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McIntosh RR, Sorrell KJ, Thalmann S, Mitchell A, Gray R, Schinagl H, Arnould JPY, Dann P, Kirkwood R. Sustained reduction in numbers of Australian fur seal pups: Implications for future population monitoring. PLoS One 2022; 17:e0265610. [PMID: 35303037 PMCID: PMC8932563 DOI: 10.1371/journal.pone.0265610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 03/05/2022] [Indexed: 12/04/2022] Open
Abstract
Fur seal populations in the Southern Hemisphere were plundered in the late 1700s and early 1800s to provide fur for a clothing industry. Millions of seals were killed resulting in potentially major ecosystem changes across the Southern Hemisphere, the consequences of which are unknown today. Following more than a century of population suppression, partly through on-going harvesting, many of the fur seal populations started to recover in the late 1900s. Australian fur seals (Arctocephalus pusillus doriferus), one of the most geographically constrained fur seal species, followed this trend. From the 1940s to 1986, pup production remained at approximately 10,000 per year, then significant growth commenced. By 2007, live pup abundance had recovered to approximately 21,400 per year and recovery was expected to continue However, a species-wide survey in 2013 recorded a 20% decline, to approximately 16,500 live pups. It was not known if this decline was due to 2013 being a poor breeding year or a true population reduction. Here we report the results of a population-wide survey conducted in 2017 and annual monitoring at the most productive colony, Seal Rocks, Victoria that recorded a large decline in live pup abundance (-28%). Sustained lower pup numbers at Seal Rocks from annual counts between 2012–2017 (mean = 2908 ± 372 SD), as well as the population-wide estimate of 16,903 live pups in 2017, suggest that the pup numbers for the total population have remained at the lower level observed in 2013 and that the 5-yearly census results are not anomalies or representative of poor breeding seasons. Potential reasons for the decline, which did not occur range-wide but predominantly in the most populated and long-standing breeding sites, are discussed. To enhance adaptive management of this species, methods for future monitoring of the population are also presented. Australian fur seals occupy several distinct regions influenced by different currents and upwellings: range-wide pup abundance monitoring enables comparisons of ecosystem status across these regions. Forces driving change in Australian fur seal pup numbers are likely to play across other marine ecosystems, particularly in the Southern Hemisphere where most fur seals live.
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Affiliation(s)
- Rebecca R. McIntosh
- Conservation Department, Phillip Island Nature Parks, Cowes, Victoria, Australia
- * E-mail:
| | - Karina J. Sorrell
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
| | - Sam Thalmann
- Department of Natural Resources and Environment, Hobart, Tasmania, Australia
| | - Anthony Mitchell
- Department of Environment, Land, Water and Planning, Orbost, Victoria, Australia
| | - Rachael Gray
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, New South Wales, Australia
| | - Harley Schinagl
- Conservation Department, Phillip Island Nature Parks, Cowes, Victoria, Australia
| | - John P. Y. Arnould
- School of Biological and Chemical Sciences, Deakin University, Burwood, Victoria, Australia
| | - Peter Dann
- Conservation Department, Phillip Island Nature Parks, Cowes, Victoria, Australia
| | - Roger Kirkwood
- South Australian Research and Development Institute—Aquatic Sciences, West Beach, South Australia, Australia
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Environmental influences on foraging effort, success and efficiency in female Australian fur seals. Sci Rep 2020; 10:17710. [PMID: 33077806 PMCID: PMC7572486 DOI: 10.1038/s41598-020-73579-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 09/16/2020] [Indexed: 11/08/2022] Open
Abstract
Understanding the factors which influence foraging behaviour and success in marine mammals is crucial to predicting how their populations may respond to environmental change. The Australian fur seal (Arctocephalus pusillus doriferus, AUFS) is a predominantly benthic forager on the shallow continental shelf of Bass Strait, and represents the greatest biomass of marine predators in south-eastern Australia. The south-east Australian region is experiencing rapid oceanic warming, predicted to lead to substantial alterations in prey diversity, distribution and abundance. In the present study, foraging effort and indices of foraging success and efficiency were investigated in 138 adult female AUFS (970 foraging trips) during the winters of 1998–2019. Large scale climate conditions had a strong influence on foraging effort, foraging success and efficiency. Foraging effort and foraging success were also strongly influenced by winter chlorophyll-a concentrations and sea-surface height anomalies in Bass Strait. The results suggest increasing foraging effort and decreasing foraging success and efficiency under anticipated environmental conditions, which may have population-level impacts.
