. Most (77%) were recorded from July to October and 83% of all records were juveniles. All but two specimens were collected between July and November. Sightings were prevalent during the same period, but there were also nine sightings during summer (December–February), several of healthy-looking adults. Notable concentrations were near Victor Harbor, on Kangaroo Island and Eyre Peninsula. Likely sources of subantarctic fur seals seen in South Australia are Macquarie and Amsterdam Islands in the South Indian Ocean, ~2700 km south-east and 5200 km west of SA, respectively. There were two sightings of Antarctic fur seals, both of adults, on Kangaroo Island at New Zealand fur seal breeding colonies. Records of this species for continental Australia and nearby islands are infrequent.
8
Wickens, P. "Conflict between Cape (South African) fur seals and line fishing operations". Wildlife Research 23, n. 1 (1996): 109. http://dx.doi.org/10.1071/wr9960109.
Testo completoAbstract (sommario):
Cape (South African) fur seals (Arctocephalus pusillus pusillus) interact with line-fishermen in South Africa, particularly during fishing for the migratory species snoek (Thyrsites atun), and mostly when snoek are specifically being targeted. Loss of fish and tackle as a result of seals is estimated to be between at least a half and one million Rand (A$l75000-372000) annually or 3.3-7% of the total annual landed value of snoek. The presence of seals may also disturb fishing operations by causing fish to sound although this is difficult to quantify. Deliberate killing of seals by fishermen during line-fishing occurs indiscriminately and particularly during the peak snoek fishing period; however, estimation of this mortality is currently impossible.
9
Townrow, K., e P. D. Shaughnessy. "Fur seal skull from sealers' quarters at Sandy Bay, Macquarie Island, Southern Ocean". Polar Record 27, n. 162 (luglio 1991): 245–48. http://dx.doi.org/10.1017/s0032247400012651.
Testo completoAbstract (sommario):
AbstractFur seals were exterminated from Macquarie Island about 20 years after discovery of the island in 1810. Their specific identity is unknown. Few fur seals were reported at the island until it was occupied by the Australian National Antarctic Research Expeditions in 1948. Fur seal numbers are now increasing. An archaeological excavation at a sealers' quarters at Sandy Bay in 1988 revealed the fragmented skull of a young Antarctic fur sealArctocephalus gazella1.1 m below the surface in a layer dated in the 1870s and 1880s. This period coincides with the recovery of fur seal populations in the South Atlantic Ocean following earlier harvesting. Elsewhere it has been argued that the Antarctic fur seal is unlikely to have been the original fur seal at Macquarie Island because few individuals of that species are ashore in winter, which is the season when the island was discovered and fur-seal harvesting began. It is concluded that the Sandy Bay skull is from a vagrant animal.
10
Ling, JK. "Impact Of Colonial Sealing On Seal Stocks Around Australia, New Zealand And Subantarctic Islands Between 150 And 170 Degrees East". Australian Mammalogy 24, n. 1 (2002): 117. http://dx.doi.org/10.1071/am02117.
Testo completoAbstract (sommario):
Details of southern elephant seal oil and fur seal and sea lion skin cargoes have been extracted from a large number of secondary sources dealing with Australian and New Zealand maritime history, which in turn referred to numerous primary sources of information. The data were collated and analysed for ten areas in the south-west Pacific region and published recently in two separate larger works. This review is a synthesis and analysis of the impact of the colonial sealing industry on seal stocks in the region, based on those papers, with some minor revisions and reference to works by other authors. Colonial sealing lasted from the late 18th to the mid- 19th century and was followed by sporadic hunting until the late 1940s. Southern elephant seals (Mirounga leonina) were hunted for their oil; and Australian fur seals (Arctocephalus pusillus doriferus), New Zealand fur seals (Arctocephalus forsteri), Australian sea lions (Neophoca cinerea) and New Zealand sea lions (Phocarctos hookeri) were targeted for their skins and some oil. At least 1,081 tons of elephant seal oil were shipped from King Is. between 1802 and 1819, while 8,380 tons were shipped from Macquarie Is. between 1810 and 1919. More than 1.4 million skins of both species of fur seals were harvested between 1792 and 1949, but only 4,000 Neophoca and 5,700 Phocarctos pelts are recorded as having been shipped by 1840. The Antipodes Islands yielded more than a quarter of the total fur seal skin harvest, and New Zealand and southern Australia each delivered a quarter of the total. Current numbers of the two species of fur seals combined are about a tenth of the crudely estimated size (1.5 million) of the original population. The exploited fur seals and sea lions were probably the same species as occur today at the original sealing localities, apart from Macquarie Is. where the identity of the exploited fur seals remains in doubt. There is some evidence that Maoris and Australian Aborigines hunted seals in pre-European times, resulting in reduced ranges and depleted stocks that were exploited later by colonial sealers.
