NEW PAPER: Marion Island killer whales are more social when there's more food

The Marion Island Marine Mammal Programme (MIMMP) continuously monitors the killer whale population at Marion Island, and since 2006 (when the current photoidentification catalogue was started) 69 individuals have been observed, of which 21 are calves born during this period.

An adult female (M002) spy-hops after a successful king penguin hunt at Ship’s Cove. PHOTO CREDIT: Rowan JordaaN

A new study led by MIMMP PhD student, Rowan Jordaan, made use of this long-term data in a recently published article in Animal Behaviour. They used nearly 90 000 photographs (from 4739 sightings over 12 years) to assess the social structure of killer whales at sub-Antarctic Marion Island across different periods of the year corresponding to fluctuations in prey availability: southern elephant seals, sub-Antarctic fur seals, king and macaroni penguins are most abundant between September to December (“peak”) and least abundant between January to August (“off-peak”). Analyses showed significant differences between various measures of social structure between these peak and off-peak periods.

Killer whales were more social during the peak period when there was more prey available, by exhibiting higher probabilities of socialising with other individuals, forming stronger associations, showing less division in the population and social groups consisting of more individuals. As a whole, the social network during the peak period was compact with very short distances between all individuals. In contrast, killer whales were less sociable during the off-peak periods as individuals formed smaller groups that were less likely to socialise with others.

FIGURE FROM JORDAAN ET AL. 2021. Network plots for Marion Island killer whales over (a) all peak periods (September - December) and (b) all off-peak periods (January - August) during 2006- 2018. Each node (coloured circle) represents an individual killer whale and each vertex/edge (line between two nodes) represents the association between two killer whales. Numbers in nodes indicate the unique ID code for each individual. Size of nodes and thickness of edges are a direct representation of how social individuals are.Individuals were grouped into social units, represented by different colours

These results are typical of a process called fission-fusion, which occurs in a population when individuals leave social groups to form smaller groups (fission) or come together to form larger groups (fusion). For killer whales at Marion Island, this balance appears to shift during the year in relation to the amount of prey available in an effort to reduce competition and to maximise the net energy intake per individual, ultimately benefitting the population as a whole. Similar responses to changes in prey availability have been observed in various animal societies such as wolves, whales, lions, wild dogs and spotted hyenas.

Well done to Rowan and colleagues on this publication, which provides further support to the idea that prey availability is an important determinant of social structure in social predators.

Read the full article HERE.

SHIP IN THE BAY - the M78 team arrives on Marion Island!

The SA Agulhas II arrives at Marion Island for the 2021 relief voyage. PHOTO CREDIT: Nico de Bruyn

The new overwintering team M78 has arrived on Marion Island!

For these team members, like our killer whale researcher Danielle Conry, this moment has not only been a life-long dream but also one that has been filled with uncertainty over the last year due to the restrictions (and almost entire halting of the 2020/2021 scientific programme on Marion Island) caused by the COVID-19 pandemic.

After two weeks in quarantine in Cape Town and a few negative COVID tests later, Danielle and her team mates now finally get to enjoy the freedoms and adventures of Marion Island. Danielle joins up with her experienced sealer team mates Yinhla Shihlomule and Frikkie van der Vyver (who were part of the greatly reduced scientific voyage in September 2020) and they will now show her the ropes (and hopefully some mires) associated with the MIMMP field work.

A big welcome to our MIMMP team for the 2021/2022 overwintering period!

MIMMP’s killer whale researcher, Danielle Conry (middle), joins her fellow team mates Yinhla Shihlomule (left) and Frikkie van der Vyver (right) on Marion Island. PHOTO CREDIT: Nico de Bruyn

NEW ECOLOGY PAPER : Female seals that breed young have a slower rate of ageing

At Marion Island, some elephant seal pups have a ‘golden spoon’ start to life. We measure this through their weaning mass, with the ‘golden spoon’ pups being the heavier ones.

‘Golden spoon’ females tend to reproduce at a younger age than those that were relatively small at weaning. In a new paper published in Ecology, Chris Oosthuizen and colleagues show that an early age of first reproduction also correlates with a slower rate of ageing, and a higher expected fitness. 

A 17-year old southern elephant seal mother with her 10-day old pup at Ship’s Cove, Marion Island. Female seals that breed young, also enjoy a slower rate of ageing and produce more offspring in their lifetime than those that delay breeding. Photo credit: Chris Oosthuizen

How animals age in the wild is central to understanding their life-history evolution. Senescence (age-related declines in fitness components) stems from a weakening in the strength of natural selection with age. Rapid development may accelerate the onset of senescence (the “developmental theory of aging”) or allocation to early life performance may come at a cost to late-life performance (the “disposable soma theory”).

