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John P. Y. Arnould - One of the best experts on this subject based on the ideXlab platform.
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dive behaviour and foraging effort of female cape fur seals Arctocephalus pusillus pusillus
Royal Society Open Science, 2019Co-Authors: S P Kirkman, W. H. Oosthuizen, Daniel P Costa, Autumnlynn Harrison, P G H Kotze, Michael Weise, Jonathan A Botha, John P. Y. ArnouldAbstract: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.
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cape and australian fur seals Arctocephalus pusillus pusillus and a p doriferus
2018Co-Authors: S P Kirkman, John P. Y. ArnouldAbstract:Summary The Cape fur seal Arctocephalus pusillus pusillus and the Australian fur seal A. p. doriferus are the two recognized subspecies of A. pusillus (family Otariidae, subfamily Arctocephelinae). Their subspecific status is based on separate geographic ranges and a difference in one cranial character, but the two subspecies are otherwise identical in anatomy and behavior. Molecular studies have indicated that A. pusillus aligns more closely with sea lion species (subfamily Otariinae), with which they share several morphological and behavioral commonalities than with other fur seal species. Differences in foraging behavior between the subspecies and in their population trajectories are likely related to differences in local productivity. Bass Strait where the bulk of the Australian fur seal population occurs is dominated by warm-nutrient impoverished waters and relatively low productivity, whereas the Benguela current upwelling system, which largely coincides with the range of the Cape fur seal is characterized by high productivity.
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RESEARCH ARTICLE Identification of Prey Captures in Australian Fur Seals (Arctocephalus pusillus doriferus) Using Head-Mounted Accelerometers: Field Validation with Animal-Borne Video Cameras
2016Co-Authors: Beth L. Volpov, Greg Marshall, Kyler Abernathy, John P. Y. Arnould, Morgane Viviant, Andrew J. Hoskins¤a, Brian C. Battaile¤b, E. Wheatley, States Of AmericaAbstract:This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey cap-tures (APC), and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were un-able to distinguish among prey types (fish, cephalopod, stingray) or between successful captures and unsuccessful capture attempts. Mean detection rate (true positive rate) on in-dividual animals in the testing subset ranged from 67-100%, and mean detection on the testing subset averaged across 4 animals ranged from 82-97%. Mean False positive (FP) rate ranged from 15-67 % individually in the testing subset, and 26-59 % averaged across 4 animals. Surge and sway had significantly greater detection rates, but also conversely greater FP rates compared to heave. Video data also indicated that some head movements recorded by the accelerometers were unrelated to APC and that a peak in acceleration vari-ance did not always equate to an individual prey item. The results of the present study indi
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EXTENDED MATERNAL DEPENDENCE BY JUVENILE AUSTRALIAN FUR SEALS (Arctocephalus pusillus DORIFERUS)
2015Co-Authors: Fiona Hume, John P. Y. Arnould, Roger Kirkwood, Paul DavisAbstract:AUSTRALIAN fur seal (Arctocephalus pusillus doriferus) cows mature at 3- 6 years of age and, thereafter, are able to give birth to a single pup each year (Warneke and Shaughnessy 1985; Warneke 1995). Pups are born from late October to December and are usually nursed for 8- 11 months (Warneke and Shaughnessy 1985), however, extended dependency into a second or third year has been recorded (Stirling and Warneke 1971). At Seal Rocks, Victoria, one of nine breeding sites for A. p
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Identification of prey captures in Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted accelerometers: field validation with animal-borne video cameras
PLoS ONE, 2015Co-Authors: Beth L. Volpov, Brian C. Battaile, Greg Marshall, Kyler Abernathy, Andrew J. Hoskins, Kathryn E Wheatley, Morgane Viviant, John P. Y. ArnouldAbstract:This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey captures (APC), and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were unable to distinguish among prey types (fish, cephalopod, stingray) or between successful captures and unsuccessful capture attempts. Mean detection rate (true positive rate) on individual animals in the testing subset ranged from 67-100%, and mean detection on the testing subset averaged across 4 animals ranged from 82-97%. Mean False positive (FP) rate ranged from 15-67% individually in the testing subset, and 26-59% averaged across 4 animals. Surge and sway had significantly greater detection rates, but also conversely greater FP rates compared to heave. Video data also indicated that some head movements recorded by the accelerometers were unrelated to APC and that a peak in acceleration variance did not always equate to an individual prey item. The results of the present study indicate that head-mounted accelerometers provide a complementary tool for investigating foraging behaviour in pinnipeds, but that detection and FP correction factors need to be applied for reliable field application.