11
Shaughnessy, Peter D., e Simon D. Goldsworthy. "Dispersion of long-nosed fur seals (Arctocephalus forsteri) determined by tagging". Australian Journal of Zoology 67, n. 3 (2019): 173. http://dx.doi.org/10.1071/zo20032.
Testo completoAbstract (sommario):
Long-nosed fur seals (Arctocephalus forsteri) were tagged as pups in colonies on Kangaroo Island, South Australia in eight consecutive pupping seasons from 1988–89 to 1995–96. Thirty-nine tagged animals were sighted on the southern Australian coast, being 0.89% of those tagged. They were aged from 9 months to 14 years 6 months, with half in their second and third years. Most records (88%) were of animals that moved eastwards. The most distant records were from Sydney in the east (1700 km), south of Tasmania in the south (1240 km) and Head of Bight in the west (700 km). One animal was seen twice, both times on the north coast of Kangaroo Island, once underwater and two years later ashore. Satellite telemetry studies of juvenile A. forsteri from Kangaroo Island showed that they typically forage in pelagic waters ~1000 km further south in association with the subtropical front. The study reported here shows that some animals tagged as pups disperse widely as juveniles around the southern Australian coast. The possibility of genetic interchange between breeding colonies is suggested by sightings of three tagged females aged 4 years and older at non-natal colonies.
12
Túnez, Juan I., Humberto L. Cappozzo e Marcelo H. Cassini. "Regional factors associated with the distribution of South American fur seals along the Atlantic coast of South America". ICES Journal of Marine Science 65, n. 9 (20 ottobre 2008): 1733–38. http://dx.doi.org/10.1093/icesjms/fsn168.
Testo completoAbstract (sommario):
Abstract Túnez, J. I., Cappozzo, H. L., and Cassini, M. H. 2008. Regional factors associated with the distribution of South American fur seals along the Atlantic coast of South America. – ICES Journal of Marine Science, 65: 1733–1738. Breeding colonies of the South American fur seal (Arctocephalus australis) are not homogeneously distributed along the coast of the Atlantic Ocean, but show an unusual patchiness, with colonies located only at the northern and southern extremities of the breeding range. We used bibliographic data of censuses carried out in the mid- and late 20th century, along with a Geographic Information System, to compare the pattern of distribution of colonies during these two periods, and to identify the anthropogenic and natural factors associated with the present pattern at a regional scale, using principal components analysis. The distribution of colonies did not vary in the period analysed even when the population abundance increased tenfold. The distribution was associated with the distance to the continental shelf break, and the availability of island and protected areas. We conclude that A. australis colonies are located in places where the continental shelf is narrow and there is no human disturbance.
13
Shaughnessy, PD, NJ Gales, TE Dennis e SD Goldsworthy. "Distribution and abundance of New Zealand fur seals, Arctocephalus forsteri, in South Australia and Western Australia". Wildlife Research 21, n. 6 (1994): 667. http://dx.doi.org/10.1071/wr9940667.
