Variation in breeding phenology provides insights into drivers of long-term population change in harbour seals

Phenological trends provide important indicators of environmental change and population dynamics. However, the use of untested population-level measures can lead to incorrect conclusions about phenological trends, particularly when changes in population structure or density are ignored. We used individual-based estimates of birth date and lactation duration of harbour seals (Phoca vitulina) to investigate energetic consequences of changes in pupping phenology. Using generalized linear mixed models, we first demonstrate annual variation in pupping phenology. Second, we show a negative relationship between lactation duration and the timing of pupping, indicating that females who pup early nurse their pups longer, thereby highlighting lactation duration as a useful proxy of female condition and resource availability. Third, individual-based data were used to derive a population-level proxy that demonstrated an advance in pupping date over the last 25 years, co-incident with a reduction in population abundance that resulted from fisheries-related shootings. These findings demonstrate that phenological studies examining the impacts of climate change on mammal populations must carefully control for changes in population density and highlight how joint investigations of phenological and demographic change provide insights into the drivers of population declines.     

Surface temperature patterns in seals and sea lions: A validation of temporal and spatial consistency

We assessed infrared thermography (IRT) as a tool for evaluating spatial and temporal surface temperature patterns in juvenile female harbor seals (Phoca vitulina, n=6) and adult female Steller sea lions (Eumetopias jubatus, n=2). Following a technical assessment of the influence of environmental parameters on the specific camera to be used, we identified regional and seasonal variability of surface temperatures. Variation was observed in several seasonal transitions (winter, reproductive, molt) in ten monitored body regions. Spatially and temporally consistent thermal patterns in the shoulder, axillae, foreflipper and hindflipper suggest thermal windows in both species.     

The effect of feeding on the metabolic rate in harbour seals (Phoca vitulina)

The heat increment of feeding was estimated in harbour seals (Phoca vitulina). Seals were given different amounts of herring, ranging from 0.8 to 2.65 kg. The caloric content of the herring ranged from 6575 to 12560 kJ·kg^-1 depending on time of year. Metabolic rate increased within 30 min after feeding, and the magnitude and duration of heat increment of feeding depended on the size of the meal and the caloric content of the herring. Measured heat increment of feeding was up to 14.9% of gross energy intake and metabolic rate increased as much as 46% above resting, postabsorptive metabolic rate for 15 h duration in a harbour seal with a body weight of approximately 40 kg.     

The identification of a new Giardia duodenalis assemblage in marine vertebrates and a preliminary analysis of G. duodenalis population biology in marine systems

Giardia duodenalis is an intestinal parasite of many vertebrates. The presence of G. duodenalis in the marine environment due to anthropogenic and wildlife activity is well documented, including the contributions from untreated sewage and storm water, agricultural run-off and droppings from terrestrial animals. Recently, studies have detected this protistan parasite in the faeces of marine vertebrates such as whales, dolphins, seals and shore birds. To explore the population biology of G. duodenalis in marine life, we determined the prevalence of G. duodenalis in two species of seal (Halichoerus grypus, Phoca vitulina vitulina and Phoca vitulina richardsi) from the east and west coasts of the USA, sequenced two loci from G. duodenalis-positive samples to assess molecular diversity and examined G. duodenalis distribution amongst these seals and other marine vertebrates along the east coast. We found a significant difference in the presence of G. duodenalis between east and west coast seal species. Only the zoonotic lineages of G. duodenalis, Assemblages A and B and a novel lineage, which we designated as Assemblage H, were identified in marine vertebrates. Assemblages A and B are broadly distributed geographically and show a lack of host specificity. Only grey seal (Halichoerus grypus) samples and one gull sample (Larus argentatus) from a northern location of Cape Cod, Massachusetts, USA, showed the presence of Assemblage H haplotypes; only one other study of harbour seals from the Puget Sound region of Washington, USA previously recorded the presence of an Assemblage H haplotype. Assemblage H sequences form a monophyletic clade that appears as divergent from the other seven Assemblages of G. duodenalis as these assemblages are from each other. The discovery of a previously uncharacterised lineage of G. duodenalis suggests that this parasite has more genetic diversity and perhaps a larger host range than previously believed.     