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Abstract
Condition indices correlating body lipid content with mass and morphometric measurements have been developed for a variety of taxa. However, for many large species, the capture and handling of enough animals to obtain representative population estimates is not logistically feasible. The relatively low cost and reduced disturbance effects of UAVs make them ideal for the rapid acquisition of high volume data for monitoring large species. This study examined the imagery collected from two different UAVs, flown at 25 m altitude, and the subsequent georeferenced orthomosaics as a method for measuring length and axillary girth of Australian fur seals (Arctocephalus pusillus doriferus) to derive an index of body condition. Up to 26% of individuals were orientated correctly (prostrate/sternal recumbent) to allow for body measurements. The UAV-obtained images over-estimated axillary girth diameter due to postural sag on the lateral sides of the thorax while the animals are lying flat in the sternal recumbent position on granite rocks. However, the relationship between axillary girth and standard length was similarly positive for the remotely- and physically-obtained measurements. This indicates that residual values from the remotely-obtained measurements can be used as a relative index of body condition.
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McIntosh RR, Kirkwood R, Sutherland DR, Dann P. Drivers and annual estimates of marine wildlife entanglement rates: A long-term case study with Australian fur seals. MARINE POLLUTION BULLETIN 2015; 101:716-725. [PMID: 26475026 DOI: 10.1016/j.marpolbul.2015.10.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 10/06/2015] [Accepted: 10/06/2015] [Indexed: 06/05/2023]
Abstract
Methods of calculating wildlife entanglement rates are not standardised between studies and often ignore the influence of observer effort, confounding comparisons. From 1997-2013 we identified 359 entangled Australian fur seals at Seal Rocks, south-eastern Australia. Most entanglement materials originated from commercial fisheries; most frequently entangling pups and juveniles. Using Generalized Additive Mixed Models, which incorporated observer effort and survey frequency, we identified that entanglements were observed more frequently amongst pups from July to October as they approached weaning. Neither the decline in regional fishing intensity nor changing seal population size influenced the incidence of entanglements. Using the models, we estimated that 302 (95% CI=182-510) entangled seals were at Seal Rocks each year, equivalent to 1.0% (CI=0.6-1.7%) of the site population. This study highlights the influence of observer effort and the value of long-term datasets for determining the drivers of marine debris entanglements.
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Affiliation(s)
| | - Roger Kirkwood
- IMARES Wageningen UR, Postbus 57, 1780 AB Den Helder, The Netherlands
| | | | - Peter Dann
- Phillip Island Nature Parks, P.O. Box 97, Cowes, VIC 3922, Australia
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Lukas D, Huchard E. Sexual conflict. The evolution of infanticide by males in mammalian societies. Science 2014; 346:841-4. [PMID: 25395534 DOI: 10.1126/science.1257226] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Male mammals often kill conspecific offspring. The benefits of such infanticide to males, and its costs to females, probably vary across mammalian social and mating systems. We used comparative analyses to show that infanticide primarily evolves in social mammals in which reproduction is monopolized by a minority of males. It has not promoted social counterstrategies such as female gregariousness, pair living, or changes in group size and sex ratio, but is successfully prevented by female sexual promiscuity, a paternity dilution strategy. These findings indicate that infanticide is a consequence, rather than a cause, of contrasts in mammalian social systems affecting the intensity of sexual conflict.
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Affiliation(s)
- Dieter Lukas
- Large Animal Research Group, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
| | - Elise Huchard
- Large Animal Research Group, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS - Université de Montpellier, 1919 Route de Mende, 34293 Montpellier Cedex 5, France
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Linking reproduction and survival can improve model estimates of vital rates derived from limited time-series counts of pinnipeds and other species. PLoS One 2013; 8:e77389. [PMID: 24324541 PMCID: PMC3855591 DOI: 10.1371/journal.pone.0077389] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 09/10/2013] [Indexed: 11/23/2022] Open
Abstract
We propose a method to model the physiological link between somatic survival and reproductive output that reduces the number of parameters that need to be estimated by models designed to determine combinations of birth and death rates that produce historic counts of animal populations. We applied our Reproduction and Somatic Survival Linked (RSSL) method to the population counts of three species of North Pacific pinnipeds (harbor seals, Phoca vitulina richardii (Gray, 1864); northern fur seals, Callorhinus ursinus (L., 1758); and Steller sea lions, Eumetopias jubatus (Schreber, 1776))—and found our model outperformed traditional models when fitting vital rates to common types of limited datasets, such as those from counts of pups and adults. However, our model did not perform as well when these basic counts of animals were augmented with additional observations of ratios of juveniles to total non-pups. In this case, the failure of the ratios to improve model performance may indicate that the relationship between survival and reproduction is redefined or disassociated as populations change over time or that the ratio of juveniles to total non-pups is not a meaningful index of vital rates. Overall, our RSSL models show advantages to linking survival and reproduction within models to estimate the vital rates of pinnipeds and other species that have limited time-series of counts.
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Lynch M, Kirkwood R, Mitchell A, Duignan P, Arnould JPY. Prevalence and significance of an alopecia syndrome in Australian fur seals (Arctocephalus pusillus doriferus). J Mammal 2011. [DOI: 10.1644/10-mamm-a-203.1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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