Testo completoAbstract (sommario):
A survey to determine the distribution and abundance of New Zealand fur seals, Arctocephalus forsteri, in South Australia and Western Australia was conducted in January-March 1990. Minor surveys were conducted in the summers of 1987-88, 1988-89 and 1990-91. Although the surveys were primarily of black pups in breeding colonies, opportunity was taken to count fur seals of all age-classes, including those in non-breeding colonies. Pups were counted and, in more accessible and larger colonies, numbers of pups were estimated by a mark-recapture technique. The latter technique gave higher estimates than counting, and was considered more accurate. In South Australia, the seals extend from The Pages in Backstairs Passage to Nuyts Reef in the Great Australian Bight. In Western Australia, the range comprised islands on the south coast from the Recherche Archipelago to islands near Cape Leeuwin. There are 29 breeding localities; 13 are in South Australia and 16 in Western Australia. Eighteen of these have not been reported previously. The term ''breeding locality'' is used for aggregations of breeding colonies as well as for isolated breeding colonies. Estimates of the number of pups for the 1989-90 breeding season were 5636 in South Australia and 1429 in Western Australia. This leads to a population estimate of approximately 34600 seals in these two states (using a multiplier of 4.9). But such estimates of overall abundance must be treated cautiously as the multiplier incorporates estimates of population parameters not available for A. forsteri. Most of the population (77%) is in central South Australian waters (from Kangaroo Island to the southern end of Eyre Peninsula). With the estimate of 100 for a breeding colony in southern Tasmania, the population of New Zealand fur seals in Australia can be estimated at 34700. Historical aspects of some colonies are outlined and evidence for increases described. The largest breeding localities are at South Neptune Islands (1964 pups) and North Neptune Islands (1472). The combined Neptunes group accounts for 49% of the pup estimate for Australia. One-fifth of the pups are from colonies on Kangaroo Island and the nearby Casuarinas.
14
Brown, DJ, Il Boyd, GC Cripps e PJ Butler. "Fatty acid signature analysis from the milk of Antarctic fur seals and Southern elephant seals from South Georgia:implications for diet determination". Marine Ecology Progress Series 187 (1999): 251–63. http://dx.doi.org/10.3354/meps187251.
Testo completo
15
Walker, T. R., I. L. Boyd, D. J. McCafferty, N. Huin, R. I. Taylor e K. Reid. "Seasonal occurrence and diet of leopard seals (Hydrurga leptonyx) at Bird Island, South Georgia". Antarctic Science 10, n. 1 (marzo 1998): 75–81. http://dx.doi.org/10.1017/s0954102098000108.
Testo completoAbstract (sommario):
Seasonal haul-out patterns and diet of individually marked leopard seals (Hydrurga leptonyx) were investigated at Bird Island, South Georgia during the 1983–96 winters. A total of 2956 leopard seal sightings were made, and 121 seals were tagged during the study, mainly between 1993 and 1996. Photographs of scars and pelage patterns were also used to identify a subset of these individuals across years, which provided no evidence of tag loss between or within years. Leopard seals were observed between April and November; the mean time between the first and last sightings in each year was 208 d (s d ± 48). Between 1993–96, eight seals were resident around the island for more than 100 d, and the longest recorded residence was 130 d. The proportion of tagged seals resighted was 0.35 and 0.17 in 1995 and 1996 respectively. Based on estimates of body length, <5% of the seals were juveniles (0–1 years) and >70% were not sexually mature. There was considerable inter-annual variation in abundance, with a maximum of 502 sightings during 1994, compared with a minimum of 21 during 1986 and 1989. Antarctic fur seals (Arctocephalus gazella) were the main prey item (58% of kills observed and 53% of scats). Other items included penguins (28% of kills observed and 20% of scats) and fish (24% of scats). Antarctic krill (Euphausia superba), southern elephant seals (Mirounga leonina) and seabirds other than penguins were also present in the diet in small quantities.