Successful foraging zones of southern elephant seals from the Kerguelen Islands in relation to oceanographic conditions

Southern elephant seals, Mirounga leonina, undertake large-scale oceanic movements to access favourable foraging areas. Successful foraging areas of elephant seals from the Kerguelen Islands are investigated here in relation to oceanographic parameters. Movements and diving activity of the seals as well as oceanographic data were collected through a new generation of satellite relayed devices measuring and transmitting locations, pressure, temperature and salinity. For the first time, we have associated foraging behaviour, determined by high increased sinuosity in tracks, and dive density (i.e. number of dives performed per kilometre covered), and changes in body condition, determined by variations in drift rate obtained from drift dives, to identify the oceanographic conditions of successful foraging zones for this species. Two main sectors, one close to the Antarctic continent and the other along the Polar Front (PF), where both foraging activity and body condition increase, seem to be of particular interest for the seals. Within these regions, some seals tended to focus their foraging activity on zones with particular temperature signatures. Along the Antarctic continent, some seals targeted colder waters on the sea bottom during benthic dives, while at the PF the favourable zones tended to be warmer. The possible negative effect of colder waters in Antarctic on the swimming performances of potential fish or squid prey could explain the behaviour of elephant seals in these zones, while warmer waters within the PF could correspond to the optimal conditions for potential myctophid prey of elephant seals.     

Historical population size of the harbour seal,Phoca vitulina,in the Delta area,SW Netherlands

Seals in the Dutch Delta area have been subject to hunting pressure for centuries, promoted by a bounty system which generated a sort of hunting statistics. Hunting mortality is used to estimate historical population size. Based on ranges for most likely net recruitment rates, corresponding population trajectories are back calculated from an assessed population size of 350 seals in 1960. It is concluded that the size of the harbour seal population in the Delta area in 1900 will have been close to 11 500 animals. Significant loss of habitat has occurred due to closing off parts of the larger estuaries and the enlargement of the entrance to the harbour of Rotterdam in the 1960s and early 1970s. It is estimated that about 4000 harbour seals could inhabit the remaining Delta area under tidal influence. This outcome, based on retrospective population analysis, will be an important reference in defining management objectives for the recovery of the harbour seal population in the Delta area, which amounted to 18 seals in 1992.     

Beneath the surface: Profiling blubber depth in pinnipeds with infrared imaging

Infrared thermography (IRT) was assessed as a non-invasive tool to evaluate body condition in juvenile female harbor seals (Phoca vitulina), (n=6) and adult female Steller sea lions (Eumetopias jubatus), (n=2). Surface temperature determined by IRT and blubber depth assessed with portable imaging ultrasound were monitored concurrently at eight body sites over the course of a year in long-term captive individuals under controlled conditions. Site-specific differences in surface temperature were noted between winter and summer in both species. Overall, surface temperature was slightly higher and more variable in harbor seals (9.8±0.6 °C) than Steller sea lions (9.1±0.5 °C). Limited site-specific relationships were found between surface temperature and blubber thickness, however, insulation level alone explained a very small portion of the variance. Therefore, while validated IRT data collection can potentially provide valuable information on the health, condition and metabolic state of an animal, it cannot provide a generalized proxy for blubber depth.     

Diving behaviour, dive cycles and aerobic dive limit in the platypus Ornithorhynchus anatinus

We investigated the diving behaviour, the time allocation of the dive cycle and the behavioural aerobic dive limit (ADL) of platypuses (Ornithorhynchus anatinus) living at a sub-alpine Tasmanian lake. Individual platypuses were equipped with combined data logger-transmitter packages measuring dive depth. Mean dive duration was 31.3 s with 72% of all dives lasting between 18 and 40 s. Mean surface duration was 10.1 s. Mean dive depth was 1.28 m with a maximum of 8.77 m. Platypuses performed up to 1600 dives per foraging trip with a mean of 75 dives per hour. ADL was estimated by consideration of post-dive surface intervals vs. dive durations. Only 15% of all dives were found to exceed the estimated ADL of 40 s, indicating mainly aerobic diving in the species. Foraging platypuses followed a model of optimised recovery time, the optimal breathing theory. Total bottom duration or total foraging duration per day is proposed as a useful indicator of foraging efficiency and hence habitat quality in the species.     

