Temporal Allocation of Foraging Effort in Female Australian Fur Seals (Arctocephalus pusillus doriferus)

Across an individual''s life, foraging decisions will be affected by multiple intrinsic and extrinsic drivers that act at differing timescales. This study aimed to assess how female Australian fur seals allocated foraging effort and the behavioural changes used to achieve this at three temporal scales: within a day, across a foraging trip and across the final six months of the lactation period. Foraging effort peaked during daylight hours (57% of time diving) with lulls in activity just prior to and after daylight. Dive duration reduced across the day (196 s to 168 s) but this was compensated for by an increase in the vertical travel rate (1500–1600 m·h⁻¹) and a reduction in postdive duration (111–90 s). This suggests physiological constraints (digestive costs) or prey availability may be limiting mean dive durations as a day progresses. During short trips (<2.9 d), effort remained steady at 55% of time diving, whereas, on long trips (>2.9 d) effort increased up to 2–3 d and then decreased. Dive duration decreased at the same rate in short and long trips, respectively, before stabilising (long trips) between 4–5 d. Suggesting that the same processes (digestive costs or prey availability) working at the daily scale may also be present across a trip. Across the lactation period, foraging effort, dive duration and vertical travel rate increased until August, before beginning to decrease. This suggests that as the nutritional demands of the suckling pup and developing foetus increase, female effort increases to accommodate this, providing insight into the potential constraints of maternal investment in this species.     

Australian Fur Seals (Arctocephalus pusillus doriferus) Use Raptorial Biting and Suction Feeding When Targeting Prey in Different Foraging Scenarios

Foraging behaviours used by two female Australian fur seals (Arctocephalus pusillus doriferus) were documented during controlled feeding trials. During these trials the seals were presented with prey either free-floating in open water or concealed within a mobile ball or a static box feeding device. When targeting free-floating prey both subjects primarily used raptorial biting in combination with suction, which was used to draw prey to within range of the teeth. When targeting prey concealed within either the mobile or static feeding device, the seals were able to use suction to draw out prey items that could not be reached by biting. Suction was followed by lateral water expulsion, where water drawn into the mouth along with the prey item was purged via the sides of the mouth. Vibrissae were used to explore the surface of the feeding devices, especially when locating the openings in which the prey items had been hidden. The mobile ball device was also manipulated by pushing it with the muzzle to knock out concealed prey, which was not possible when using the static feeding device. To knock prey out of this static device one seal used targeted bubble blowing, where a focused stream of bubbles was blown out of the nose into the openings in the device. Once captured in the jaws, prey items were manipulated and re-oriented using further mouth movements or chews so that they could be swallowed head first. While most items were swallowed whole underwater, some were instead taken to the surface and held in the teeth, while being vigorously shaken to break them into smaller pieces before swallowing. The behavioural flexibility displayed by Australian fur seals likely assists in capturing and consuming the extremely wide range of prey types that are targeted in the wild, during both benthic and epipelagic foraging.     

Activity Budgets of Captive Cape Fur Seals (Arctocephalus pusillus) Under a Training Regime

Ethograms and time budgets are crucial for the behavioral assessment of nonhuman animals in zoos, and they serve as references for welfare research. This study was conducted to obtain detailed time budgets of trained Cape fur seals (Arctocephalus pusillus) in captivity, to evaluate variations of these patterns, and to determine whether abnormal behaviors had been displayed. Behavioral data for 3 Cape fur seals in the Wroclaw Zoo were collected, and more than 300 observation hours (during a 12-month period) per individual were analyzed. The studied animals exhibited a diversified repertoire of natural behaviors with apparent seasonal and daily patterns, and they did not present stereotypic behaviors. Significant differences of interaction rates between individuals suggest more frequent affiliative interactions among related animals. The absence of stereotypic behaviors, good health of individuals, and the presence of diversified natural behaviors indicated relatively good welfare of Cape fur seals kept in the Wroclaw Zoo.     

Identification of Prey Captures in Australian Fur Seals (Arctocephalus pusillus doriferus) Using Head-Mounted Accelerometers: Field Validation with Animal-Borne Video Cameras

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.     

Behavioral responses of Australian fur seals (Arctocephalus pusillus doriferus) to environmental variations

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.     

The composition of Australian fur seal (Arctocephalus pusillus doriferus) milk throughout lactation.