This study used capture-recapture data of over 7000 female southern elephant seals collected over almost 40 years at Marion Island to test for negative or positive correlations between early-life and late-life traits. It specifically tested whether the onset and rate of actuarial senescence (the increase in mortality hazards with age) correlated with the age of first reproduction.

Because marine mammals spend most of their lives at sea, the analysis was specifically designed to study early-late life-history correlations in wild animal populations where some breeding attempts and all deaths go undetected.

Fig. 1 (a) Survival trajectory of female elephant seals breeding for the first time at age 3. (b) Survival trajectory of females breeding for the first time at ages 4 or later. Solid circles correspond to the annual survival probability of experienced breeders. The regression line indicates the logit-linear relationship between age and survival of experienced breeders. Early breeders had a lower senescence rate than delayed breeders. The age at the onset of senescence (where survival probability starts to decline at old age) is indicated with a dotted line. (Oosthuizen et al. 2021)

Females with an early age of first reproduction survived better than those with delayed reproduction in both the short- and the long-term. Females breeding at a young age had lower rates of senescence when they were old (above 17 years of age), and produced more offspring during their lives than those that delayed breeding.

Congratulations to Chris and colleagues for this excellent publication and for translating the almost 40 years of MIMMP field research into scientific outputs which further our understanding of marine mammals!

Read more and access the paper HERE

NEW PAPER: Stable isotope analysis reveals the ecology of a dominant prey species around the Prince Edward Islands

The foraging patterns of marine predators largely depend on the ecology and distribution of their prey. However, little information is available for the mid-trophic levels (including fish and squid) from the marine systems around the Prince Edward Islands.

New research published in Marine Ecology Progress Series by MIMMP MSc student Andre van Tonder and colleagues entitled “Ecology of Moroteuthopsis longimana at the sub-Antarctic Prince Edward Islands, revealed through stable isotope analysis of squid beaks” investigates the ecology of the giant warty squid, Moroteuthopsis longimana, which is eaten by many bird species and marine mammals in the Southern Ocean.

Fig. 2. from Van Tonder et al. (2021) showing the sampling technique for the stable isotope analysis of squid beaks from grey-headed albatross nests on marion island

Squids beaks are identifiable to species level and also act as archives of chemical information, with stable isotope ratios of carbon and nitrogen accrued throughout the squid’s lifetime. This stable isotope archive not only provides insights to the ecology of the squid, but also allows us to establish links with its enigmatic marine predators. The stable isotope ratio of carbon gives a broad idea of the latitudinal distribution of the squid, and the stable nitrogen isotope ratio provides information on the relative position in the food chain that the squid occupies.

Fig. 3. Overall isotopic niche, plotted as beak δ15N values over δ13C values, of Moroteuthopsis longimana eaten by albatrosses breeding at the Prince Edward Islands (blue), Îles Crozet (green) and Îles Kerguelen (red). The lighter dashed outlines represent the convex hulls (total area, TA) and the bold ellipses represent the standard ellipse areas corrected for the populations (SEAc). AZ: Antarctic Zone; SAZ: Sub-Antarctic Zone; STZ: Subtropical Zone (Van Tonder et al. 2021)

This study used naturally regurgitated squid beaks from around grey-headed albatross nests on Marion Island, and found that these albatross were foraging at the Southwest Indian Ridge rather than making use of broader foraging zones as seen in albatross from the neighbouring Îles Crozet (~1000 km east) and the more distant Îles Kerguelen (~2400 km east) (Fig. 3). Interestingly, the study found scant evidence of the grey-headed albatross feeding on squid closer to their breeding grounds around the Prince Edward Islands, which sparked intrigue: is it due to low densities of squid or increased competition with other species for this prey?

The diet of the squid showed a dependence on crustaceans, although fish and other squid are also likely included.

Well done to Andre and colleagues for this paper which lays the groundwork for estimating the contribution of Moroteuthopsis longimana to the diet of marine predators! The isotopic values reported here are likely to act as potential source values for future research into the diet of marine mammal predators, which also depend on this squid species as a prey source.

Read more and access the article HERE.

MIMMP MSc student Sean Evans travels to Gothenburg University, Sweden

MIMMP student Sean Evans, also a member of the M76 team (2019-2020), was recently given the opportunity to visit his MSc co-supervisor Dr Marcel du Plessis at the University of Gothenburg in Sweden.

MIMMP MSc student Sean Evans (left) and Co-supervisor dr. Marcel du Plessis (right) enjoying a South African braai in a frozen Swedish park. Photo Credit: Sean Evans.

Sean’s MSc research focuses on the influence of upper ocean structure and variability on Sub-Antarctic fur seal (Arctocephalus tropicalis) diving behaviour and what seal-borne loggers can tell us about the submesoscale ocean landscape around Marion Island. During his three-week visit, Sean gained valuable input to his research by working with Dr. Marcel du Plessis in-person and presenting his work to some of the world’s leading researchers in the field of upper ocean dynamics from the University of Gothenburg.