Roger Kirkwood - One of the best experts on this subject based on the ideXlab platform.
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EXTENDED MATERNAL DEPENDENCE BY JUVENILE AUSTRALIAN FUR SEALS (Arctocephalus pusillus DORIFERUS)
2015Co-Authors: Fiona Hume, John P. Y. Arnould, Roger Kirkwood, Paul DavisAbstract:AUSTRALIAN fur seal (Arctocephalus pusillus doriferus) cows mature at 3- 6 years of age and, thereafter, are able to give birth to a single pup each year (Warneke and Shaughnessy 1985; Warneke 1995). Pups are born from late October to December and are usually nursed for 8- 11 months (Warneke and Shaughnessy 1985), however, extended dependency into a second or third year has been recorded (Stirling and Warneke 1971). At Seal Rocks, Victoria, one of nine breeding sites for A. p
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behavioral responses of australian fur seals Arctocephalus pusillus doriferus to environmental variations
Marine Mammal Science, 2014Co-Authors: Linda Nancy Garlepp, Murray Logan, Roger KirkwoodAbstract:Observing how pinnipeds respond to variations in climatic and oceanographic conditions informs marine managers on factors that could limit their range, foraging ability and breeding success. Here, we examine how Australian fur seals (Arctocephalus pusillus doriferus) at Seal Rocks, Victoria, Australia, responded to normal climatic conditions from August 2009 to January 2010, which included their Austral spring-summer breeding period, to investigate their tolerances to a range of environmental stimuli. Seal numbers ashore and a range of climatic variables were collected hourly during daylight periods and compared using Generalized Additive Mixed Models (GAMMs). Air temperature was the most consistent predictor of haul-out behavior, with seal numbers ashore declining as air temperature increased (effect size -50%, edf 1.00, P <0.001). Increased wave height (effect size 74%, edf 1.00, P <0.001) and wind speed (effect size 79%, edf 1.00, P <0.001) were associated with increased seal numbers ashore. Potentially, higher air temperatures reduce the seals tolerance to remain out of the water, while high wind/wave action increases at-sea metabolic costs. These results demonstrate how changes in climate could alter a seal's ability to remain ashore, to rest or breed, and its ability to forage effectively, thus driving changes in population status and range.
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characterization and causal investigations of an alopecia syndrome in australian fur seals Arctocephalus pusillus doriferus
Journal of Mammalogy, 2012Co-Authors: Michael D Lynch, Roger Kirkwood, Rachael Gray, David Robson, Greg Burton, Leslie Jones, Rodney Sinclair, John P. Y. ArnouldAbstract:Fur seals rely on pelage consisting of dense, fine underfur protected by guard hairs as their primary means of limiting thermoregulatory cost. A distinctive syndrome of alopecia occurs at high prevalence in 1 colony of Australian fur seals (Arctocephalus pusillus doriferus). It is characterized by bilaterally symmetrical hair loss on the dorsal body surface and a biased prevalence toward juvenile females. Light and scanning electron microscopy demonstrated that alopecia is due to fracture of the hair shaft above the skin level. No evidence of viral, bacterial, fungal, or parasite infection was found and histological examination of skin biopsies revealed no pathological variation between case and control seals. Affected animals had statistically significant lower tyrosine and zinc concentrations in hair than unaffected seals. This may increase hair brittleness and, therefore, predispose its fracture. Alopecia cases also had higher levels of heavy metals and persistent organic pollutants, which may indicate they forage in ecosystems where concentrations of pollutants are higher.