The proximate chemical composition of milk was determined throughout lactation in the Australian fur seal (Arctocephalus pusillus doriferus Wood Jones), a temperate species with an 11-mo lactation period typical of most temperate otariids. Average lipid and protein contents were 42% and 10%, respectively, which is similar to that recorded for the polar otariid species but higher than reported in other temperate, long-lactation species. Milk composition, however, varied substantially throughout lactation, with lipid content rising from 30% soon after parturition to 50% at 230 d postpartum before decreasing to 45% toward weaning. The trend in water content was opposite to that of lipid, while protein content increased only slightly during lactation from 10% to 12%. The peak in lipid content occurred at approximately 70% of the way through lactation, similar to that found in the Australian sea lion and several phocid seal species. Significant positive relationships were found between milk lipid content and both the duration of the preceding foraging trip and body mass. A highly significant and close correlation was found between milk water and lipid contents such that gross energy content may be accurately predicted from water content alone. Similar predictive equations have been found for several other otariid and phocid species, but these appear to differ between phylogenetic groups.     

Increased alertness behavior in Australian fur seals (Arctocephalus pusillus doriferus) at a high vessel traffic haul-out site

Vessel impacts on marine mammals are of growing concern, and marine mammals in urbanized marine environments are at particular risk of exposure. Port Phillip Bay (Victoria, Australia) is one such environment, in which Australian fur seals (AUFS; Arctocephalus pusillus doriferus) haul-out to rest, yet little is known about the impacts of vessels on resting seals. We used remote camera traps to investigate the influence of vessel traffic on AUFS behavior at a nonbreeding haul-out site. Environmental, temporal, and vessel-related variables were all associated with changes in AUFS alertness at this site. All vessel types elicited increased alertness above base-line levels (25%), with recreational and commercial motorized vessels associated with a 5.7%–10.8% increase in alertness. Unidentified vessels, the government vessel, and kayaks were associated with significantly increased alertness of 21.7%, 46.4%, and 60.7%, respectively, though accounted for only 6.2% of vessel observations. Vessels breaching current approach regulations (<5 m) showed a 32% increase in alertness, significantly higher than nonbreach approaches. Partial and complete flushing of the platform was rare, occurring in 1.0% of images analyzed. These results suggest that vessels do elicit a response from AUFS at this haul-out site, and that further monitoring of vessel activity and compliance is required.     

Chemical characterisation of the oligosaccharides in hooded seal (Cystophora cristata) and Australian fur seal (Arctocephalus pusillus doriferus) milk

Carbohydrates were extracted from hooded seal milk, Crystophora cristata (family Phocidae). Free oligosaccharides were separated by gel filtration and then purified by ion exchange chromatography, gel filtration and preparative thin layer or paper chromatography and their structures determined by 1H-NMR. The hooded seal milk was found to contain inositol and at least nine oligosaccharides, most of which had lacto-N-neotetraose or lacto-N-neohexaose as core units, similar to those in milk of other species of Carnivora such as bears (Ursidae). Their structures were as follows: Gal(beta1-4)Glc (lactose); Fuc(alpha1-2)Gal(beta1-4)Glc (2'-fucosyllactose); Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (lacto-N-neotetraose); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (lacto-N-fucopentaose IV); Gal(beta1-4)GlcNAc(beta1-3)[Gal(beta1-4)GlcNAc(beta1-6)]Gal(1-4)Glc (lacto-N-neohexaose); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)[Gal(beta1-4)GlcNAc(beta1-6)]Gal(beta1-4)Glc (monofucosyl lacto-N-neohexaose a); Gal(beta1-4)GlcNAc(beta1-3)[Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-6)]Gal(beta1-4)Glc (monofucosyl lacto-N-neohexaose b); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)[Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-6)]Gal(beta1-4)Glc (difucosyl lacto-N-neohexaose); Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (para lacto-N-neohexaose); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (monofucosyl para lacto-N-neohexaose). Milk of the Australian fur seal, Arctophalus pusillus doriferus (family Otariidae) contained inositol but no lactose or free oligosaccharides. These results, therefore, support the hypothesis that the milk of otariids, unlike that of phocids, contains no free reducing saccharides.     

Cephalopods in the diet of the South African fur seal (Arctocephalus pusillus pusillus)

The stomach contents of 1522 adult seals ( Arctocephalus pusillus pusillus ) and 673 pups, which were collected around the West and South Coasts of Southern Africa, were examined and cephalopod prey identified. About 20 cephalopod species (some identifications were uncertain) were found in the stomachs, of which only six were significant: Loligo vulgaris reynaudii. Sepia spp., Octopus sp., Todaropsis eblanae, Todarodes angolensis and Ocythoe tuberculata. This list suggests that A. pusillus feeds exclusively on the continental shelf, frequently on or near the bottom. Among adults, cephalopod prey varied in importance around the coast. It was most important on the South Coast of South Africa where it comprised 35.0% of the weight of all prey, of which L. v. veynaudii constituted about 88%. On the West Coast cephalopods comprised about 26.6% by weight of all prey, and Octopus sp. predominated, whereas in Namibian waters cephalopods were least important, constituting only 3.4% by weight of all prey, with Todarodes angolensis and Octopus sp. being most significant. Among pups (aged 8–10 months) in the Lüderitz (Namibia) area, cephalopods were about 16.9% of prey by weight, of which Ocythoe tuberculata , small Sepia spp. and Octopoda were most important.     