Data loggers were deployed on Arctocephalus tropicalis seals at Marion Island from 2009-2015 to obtain dive profiles and physical ocean properties (e.g. temperature). Seals tended to forage directly to the west and east of Marion Island within the Antarctic Circumpolar Current, thereby allowing a case study of ocean dynamics within this region. A major aim of this research is to use the seals as ocean samplers in order to access the topographic influence of Marion Island on downstream submesoscale variability and vertical stratification. These upper ocean dynamics drive air-sea fluxes of carbon and heat, and understanding these processes is therefore critical for climate modelling and climate change predictions.

Well done to Sean on this incredible opportunity for showcasing the MIMMP’s research on the international stage… and having some fun along the way!

As Christmas approached, Gothenburg bursts into a festival of lights and decorations, and there was even a parade of over 2000 motorcyclists dressed up as Santa Claus. Photo credit: Sean Evans

Congratulations to Chris Oosthuizen on winning the Population Ecology Young Author Award

MIMMP research associate Chris Oosthuizen was recently awarded the Population Ecology Young Author award for his paper entitled: Individual heterogeneity in life‐history trade‐offs with age at first reproduction in capital breeding elephant seals.

Each year, the Society of Population Ecology nominates candidates for this award recognizing early career researchers publishing the best papers in the journal Population Ecology. This year we are proud to boast with a MIMMP winner!

In an interview with the University of Pretoria, Dr Oosthuizen acknowledges that “This award highlights the collective efforts of those who have led the MIMMP, and the nearly 100 field assistants who have walked the extra mile to collect demographic data on marine mammals at Marion Island”. He goes on to highlight the important role of long-term research and data sets such as those made possible through the MIMMP: “Our research would have been impossible without the support of funding bodies, and the dedicated work of MIMMP field assistants over a period of nearly 40 years.”

Congratulations to Chris on this prestigious award and fantastic article!

To read more about the Population Ecology Young Author Awards and see the announcement click HERE.

Happy birthday elephant seals! 15 October - median pupping date

The southern elephant seal annual breeding season peaks today, 15 October. This is the day in the year when most pups are born at Marion Island, and therefore we celebrate the island populations’ birthday today.

One of many southern elephant seal harems at peak breeding season on Marion Island. Photo: Frikkie van der Vyver

A southern elephant seal guards his beach filled with females and pups during the 2020 breeding season. Photo: Frikkie van der Vyver

However, this year is an extra special elephant seal birthday to us seal biologists (aka “Sealers”), because not too long ago we anticipated that for the first time in four decades we would not have a presence on Marion Island in this breeding season!

Thankfully our efforts were rescued and Frikkie and Yinhla are on the island to conduct the total island count today, but even more importantly, to continue with our globally valued 39-year old ‘mark-resight’ research on this species.

Cheers to the ellies and our continued efforts to understand and conserve them and their beautiful habitats!

NEW PAPER: Long-term population demographics of Marion Island killer whales

NOTCHES AND SCRATCHES MAKE IT POSSIBLE FOR RESEARCHERS TO IDENTIFY INDIVIDUAL KILLER WHALES. THIS IS M002 CLOSELY FOLLOWED BY HER 3-YEAR OLD CALF, M062 BORN INTO THE POPULATION IN 2014. PHOTO CREDIT: ROWAN JORDAAN.

In the latest MIMMP research published in Wildlife Biology, PhD student Rowan Jordaan analysed nearly 90 000 photographs (taken over 4739 sightings) to assess the abundance, survival and population growth of the Marion Island killer whale population.

Since 2006, our over-wintering researchers have conducted dedicated killer whale research at Marion Island in the Southern Ocean. Killer whale research here is unique in that all observations are shore-based, with killer whales observed swimming in deep water close to cliffs and in shallow waters leading onto beaches where their prey (seals and penguins) haul out.

A photographic identification catalogue has been maintained over the last 14 years through structured dedicated observation sessions and opportunistic sightings of killer whales. Unique notches and scratches on killer whale dorsal fins enable individual identification.

To date, 67 individuals are present around Marion Island including 19 calves born into the population since 2006. Eight individuals have also been observed at the nearby Îles Crozet (~ 950 km away). This research revealed that killer whales at Marion Island have an annual survival probability of 0.98 equating to an approximate life expectancy of 48 years. This population has a healthy mean growth rate of 1.012 and a calving rate of 0.13 calves born per year per reproductive female.

AN OBSERVER TAKES PHOTOS OF A KILLER WHALE passing THE OBSERVATION POINT. SHORE BASED OBSERVATIONS MAKES MARION ISLAND KILLER WHALE RESEARCH UNIQUE. PHOTO CREDIT: YINHLA SHIHLOMULE.