16
Blyde, DJ, D. March, P. Howard, V. Sintchenko, E. Rousselet e C. Atkin. "An outbreak of multidrug-resistant Salmonella Kentucky infection in long-nosed fur seals". Diseases of Aquatic Organisms 142 (3 dicembre 2020): 119–24. http://dx.doi.org/10.3354/dao03540.
Testo completoAbstract (sommario):
An outbreak of salmonellosis occurred in a group of 7 long-nosed fur seals Arctocephalus forsteri undergoing rehabilitation after being found injured and malnourished on beaches along the northern New South Wales and southern Queensland coasts of Australia. Three of the 7 individuals developed clinical disease and died within 3 d. Clinical signs included profuse diarrhea, vomiting, depression, and lethargy. Salmonella enterica subsp. enterica serovar Kentucky (S. Kentucky) was cultured from 2 of the 3 deceased animals. The other 4 animals showed similar signs and recovered following treatment. S. Kentucky (antigenic formula 8,20:i:z6) was isolated from the survivors and tissues recovered from post-mortem samples of deceased animals. The bacterium was susceptible to cephalothin and sulfamethoxazole/trimethoprim and resistant to amoxicillin-clavulanate, ampicillin/amoxicillin, tetracycline, and enrofloxacin. This organism has the potential to cause disease in aquatic wildlife, as well as posing a zoonotic threat to people who utilise the aquatic environment.
17
Davis, Dexter, Iain J. Staniland e Keith Reid. "Spatial and temporal variability in the fish diet of Antarctic fur seal (Arctocephalus gazella) in the Atlantic sector of the Southern Ocean". Canadian Journal of Zoology 84, n. 7 (1 luglio 2006): 1025–37. http://dx.doi.org/10.1139/z06-071.
Testo completoAbstract (sommario):
The spatial and temporal variability in the fish component of the diet of Antarctic fur seals (Arctocephalus gazella (Peters, 1875)) in the Atlantic sector of the Southern Ocean was examined using diet data from 10 sites in the region including a 13-year time series from South Georgia. The fish species composition in the diet at each site showed a strong relationship with the local marine habitat / topography. The absence of formerly harvested fish species indicates a lack of recovery of stocks of Notothenia rossii Richardson, 1844 at South Georgia and Champsocephalus gunnari Lönnberg, 1905 at the South Orkney Islands. At South Georgia, Protomyctophum choriodon Hulley, 1981, Lepidonotothen larseni (Lönnberg, 1905), and C. gunnari were the most important species in the diet between 1991 and 2004. Variability in the occurrence of C. gunnari was driven mainly by annual scale processes, particularly those that influence the availability of Antarctic krill (Euphausia superba (Dana, 1852)). The occurrence of the pelagic P. choriodon was primarily influenced by shorter-term water mass changes within the foraging range of the seals. The fish composition in the diet reflects differences in marine habitat / topography, as well as variability, at a range of time scales that reflect environmental variability and harvesting.
18
Shaughnessy, PD, SD Goldsworthy e JA Libke. "Changes in the abundance of New Zealand fur seals, Arctocephalus forsteri, on Kangaroo Island, South Australia". Wildlife Research 22, n. 2 (1995): 201. http://dx.doi.org/10.1071/wr9950201.
Testo completoAbstract (sommario):
Kangaroo Island was an important seal-harvesting site during the early years of European colonisation of Australia. A recent survey of the New Zealand fur seal, Arctocephalus forsteri, in South and Western Australia indicates that Kangaroo I. is still an important centre for the species. In order to determine changes in the abundance of the population, numbers of pups were determined at four colonies on Kangaroo Island by mark-recapture in up to five breeding seasons from 1988-89 to 1992-93. Clipping was the preferred technique for mark-recapture estimation of pups because it was quick, easy and effective. Recaptures were conducted visually; they were repeated several times in each season to improve precision of the estimates. No pups were marked between recaptures in order to minimise disturbance. Assumptions made in estimating population size by the mark-recapture technique pertinent to this study are reviewed. Pup numbers increased at three colonies: at Cape Gantheaume, from 458 to 867 over five years (with exponential rate of increase r = 0.16, n = 5); at Nautilus North, from 182 to 376 over five years (at r = 0.19, n = 4); and at North Casuarina Islet, from 442 to 503 over four years (at r = 0.043, n = 2). Rates of increase in the first two colonies are similar to those at the most rapidly increasing fur seal populations in the Southern Hemisphere. The Kangaroo I. population is estimated to be 10000 animals in 1992-93. It is likely to be at the recolonisation phase of growth, with high rates of increase at individual colonies (or parts of colonies) resulting from local immigration. As space does not appear to be limiting expansion in these colonies, fur seal numbers may continue to increase there.
