scholarly journals The cost of a meal: factors influencing prey profitability in Australian fur seals

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12608
Author(s):  
Nelle Meyers ◽  
Cassie N. Speakman ◽  
Nicole A.S.-Y. Dorville ◽  
Mark A. Hindell ◽  
Jayson M. Semmens ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Prey Type ◽  
Video Data ◽  
Foraging Strategies ◽  
Costs And Benefits ◽  
Fur Seals ◽  
Data Loggers ◽  
Eastern Australia ◽  
Survival And Reproduction ◽  
Gross Energy

Knowledge of the factors shaping the foraging behaviour of species is central to understanding their ecosystem role and predicting their response to environmental variability. To maximise survival and reproduction, foraging strategies must balance the costs and benefits related to energy needed to pursue, manipulate, and consume prey with the nutritional reward obtained. While such information is vital for understanding how changes in prey assemblages may affect predators, determining these components is inherently difficult in cryptic predators. The present study used animal-borne video data loggers to investigate the costs and benefits related to different prey types for female Australian fur seals (Arctocephalus pusillus doriferus), a primarily benthic foraging species in the low productivity Bass Strait, south-eastern Australia. A total of 1,263 prey captures, resulting from 2,027 prey detections, were observed in 84.5 h of video recordings from 23 individuals. Substantial differences in prey pursuit and handling times, gross energy gain and total energy expenditure were observed between prey types. Importantly, the profitability of prey was not significantly different between prey types, with the exception of elasmobranchs. This study highlights the benefit of animal-borne video data loggers for understanding the factors that influence foraging decisions in predators. Further studies incorporating search times for different prey types would further elucidate how profitability differs with prey type.

scholarly journals Multi-predator assemblages, dive type, bathymetry and sex influence foraging success and efficiency in African penguins

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9380 ◽  
Author(s):  
Grace Sutton ◽  
Lorien Pichegru ◽  
Jonathan A. Botha ◽  
Abbas Z. Kouzani ◽  
Scott Adams ◽  
...  
Keyword(s):  
Prey Capture ◽  
Prey Availability ◽  
Video Recording ◽  
Video Data ◽  
Foraging Strategies ◽  
Predatory Fish ◽  
Specific Information ◽  
Single Individual ◽  
Foraging Success ◽  
Data Loggers

Marine predators adapt their hunting techniques to locate and capture prey in response to their surrounding environment. However, little is known about how certain strategies influence foraging success and efficiency. Due to the miniaturisation of animal tracking technologies, a single individual can be equipped with multiple data loggers to obtain multi-scale tracking information. With the addition of animal-borne video data loggers, it is possible to provide context-specific information for movement data obtained over the video recording periods. Through a combination of video data loggers, accelerometers, GPS and depth recorders, this study investigated the influence of habitat, sex and the presence of other predators on the foraging success and efficiency of the endangered African penguin, Spheniscus demersus, from two colonies in Algoa Bay, South Africa. Due to limitations in the battery life of video data loggers, a machine learning model was developed to detect prey captures across full foraging trips. The model was validated using prey capture signals detected in concurrently recording accelerometers and animal-borne cameras and was then applied to detect prey captures throughout the full foraging trip of each individual. Using GPS and bathymetry information to inform the position of dives, individuals were observed to perform both pelagic and benthic diving behaviour. Females were generally more successful on pelagic dives than males, suggesting a trade-off between manoeuvrability and physiological diving capacity. By contrast, males were more successful in benthic dives, at least for Bird Island (BI) birds, possibly due to their larger size compared to females, allowing them to exploit habitat deeper and for longer durations. Both males at BI and both sexes at St Croix (SC) exhibited similar benthic success rates. This may be due to the comparatively shallower seafloor around SC, which could increase the likelihood of females capturing prey on benthic dives. Observation of camera data indicated individuals regularly foraged with a range of other predators including penguins and other seabirds, predatory fish (sharks and tuna) and whales. The presence of other seabirds increased individual foraging success, while predatory fish reduced it, indicating competitive exclusion by larger heterospecifics. This study highlights novel benthic foraging strategies in African penguins and suggests that individuals could buffer the effects of changes to prey availability in response to climate change. Furthermore, although group foraging was prevalent in the present study, its influence on foraging success depends largely on the type of heterospecifics present.