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mycoplasmas in australian fur seals Arctocephalus pusillus doriferus identification and association with abortion
Journal of Veterinary Diagnostic Investigation, 2011Co-Authors: Michael D Lynch, John P. Y. Arnould, Trevor Taylor, Padraig J Duignan, Jane Swingler, Marc S Marenda, Roger KirkwoodAbstract:Bacteria from the genus Mycoplasma are common inhabitants of the respiratory, gastrointestinal, and genital tracts of mammals. The understanding of the pathological significance of mycoplasmas in seals is poor, as few studies have utilized the specific culture techniques required to isolate these bacteria. The current study surveyed for the Mycoplasma species present in Australian fur seals (Arctocephalus pusillus doriferus) and investigated the association between infection and pathology. Mycoplasmas were found in the nasal cavities of 55/80 (69%) of apparently healthy individuals. Isolates from 18 individuals were investigated through 16S ribosomal RNA sequencing, and 3 species were identified: M. zalophi, M. phocae, and Mycoplasma sp. (GenBank no. EU714238.1), all of which had previously been isolated from Northern Hemisphere pinnipeds. In addition, mycoplasmas were isolated from the lungs of 4 out of 16 juveniles and 1 out of 5 adults sampled at necropsy. Isolates obtained were M. zalophi, Mycoplasma sp. EU714238.1, and M. phocicerebrale, but infection was not associated with lung pathology in these age classes. Inflammatory disease processes of the heart and/or lungs were present in 12 out of 32 (38%) aborted fetuses on microscopic examination. Predominant findings were interstitial pneumonia, pericarditis, and myocarditis. Mycoplasma phocicerebrale was isolated from the thymus of an aborted fetus, and 3 out of 11 (27%) fetuses with inflammatory heart or lung lesions were PCR-positive for Mycoplasma. In conclusion, several species of Mycoplasma are part of the normal flora of the nasal cavity of Australian fur seals, and some mycoplasmas may be associated with abortion in this species of seal.
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habitat selection by female australian fur seals Arctocephalus pusillus doriferus
Aquatic Conservation-marine and Freshwater Ecosystems, 2007Co-Authors: John P. Y. Arnould, Roger KirkwoodAbstract:1. Numerous studies have determined the foraging areas of marine apex predators and investigated their relationship to oceanographic features. Most of these, however, have concentrated on surface-feeding seabirds or epipelagic-foraging marine mammals and there is little information on habitat selection in benthic divers. 2. Satellite telemetry was used during the winters of 2001-2003 to determine the foraging areas of 48 female Australian fur seals (Arctocephalus pusillus doriferus) from four breeding sites in northern Bass Strait whose colonies together represent > 80% of the total species population. 3. All individuals foraged over the shallow continental shelf of Bass Strait supporting earlier studies that suggested the species is an exclusively benthic forager. Individual females showed a high degree of foraging site-fidelity and several foraging 'hot spot' areas could be identified. 4. Analysis of habitat use indicated that individuals selected areas with depths of 60-80 m significantly more (λ = 0.216, P 0.05). 5. Temporal analysis of at-sea movements indicated, due to their primarily benthic foraging mode, the areas frequented by female Australian fur seals did not overlap substantially with areas targeted by commercial fisheries. An exception to this was in far eastern Bass Strait where the Otter Trawl component of the Commonwealth Trawl Sector is highly active over the continental shelf and encompasses the areas frequented by females from The Skerries colony.
C. L. Stewardson - One of the best experts on this subject based on the ideXlab platform.
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climate of a south african fur seal Arctocephalus pusillus pusillus breeding island off the south east coast of south africa
South African Geographical Journal, 2012Co-Authors: C. L. Stewardson, T Prvan, Raymond J RitchieAbstract:The Bird Island in Algoa Bay supports a breeding colony of South African (Cape) fur seals, Arctocephalus pusillus pusillus (n = 1000–3000) on Black Rocks which is the easternmost extreme of their breeding range and so it is likely to be the most environmentally marginal of the existing fur seal colonies. Conditions on Bird Island for seal pups are not as benign as they might first appear, particularly with regard to air temperatures. Climatic conditions on Bird Island were recorded in 1993–1995 and are compared to the conditions at Port Elizabeth Airport 63 km W-SW from the Bird Islands. Daily maximum and minimum temperatures, sea surface temperatures (SSTs) and rainfall were compared to concurrent Port Elizabeth data. Wind speeds and directions and sea swell heights at Bird Island were also recorded. Air temperatures ranged from 9°C to 33°C, SSTs ranged from 12°C to 23°C, total annual rainfall was ≈ 600 mm and there were typically relatively strong winds (13–15 knots/7–8 m s− 1) predominantly W-SW and E-...
