Dive behaviour, foraging locations and maternal-attendance patterns in Australian fur seals (Arctocephalus pusillus doriferus)

The dive behaviour, foraging locations, and colony-attendance patterns of female Australian fur seals (Arctocephalus pusillus doriferus) from Kanowna Island (39&deg;10\u27S, 146&deg;18\u27E) in Bass Strait, southeastern Australia, were determined throughout lactation during 1997&ndash;1999. Foraging-trip durations increased as lactation progressed, being shortest in summer (3.71 &plusmn; 0.24 days; mean &plusmn; 1 SE) and longest in winter (6.77 &plusmn; 0.57 days, P &lt; 0.05), but maternal-attendance periods did not differ in duration (1.70 &plusmn; 0.10 days, P &gt; 0.5). Individual mean attendance periods and trip durations were positively correlated (r2 = 0.21, P &lt; 0.005). Diving commenced shortly after seals left the colony (2.6 &plusmn; 0.4 h), was continuous for long periods (up to 36 h), occurred mostly during daylight hours, and lacked regular diel variation in depth. The majority of dives (78%) were typically U-shaped and reached depths corresponding to the prevailing depths in Bass Strait (65&ndash;85 m), indicating that these animals forage mostly on the benthos of the shallow continental shelf in this region. Such behaviour is unusual for fur seals but is reminiscent of that of some sea lion species. Mean dive durations varied between 2.0 and 3.7 min (maximum 8.9 min) and the theoretical aerobic dive limit (3.91&ndash;4.26 min) was exceeded on 17.3% of dives. Dive frequency (8.3 &plusmn; 0.6/h) and the proportion of time at sea spent diving (40.7 &plusmn; 2.1%) were weakly negatively related to the duration of the foraging trip (r2= 0.07, P &lt; 0.004, and r2 = 0.13, P &lt; 0.0001, respectively). Data from at-sea locations showed that lactating females forage almost exclusively within Bass Strait during all seasons. <br /

Australian fur seal

&quot;Now in it\u27s third edition, and with over 850 pages, this book provides an account of every species of native mammal known to have existed in Australia.&quot;--Publisher\u27s website. <br /

Utilisation of intensive foraging zones by female Australian fur seals.

Within a heterogeneous environment, animals must efficiently locate and utilise foraging patches. One way animals can achieve this is by increasing residency times in areas where foraging success is highest (area-restricted search). For air-breathing diving predators, increased patch residency times can be achieved by altering both surface movements and diving patterns. The current study aimed to spatially identify the areas where female Australian fur seals allocated the most foraging effort, while simultaneously determining the behavioural changes that occur when they increase their foraging intensity. To achieve this, foraging behaviour was successfully recorded with a FastLoc GPS logger and dive behaviour recorder from 29 individual females provisioning pups. Females travelled an average of 118 ± 50 km from their colony during foraging trips that lasted 7.3 ± 3.4 days. Comparison of two methods for calculating foraging intensity (first-passage time and first-passage time modified to include diving behaviour) determined that, due to extended surface intervals where individuals did not travel, inclusion of diving behaviour into foraging analyses was important for this species. Foraging intensity 'hot spots' were found to exist in a mosaic of patches within the Bass Basin, primarily to the south-west of the colony. However, the composition of benthic habitat being targeted remains unclear. When increasing their foraging intensity, individuals tended to perform dives around 148 s or greater, with descent/ascent rates of approximately 1.9 m•s-1 or greater and reduced postdive durations. This suggests individuals were maximising their time within the benthic foraging zone. Furthermore, individuals increased tortuosity and decreased travel speeds while at the surface to maximise their time within a foraging location. These results suggest Australian fur seals will modify both surface movements and diving behaviour to maximise their time within a foraging patch

Body composition changes, metabolic fuel use and energy expenditure during extended fasting in subantarctic fur seal (Arctocephalus tropicalis) pups at Amsterdam Island

The fasting metabolism of 71- to 235-d-old subantarctic fur seal (Arctocephalus tropicalis) pups from Amsterdam Island, southern Indian Ocean, was investigated during the long foraging trips of their mothers. Body lipid reserves were proportionally greater in female than male pups and higher in postmoult (37%) than premoult (10%) animals. The mass-specific rate of mass loss did not differ between the sexes but was lower than observed in other species. Daily mass loss was estimated to 56% fat, 10% protein, and 34% water. The rate of protein catabolism (15 g d&minus;1) was negatively related to the size of initial lipid stores and accounted for 9% (&plusmn;1%) of total energy expenditure. However, body composition changes during the fast were not equal between the sexes, with females relying more on protein catabolism than males (11% and 5% of total energy expenditure, respectively). Energy expenditure (270 kJ kg&minus;1 d&minus;1) and metabolic water production (11.5 mL kg&minus;1 d&minus;1) rates are the lowest reported for an otariid species. These results suggest that subantarctic fur seal pups greatly reduce activity levels to lower energy expenditure in addition to adopting protein-sparing metabolic pathways in order to survive the extreme fasts they must endure on Amsterdam Island.<br /

Diet of common diving-petrels (Pelecanoides Urinatrix Urinatrix) in Southeastern Australia during chick rearing

