Marine ecosystem assessment for the Southern Ocean: birds and marine mammals in a changing climate

The massive number of seabirds (penguins and procellariiformes) and marine mammals (cetaceans and pinnipeds) – referred to here as top predators – is one of the most iconic components of the Antarctic and Southern Ocean. They play an important role as highly mobile consumers, structuring and connecting pelagic marine food webs and are widely studied relative to other taxa. Many birds and mammals establish dense breeding colonies or use haul-out sites, making them relatively easy to study. Cetaceans, however, spend their lives at sea and thus aspects of their life cycle are more complicated to monitor and study. Nevertheless, they all feed at sea and their reproductive success depends on the food availability in the marine environment, hence they are considered useful indicators of the state of the marine resources. In general, top predators have large body sizes that allow for instrumentation with miniature data-recording or transmitting devices to monitor their activities at sea. Development of scientific techniques to study reproduction and foraging of top predators has led to substantial scientific literature on their population trends, key biological parameters, migratory patterns, foraging and feeding ecology, and linkages with atmospheric or oceanographic dynamics, for a number of species and regions. We briefly summarize the vast literature on Southern Ocean top predators, focusing on the most recent syntheses. We also provide an overview on the key current and emerging pressures faced by these animals as a result of both natural and human causes. We recognize the overarching impact that environmental changes driven by climate change have on the ecology of these species. We also evaluate direct and indirect interactions between marine predators and other factors such as disease, pollution, land disturbance and the increasing pressure from global fisheries in the Southern Ocean. Where possible we consider the data availability for assessing the status and trends for each of these components, their capacity for resilience or recovery, effectiveness of management responses, risk likelihood of key impacts and future outlook

The ecophysiology of seed dispersal by Orangutans in Bornean peat swamp forest

The study of an ecosystem process like seed dispersal is at the forefront of the dynamic field of ecophysiology, the study of how animals and environments interact. Understanding spatial movements is essential to unravelling how animals interact with their ecosystem and tie animal ecology to ecosystem processes, particularly to animal mediated seed dispersal (zoochory). The movement of seeds through an animal gut (endozoochory), from one place to another is an essential driver of forest structure and is a complex process that depends on a variety of environmental and physiological factors. Seed dispersal is a crucial component of plant population dynamics, influencing plant populations and communities through both short and long distance dispersal. The spatial arrangement of seed deposition also contributes to at least half the gene-flow of plants, and their population genetic structure can be highly dependent on fauna-mediated seed dispersal, particularly in tropical regions. A review on the role of physiology in conservation translocation was evaluated for over a decade worth of peer-reviewed studies (2000-2010) to highlight both the relative rarity of including physiological analyses in such a significant conservation undertaking, and the absolute essentiality of addressing this lack, especially in the face of todays changing world. The data here link a number of stages in endozoochorous provision by the orangutan. In an ex-situ setting, the first ever measurement of the transit time of indigestible seed mimics was made, with study subjects that were fed a diet consisting largely of plant matter. Elimination pattern of seed mimics was measured, demonstrating a pulse dose excretion, often in one or two single defecation events, with smaller amounts both before and after this peak. The average transit time of seed mimics across all bead sizes was 76 hours, a figure that was later used to create a predictive model of faecal deposition patterns of seeds in an in-situ situation. Orangutans were shown to have the potential to provide very long distance dispersal from the parent plant due to their long transit times and large home ranges. Large bodied frugivores, such as the orangutan, are likely to be critically important seed dispersers as there are typically few animals that can effectively disperse large-seeded species. This has often lead to coevolution of the plant-animal interaction particularly with regards to large seeds which many other frugivores cannot swallow intact. The application of Time Local Convex Hull (T-LoCoH) is the first objective tool of its kind in orangutan ecological research in tropical peat swamp forest (TPSF), and the first application of T-LoCoH to ecological service provision anywhere. T-LoCoH is a new technique that models animal movement over both time and space. This modeling accurately predicted where orangutans would deposit faeces when compared to real-time data gathered in the Sabangau Forest, Central Kalimantan, Indonesia (Indonesian Borneo). This environment exhibits a relative lack of secondary seed removal and orangutans can be expected to play a disproportionate role in seed dispersal here, particularly of large sized seeds and over wide ranging areas. This method provides a basis to establish a training method to make a priori projections of seed dispersal dynamics in novel ecosystems. Evaluation of post-defecation germination potential of seeds provided further insight into the orangutan;s role in dispersal of 13 different seed species. Surprisingly endozoochorous travel through the orangutan gut was not the most significant factor in germination as manually extracted seeds showed the highest rates of germination over both orangutan “gut-treated” seeds and whole fruits. However seeds passed intact via orangutan faeces still germinated and contributed to the primary dispersal of many plant species. Orangutans might also play a more important role in germination when seeds are moved, by spitting whole seeds out