Isolation and Characterization of Campylobacter spp. from Antarctic Fur Seals (Arctocephalus gazella) at Deception Island,Antarctica

The presence of Campylobacter spp. was investigated in 41 Antarctic fur seals (Arctocephalus gazella) and 9 Weddell seals (Leptonychotes weddellii) at Deception Island, Antarctica. Infections were encountered in six Antarctic fur seals. The isolates, the first reported from marine mammals in the Antarctic region, were identified as Campylobacter insulaenigrae and Campylobacter lari.The Antarctic and sub-Antarctic regions are often regarded as pristine landscapes, unaffected by human activity. A limited number of surveys have been carried out to investigate the possible occurrence of zoonotic enteropathogens and if certain bacteria could be used as tools for evaluating biological pollution in this area (4, 11). In the case of Campylobacter species, there have been only three reports in the literature, but in all of them Campylobacter was isolated from marine seabirds but not from marine mammals. Campylobacter jejuni was isolated in Antarctic and sub-Antarctic areas from Macaroni penguins (Eudyptes chrysolophus) (4), and Campylobacter lari was isolated from Brown skuas, South Polar skuas, and Adelie penguins (2, 11).Reports of Campylobacter species isolated from marine mammals are rare. Campylobacter insulaenigrae was isolated from three harbor seals (Phoca vitulina) and a harbor porpoise (Phocoena phocoena) in Scotland (7). The isolation of C. jejuni, C. lari, and an unknown Campylobacter species from juvenile northern elephant seals (Mirounga angustirostris) in California was also reported (22). Finally, 71 isolates of C. insulaenigrae and 1 isolate similar to but distinct from both Campylobacter upsaliensis and Campylobacter helveticus were isolated from northern elephant seals in California (23). In the South Georgia Archipelago, fecal swabs were taken from 206 Antarctic fur seal pups, but no isolates could be obtained (4). In this study, we successfully isolated C. lari from 7.3% of Antarctic fur seals (Arctocephalus gazella) sampled and C. insulaenigrae from a further 7.3%. On the other hand, Campylobacter was not detected in the nine Weddell seals (Leptonychotes weddellii) sampled. To our knowledge, this is the first report on the isolation of C. lari and C. insulaenigrae from marine mammals in the Antarctic region.Fieldwork was conducted at Deception Island (latitude of 62°58′S and longitude of 60°40′W), in the South Shetland Islands. During January to February 2007, Antarctic fur seals (Arctocephalus gazella) and Weddell seals (Leptonychotes weddellii) were captured and fecal samples were collected by insertion of sterile cotton wool swabs into the rectum of the marine mammals. A total of 41 Antarctic fur seals and 9 Weddell seals were sampled. The distribution by ages was of 7 adults (over 4 years of age with breeding activity), 19 subadults (2 to 4 years of age), and 15 juvenile Antarctic fur seals (less than 2 years of age), and 8 adult Weddell seals and 1 juvenile. All animals presented a good body condition and showed no symptoms at the time of sampling.Three swabs were taken from each animal and were placed in FBP medium (8) with 0.5% active charcoal (Sigma Ltd.), Amies transport medium with charcoal, and Cary Blair transport medium, respectively. All samples were kept at +4 to 8°C until culture in the lab. The number of days between sampling and cultivation varied from 96 to 124 days, with a median value of 105 days.Each swab was placed in 10 ml of Campylobacter enrichment broth (Lab M) with 5% laked horse blood and CAT supplement (cefoperazone [8 μg/ml], teicoplanin [4 μg/ml], and amphotericin B [10 μg/ml]) at 37°C. The broth was incubated at 37°C for 48 h and 5 days in 3.5-liter anaerobic containers using CampyGen sachets (Oxoid), before an aliquot of 100 μl was plated onto CAT agar and the plates were incubated at 37°C for 72 h in a microaerobic atmosphere. In addition, a 47-mm-diameter cellulose membrane with 0.60-μm pores was placed on the surface of an anaerobe agar base (Oxoid) with 5% laked horse blood. Eight to 10 drops of enrichment broth (200 μl) were placed onto the surface of the membrane. The membrane was left for 20 to 30 min on the agar