Trevor McIntyre

Estimates of the Southern Ocean general circulation improved by animal‐borne instruments

Over the last decade, several hundred seals have been equipped with conductivity-temperature-depth sensors in the Southern Ocean for both biological and physical oceanographic studies. A calibrated collection of seal-derived hydrographic data is now available, consisting of more than 165,000 profiles. The value of these hydrographic data within the existing Southern Ocean observing system is demonstrated herein by conducting two state estimation experiments, differing only in the use or not of seal data to constrain the system. Including seal-derived data substantially modifies the estimated surface mixed-layer properties and circulation patterns within and south of the Antarctic Circumpolar Current. Agreement with independent satellite observations of sea ice concentration is improved, especially along the East Antarctic shelf. Instrumented animals efficiently reduce a critical observational gap, and their contribution to monitoring polar climate variability will continue to grow as data accuracy and spatial coverage increase.

Sex at sea: alternative mating system in an extremely polygynous mammal

Financial support was provided by the South African Department of Science and Technology, through the National Research Foundation, in support of the Marine Mammal Programme of the MRI.

Median pupping date, pup mortality and sex ratio of fur seals at Marion Island

Modelling fur seal populations requires the accurate assessment of demographic parameters such as age-specific mortality. Owing to the highly variable mortality rates that pups are subject to, mortality of this age class is perhaps the most important factor determining the number of surviving individuals within each cohort. Early pup mortality,sex ratio and median pupping date were determined for sympatric populations of Subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) at Marion Island, Southern Ocean. Mortality for this species was density dependent, varying from 0.8% at low density sites to 10.9% at high density sites. More accurate methods employed at low-density sites showed a substantially higher pup mortality at three weeks of 1.3–3.4% for Subantarctic fur seals. The same method yielded a mortality estimate at four weeks of age of 1.1–5.1% for Antarctic fur seals. Despite the underestimate inherent in island-wide counts for Subantarctic fur seals, these estimates are still useful for observing temporal and spatial patterns. Sex ratios were at parity for newborns of both species. The sex ratio of eight-week-old Subantarctic fur seal pups was also at parity, which is unusual for fur seal populations. The median pupping dates determined for Subantarctic fur seals and Antarctic fur seals did not differ substantially from previous estimates.

The Marine Mammal Programme at the Prince Edward Islands: 38 years of research

The Marine Mammal Programme (MMP) conducts research on pinnipeds and killer whales Orcinus orca at Marion Island, Prince Edward Islands, under the auspices of the Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria. The history of the MMP, which has benefited from collaboration with leading national and international researchers, is described from its start through to current research. The setting up of long-term studies such as the mark-resighting of southern elephant seals Mirounga leonina commenced in 1983. The elephant seal population declined by 87% between an initial census in 1951 and 2004. This was followed by a stabilisation period and a current increase. The recovery, and subsequent increase of sympatric populations of Subantarctic fur seals Arctocephalus tropicalis and Antarctic fur seals A. gazella (following cessation of commercial sealing), are documented. Insights into many aspects of elephant seal and fur seal biology, including life history, demography, diet, growth, foraging and ranging behaviour are described. Ancillary work on morphology, genetics, anthropogenic influences and rare events are mentioned, as well as the extent of current research that addresses population dynamics in an ecosystem context. Opportunistic photographic identification of killer whales and recent dedicated observations at Marion Island are used to determine population size, seasonal abundance and sociality of this population, and to further understanding of its potential impact on resident pinniped populations.

Decomposing the variance in southern elephant seal weaning mass: partitioning environmental signals and maternal effects

Predator populations are likely to respond to bottom-up processes, but there remains limited understanding of how wide-ranging marine predators respond to environmentally driven temporal variation in food availability. Widespread declines of several Southern Ocean predators, including southern elephant seals Mirounga leonina, have been attributed to decreases in food availability following environmental changes. We used linear mixed models to examine temporal process variance in weaning mass (a key fitness component) of southern elephant seals at Marion Island over a 27-year period (1986–2013). We quantified the contribution of within- and between-year covariates to the total phenotypic variance in weaning mass and determined whether the observed reversal of population decline was associated with a continued increase in weaning mass, suggesting improvement in per capita food availability to adult females. Weaning mass initially increased rapidly with maternal age, but reached an asymptote when females wer...