Hindgut plasticity in wallabies fed hay either unchopped or ground and pelleted: fiber is not the only factor

Phenotypic plasticity of the gastrointestinal tract is crucial for optimal food processing and nutrient balance in many vertebrate species. For mammalian herbivores, gut plasticity is typically correlated with the fiber content of forage; however, we show here that other factors such as ingesta particle size may effect profound phenotypic plasticity of the fermentative hind-gut in a medium-sized (10-kg body mass) marsupial herbivore, the red-necked wallaby (Macropus rufogriseus). When dietary fiber contents were comparable, red-necked wallabies that were fed a finely ground, pelleted hay for 60-72 d had hindguts that were some 28% heavier (empty wet mass) than those fed unchopped hay. The hindguts of pellet-fed wallabies contained more wet ingesta, which was also of a finer particle size, than those fed hay, indicating some separation of large- and small-particle fermentation between the foregut and the hindgut, respectively. Such a digestive strategy would benefit animals by allowing fermentation of a range of ingesta particle sizes that are expected for free-ranging animals faced with a spectrum of diet types and qualities. The heavier hindgut of pellet-fed wallabies was correlated with increased concentrations of short-chain fatty acids (SCFAs) in the fermentative hindgut (cecum and proximal colon) and particularly with increases in the molar proportions of n-butyric acid. The mechanisms facilitating gut plasticity in herbivorous mammals are uncertain, but we suggest that manipulating ingesta particle size rather than dietary fiber could provide a useful tool for evaluating causal explanations. In particular, altering ingesta particle size could help to distinguish possible direct processes (e.g., the favoring of smaller intestinal microbes and production of specific SCFAs) from indirect affects of feed structure (e.g., muscular hypertrophy to compensate for increased intakes and digesta bulk or the fermentation of mucus secreted to promote the flow of viscous, fine-particle material)

An ecophysiologically informed model of seed dispersal by orangutans: linking animal movement with gut passage across time and space

Fauna-mediated ecosystem service provision (e.g. seed dispersal) can be difficult to quantify and predict because it is underpinned by the shifting niches of multiple interacting organisms. Such interactions are especially complex in tropical ecosystems, including endangered peat forests of Central Borneo, a biodiversity hot spot and home to the critically endangered orangutan (Pongo pygmaeus wurmbii). We combined studies of the digestive physiology of captive orangutans in Australia with detailed field studies of wild orangutans in the Natural Laboratory of Peat-Swamp Forest of Sabangau, Central Kalimantan, Indonesia. By measuring the gut transit time (TT) of indigestible seed mimics (beads) in captivity and applying this as a temporal constraint to movement data of wild orangutans, we developed a mechanistic, time-explicit spatial model to project the seed dispersal patterns by these large-bodied, arboreal frugivores. We followed seven orangutans and established home range kernels using Time Local Convex Hull (T-LoCoH) modelling. This allowed us to model individual orangutan movements and to adjust these models according to gut transit times to estimate seed dispersal kernels. Female movements were conservative (core ranges of 55 and 52 ha in the wet and dry seasons, respectively) and revisitation rates to the same location of n = 4 in each 24-h block. Male movements were more unpredictable, yielding fragmented core ranges and revisitation rates to the same location of only 1.2 times each 24 h; males also demonstrated large disjunctions where they moved rapidly over long distances and were frequently lost from view. Seed dispersal kernels were nested predictably within the core ranges of females, but not males. We used the T-LoCoH approach to analyse movement ecology, which offered a powerful tool to predict the primary deposition of seeds by orangutans, thereby providing a reliable method for making a priori predictions of seed dispersal dynamics by other frugivores in novel ecosystems

An ecophysiologically informed model of seed dispersal by orangutans: linking animal movement with gut passage across time and space