19
Canova, R., R. F. Budaszewski, M. N. Weber, M. S. da Silva, D. E. Puhl, L. O. Battisti, J. F. Soares et al. "Spleen and lung virome analysis of South American fur seals (Arctocephalus australis) collected on the southern Brazilian coast". Infection, Genetics and Evolution 92 (agosto 2021): 104862. http://dx.doi.org/10.1016/j.meegid.2021.104862.
Testo completo
20
Pemberton, D., e RJ Kirkwood. "Pup production and distribution of the Australian fur seal, Arctocephalus pusillus doriferus, in Tasmania". Wildlife Research 21, n. 3 (1994): 341. http://dx.doi.org/10.1071/wr9940341.
Testo completoAbstract (sommario):
In Tasmanian waters Australian fur seals, Arctocephalus pusillus doriferus, breed on five islands in Bass Strait with non-breeding haul-out sites situated in Bass Strait and along the south-eastern and southern Tasmanian coastline. Estimates of pup production were obtained over four breeding seasons between 1989 and 1993 by aerial photography, ground counts and mark-recapture censuses. Pupping commences in late October, with 90% of pups born between 2 and 20 December. Pup mortality is estimated at 15% by early January, when ground censusing was conducted. Pup production of breeding colonies in Tasmanian waters was highest in 1991, with 5130 pups estimated to have been born.
21
Martin, R. A. "Natural mortality of puffadder shysharks due to Cape fur seals and black-backed kelp gulls at Seal Island, South Africa". Journal of Fish Biology 64, n. 3 (marzo 2004): 711–16. http://dx.doi.org/10.1111/j.1095-8649.2004.00339.x.
Testo completo
22
Harcourt, Robert. "Maternal aggression in the South American fur seal in Peru". Canadian Journal of Zoology 70, n. 2 (1 febbraio 1992): 320–25. http://dx.doi.org/10.1139/z92-048.
Testo completoAbstract (sommario):
Maternal aggression was examined with regard to its role in maternal defense of offspring in the South American fur seal (Arctocephalus australis) at Punta San Juan, Peru (15°22′S, 75°12′W). Female fur seals' responses to conspecifics and to predatory southern sea lions (Otaria byronia) were examined pre- and post-partum. Although the defense of offspring from predators may be expected to be a major component of maternal care, mothers rarely defended their offspring from raiding sea lions, possibly due to the high risks involved in attacking a large and potentially very dangerous predator. The costs of defending the pup from sea lions appeared to outweigh the potential benefit of increased survival of the pup, due to the already high pup mortality at the site. Maternal defense from conspecifics may also be a possible function of female aggression. Females with newborn pups were more aggressive towards other females than were females without pups, particularly during the perinatal attendance period. They threatened a higher proportion of approaching females and won more aggressive encounters postpartum. However, mothers of surviving pups did not appear to be any more aggressive, their pups did not receive any fewer threats from unrelated females, nor did they reside in areas of less aggression, than mothers whose pups died. Aggression towards male conspecifics appeared to serve a further purpose, as females threatened approaching adult and subadult males regardless of whether the females had a pup. Unlike colonially breeding phocid pinnipeds, there seems to be no correlation between increased maternal aggression and neonate survival in the South American fur seal. This may be because females have to leave their offspring to forage when the offspring are still vulnerable to attack by unrelated conspecifics. Alternatively, maternal aggression may have been subjected to such intense selection that although it is responsible for increased pup mortality at the site, there is insufficient variability to measure differential consequences.