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suture index and growth in the male south african fur seal Arctocephalus pusillus pinnipedia otariidae
Proceedings of the Linnean Society of New South Wales, 2011Co-Authors: C. L. Stewardson, M A Meyer, T Prvan, S Swanson, Raymond J RitchieAbstract:The South African furs seal (Arctocephalus pusillus pusillus) is very closely related to the Australian fur seal (A. pusillus doriferus). We examine the relationship between skull suture index (SI*) and growth parameters in the male South African fur seal, based on 42 animals of known age ranging from 10 m to 11 y 11 m. Twenty one (21) animals were aged based upon tagging as pups and 21 were aged based on dentine growth layers (1 to 11 y). Suture index and morphometric information was available on an additional 27 males; 17 had no age information but 10 were known from their dentition to be >= 12 y. Age has previously been found to be approximately directly proportional to suture index. Here we estimate asymptotic size and growth kinetics from SI* using nonlinear growth models [exponential saturation (von Bertalanffy), Logistic, Gompertz] fitted to cross-sectional morphometric data (n = 8 variables). The relationship between the following measurements was examined and suture index are presented in the present study: external body (standard body length, SBL; length of front flipper; length of hind flipper), skull (condylobasal length, CBL; Bizygomatic breadth; mastoid breadth; length of Mandible or Ramus length) and baculum (bacular length, BL). The asymptote values of these parameters are compared to those derived from chronological age and show very good agreement. The growth kinetic parameters calculated in terms of SI* when converted into years using the relationship between SI* and true Age (y) are also in close agreement with those calculated on tag and dentition aged animals.
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suture index as an indicator of chronological age in the male south african fur seal Arctocephalus pusillus pinnipedia otariidae
Proceedings of the Linnean Society of New South Wales, 2011Co-Authors: C. L. Stewardson, M A Meyer, T Prvan, S Swanson, Raymond J RitchieAbstract:The South African fur seal (Arctocephalus pusillus pusillus) is very closely related to the Australian fur seal (A. pusillus doriferus). We examine skull suture index (SI*) as an indicator of chronological age in the male South African fur seal, based on 42 animals of known age ranging from 10 m to 11 y 11 m. Twenty one (21) animals were aged based upon tagging as pups and 21 were aged based on dentine growth layers (1 to 11 y). Age is approximately directly proportional to suture index [Age = (0.7990 +/- 0.02354) SI*, r = 0.8887, n = 42, valid SI* range 0 - 16, useful predictive range 0-≈14 y)]. We describe the sequence of cranial suture closure (n = 11 sutures, 69 animals) and determine whether suture index (SI*) reliably corresponds to chronological age. Sutures do not close in a definitive order in all individuals and some sutures take longer to close than others. In animals <= 12 y, the general sequence of full suture closure was the Basioccipito-basisphenoid, Occipito- parietal, Interparietal, Coronal and finally the Squamosal-jugal. The Maxillary, Squamosal-parietal, Interfrontal, Basisphenoid-presphenoid, Internasal were used in the SI* calculation even though none showed any sign of closure in the known-age individuals but did show some closure in very old animals of indeterminate age. Suture closure criteria are useful in classifying males into juveniles, subadults and adults. Multiple linear regression might also prove to be useful to predict chronological age from suture closure data but its utility was limited in the present study by both the size of the data set available and the lack of animals with a known age older than 12y. More data is needed on old animals of known age but the relationship between skull sutures and age found in the present study would be sufficient for aging most male skull material because very few males are likely to reach ages greater than about 12-14 y.