Fauna-mediated ecosystem service provision (e.g. seed dispersal) can be difficult to quantify and predict because it is underpinned by the shifting niches of multiple interacting organisms. Such interactions are especially complex in tropical ecosystems, including endangered peat forests of Central Borneo, a biodiversity hot spot and home to the critically endangered orangutan (Pongo pygmaeus wurmbii). We combined studies of the digestive physiology of captive orangutans in Australia with detailed field studies of wild orangutans in the Natural Laboratory of Peat-Swamp Forest of Sabangau, Central Kalimantan, Indonesia. By measuring the gut transit time (TT) of indigestible seed mimics (beads) in captivity and applying this as a temporal constraint to movement data of wild orangutans, we developed a mechanistic, time-explicit spatial model to project the seed dispersal patterns by these large-bodied, arboreal frugivores. We followed seven orangutans and established home range kernels using Time Local Convex Hull (T-LoCoH) modelling. This allowed us to model individual orangutan movements and to adjust these models according to gut transit times to estimate seed dispersal kernels. Female movements were conservative (core ranges of 55 and 52 ha in the wet and dry seasons, respectively) and revisitation rates to the same location of n = 4 in each 24-h block. Male movements were more unpredictable, yielding fragmented core ranges and revisitation rates to the same location of only 1.2 times each 24 h; males also demonstrated large disjunctions where they moved rapidly over long distances and were frequently lost from view. Seed dispersal kernels were nested predictably within the core ranges of females, but not males. We used the T-LoCoH approach to analyse movement ecology, which offered a powerful tool to predict the primary deposition of seeds by orangutans, thereby providing a reliable method for making a priori predictions of seed dispersal dynamics by other frugivores in novel ecosystems

Regional variation in winter foraging strategies by Weddell seals in Eastern Antarctica and the Ross Sea

International audienceThe relative importance of intrinsic and extrinsic determinants of animal foraging is often difficult to quantify. The most southerly breeding mammal, the Weddell seal, remains in the Antarctic pack-ice year-round. We compared Weddell seals tagged at three geographically and hydrographically distinct locations in East Antarctica (Prydz Bay, Terre Adélie , and the Ross Sea) to quantify the role of individual variability and habitat structure in winter foraging behaviour. Most Weddell seals remained in relatively small areas close to the coast throughout the winter, but some dispersed widely. Individual utilisation distributions ( UDi , a measure of the total area used by an individual seal) ranged from 125 to 20,825 km2 . This variability was not due to size or sex but may be due to other intrinsic states for example reproductive condition or personality. The type of foraging (benthic vs. pelagic) varied from 56.6 ± 14.9% benthic dives in Prydz Bay through 42.1 ± 9.4% Terre Adélie to only 25.1 ± 8.7% in the Ross Sea reflecting regional hydrographic structure. The probability of benthic diving was less likely the deeper the ocean. Ocean topography was also influential at the population level; seals from Terre Adélie , with its relatively narrow continental shelf, had a core (50%) UD of only 200 km2 , considerably smaller than the Ross Sea (1650 km2) and Prydz Bay (1700 km2). Sea ice concentration had little influence on the time the seals spent in shallow coastal waters, but in deeper offshore water they used areas of higher ice concentration. Marine Protected Areas (MPAs) in the Ross Sea encompass all the observed Weddell seal habitat, and future MPAs that include the Antarctic continental shelf are likely to effectively protect key Weddell seal habitat

Marine ecosystem assessment for the southern ocean : birds and marine mammals in a changing climate

The massive number of seabirds (penguins and procellariiformes) and marine mammals (cetaceans and pinnipeds) – referred to here as top predators – is one of the most iconic components of the Antarctic and Southern Ocean. They play an important role as highly mobile consumers, structuring and connecting pelagic marine food webs and are widely studied relative to other taxa. Many birds and mammals establish dense breeding colonies or use haul-out sites, making them relatively easy to study. Cetaceans, however, spend their lives at sea and thus aspects of their life cycle are more complicated to monitor and study. Nevertheless, they all feed at sea and their reproductive success depends on the food availability in the marine environment, hence they are considered useful indicators of the state of the marine resources. In general, top predators have large body sizes that allow for instrumentation with miniature datarecording or transmitting devices to monitor their activities at sea. Development of scientific techniques to study reproduction and foraging of top predators has led to substantial scientific literature on their population trends, key biological parameters, migratory patterns, foraging and feeding ecology, and linkages with atmospheric or oceanographic dynamics, for a number of species and regions. We briefly summarize the vast literature on Southern Ocean top predators, focusing on the most recent syntheses. We also provide an overview on the key current and emerging pressures faced by these animals as a result of both natural and human causes. We recognize the overarching impact that environmental changes driven by climate change have on the ecology of these species. We also evaluate direct and indirect interactions between marine predators and other factors such as disease, pollution, land disturbance and the increasing pressure from global fisheries in the Southern Ocean. Where possible we consider the data availability for assessing the status and trends for each of these components, their capacity for resilience or recovery, effectiveness of management responses, risk likelihood of key impacts and future outlook.Australian Research Council DECRA and WWF-UK.http://frontiersin.org/Ecology_and_Evolutionpm2021Zoology and Entomolog