Unlike conspecifics in the subantarctic region, which typically begin breeding in mid-spring to summer, Common Diving-petrels Pelecanoides urinatrix urinatrix in southeastern Australia (towards the northern limit of the species\u27 distribution) commence breeding mid winter. Knowledge of the foraging ecology of this species is crucial to understanding the factors that influence its timing of breeding in the region, yet there is currently little information available. Analysis of 43 stomachs of breeding adults, collected opportunistically after they were killed in a fire which burned through their colony, indicated that their diet was dominated by two taxa: a euphausiid Nyctiphanes australis which comprised 87% of the diet by number; and a hyperiid amphipod Themisto australis which constituted a further 12.5%. Mean lengths (&plusmn;SE) of N. australis (n = 39) and T. australis (n = 41) were 12 mm (&plusmn;0.3) and 5.2 mm (&plusmn;0.2), respectively. The importance of N. australis in the diet of Common Diving-petrels is discussed in relation to their timing of breeding and the euphausiid\u27s potential role in the Bass Strait pelagic ecosystem.<br /

The lactation cycle of the fur seal

The fur seal is a mammal with an unusual ability to turn its milk production on and off without significantly altering the gross morphology of the mammary gland. This atypical lactation cycle is due to the fact that maternal foraging and infant nursing are spatially and temporally separate (Bonner, 1984). Maternal care involves the suckling of offspring over a period of at least 4 months, but lactation can extend to more than 12 months. Following a perinatal fast of approximately 1 week, females depart the breeding colony to forage at sea and, for the remainder of lactation, alternate between short periods ashore suckling their young with longer periods of up to 4 weeks foraging at sea. Whilst foraging at sea, milk production in the fur seal mammary gland either ceases or is reduced (Arnould &amp; Boyd, 1995b).<br /

Timing of breeding and diet of the Black-faced cormorant Phalacrocorax fuscescens

Previous anecdotal reports have suggested that Black-faced Cormorant Phalacrocorax fuscescens breeds only in winter in southeastern Australia, but detailed reports confirming this are lacking. Here we examine the timing of breeding in Black-faced Cormorants at Notch Island in northern Bass Strait in 2006. Peak laying occurred during winter (ca 26 July). The diet of Black-faced Cormorants was predominantly fish (97% of identified prey) and varied between breeding and post-breeding periods. Black-faced Cormorants consumed a total of 14 different species with four species having a frequency of occurrence in the diet of ?5% during the breeding season and six species during the post-breeding period. We provide data for the first time on the chronology of breeding of Black-faced Cormorants in one year and give a preliminary description of their diet based on pellet analyses. We propose that late winter breeding may be a strategy to avoid the high ambient temperatures in northern Bass Strait during summer, the associated higher thermoregulatory costs for adults and the increased mortality for chicks

The effect of the G-Layer on the viscoelastic properties of tropical hardwoods

International audienceContext and aim : This study aimed to examine the effect of the tension wood G‐layer on the viscoelastic properties of wood. Methods : Tension wood and opposite wood samples were obtained from six French Guianese tropical rainforest species (Sextonia rubra, Ocotea guyanensis, Inga alba, Tachigali melinoni, Iyranthera sagotiana and Virola michelii); the tension wood of the former three of these species had a Glayer, whilst the tension wood from the latter three had no Glayer. Tensile dynamic mechanical analysis (DMA) was performed on green never dried wood samples in the longitudinal direction with samples submerged in a water bath at a temperature (30°C) and frequency (1 Hz) representative of the conditions experienced by wood within a living tree. Then, DMA was repeated with samples conditioned to an air-dried state. Finally, samples were oven-dried to measure longitudinal shrinkage. Results : Tension wood did not always have a higher longitudinal storage (elastic) modulus than opposite wood from the same tree regardless of the presence or absence of a G‐layer. For the species containing a G‐layer, tension wood had a higher damping coefficient and experienced a greater longitudinal shrinkage upon drying than opposite wood from the same species. No difference was found in damping coefficients between tension wood and opposite wood for the species that had no G‐layer. Conclusion : It is proposed that the different molecular composition of the G-layer matrix has an influence on the viscoelasticity of wood, even if a biomechanical gain is not yet clear. This study shows that rheological properties and longitudinal shrinkage can be used to detect the presence of a G‐layer in tension wood

Ontogeny of body size and shape of Antarctic and subantarctic fur seals

Pre- and post-weaning functional demands on body size and shape of mammals are often in conflict, especially in species where weaning involves a change of habitat. Compared with long lactations, brief lactations are expected to be associated with fast rates of development and attainment of adult traits. We describe allometry and growth for several morphological traits in two closely related fur seal species with large differences in lactation duration at a sympatric site. Longitudinal data were collected from Antarctic (Arctocephalus gazella (Peters, 1875); 120 d lactation) and subantarctic (Arctocephalus tropicalis (Gray, 1872); 300 d lactation) fur seals. Body mass was similar in neonates of both species, but A. gazella neonates were longer, less voluminous, and had larger foreflippers. The species were similar in rate of preweaning growth in body mass, but growth rates of linear variables were faster for A. gazella pups. Consequently, neonatal differences in body shape increased over lactation, and A. gazella pups approached adult body shape faster than did A. tropicalis pups. Our results indicate that preweaning growth is associated with significant changes in body shape, involving the acquisition of a longer, more slender body with larger foreflippers in A. gazella. These differences suggest that A. gazella pups are physically more mature at approximately 100 d of age (close to weaning age) than A. tropicalis pups of the same age<br /