These population parameters are similar to those of other killer whale populations in the Eastern North Pacific, Norway and Îles Crozet. Observed variations are attributed to dietary difference and resource abundance, historical negative impacts on social structure (e.g. mortalities caused by illegal fishing vessels), environmental conditions and the presence and scale of legal and illegal fisheries. Fisheries may provide opportunities for direct interactions with vessels resulting in variable impact on survival and reproduction rates.

These findings increase our knowledge of killer whales in the Southern Ocean, an area that is surprisingly understudied. A population study of this caliber and detail would not have been possible without the continuous and long-term research effort by MIMMP and the numerous field assistants that have contributed to this data set over the years.

Read the full paper here

A mother and young calf observed from the cliffs above. photo credit: Rowan Jordaan.

Our M77 Sealers have arrived at Marion Island!!

After a grueling 8 days of wind, waves and storms crossing the legendary Southern Ocean’s “Roaring 40s” in a 12-man sailing vessel, OUR SEALERS HAVE ARRIVED AT MARION ISLAND! This significant event marks the culmination of a remarkable collaborative effort to ensure our 39 years of research and monitoring continue - read more about that here!

Antarctic skua overlooking the pelagic australis sailing vessel in the bay. photo credit: Frikkie van der vyver.

Frikkie van der Vyver (left) and Yinhla Shihlomule (right) have arrived at Marion Island to resume the MIMMP long-term research on seals and killer whales. PHOTO CREDIT: Frikkie van der Vyver

The trip was far from usual as the science team set off in the Pelagic Australis for Marion Island on the 18th September from Cape Town harbour. Instead of the usual 4-day trip on the SA Agulhas II, our sealers got to try their hand at sailing as they set off to restart the Marion Island science programmes that have been halted since early May 2020.

Crossing the legendary Southern Ocean lived up to its reputation of being rough and rife with storms, but our team arrived safely on Marion Island and many sent messages to friends and family back on mainland South Africa saying ‘We are Home Sweet Home’.

Sailing to Marion Island on the pelagic australis. photo credit: Frikkie van der vyver.

the 8-day voyage of the pelagic australis from cape town harbour to marion island. www.tracking.redportglobal.com

Our sealers certainly feel right at home on Marion Island, and have hit the ground running as they arrived at the start of the busiest time of the year: southern elephant seal breeding season. Only a few days after arrival, our sealers set off on their first southern elephant seal census along the eastern coastline to Repetto’s hut and spotted the first of the newborn southern elephant seal pups!

We can now breathe a sigh of relief as the MIMMP’s 39-year long-term data collection continues without missing a breeding season, in the experienced hands of our M77 sealers: Frikkie van der Vyver and Yinhla Shihlomule.

Arriving at boulders beach on a motor boat. photo credit: Frikkie van der vyver.

Sealers noting tag numbers during a routine southern elephant seal census. Photo credit: frikkie van der vyver.

And they're off! Marion Island researchers set sail to resume science activities in the sub-Antarctic

Marion Island Science team setting sail from cape town harbour on the Pelagic Australis sailing vessel. Photo Credit: Kim Stevens

After 5 months of despair, contingency plans and some creative collaboration, our science programmes are set to resume on Marion Island!

But this is no usual voyage… instead of the usual SA Agulhas II icebreaking polar supply and research ship, our science team is embarking on a 6-day journey to Marion Island on the Pelagic Australis, an Antarctic sailing vessel. Click here for a tour of the vessel.

Earlier this year, scientific research came to an abrupt halt on Marion Island due to concerns around the COVID-19 pandemic and the subsequent hard lock-down in South Africa. This was a massive blow to the scientific community, but particularly so for programmes with long-term data collections like our MIMMP, that would be missing out on the entire 2020 field season.

Fortunately, the day has been saved due to a historical collaboration between the MIMMP, Plimsoll Productions and the Department of Environment, Forestry and Fisheries (DEFF), and our science crew has set sail TODAY from Cape Town harbour to resume scientific activities on Marion Island.

Our experienced sealers are getting some sailing practice on this voyage of a lifetime! Photo credit: Leandri de Kock

Congratulations to all parties involved for this milestone in science, conservation and society. Thanks to these tireless efforts, the integrity of long-term science programmes like the MIMMP can continue and result in achievements like our 39-years of uninterrupted Southern elephant seal monitoring!

Safe travels to our experienced MIMMP sealers Yinhla Shihlomule (going for his 3rd Marion Island expedition) and Frikkie van der Vyver (going for his 2nd expedition), who will have to hit the ground running as they arrive during the busiest field season of all - the Southern elephant seal breeding season.

Bon voyage!

Job vacancy: Mouse Free Marion

https://mousefreemarion.org/

Marion Island is home to nearly a quarter of a million endangered seabirds that breed on this South African sub-Antarctic island each year.