23
Crawford, Robert J. M., Benedict L. Dundee, Bruce M. Dyer, Norbert T. W. Klages, Michael A. Meÿer e Leshia Upfold. "Trends in numbers of Cape gannets (Morus capensis), 1956/1957–2005/2006, with a consideration of the influence of food and other factors". ICES Journal of Marine Science 64, n. 1 (2 novembre 2006): 169–77. http://dx.doi.org/10.1093/icesjms/fsl011.
Testo completoAbstract (sommario):
Abstract Crawford, R. J. M., Dundee, B. L., Dyer, B. M., Klages, N. T., Meÿer, M. A., and Upfold, L. 2007. Trends in numbers of Cape gannets (Morus capensis), 1956/57–2005/06, with a consideration of the influence of food and other factors – ICES Journal of Marine Science, 64, 169–177. Cape gannets (Morus capensis) breed at six colonies in Namibia and South Africa. Population size averaged about 250 000 pairs over the period 1956/1957–1968/1969 and about 150 000 pairs from 1978/1979 to 2005/2006. Over the whole 50-y period, numbers at the three Namibian colonies fell by 85–98%, with greater proportional decreases in the south. There were increases at two South African colonies between 1956/1957 and 2005/2006. The colony at Lambert's Bay increased between 1956/1957 and 2003/2004, but attacks by Cape fur seals (Arctocephalus pusillus) on birds at nests caused abandonment of the entire colony in 2005/2006. Long-term changes at colonies are thought to be largely attributable to an altered abundance and distribution of prey, especially sardine (Sardinops sagax) and anchovy (Engraulis encrasicolus). In both Namibia and South Africa, the numbers of Cape gannets breeding were significantly related to the biomass of epipelagic fish prey. Over the 50-y period, there was also a marked similarity in the proportions of gannets and epipelagic fish in the Benguela system, which were present in Namibia and South Africa. In the 2000s, there was an eastward shift in the distribution of sardine off South Africa and a large increase in the number of gannets breeding at South Africa's easternmost colony. When sardine were scarce off South Africa, gannets fed on anchovy, but off Namibia anchovy only temporarily and partially replaced sardine. Ecosystem management measures that might improve the conservation status of Cape gannets are considered.
24
Machado, R., LR de Oliveira, PH Ott, M. Haimovici, LG Cardoso, L. Milmann, MA Romero, RA dos Santos e M. Borges-Martins. "Trophic overlap between marine mammals and fisheries in subtropical waters in the western South Atlantic". Marine Ecology Progress Series 639 (2 aprile 2020): 215–32. http://dx.doi.org/10.3354/meps13284.
Testo completoAbstract (sommario):
Marine mammals and humans are apex predators and both may compete for fish in ecosystems under continuous fishing pressure. We assessed the degree of trophic overlap between prey species found in the diet of 5 marine mammals (39 specimens of sea lion Otaria flavescens, 61 fur seals Arctocephalus australis, 76 franciscana dolphins Pontoporia blainvillei, 25 bottlenose dolphins Tursiops truncatus and 28 Lahille’s bottlenose dolphins T. gephyreus) and the catches of the 6 main commercial fishing gears used in southern Brazil (coastal gillnets, oceanic gillnets, purse seine, demersal pair trawling, bottom [single] trawl and double-rig trawling) between 1993 and 2016. An adjusted general overlap index indicated an overall moderate to high overlap. Specific overlap analysis showed that O. flavescens and T. truncatus presented high trophic relationships with fisheries, followed by T. gephyreus. Smaller interactions were observed for A. australis and P. blainvillei, even though they also exploit commercial fishing resources. Coastal gillnet and pair bottom trawling are the fisheries that most target the fish species favoured by O. flavescens, T. gephyreus and T. truncatus. The information presented in this study on trophic interactions may assist decision making for both fishery management and conservation measures for these apex predators. Commercial fishing activities are a major threat to marine mammals both regionally and globally. Current levels of fishing or its intensification may lead to dramatic changes in the coastal marine food web, including additional threats to coastal marine mammal populations in southern Brazil.