Trends in tagging of marine mammals: a review of marine mammal biologging studies

The number of scientific papers resulting from biologging instruments deployed on marine mammals is increasing as improved technologies result in smaller devices and improved sensor-, storage- and transmission capabilities. I undertook a comprehensive review of papers resulting from biologging deployments on free-ranging marine mammals between 1965 and 2013 (n = 620) to summarise where (e.g. on which species, as well as in which geographic areas) deployment efforts were focused, the impacts of the resulting papers, and where there are shortcomings in the literature. Species-, sex- and age-class biases were evident in terms of animals instrumented. Also, large proportions of the papers resulted from deployments on a small number of species (particularly among the pinnipeds) and were more often on adult females than other demographic classes. The mean impact of papers (as assessed using journal impact factors and numbers of citations) was consistent over time, and was influenced by the number of species studied, sample sizes and instrument capabilities. I found a paucity of papers addressing device influences on animals, as well as studies with explicit conservation and/or management implications. This review aims to increase awareness of marine mammal biologging data already collected, stimulate appropriate further studies, and encourage the reuse of existing data.

Goose barnacles hitchhike on satellite-tracked southern elephant seals

Goose barnacles (Lepas australis) attached to satellite-relay data loggers were carried by three southern elephant seals (Mirounga leonina) from Marion Island. Their movements across the Polar Frontal Zone are presented, providing further evidence that megafauna are potential vectors for the transport of species into the Southern Ocean.

Deep divers in even deeper seas: habitat use of male southern elephant seals from Marion Island

Abstract We describe the habitat use of 22 male southern elephant seals (Mirounga leonina) satellite tagged at Marion Island between 2004 and 2008. While a few areas of increased utilization appeared to be associated with areas of shallower bathymetry (such as sea-floor ridges and fracture zones), seals in our study did not target other areas of shallow bathymetry within close proximity to Marion Island. Rather, most elephant seals foraged pelagically over very deep water where much variation was evident in diel vertical migration strategies. These strategies resulted in generally deeper and longer dives than what has been reported for male elephant seals from other colonies. No significant differences were recorded for dive durations or dive depths between adults and sub-adults. However, younger animals displayed a positive relationship between dive durations and age, as well as between dive depths and age, while these relationships became negative for older animals. Mixed model outputs suggested that seals increased their aerobic fitness as migrations progressed, enabling them to undertake longer dives. We conclude that Marion Island male elephant seals exhibit much variability in dive strategy and are seemingly capable of exploiting a range of different prey types occurring in various depth layers.

Environmental influences on the at-sea behaviour of a major consumer, Mirounga leonina, in a rapidly changing environment

Understanding the distribution and foraging ecology of major consumers within pelagic systems, specifically in relation to physical parameters, can be important for the management of bentho-pelagic systems undergoing rapid change associated with global climate change and other anthropogenic disturbances such as fishing (i.e., the Antarctic Peninsula and Scotia Sea). We tracked 11 adult male southern elephant seals (Mirounga leonina), during their five-month post-moult foraging migrations from King George Island (Isla 25 de Mayo), northern Antarctic Peninsula, using tags capable of recording and transmitting behavioural data and in situ temperature and salinity data. Seals foraged mostly within the Weddell–Scotia Confluence, while a few foraged along the western Antarctic Peninsula shelf of the Bellingshausen Sea. Mixed model outputs suggest that the at-sea behaviour of seals was associated with a number of environmental parameters, especially seafloor depth, sea-ice concentrations and the temperature structure of the water column. Seals increased dive bottom times and travelled at slower speeds in shallower areas and areas with increased sea-ice concentrations. Changes in dive depth and durations, as well as relative amount of time spent during the bottom phases of dives, were observed in relation to differences in overall temperature gradient, likely as a response to vertical changes in prey distribution associated with temperature stratification in the water column. Our results illustrate the likely complex influences of bathymetry, hydrography and sea ice on the behaviour of male southern elephant seals in a changing environment and highlight the need for region-specific approaches to studying environmental influences on behaviour.

Referencing practices in physical geography How well do we cite what we write

Accurate citation practices are important, from both an ethical and a scientific point of view. Using an easily reproducible, previously published method, we assess citation accuracy in 120 articles published in the first half of 2011 and listed under ‘Physical Geography’ in Thomson Reuters’ ISI Web of Knowledge Science Citation Index. Our results indicate that at least 19% of citations in physical geography do not provide clear support for the statements they are meant to support. These results are in line with previously published findings for ‘field-orientated’ sciences. We propose that both authors and editors help remedy this problem, by employing more rigorous writing and editing practices.