Influence of shelf oceanographic variability on alternate foraging strategies in long-nosed fur seals

2019 ◽  
Vol 615 ◽  
pp. 189-204 ◽  
Author(s):  
D Foo ◽  
C McMahon ◽  
M Hindell ◽  
S Goldsworthy ◽  
F Bailleul
Keyword(s):  
Foraging Strategies ◽  
Fur Seals

scholarly journals Diving deep into trouble: the role of foraging strategy and morphology in adapting to a changing environment

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Monique Ladds ◽  
David Rosen ◽  
Carling Gerlinsky ◽  
David Slip ◽  
Robert Harcourt
Keyword(s):  
Foraging Strategy ◽  
Central Place ◽  
Dive Duration ◽  
Foraging Strategies ◽  
Body Morphology ◽  
Sea Lions ◽  
Fur Seals ◽  
Adequate Food ◽  
Physiological Capacity ◽  
Total Body Oxygen

Abstract Physiology places constraints on an animal’s ability to forage and those unable to adapt to changing conditions may face increased challenges to reproduce and survive. As the global marine environment continues to change, small, air-breathing, endothermic marine predators such as otariids (fur seals and sea lions) and particularly females, who are constrained by central place foraging during breeding, may experience increased difficulties in successfully obtaining adequate food resources. We explored whether physiological limits of female otariids may be innately related to body morphology (fur seals vs sea lions) and/or dictate foraging strategies (epipelagic vs mesopelagic or benthic). We conducted a systematic review of the increased body of literature since the original reviews of Costa et al. (When does physiology limit the foraging behaviour of freely diving mammals? Int Congr Ser 2004;1275:359–366) and Arnould and Costa (Sea lions in drag, fur seals incognito: insights from the otariid deviants. In Sea Lions of the World Fairbanks. Alaska Sea Grant College Program, Alaska, USA, pp. 309–324, 2006) on behavioural (dive duration and depth) and physiological (total body oxygen stores and diving metabolic rates) parameters. We estimated calculated aerobic dive limit (cADL—estimated duration of aerobic dives) for species and used simulations to predict the proportion of dives that exceeded the cADL. We tested whether body morphology or foraging strategy was the primary predictor of these behavioural and physiological characteristics. We found that the foraging strategy compared to morphology was a better predictor of most parameters, including whether a species was more likely to exceed their cADL during a dive and the ratio of dive time to cADL. This suggests that benthic and mesopelagic divers are more likely to be foraging at their physiological capacity. For species operating near their physiological capacity (regularly exceeding their cADL), the ability to switch strategies is limited as the cost of foraging deeper and longer is disproportionally high, unless it is accompanied by physiological adaptations. It is proposed that some otariids may not have the ability to switch foraging strategies and so be unable adapt to a changing oceanic ecosystem.

The composition of the milk of antarctic (Arctocephalus gazella) and subantarctic (A. tropicalis) fur seals at Macquarie Island

1999 ◽  
Vol 47 (6) ◽  
pp. 593 ◽  
Author(s):  
Simon D. Goldsworthy ◽  
Helen M. Crowley
Keyword(s):  
Water Content ◽  
Energy Content ◽  
Post Partum ◽  
Milk Composition ◽  
Arctocephalus Gazella ◽  
Macquarie Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Gross Energy ◽  
Subantarctic Fur Seals

The composition of milk collected from 36 antarctic (Arctocephalus gazella) and 17 subantarctic fur seals (A. tropicalis) breeding sympatrically at Macquarie Island was examined over the first 100 days of lactation in the 1990/91 season. The mean composition of milk in A. gazella and A. tropicalis was 41.3% and 44.6% water, 39.8% and 38.6% lipid, 18.1% and 16.1% protein, and the estimated gross energy content of milk was 19.9 and 18.9 kJ g–1, respectively. Neither the composition of milk nor its energy density differed significantly between species, despite a difference of 4–6 months in lactation length. Water content of milk could be used to predict lipid (r2 = 0.67) and protein (r2 = 0.57) content, but was most accurate at predicting gross energy content (r2 = 0.97). These relationships were the same for each species. The water content of milk decreased throughout the first 100 days of lactation in both species, while lipid, protein and energy content all increased. The addition of maternal mass into regression analysis with days post-partum increased the significance of models predicting the content of lipid and proteins in the milk, but not those predicting the water or gross energy content. Milk collected on the first day of 2-day attendance bouts had, on average, 9% greater lipid content, and 5% greater protein content than milk collected on the second day. The growth rates of subantarctic fur seal pups were significantly lower than those of antarctic fur seal pups over the first month of growth, suggesting that (despite similar milk composition, attendance patterns and diet of the two species of fur seal) the overall rates of energy transfer from mother to pup in subantarctic fur seals is lower than in antarctic fur seals.

scholarly journals Ambient temperature and algal prey type affect essential fatty acid incorporation and trophic upgrading in a herbivorous marine copepod

2020 ◽  
Vol 375 (1804) ◽  
pp. 20200039 ◽  
Author(s):  
Laura Helenius ◽  
Suzanne M. Budge ◽  
Heather Nadeau ◽  
Catherine L. Johnson
Keyword(s):  
Fatty Acids ◽  
Ambient Temperature ◽  
Environmental Variability ◽  
Essential Fatty Acids ◽  
Prey Type ◽  
Growth Efficiency ◽  
Dietary Fatty Acids ◽  
Calanus Finmarchicus ◽  
Marine Copepod ◽  
Gross Growth Efficiency