25
Morse, P., MA Mole, MN Bester, R. Johnson, U. Scacco e E. Gennari. "Cape fur seals (Arctocephalus pusillus pusillus) adjust traversing behaviour with lunar conditions in the high white shark (Carcharodon carcharias) density waters of Mossel Bay, South Africa". Marine Ecology Progress Series 622 (18 luglio 2019): 219–30. http://dx.doi.org/10.3354/meps13051.
Testo completo
26
Hammerschlag, Neil, R. Aidan Martin e Chris Fallows. "Effects of environmental conditions on predator–prey interactions between white sharks (Carcharodon carcharias) and Cape fur seals (Arctocephalus pusillus pusillus) at Seal Island, South Africa". Environmental Biology of Fishes 76, n. 2-4 (3 giugno 2006): 341–50. http://dx.doi.org/10.1007/s10641-006-9038-z.
Testo completo
27
Goldsworthy, SD, e PD Shaughnessy. "Breeding biology and haul-out pattern of the New Zealand fur seal, Arctopehalus forsteri, at Cape Gantheaume, South Australia". Wildlife Research 21, n. 3 (1994): 365. http://dx.doi.org/10.1071/wr9940365.
Testo completoAbstract (sommario):
New Zealand fur seals, Arctocephalus forsteri, breed at Cape Gantheaume (36�04'S,137�28'E), Kangaroo Island, South Australia, on broken rock platforms. In 1988-89, pups were born between late November and mid-January, 90% of them over 34 days between 3 December and 6 January. The median date of birth was 21 December. A re-analysis of data for this species from three breeding seasons at the Open Bay Islands (South Island, New Zealand, 43�52'S,l68�53'E) indicates that: (i) the breeding season at Cape Gantheaume occurs 5-12 days later than at the Open Bay Islands, (ii) the period containing 90% of births was the same duration for both populations, and (iii) the median date of birth spanned seven days in three seasons at the Open Bay Islands. In addition, the timing and duration of the pupping season varied within the Cape Gantheaume colony, it being later in recently colonised areas. We suggest that this pattern is a consequence of changes in the age distribution of females through the colony. The sex ratio of pups born in the colony over four breeding seasons did not differ significantly from 1:l. Females were mated on average 7.4 days after birth and left for sea 2.3 days later. The mean date of observed matings was 29 December; copulations lasted about 13 min. The operational sex ratio (OSR) in the colony was 8.6 females per territorial male (the maximum ratio of territorial males to pups was 1:16), which was within the range reported for other southern fur seal species. In two consecutive breeding seasons, the estimated fecundity rate of adult females averaged 67%. Non-breeding animals (sub-adult males, juveniles and yearlings) occurred in areas not occupied by breeding animals. The number of juveniles ashore increased after the breeding season, but no pattern was found for sub-adults and yearlings. Yearlings were uncommon in the colony at all times; it is suggested that they are mostly pelagic and do not moult in their second year.
28
De Vos, Alta, M. Justin O'Riain, Michael A. Meyer, P. Gideon H. Kotze e Alison A. Kock. "Behavior of Cape fur seals (Arctocephalus pusillus pusillus) in relation to temporal variation in predation risk by white sharks (Carcharodon carcharias)around a seal rookery in False Bay, South Africa". Marine Mammal Science 31, n. 3 (1 aprile 2015): 1118–31. http://dx.doi.org/10.1111/mms.12208.
Testo completo
29
Budd, Grahame M. "Australian exploration of Heard Island, 1947–1971". Polar Record 43, n. 2 (28 marzo 2007): 97–123. http://dx.doi.org/10.1017/s0032247407006080.