surface at room temperature until all of the fluid had passed through (20). The plates were incubated as described above, but for 5 days to isolate the less common, slower growing species.Isolates were examined by dark-field microscopy to determine morphology and motility and tested to determine whether oxidase was produced. For each sample, five isolates from each of the solid media that had typical morphology and motility and for which the oxidase test was positive were frozen at −80°C in FBP medium (8) until they were tested by phenotypic and genotypic methods.Original Campylobacter identification was done by Gram staining, catalase activity, hippurate hydrolysis, ability to hydrolyze indoxyl acetate, urease activity, H₂S production on triple-sugar iron slants, growth at 25°C and 42°C in a microaerophilc environment, growth at 37°C in an aerobic atmosphere, and agglutination with Microscreen latex (Microgen, Camberley, United Kingdom).No differences between the strains were observed in any of the phenotypic tests used. All isolates showed a Gram-negative, slender, curved, seagull wing-like morphology under light microscopy and positive reactions in the catalase test. They were negative for hippurate and indoxyl acetate hydrolysis and urease and did not show H₂S production. In addition, they grew at 42°C but did not grow at 25°C or 37°C in an aerobic atmosphere. Finally, all of them were positive in the agglutination test.Because phenotypic results commonly lead to misidentification of Campylobacter species, it is recommended that a molecular method be included in the identification scheme for Campylobacter (5, 15). Identification of the isolates was performed using 16S rRNA gene PCR and sequence analysis (15, 21). Forward and reverse conserved 16S rRNA eubacterial primers 8F (5′-AGAGTTTGATCCTGGCTCAG-3′) and 1492R (5′-GGTTACCTTGTTACGACTT-3′) were used to amplify the 16S rRNA according to the protocol described by Jang et al. (9). Forward and reverse sequencing reactions were performed by the Laboratorio Central de Veterinaria''s DNA sequencing facility (LCV Algete, Madrid, Spain). Three strains were identified as C. lari and the other three as C. insulaenigrae based on both forward and reverse sequence analysis.Molecular characterization of strains was carried out using a combination of pulsed-field gel electrophoresis (PFGE) using KpnI enzyme and multilocus sequence typing (MLST). Preparation of intact Campylobacter DNA for PFGE was performed following the Pulsenet protocol (17, 24). PFGE for the restriction enzyme KpnI (Takara, Conda, Spain) was performed following the protocol described by Ribot et al. (17). DNA fragments were resolved on 0.9% Seakem Gold agarose gels (Iberlabo, Spain) with a Bio-Rad CHEF DRIII system (Bio-Rad, Spain) at 14°C and 6 V/cm. Electrophoresis was carried out for 22 h with pulse times ramping from 4 s to 20 s. The fingerprinting experiments were analyzed using the InfoQuest FP software (Bio-Rad, Spain), and the dendrogram was constructed using the unweighted-pair group method using average linkages (UPGMA).MLST of C. lari strains was performed as described by Miller et al. (13). In the case of C. insulaenigrae strains, MLST was performed following the protocol described by Stoddard et al. (23). All amplicons were sequenced by the Sequencing Service of the Instituto de Salud Carlos III (Madrid, Spain). Sequence data were collated, and alleles were assigned using the Campylobacter PubMLST database (http://pubmlst.org/campylobacter/). Novel alleles and sequence types were submitted for allele and sequence type (ST) designations when appropriate.Regarding the age distribution of animals, C. lari was isolated from 1 of 7 adult (14.3%), 1 of 19 subadult (5.3%), and 1 of 15 juvenile (6.6%) Antarctic fur seals. C. insulaenigrae was isolated from 1 of 7 adults (14.3%) and 2 of 19 of subadults (10.5%) but not from juvenile animals (Table ​(Table1).1). All strains were obtained from the swabs kept in FBP transport medium.

TABLE 1.

Source of Campylobacter isolates

Behavior of Cape fur seals (Arctocephalus pusillus pusillus) in response to spatial variation in white shark (Carcharodon carcharias) predation risk

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.     