The essential fatty acids (EFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are critical nutrients for all organisms, and the temperature sensitivity of their trophic transfer in marine systems is of concern because of rising ocean temperatures. Laboratory-reared copepodites of the marine calanoid Calanus finmarchicus were used to test the effects of temperature (at 6°C, 12°C and increasing temperature stress) and prey type (the dinoflagellate Heterocapsa triquetra and the diatom Thalassiosira weissflogii ) on the extent and efficiency of dietary EPA and DHA incorporation from phytoplankton to copepods in a set of feeding experiments using 13 C labelling. Temperature was a significant determinant of C . finmarchicus copepodites' EFA incorporation and gross growth efficiency, defined as the fraction of ingested EFA retained in copepod tissue. Ingestion and incorporation of both EFA were higher at warmer temperature, except in the case of DHA in copepods feeding on diatoms. DHA-associated growth efficiency was higher at the higher temperature for copepodites consuming the dinoflagellate, but temperature-related variation in algal EFA content was also a predictive factor. Moreover, our results strongly suggest that copepodites are capable of synthesizing EPA when consuming an EPA-depleted diet. Our study implies that the copepod link of marine food webs is resilient in terms of EFA transfer when confronted with alterations of ambient temperature and prey type availability. Measurements presented here are critical for estimating how EFA transfer dynamics respond to intra- and interannual environmental variability. This article is part of the theme issue ‘The next horizons for lipids as ‘trophic biomarkers’: evidence and significance of consumer modification of dietary fatty acids’.

Digestible energy content of cereals and wheat by-products for growing pigs

1980 ◽  
Vol 31 (3) ◽  
pp. 259-271 ◽  
Author(s):  
E. S Batterham ◽  
C. E. Lewis ◽  
R. F. Lowe ◽  
C. J. McMillan
Keyword(s):  
Energy Content ◽  
Growing Pigs ◽  
Crude Fibre ◽  
Digestible Energy ◽  
Eastern Australia ◽  
Gross Energy ◽  
The Mean ◽  
Physical And Chemical ◽  
By Products ◽  
Proximate Analyses

ABSTRACT1. The digestible energy content of eight samples of barley, sorghum, wheat, weather-damaged wheat and wheat by-products produced from different regions of eastern Australia was determined using growing pigs. The relationships between physical and chemical composition and digestible energy content of the meals were studied.2. The mean and range in digestible energy (MJ/kg, air-dry basis) were, respectively: barleys 12·7 (12·4 to 13·0), sorghums 14·4 (14·1 to 14·9), wheats 14·4 (14·0 to 15·0), weather-damaged wheats 14·1 (12·9 to 14·9) and wheat by-products 12·4 (10·9 to 14·1).3. All possible regressions of digestible energy content against density, gross energy and proximate analyses of the meals were screened to select useful relationships. These screens indicated that, with the exception of wheat by-products, the majority of variation in digestible energy was due to gross energy and fibre. For wheat by-products, a combination of density and fibre accounted for most of the variation.4. Prediction equations had the most application to weather-damaged wheats, wheat by-products and a combination of all samples.5. There was no indication that neutral-detegent fibre was superior to crude fibre as a predictor of digestible energy in cereals for pigs.

Environmental and physiological determinants of successful foraging by naive southern elephant seal pups during their first trip to sea

1999 ◽  
Vol 77 (11) ◽  
pp. 1807-1821 ◽  
Author(s):  
Mark A Hindell ◽  
Bernie J McConnell ◽  
M A Fedak ◽  
David J Slip ◽  
Harry R Burton ◽  
...  
Keyword(s):  
Elephant Seal ◽  
The Body ◽  
Diving Behaviour ◽  
Foraging Strategies ◽  
Southern Elephant Seal ◽  
Mirounga Leonina ◽  
Diurnal Pattern ◽  
Data Loggers ◽  
Southern Elephant Seals ◽  
Light Group