Testo completoAbstract (sommario):
In 1947 knowledge of Heard Island was confined to a rough mapping compiled by nineteenth-century sealers, and the results of four scientific expeditions that had briefly investigated the Atlas Cove area. Exploration continued in two distinct periods between 1947 and 1971. In the first period the Australian National Antarctic Research Expeditions (ANARE) built a scientific station at Atlas Cove in 1947, and occupied it continuously until 1955 as an ‘A Class’ meteorological station, a seismic and magnetic observatory, and a base for other scientific studies and for exploration of the island. In the second period four summer expeditions and one wintering expedition worked on the island between 1963 and 1971. The summer expeditions were an ANARE expedition in 1963, an Australian private expedition (The South Indian Ocean Expedition to Heard Island) in 1965, and ANARE expeditions in 1969 and 1971 associated with United States and French expeditions. A United States expedition wintered in 1969. There were no further expeditions until 1980. The years 1947–1971 saw many achievements. Expedition members recorded seven years of synoptic meteorological observations and four years of seismic and magnetic observations. They developed empirical techniques of work, travel, and survival that shaped the collective character of ANARE and were later applied in Antarctica. Despite difficult terrain and consistently bad weather, and the accidental deaths of two men in 1952, unsupported field parties of two or three men travelling on foot explored and mapped in detail the heavily glaciated island, and documented its topography, geology, glaciology and biology. They made three overland circuits of the island, the first ascent of Big Ben (2745 m), and the first recorded landing on the nearby McDonald Islands. Expedition members bred and trained dog teams for later use in Antarctica. They reported the commencement and subsequent progress of massive glacier retreat caused by regional warming, and of the island's colonisation by king penguins (Aptenodytes patagonicus) and antarctic fur seals (Arctocephalus gazella). They also reported measurements of glacier flow and thickness, the palaeomagnetism of Heard Island rocks, behavioural and population studies of southern giant petrels (Macronectes giganteus) and other birds, studies of southern elephant seals (Mirounga leonina) and leopard seals (Hydrurga leptonyx), and the cold stress and acclimatisation experienced by humans working in the island's wet-cold climate. In addition, Heard Island served as a testing ground for men, equipment, scientific programmes, huskies, general administration, and logistics, without which Mawson station could not have been established as successfully as it was in 1954. The American wintering expedition and the French summer expedition contributed to major international geodetic and geophysical investigations. In sum, the expeditions between 1947 and 1971 added much to our knowledge of Heard Island, and they laid down a solid foundation for the work of later expeditions.
30
Echenique, J., E. Pereira, J. Prado, A. L. Schild e A. L. Valente. "New host and geographical records for Parafilaroides normani (Nematoda: Filaroididae) Dailey, 2009 in South American fur seal, Arctocephalus australis, from southern Brazil". Journal of Helminthology 94 (2020). http://dx.doi.org/10.1017/s0022149x20000826.
Testo completoAbstract (sommario):
Abstract Lungworms are a common finding in seals and fur seals around the world. However, from existing records, the biogeographical distribution of filaroid helminths appears to be restricted, and these parasites are endemic in only certain areas and species, mainly in the Northern Hemisphere. The occurrence of infection in pinniped species in the Southern Hemisphere is scarce. The objective of this work is to verify the prevalence of lungworms in Arctocephalus australis in waters off the southern coast of Brazil. Twenty subadult specimens of A. australis found recently dead on the southern coast of Brazil were necropsied and their lungs were examined. Parasitic cysts were found in only one specimen (prevalence of 5%). The helminths were morphologically identified as Parafilaroides normani (Metastrongyloidea: Filaroididae). This helminth species has been reported in pinnipeds from Australia, New Zealand and South Africa. This is the first record of P. normani in A. australis and for the western South Atlantic, providing additional data regarding the biogeographic distribution of the parasite.