Olfactory discrimination ability of South African fur seals (Arctocephalus pusillus) for enantiomers

Using a food-rewarded two-choice instrumental conditioning paradigm we assessed the ability of South African fur seals, Arctocephalus pusillus, to discriminate between 12 enantiomeric odor pairs. The results demonstrate that the fur seals as a group were able to discriminate between the optical isomers of carvone, dihydrocarvone, dihydrocarveol, menthol, limonene oxide, α-pinene, fenchone (all p < 0.01), and β-citronellol (p < 0.05), whereas they failed to distinguish between the (+)- and (?)-forms of limonene, isopulegol, rose oxide, and camphor (all p > 0.05). An analysis of odor structure–activity relationships suggests that a combination of molecular structural properties rather than a single molecular feature may be responsible for the discriminability of enantiomeric odor pairs. A comparison between the discrimination performance of the fur seals and that of other species tested previously on the same set of enantiomers (or subsets thereof) suggests that the olfactory discrimination capabilities of this marine mammal are surprisingly well developed and not generally inferior to that of terrestrial mammals such as human subjects and non-human primates. Further, comparisons suggest that neither the relative nor the absolute size of the olfactory bulbs appear to be reliable predictors of between-species differences in olfactory discrimination capabilities. Taken together, the results of the present study support the notion that the sense of smell may play an important and hitherto underestimated role in regulating the behavior of fur seals.     

An Empirical Case Study Examining Effectiveness of Environmental Enrichment in Two Captive Australian Sea Lions (Neophoca cinerea)

This case study examined the effect of environmental enrichment on the activity budgets of a male and female Australian Sea Lion (Neophoca cinerea) housed together at Adelaide Zoo. Using non-food-related (intrinsic) and food-related (extrinsic) enrichment objects, the study conducted an ABABA (withdrawal) experimental design over a 30-day period (180 hr). The study expected extrinsically reinforcing objects to be more effective than intrinsically reinforcing objects in reducing pattern swimming. The male sea lion spent more than 45% of scans engaged in pattern swimming during the initial baseline, which was reduced by at least 25% when enrichment items were present. However, there was no evidence of stereotypic behavior in the female sea lion, indicating that individual differences may exist. When enrichment was present, the study observed more active behaviors in both nonhuman animals. They spent more time interacting with the non-food-related objects overall. Therefore, introducing simple enrichment devices offers a cheap, practical, and effective method of adding complexity to the environment, which is likely to benefit the animals' welfare and enhance the zoo-visitor experience.     

Killing of Cape fur seal (Arctocephalus pusillus pusillus) pups by brown hyenas (Parahyaena brunnea) at mainland breeding colonies along the coastal Namib Desert

Brown hyenas (Parahyaena brunnea) scavenge and kill seal pups at mainland Cape fur seal (Arctocephalus pusillus pusillus) colonies. The prey encounter interval and interval between kills depended on seal density, and increased density resulted in an increase of the capture rate and increase in hunting efficiency from 14% in November to 47% in January. The time brown hyenas spent at the seal colony decreased with increasing seal density and increasing air temperatures. Nevertheless, they were regularly active during the day when less adult seals were present at the colony, which indicates that the attendance of adult seals might play a role in the choice of foraging time. Brown hyenas killed seal pups throughout the study period. The predation rate was independent of the availability of non-violent mortalities, but the absolute number of kills was positively density-dependent. Mass kill events were recorded throughout the study period and are therefore not unusual occurrences. The overabundance of easy and vulnerable prey may lead to an over stimulus situation that triggers killing independent of the consumption of the prey or the hunger state.     

The physiological and behavioural development of diving in Australian fur seal (<Emphasis Type="Italic">Arctocephalus pusillus doriferus</Emphasis>) pups

The physiological and behavioural development of diving was examined in Australian fur seal (Arctocephalus pusillus doriferus) pups to assess whether animals at weaning are capable of exploiting the same resources as adult females. Haematocrit, haemoglobin and myoglobin contents all increased throughout pup development though total body oxygen stores reached only 71% of adult female levels just prior to weaning. Oxygen storage components, however, did not develop at the same pace. Whereas blood oxygen stores had reached adult female levels by 9 months of age, muscle oxygen stores were slower to develop, reaching only 23% of adult levels by this age. Increases in diving behaviour corresponded to the physiological changes observed. Pups spent little time (<8%) in the water prior to moulting (age 1–2 months) whereas following the moult, they spent >27% of time in the water and made mid-water dives (maximum depth 35.7 ± 2.9 m) with durations of 0.35 ± 0.03 min. By 9 months (just prior to weaning), 30.5 ± 9.3% of all dives performed were U-shaped benthic dives (maximum depth 65.0 ± 6.0 m) with mean durations of 0.87 ± 0.25 min, significantly shorter than those of adult females. These results suggest that while Australian fur seal pups approaching the age of weaning are able to reach similar depths as adult females, they do not have the physiological capacity to remain at these depths for sufficient durations to exploit them to the same efficiency.