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bacular measurements for age determination and growth in the male south african fur seal Arctocephalus pusillus pusillus pinnipedia otariidae
Proceedings of the Linnean Society of New South Wales, 2010Co-Authors: C. L. Stewardson, T Prvan, Raymond J RitchieAbstract:Morphology, relative size and growth of the baculum in 103 South African fur seals, Arctocephalus pusillus pusillus, from the Eastern Cape coast of South Africa are described. Bacular measurements (n = 8 linear variables and mass) were examined in relation to standard body length (SBL), bacular length (BL) and chronological age (y) using linear regression. Animals ranged from < 1 month to greater or equal 12 y. Bacular shape was most similar to Callorhinus ursinus (Northern fur seal) and Zalophus californianus (California sea lion). For the range of ages represented in this study, the baculum continued to increase in size until at least 10 y; with growth slowing between 8-10 y, when social maturity (full reproductive capacity) is attained. Growth in bacular length (BL), distal height and bacular mass peaked at 8 y; middle shaft height and distal shaft height peaked at 9 y; proximal height, proximal width, distal width and proximal shaft height peaked at 10 y. In the largest animal (age greater or equal 12 y), maximum bacular length was 139 mm and mass 12.5 g. Relative to SBL, bacular length (BL) increased rapidly in young animals, peaked at 9 y (6.9%), and then declined. Bacular mass and distal height expressed greatest overall growth, followed by proximal height, proximal shaft height and bacular length. At 9 y, mean bacular length and mass was 117 lplus-or-minus 2.7 (plus-or-minus SE, n = 4) mm and 7 plus-or-minus 0.7 (4) g; growth rates in bacular length and mass were 311% and 7125% (relative to age zero), and 5% and 27% (between years); and bacular length (BL) was about 6.9% of SBL. For all males greater or equal 12 months, most bacular variables grew at a faster rate than SBL and BL. Exceptions included proximal width which was isometric to SBL; distal width and distal shaft height which were isometric to bacular length; and proximal width which was negatively allometric relative to BL. Bacular length (BL) was found to be a useful predictor of SBL and seal age group (pup, yearling, subadult, adult), but only a 'rough indicator' of absolute age.
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sexual dimorphism in the adult south african cape fur seal Arctocephalus pusillus pusillus pinnipedia otariidae standard body length and skull morphology
Proceedings of the Linnean Society of New South Wales, 2010Co-Authors: C. L. Stewardson, M A Meyer, T Prvan, Raymond J RitchieAbstract:We examine differences in standard body length and skull morphology of male (n = 65) and female (n = 18) South African (Cape) fur seals, 'Arctocephalus pusillus pusillus', from the coast of southern Africa with the aim to develop an objective method for determining the sex of fur seal skulls. Males were found to be significantly larger than females in standard body length, with K-means cluster analysis successfully identifying 2 relatively homogeneous groups. Principal component analysis (covariance matrix) showed that the underlying data structure for male and female skull variables was different, and that most of this variation was expressed in overall skull size rather than shape. Males were significantly larger than females in 30 of the 31 skull variables. Breadth of brain case was significantly different for the genders. Relative to condylobasal length, males were significantly larger than females in 13 of the 31 skull variables used in the present study. These were gnathion to posterior end of nasals, breadth at preorbital processes, least interorbital constriction, breadth at supraorbital processes, greatest bicanine breadth, breadth of palate at postcanine 1 and 3, calvarial breadth, mastoid breadth, gnathion to anterior of foramen infraorbital, gnathion to posterior border of preorbital process, height of skull at base of mastoid and height of mandible at meatus. In males, these variables were associated with the acquisition and defense of territory (e.g., large head size and mass; increased structural strength of the skull; increased bite capacity). Two skull ratio parameters, breadth of braincase/condylobasal length and length of upper postcanine row/condylobasal length were significantly higher in females compared to males. Based solely on the skull data, mature males can be reliably distinguished from immature males and females using both (a) Classification and Regression Tree (CART) and (b) Hierarchical Cluster Analysis. Both approaches had difficulty in reliably distinguishing immature males from females. The Classification and Regression Tree method was the more successful in correctly distinguishing immature males from females.
W. H. Oosthuizen - One of the best experts on this subject based on the ideXlab platform.
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dive behaviour and foraging effort of female cape fur seals Arctocephalus pusillus pusillus
Royal Society Open Science, 2019Co-Authors: S P Kirkman, W. H. Oosthuizen, Daniel P Costa, Autumnlynn Harrison, P G H Kotze, Michael Weise, Jonathan A Botha, John P. Y. ArnouldAbstract: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.