Unfortunately, the invasive mouse population on Marion Island has increased substantially over recent decades. This has resulted in severe impacts on invertebrates (such as the flightless moths and weevils), plant communities and most recently the seabird populations. While impacts specifically on seals at the island are not clear, the devastating effects of mice on the entire ecosystem certainly are, and the MIMMP fully supports the Mouse Free Marion mission!

JOB VACANCY: BirdLife South Africa is seeking a highly qualified, dedicated and dynamic Project Manager to co-ordinate and implement the Mouse-Free Marion project which aims to eradicate mice from Marion Island. The planning and implementation of this project is overseen by a collaboration between BirdLife South Africa and the South African Department of Environment, Forestry and Fisheries through various committees including the Mouse-Free Marion Project Management Committee and the Project Steering Committee, and in consultation with various partner organizations and funders. APPLICATION DEADLINE: 30 SEPTEMBER 2020. For more details about this position and to apply, please visit: https://www.birdlife.org.za/who-we-are/vacancies/

Visit https://mousefreemarion.org/ for more information on this historic endeavor and to sponsor your share of ‘Mouse Free Marion’.

MIMMP contributes to establishment of 13 new IMPORTANT MARINE MAMMAL AREAS

The Southern Ocean is critical to the survival of more than a quarter of the worlds’ marine mammals, which depend on this vast wilderness for feeding and breeding grounds. Despite being one of the most marine mammal-rich places on earth, the majority of the Southern Ocean falls outside national jurisdictions and protected areas.

PHOTO CREDIT: CHRIS oosthuizen

In August 2020, the IUCN SSC/WCPA Marine Mammal Protected Areas Task Force made massive strides in Southern Ocean conservation, by announcing the approval of thirteen newly motivated Important Marine Mammal Areas (IMMAs) within the Extended Southern Ocean Region. MIMMPs’ Nico de Bruyn and Ryan Reisinger were among the 20 scientists from 11 countries that participated in a prestigious workshop by the IMMA Secretariat, which saw to the peer-review and subsequent approval of these new IMMAs. This workshop held in Brest, France in 2018, was a collaboration between various stakeholders, including the French Biodiversity Agency (Office Français de la Biodiversité — OFB), IUCN Global Marine and Polar Programme, and the Scientific Committee on Antarctic Research (SCAR).

The global network of Important Marine Mammal Areas (IMMAs) welcomes the addition of the Extended Southern Ocean Region. Visit https://www.marinemammalhabitat.org/ for more information

Important Marine Mammal Areas are “discrete portions of habitat, important to marine mammal species, that have the potential to be delineated and managed for conservation”. While they are not necessarily protected areas themselves, IMMAs are an incredibly useful conservation management tool because they provide expert, data-driven information that is accessible and relevant to policy makers. This includes the identification of biodiversity hotspots, which can be used to monitor general ecosystem health and incorporated into marine spatial planning or protected area establishment or expansion.

Included in the newly approved IMMAs are (some of the MIMMPs’ favourites) ‘The Prince Edwards Islands and western oceanic waters’, ‘Gough Island and surrounding waters’, and ‘Bouvet Island and surrounding waters’.

Congratulations to Nico and Ryan for contributing to this milestone in Southern Ocean conservation, and showcasing the value of MIMMPs’ ongoing research in the Southern Oceans on a global platform available to researchers and policy makers.

Follow these links for further reading on this exciting development in Important Marine Mammal Areas or to access the IMMAs searchable database and e-Atlas.

Are whisker isotopes of elephant seal pups related to moms’ diet? New insights into fetal metabolism and nutrition

Studying the diets of large, free-ranging marine mammals is notoriously difficult. As such, there is a drive towards using minimally invasive sampling methods, and previous MIMMP research has shown that seal whiskers can tell us a great deal about their diet (click HERE). When it comes to southern elephant seals, there are also advantages to working with pups as they are easier to handle than their larger and more aggressive grown-up counterparts.

PHOTO CREDIT: Nico Lübcker

Literature suggests that whiskers from seal pups can indirectly tell us about their moms’ diet because they are entirely dependent on their mother for sustenance during gestation and while suckling. MIMMP researchers investigated this proposition in the recent publication ‘Can the carbon and nitrogen isotope values of offspring be used as a proxy for their mother’s diet? Using fetal physiology to interpret bulk tissue and amino acid δ15N values’. The findings were surprising.

In this study, Nico Lübcker, John P. Whiteman, Seth D. Newsome, Robert P. Millar & P. J. Nico de Bruyn tested the validity of using the biomolecules deposited chronologically along the length of whisker sampled from neonate pups to obtain a longitudinal record of their mothers’ foraging habits during gestation. They sequentially measured bulk tissue and amino acid δ15N values along the length of whiskers from southern elephant seal mother-offspring pairs from Marion Island.