The ability to forage successfully during their first trip to sea is fundamental to the ultimate survival of newly weaned southern elephant seals (Mirounga leonina). However, there is considerable variation in the body mass and fat content of seal pups at weaning, which results in some individuals having larger energy and oxygen stores than others, which may confer advantages on them. The diving behaviour of 21 newly weaned seals was studied using satellite relayed data loggers. Seals were captured at Macquarie Island in December 1995 and 1996, approximately 4 weeks after weaning. Two groups of seals were specifically targeted: a heavy group from the top quartile of weaning masses (n = 6) and a light group from the lower quartile (n = 15). Most of the seals made dives in excess of 100 m depth and 5 min before final departure from the island. However, for the first 60-80 d, all of the seals exhibited behaviour quite distinct from the patterns reported for older conspecifics, and made relatively shallow (100 ± 39 m; mean ± SD) and short (5.7 ± 1.23 min) dives. During this time the seals spent 74.3 ± 12.6% of each day diving, and the depth of the dives did not follow any diurnal pattern. The diving behaviour of all seals changed abruptly when they started on their return to land. During this time their behaviour was more like that of adults: they made deeper (159 ± 9 m) and longer dives (9.01 ± 1.69 min) than previously, and the dives showed a strong diurnal pattern in depth. There is no obvious explanation for this change in behaviour, although its abrupt nature suggests that it is unlikely to have been due to physiological changes in the seals. The size of the seals at weaning was an important influence on diving behaviour. Heavy weaners made significantly deeper (130 ± 40 m) and longer dives (7.36 ± 0.55 min) than light weaners (88 ± 32 m and 5.04 ± 0.64 min, respectively). This indicates that smaller seals are constrained to some extent by their physiological capabilities, which perhaps requires some individuals to adopt different foraging strategies.

Foraging trip strategies and habitat use during late pup rearing by lactating Australian fur seals

2011 ◽  
Vol 59 (4) ◽  
pp. 216 ◽  
Author(s):  
Roger Kirkwood ◽  
John P. Y. Arnould
Keyword(s):  
Habitat Use ◽  
Marine Mammal ◽  
Hot Spots ◽  
Marine Reserves ◽  
Central Place ◽  
Shelf Edge ◽  
Fur Seals ◽  
Eastern Australia ◽  
Management Perspective ◽  
Latitudinal Range

Australian fur seals (Arctocephalus pusillus doriferus) are the most conspicuous and abundant marine mammal in shelf waters of south-eastern Australia. To successfully rear offspring, the females must encounter sufficient prey on each foraging trip out of a central place for periods up to11 months each year. We investigated foraging trip strategies and habitat use by the females in three winter–spring periods, 2001–03, from four colonies that span the species’ latitudinal range and contribute 80% of pup production. Trip durations of 37 females averaged 6.1 ± 0.5 (s.e.) days, although >90% of the seal’s time at sea was spent <150 km travel (<2 days) away. Most females exhibited strong fidelities to individually preferred hot-spots. Females from colonies adjacent to productive shelf-edge waters generally had shorter trips, had smaller ranges, foraged closer to colonies and exhibited less diversity in trip strategies than did those from colonies more distant from a shelf-edge. From a management perspective, there was minimal overlap (<1%) between where females foraged and a system of marine reserves established in 2007, suggesting that habitats visited by lactating Australian fur seals currently receive minimal legislative protection.

scholarly journals Evolutionary determinants of morphological polymorphism in colonial animals

2016 ◽  
Author(s):  
Carl Simpson ◽  
Jeremy B.C. Jackson ◽  
Amalia Herrera-Cubilla
Keyword(s):  
Life Histories ◽  
Competitive Ability ◽  
Environmental Variability ◽  
Temporal Position ◽  
Costs And Benefits ◽  
Isthmus Of Panama ◽  
Modular Units ◽  
Environmental Hypothesis ◽  
Colonial Ascidians

AbstractColonial animals commonly exhibit morphologically polymorphic modular units that are phenotypically distinct and specialize in specific functional tasks. But how and why these polymorphic modules have evolved is poorly understood. Across colonial invertebrates there is wide variation in the degree of polymorphism from none in colonial ascidians, to extreme polymorphism in siphonophores such as the Portuguese Man of War. Bryozoa are a phylum of exclusively colonial invertebrates that uniquely exhibit almost the entire range of polymorphism from monomorphic species to others that rival siphonophores in their polymorphic complexity. Previous approaches to understanding the evolution of polymorphism have been based upon analyses of (1) the functional role of polymorphs or (2) presumed evolutionary costs and benefits based upon evolutionary theory that postulates polymorphism should only be evolutionarily sustainable in more “stable” environments because polymorphism commonly leads to the loss of feeding and sexual competence. Here we use bryozoans from opposite shores of the Isthmus of Panama to revisit the environmental hypothesis by comparison of faunas from distinct oceanographic provinces that differ greatly in environmental variability and we then examine the correlations between the extent of polymorphism in relation to patterns of ecological succession and variation in life histories. We find no support for the environmental hypothesis. Distributions of the incidence of polymorphism in the oceanographically unstable Eastern Pacific are indistinguishable from those in the more stable Caribbean. In contrast, the temporal position of species in a successional sequence is collinear with the degree of polymorphism because species with fewer types of polymorphs are competitively replaced by species with higher numbers of polymorphs on the same substrata. Competitively dominant species also exhibit patterns of growth that increase their competitive ability. The association between degrees of polymorphism and variations in life histories is fundamental to understanding of the macroevolution of polymorphism.

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