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making sense of censuses and dealing with missing data trends in pup counts of cape fur seal Arctocephalus pusillus pusillus for the period 1972 2004
African Journal of Marine Science, 2007Co-Authors: S P Kirkman, W. H. Oosthuizen, J-p Roux, Michael A Meÿer, P G H Kotze, Les G. UnderhillAbstract:Trends in the population of Cape fur seals Arctocephalus pusillus pusillus were estimated from counts of pups on aerial photographs of colonies taken between 1972 and 2004 to determine trends in the overall population and subpopulations. Incomplete coverage resulted in missing data in some years. Various methods of determining proxy values for missing data were assessed, and it was concluded that different methods were applicable to Namibian and South African colonies. This reflected variation in trends of pup counts between the countries, which was associated with differences in productivity between the southern and northern Benguela ecosystems. In Namibia, temporal changes in pup numbers were non-linear in some years and there was correspondence in fluctuations at most colonies. This appeared to be on account of an effect of periodic, wide-scale prey shortages that reduced birth rates. There was a northward shift in the distribution of seals in the northern Benguela system. In South Africa, pup counts w...
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seabird predation by white shark carcharodon carcharias and cape fur seal Arctocephalus pusillus pusillus at dyer island research article
South African Journal of Wildlife Research - 24-month delayed open access, 2006Co-Authors: Ryan Johnson, Marthán N Bester, A Venter, W. H. OosthuizenAbstract:Both the white shark (Carcharodon carcharias) and Cape fur seal (Arctocephalus pusillus pusillus) prey on and/or attack seabirds in South Africa. The Dyer Island region abounds in these predators, as well as seabirds, including the African penguin (Spheniscus demersus), Cape cormorant (
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Mitochondrial DNA sequence data of the Cape fur seal (Arctocephalus pusillus pusillus) suggest that population numbers may be affected by climatic shifts
Marine Biology, 2006Co-Authors: C.a. Matthee, W. H. Oosthuizen, M A Meyer, F. Fourie, K.a. TolleyAbstract:The Cape fur seal, Arctocephalus pusillus pusillus is distributed along the southern African coastline from northern Namibia to the south-east coast of South Africa. The species has been impacted by sealing operations since the 1600s, and historical records suggest that the taxon experienced a bottleneck prior to the 20th century. Mitochondrial DNA control region sequences were generated for 106 individuals belonging to six breeding colonies. Haplotype diversity was found to be high (0.975±0.014) whereas levels of nucleotide diversity were much lower compared to other seal species (0.011±0.006). An analysis of molecular variance indicated that the largest percentage of haplotype diversity is distributed within colonies rather than among them. This could be attributed to either extensive gene flow among colonies, a lack of substantial female site philopatry, or incomplete lineage sorting of haplotypes. Mismatch distribution and Fu’s F _S test indicated that the population has experienced a historical population expansion probably between c. 37,000–18,000 YBP and this date coincides very well with the height of the last glacial maximum when food resources were abundant in the South Atlantic. These results also suggest that the recent sealing-induced bottleneck did not have a profound influence on the haplotype diversity and a historical bottleneck prior to a demographic expansion may have been severe enough to reduce nucleotide diversity substantially.
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morphology and distribution of sweat glands in the cape fur seal Arctocephalus pusillus pusillus carnivora otariidae
Australian Journal of Zoology, 2005Co-Authors: L S Rotherham, Marthán N Bester, M. Van Der Merwe, W. H. OosthuizenAbstract:The present study examined whether sweat glands are present in the skin of the Cape fur seal, Arctocephalus pusillus pusillus. Sweat glands have an important role in thermoregulation; the presence or absence of sweat glands in the fur-covered and naked skin areas of the Cape fur seal was investigated using standard histological procedures and light and scanning electron microscopy. Sweat glands were present in both fur-covered and naked skin areas. The skin layers in the naked skin areas were thicker than those in the fur-covered areas, presumably to protect them against abrasions in the absence of hair. The density of apocrine sweat glands did not differ among the body regions; however, both apocrine and eccrine sweat glands were larger in naked skin areas than in fur-covered areas. This increased size of the glands suggests a more active role for the glands in the naked skin areas, and a higher heat-loss capability through evaporative cooling in these body regions.
M A Meyer - One of the best experts on this subject based on the ideXlab platform.