Figure 4: Correlation between maternal and foetal bulk tissue δ15N (a) and δ13C (b) values measured sequentially along the length of whiskers during the first-to-second trimester of gestation (T1/2; solid fill symbols) and third trimester of pregnancy (T3; open symbols) of four southern elephant seal (Mirounga leonina) mother–offspring pairs. The dashed black line represents a 1:1 correlation and coloured dashed line represent fitted Loess smoothers for each mother–offspring pair. Details of fitted models are provided elsewhere (Table 3 and S3–S7).

In contrast to previous studies, the mother-offspring pairs were not in isotopic equilibrium or linearly correlated during gestation. Furthermore, both bulk nitrogen (Δ15N) and carbon (Δ13C) isotopic offsets between mothers and their offspring changed as gestation progressed and were pair specific. The observed mother-offspring δ15N differences are likely explained by the shuttling of glutamate-glutamine and glycine-serine among skeletal muscle, liver, placenta, and fetal tissue. Importantly, fetal development relies primarily on remobilized endogenous maternal proteinaceous sources suggesting that pregnant females are in a catabolic-anabolic metabolic state during pregnancy. This finding shows that fetal development is reliant on endogenous maternal protein reserves rather than maternal adipose tissue from the onset of gestation.

These findings shed new light on fetal amino acid metabolism and confirms that the isotopic signatures of elephant seal pup whiskers cannot reliably tell us what the mom ate while pregnant.

This study is the first combined bulk tissue and amino acid isotope approach to investigate the resource pool contributing to fetal development, explore fetal amino acid metabolism, and provide mechanistic explanations between mother and offspring isotope offsets in southern elephant seals. It highlights the importance of performing physiological method validations to understand the limitations of sampling approaches, and stresses the need to differentiate between ecological and physiological factors that influence tissue isotope values before drawing inferences about foraging and movement ecology.

To access the full article CLICK HERE.

NEW PAPER: Dominant breeding male elephant seals were top class from the start

PHOTO CREDIT: TRAVIS DUCK

Children of the same age can differ remarkably in terms of physical appearance and performance. These individual differences arise from various sources such as genetics, upbringing and environment which can be carried over into adulthood. The same can be seen for various traits in other vertebrate species.

For polygynous males, specific individual traits and performances are crucial for ensuring breeding success. A new publication in the journal Oikos, led by MIMMP’s recent PhD graduate, Kyle Lloyd, examined individual differences (heterogeneity) among pre-breeding male southern elephant seals at Marion Island using 34-years of mark-recapture data.

Photo credit: Kyle Lloyd

Pre-breeders expressed individual differences in survival and recruitment for most age classes, likely related to density-dependent effects experienced during early life. These stark differences in pre-breeder vital rates illustrate that the majority of dominant breeders were likely robust in quality during development. Few frail pre-breeders ever obtained social dominance as adults. 

To access the article and read more CLICK HERE

LEGACY BOOK SPECIAL - Flock to Marion Island 2021

Time on your hands? Take advantage of this opportunity to get lost in the adventure stories, entertaining first-hand accounts and beautiful photographs from researchers in the sub-Antarctic.

CLICK HERE to purchase our Legacy Book ‘Pain forms the character’ now available ON SPECIAL in support of the envisaged Flock to Marion Island voyage 2021*.

* BirdLife South Africa and MSC cruises are concerned about the current global coronavirus pandemic and has therefore put in place a number of interim and important operational measures. They have also been in regular communication with MSC Cruises about Flock to Marion, and both parties are hopeful that the voyage will still go ahead. BirdLife South Africa will take guidance from South African government directives and the World Health Organization. MSC Cruises will, without doubt, be taking the utmost precaution around passenger health and safety. More information will be made available as the situation progresses.

Science for the birds? And seals to be exact. Identifying hotspots for conservation in the Tristan da Cunha territory

PHOTO CREDIT: dr MIA WEGE

The Tristan da Cunha territory in the South Atlantic Ocean consists of remote oceanic islands home to unique biodiversity. Both Gough and Inaccessible islands are World UNESCO heritage sites (https://whc.unesco.org/en/list/740) due to their pristine conditions, high diversity and levels of endemism. The seabirds and seal species, several of which are endemic and globally threatened, rely on these islands for essential breeding grounds, but also on the rich surrounding ocean waters for food.

Tristan da Cunha island is also home to the most remote community of people in the world, and this British Overseas Territory relies heavily on crayfish fisheries as its main income. Sustainable fisheries and healthy ecosystems are therefore critical to the survival of both the Tristan da Cunha island community and its unique fauna and flora.

Unfortunately, there are illegal, unregulated and unreported (IUU) fishing activities occurring in the Tristan da Cunha Exclusive Economic Zone (EEZ), which threaten both the livelihoods of the island inhabitants and the sensitive biodiversity. The Tristan da Cunha government is in the process of establishing a marine protection regime for its entire EEZ: an area larger than 750 000 km². This provides the Tristan Government with a unique opportunity to establish a conservation area in one of the most important and pristine marine ecosystems.