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Behavior of Cape fur seals (Arctocephalus pusillus pusillus) in response to spatial variation in white shark (Carcharodon carcharias) predation risk
Marine Mammal Science, 2015Co-Authors: Alta De Vos, M A Meyer, M. Justin O'riain, P. Gideon. H. Kotze, Alison A. KockAbstract:Foraging and predation risk are often separated at rookeries of marine central place foragers, thus offering an opportunity to gain insight into how predator-avoidance shapes the behavior of prey. Here we compare the behavior of Cape fur seals (Arctocephalus pusillus pusillus) at two island rookeries with and without white shark (Carcharodon carcharias) predations, and assess seal behavior in relation to marked spatiotemporal variation in risk at the high-risk site (Seal Island, South Africa). Our results show that seal behavior at the two sites is comparatively similar in summer, when predation risk is low at both sites, but not in winter. Compared to seals at the “low-risk” site, seals at Seal Island avoided deep-water habitat around the island at high risk times and restricted their use of this habitat in favor of safe, shallow waters when engaging in social and thermoregulatory behaviors. Seals increased their frequency of jostling, porpoising, and diving when moving through the danger zone and seals in groups were safer than single individuals. Overall, our results suggest that seal behavior around the high-risk site is strongly affected by predation risk, and show this rookery to be an excellent predator-prey system at which to evaluate long-standing ecological hypotheses.
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suture index and growth in the male south african fur seal Arctocephalus pusillus pinnipedia otariidae
Proceedings of the Linnean Society of New South Wales, 2011Co-Authors: C. L. Stewardson, M A Meyer, T Prvan, S Swanson, Raymond J RitchieAbstract:The South African furs seal (Arctocephalus pusillus pusillus) is very closely related to the Australian fur seal (A. pusillus doriferus). We examine the relationship between skull suture index (SI*) and growth parameters in the male South African fur seal, based on 42 animals of known age ranging from 10 m to 11 y 11 m. Twenty one (21) animals were aged based upon tagging as pups and 21 were aged based on dentine growth layers (1 to 11 y). Suture index and morphometric information was available on an additional 27 males; 17 had no age information but 10 were known from their dentition to be >= 12 y. Age has previously been found to be approximately directly proportional to suture index. Here we estimate asymptotic size and growth kinetics from SI* using nonlinear growth models [exponential saturation (von Bertalanffy), Logistic, Gompertz] fitted to cross-sectional morphometric data (n = 8 variables). The relationship between the following measurements was examined and suture index are presented in the present study: external body (standard body length, SBL; length of front flipper; length of hind flipper), skull (condylobasal length, CBL; Bizygomatic breadth; mastoid breadth; length of Mandible or Ramus length) and baculum (bacular length, BL). The asymptote values of these parameters are compared to those derived from chronological age and show very good agreement. The growth kinetic parameters calculated in terms of SI* when converted into years using the relationship between SI* and true Age (y) are also in close agreement with those calculated on tag and dentition aged animals.
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suture index as an indicator of chronological age in the male south african fur seal Arctocephalus pusillus pinnipedia otariidae
Proceedings of the Linnean Society of New South Wales, 2011Co-Authors: C. L. Stewardson, M A Meyer, T Prvan, S Swanson, Raymond J RitchieAbstract:The South African fur seal (Arctocephalus pusillus pusillus) is very closely related to the Australian fur seal (A. pusillus doriferus). We examine skull suture index (SI*) as an indicator of chronological age in the male South African fur seal, based on 42 animals of known age ranging from 10 m to 11 y 11 m. Twenty one (21) animals were aged based upon tagging as pups and 21 were aged based on dentine growth layers (1 to 11 y). Age is approximately directly proportional to suture index [Age = (0.7990 +/- 0.02354) SI*, r = 0.8887, n = 42, valid SI* range 0 - 16, useful predictive range 0-≈14 y)]. We describe the sequence of cranial suture closure (n = 11 sutures, 69 animals) and determine whether suture index (SI*) reliably corresponds to chronological age. Sutures do not close in a definitive order in all individuals and some sutures take longer to close than others. In animals <= 12 y, the general sequence of full suture closure was the Basioccipito-basisphenoid, Occipito- parietal, Interparietal, Coronal and finally the Squamosal-jugal. The Maxillary, Squamosal-parietal, Interfrontal, Basisphenoid-presphenoid, Internasal were used in the SI* calculation even though none showed any sign of closure in the known-age individuals but did show some closure in very old animals of indeterminate age. Suture closure criteria are useful in classifying males into juveniles, subadults and adults. Multiple linear regression might also prove to be useful to predict chronological age from suture closure data but its utility was limited in the present study by both the size of the data set available and the lack of animals with a known age older than 12y. More data is needed on old animals of known age but the relationship between skull sutures and age found in the present study would be sufficient for aging most male skull material because very few males are likely to reach ages greater than about 12-14 y.
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sexual dimorphism in the adult south african cape fur seal Arctocephalus pusillus pusillus pinnipedia otariidae standard body length and skull morphology
Proceedings of the Linnean Society of New South Wales, 2010Co-Authors: C. L. Stewardson, M A Meyer, T Prvan, Raymond J RitchieAbstract:We examine differences in standard body length and skull morphology of male (n = 65) and female (n = 18) South African (Cape) fur seals, 'Arctocephalus pusillus pusillus', from the coast of southern Africa with the aim to develop an objective method for determining the sex of fur seal skulls. Males were found to be significantly larger than females in standard body length, with K-means cluster analysis successfully identifying 2 relatively homogeneous groups. Principal component analysis (covariance matrix) showed that the underlying data structure for male and female skull variables was different, and that most of this variation was expressed in overall skull size rather than shape. Males were significantly larger than females in 30 of the 31 skull variables. Breadth of brain case was significantly different for the genders. Relative to condylobasal length, males were significantly larger than females in 13 of the 31 skull variables used in the present study. These were gnathion to posterior end of nasals, breadth at preorbital processes, least interorbital constriction, breadth at supraorbital processes, greatest bicanine breadth, breadth of palate at postcanine 1 and 3, calvarial breadth, mastoid breadth, gnathion to anterior of foramen infraorbital, gnathion to posterior border of preorbital process, height of skull at base of mastoid and height of mandible at meatus. In males, these variables were associated with the acquisition and defense of territory (e.g., large head size and mass; increased structural strength of the skull; increased bite capacity). Two skull ratio parameters, breadth of braincase/condylobasal length and length of upper postcanine row/condylobasal length were significantly higher in females compared to males. Based solely on the skull data, mature males can be reliably distinguished from immature males and females using both (a) Classification and Regression Tree (CART) and (b) Hierarchical Cluster Analysis. Both approaches had difficulty in reliably distinguishing immature males from females. The Classification and Regression Tree method was the more successful in correctly distinguishing immature males from females.
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age determination and growth in the male south african fur seal Arctocephalus pusillus pusillus pinnipedia otariidae using external body measurements
Proceedings of the Linnean Society of New South Wales, 2009Co-Authors: C. L. Stewardson, M A Meyer, T Prvan, R J RitchleAbstract:Morphology, relative size and growth of the South African fur seal or Cape fur seal, Arctocephalus pusillus pusillus, from the coast of southern Africa are described and comparisons made to data available on the closely related Australian fur seal (Arctocephalus pusillus doriferus) and the New Zealand fur seal (Arctocephalus forsteri). Useful information can be gained from body measurements of seal carcasses provided canine teeth are extracted for aging. External body measurements (12 linear variables) were examined in relation to standard body length (SBL) and chronological age (y) using linear regression and non-linear least squares fitting as appropriate. Animals ranged from 10 y and unaged animals > 200 cm was 199 cm. Relative to SBL, facial variables and the fore/hind limbs scaled with negative slope relative to SBL or were negatively allometric; tip of snout to genital opening scaled with positive slope; and tip of snout to anterior insertion of the fore flipper was positively allometric. Relative to age, body variables scaled were negatively allometric. SBL was found to be a 'rough indicator' of age and age group. The growth kinetics of juvenile and adult the South African fur seal and the Australian fur seal are best described by the logistic and double exponential (Gompertz) models rather than the exponential von Bertalanffy model. Australian fur seals grow at a faster rate but asymptotic maximum sizes are similar in South African and Australian fur seals.