Overlap of marine multi-species hotspots within the Exclusive Economic Zone (EEZ) of Tristan da Cunha identified from tracking data of nine seabird and one fur seal species collected between 2000 and 2018. Shading indicates in how many seasons an area was identified as a hotspot (Figure 3, Requena et al. 2020)

In a recent paper involving MIMMP’s Prof Marthán Bester and Dr Mia Wege, tracking data from nine seabirds and one seal species around the Tristan da Cunha territory was used to identify areas of concentrated animal activity around the islands. Using a simple and effective approach by calculating “hotspots” – areas where the most species spend the majority of their time foraging – this study found that most hotspots occurred either within 100 km of breeding colonies or were associated with seamounts. These results were also spatially constant across several seasons.

This paper provides spatially explicit information on where the region’s biodiversity concentrates and can help inform the design of a marine protection regime and future fishing authorizations. Such ecological information can also be combined with economic assessments of the Tristan da Cunha EEZ to achieve conservation targets while permitting vital economic activity in the region.

Photo credit: dr mia wege

This study is particularly relevant in light of recent approvals for limited long-line and trawl fisheries on the very offshore seamounts where the marine top predators are shown to congregate, and the Tristan da Cunha Government’s aim to establishing a community-driven and science-led marine protection regime across the entire EEZ by 2020. 

It is through cross-disciplinary, multi-national collaborative efforts like these that policy makers can use scientific evidence to prioritise the protection of strategic areas to benefit a multitude of species and whole ecosystems. In doing so, a balance can be struck between the ecological and economic importance of pelagic areas - information that benefits conservation planning and marine management, even in the most remote places on earth.

Read more from this paper here or request the PDF.

Latest MIMMP research - A new tool for identifying nitrogen balance of free-ranging mammals

Photo credit: MIa Wege

It is notoriously difficult to monitor the nutritional status of free-ranging animals over time, particularly those living in the oceans. Incredibly, it is still possible for scientists to reconstruct the foraging ecology and eco-physiology of animals by using nutritional biomarkers (Nitrogen (δ15N) and Carbon (δ13C) isotopes) that are deposited chronologically along the length of keratinous tissues, such as nails or whiskers.

But are these biomarkers reliable for animals that periodically undergo extreme physiological stresses, like southern elephant seals that fast while on land? The latest MIMMP research paper by Nico Lübcker, John P. Whiteman, Robert P. Millar, P. J. Nico de Bruyn & Seth D. Newsome “Fasting affects amino acid nitrogen isotope values: a new tool for identifying nitrogen balance of free-ranging mammals“ shows that this is indeed an important consideration.

Lübcker and colleagues sequentially measured bulk tissue and amino acid δ15N values along the length of whiskers from southern elephant seals (Mirounga leonina) on Marion Island.

Comparison of the mean (± SD) bulk tissue δ15N values (left panel) and median amino acid δ15N values of juvenile southern elephant seals (n = 5) whiskers reflecting the post-weaning fast (red open symbols) and foraging at-sea (blue open symbols). Solid error bars reflect the 25% and 75% confidence intervals (CI) around the median δ15N values, while the dashed lines reflect the 5% and 95% CI. *P < 0.05, **P < 0.01, ***P < 0.001.

Whisker segments corresponding to fasting periods from juveniles and adult females had significantly higher bulk tissue δ15N values compared to segments unaffected by fasting. Fasting also resulted in a large increase in δ15N values for most glucogenic amino acids and a simultaneous depletion of alanine.

This finding enabled Lübcker and colleagues to accurately predict (74 %) the nutritional status of these animals. These findings suggest that the glucose-alanine cycle is the mechanism driving the observed depletion of alanine δ15N values during fasting in elephant seals.

While this study demonstrates that keratinaceous tissues can be used as a longitudinal nutritional biomarker to detect changes in the nitrogen balance, it is evident that physiological factors do in fact have an important influence on tissue δ15N values. Not taking this into account can lead to erroneous bulk tissue or amino acid isotope-based reconstructions of foraging habits.

For further reading click here.

NEW paper: How did extreme historical harvesting affect fur seal genetics?

Antarctic fur seal bull on Subantarctic Marion Island. Photo: Nico de Bruyn

The MIMMP’s Nico de Bruyn and Marthán Bester contributed to a new paper published in Scientific Reports and lead by collaborators Anneke Paijmans and Joseph Hoffman, assessing the genetic legacy of extreme exploitation in a polar vertebrate.

Global population structure of the Antarctic fur seal inferred by STRUCTURE analysis of 2,000 individuals from eight populations genotyped at 39 microsatellite loci.

Understanding the effects of human exploitation on the genetic composition of wild populations is important for predicting species persistence and adaptive potential.  We therefore investigated the genetic consequences of one of the most extreme episodes of commercial exploitation in history.  Antarctic fur seals were hunted virtually to extinction across their circumpolar distribution.  However, a large genetic dataset uncovered evidence for four relict populations, indicating that the species as a whole was more resilient to hunting than suggested by historical accounts.  Furthermore, despite these populations having experienced demographic declines, sufficient numbers of animals survived to retain comparably high levels of genetic variation. Our results explain the apparent contradiction between the high genetic diversity of this species and its extreme exploitation history.

Read the paper here: https://www.nature.com/articles/s41598-020-61560-8

NATURE paper: Tracking predators to protect Southern Ocean Ecosystems

Southern elephant seal with a satellite tracking device, Marion Island. Photo: Nico de Bruyn

In a rapidly changing world, we need to know which areas of our planet warrant protection from existing, developing and forthcoming threats. This is hard to do objectively in the vast realm of the oceans, and particularly so in the most remote parts, the Southern Ocean. A paper published this week in the journal Nature (together with a companion data paper in the journal Scientific Data) describes a novel solution to this problem, using electronic tracking data from birds and marine mammals.

The solution relies on a simple principle:  animals go to places where they find food. So, identifying areas of the Southern Ocean where predators most commonly go also tells us where their prey can be found. For example, humpback whales and penguins will go to places where they can feed on krill, whereas elephant seals and albatrosses go where they can find fish, squid, or other prey. If all these predators and their diverse prey are found in the same place then this area has both high diversity and abundance of species, indicating that it is of high ecological significance. 

Hindell et al 2020. https://www.nature.com/articles/s41586-020-2126-y

The project was conducted by the Scientific Committee for Antarctic Research (SCAR), with support from the Centre de Synthèse et d'Analyse sur la Biodiversité, France, and the WWF-UK.  

SCAR engaged its extensive network of Antarctic researchers to assemble existing Southern Ocean predator tracking data.  After careful validation, the result was an enormous database of over 4000 individual animal tracks from 17 species, collected by more than 70 scientists (including Nico de Bruyn and Marthan Bester) across 12 national Antarctic programs. MIMMP research associate and past student, Ryan Reisinger, was one of the joint lead authors on this study. This database is now available for public download.

Even this impressive database does not directly represent all Southern Ocean predator activity, because it is impossible to track every species from all their breeding colonies. Simple mapping would therefore provide a biased representation of animal distribution. To overcome this, sophisticated statistical models were used to predict the at-sea movements for all known colonies of each predator species across the entire Southern Ocean. These predictions were combined across the 17 predator species to provide an integrated map of those areas used by many different predators with diverse prey requirements.

The most important of these areas -  areas of ecological significance - are scattered around the Antarctic continental shelf and in two wider oceanic regions, one projecting from the Antarctic Peninsula engulfing the Scotia Arc, and another surrounding the sub-Antarctic islands in the Indian sector of the Southern Ocean.

Marine Protected Areas (MPAs) are a crucial tool in the conservation management toolbox. Existing and proposed MPAs are mostly found within the areas of ecological significance, suggesting that they are currently in the right places. Yet when using climate model projections to account for how areas of important habitat may shift by 2100, the existing MPAs with their fixed boundaries may not remain aligned with future important habitats. Dynamic management of MPAs, updated over time in response to ongoing change, are therefore needed to ensure continued protection of Southern Ocean ecosystems and their resources in the face of growing resource demand by the current and future generations.

Read the article here: https://www.nature.com/articles/s41586-020-2126-y

And the associated Scientific Data paper here: https://www.nature.com/articles/s41597-020-0406-x

Whiskers, stress and pregnancy! MIMMP paper by PhD student Nico Lübcker

Ever wondered what stories an animal’s whisker could tell? Well, a new paper published by MIMMP’s PhD student Nico Lübcker might help answer that.

Nico Lübcker and colleagues recently developed a novel method to analyze multiple steroids deposited chronologically along the length of seal whiskers. Their findings have now been published in a new article “What’s in a whisker? High-throughput analysis of twenty-eight C19 and C21 steroids in mammalian whiskers by ultra-performance convergence chromatography-tandem mass spectrometry”.

This study describes an accurate quantification method for multiple steroids, measured in a single chromatography step. The advantage of this new development is that it reduces the cost and time associated with such analyses by previous methods.

This is an exciting advancement because it contributes to our understanding of the impact of stress (associated with environmental/climatic changes) on the health and survival of organisms, and also allows us to delineate the reproductive cycles of free-living mammals. This becomes especially useful for organisms with cryptic life stages, like seals.

To read more from this study, access the online article here.

PHOTO CREDIT: NICO LÜBCKER