Side steps: the erratic pattern of hominin postcranial change through time

The hominin fossil record reveals brain-size expansion, canine reduction, premolar metaconid development, and numerous other craniodental features that become more human-like through time. In general, the postcranial skeleton also gets more human-like through time, but in some respects it does not. This is particularly apparent in the overall morphology of one of the most frequently preserved elements, the distal humerus. Some of the earliest hominins display quite human-like morphologies, whereas later specimens are quite unusual among extant species of Hominoidea: when described metrically and subjected to multivariate discriminant analyses in the context of large samples of extant hominoid humeri, the shapes of the earliest hominin fossils are more human-like than many of the later specimens. The Mahalanobis distances between many of the 1.5-2Ma hominin humeri and Homo sapiens are remarkably large. Many of the less well-represented postcranial specimens do not follow a linear path through time of increasing hominization either. This is particularly noticeable in the fore-to-hind limb joint-size proportions, ulnar morphology, and pelvic architecture. The hominin postcranial fossil record reveals many side-steps: there appears to be no simple march toward our human bodies, but a pattern better explained as adaptations to proximate conditions and constrained by ontogeny and history.     

Chemical characterization of the oligosaccharides in milk of high Arctic harbour seal (Phoca vitulina vitulina)

Carbohydrates were extracted from high Arctic harbour seal milk, Phoca vitulina vitulina (family Phocidae). Free neutral oligosaccharides were separated by gel filtration and preparative thin layer chromatography, while free sialyl oligosaccharides were separated by gel filtration and then purified by ion exchange chromatography, gel filtration and high performance liquid chromatography. Oligosaccharide structures were determined by 1H-NMR spectroscopy. The structures of the neutral oligosaccharides were as follows: lactose, 2'-fucosyllactose, lacto-N-neotetraose, lacto-N-neohexaose, monofucosyl lacto-N-neohexaose and difucosyl lacto-N-neohexaose. Thus, all of the neutral saccharides contained lactose or lacto-N-neotetraose or lacto-N-neohexaose as core units and/or non-reducing alpha(1-2) linked fucose. These oligosaccharides have also been found in hooded seal milk. The structures of the silalyl oligosaccharides were: monosialyl lacto-N-neohexaose, monosialyl monofucosyl lacto-N-neohexaose, monosialyl difucosyl lacto-N-neohexaose and disialyl lacto-N-neohexaose. These oligosaccharides contained lacto-N-neohexaose as core units, and one or two alpha(2-6) linked Neu5Ac, and/or non-reducing alpha(1-2) linked Fuc. The Neu5Ac residues were found to be linked to GlcNAc or penultimate Gal residues. The acidic oligosaccharides are the first to have been characterized in the milk of any species of seal.     

Making it through the first year: Ontogeny of movement and diving behavior in harbor seals from Svalbard,Norway

Phocid seal pups must learn successful survival strategies, largely independently, following their abrupt weaning at a relatively young age. To explore the ontogeny of aquatic skills, space use and first‐year habitat choices made by harbor seals, pups (n = 30) were instrumented with satellite relay data loggers (SRDLs) in Svalbard, Norway in 2009 and 2010. Initially, the pups had small home ranges and showed rapid changes in their activity budgets and diving capabilities, displaying steep linear increases in diving depth and duration and in the amount of time spent diving. Most pups underwent an abrupt shift in movement patterns at ca. 50 d of age, which likely marked the end of the postweaning fast. Around this same time, the steep progression in diving performance slowed, though longer, deeper dives gradually became the norm. However, bottom time, ascent and descent rates, and postdive recovery times remained stable after the postweaning fast, suggesting that most aquatic skill acquisition was completed during the first months of life. Few clear effects of environmental variables such as upwelling phenomenon, which are known to influence the diving behavior of adults from the same population, were detected in the diving patterns of pups.     

Ecological effects of pharmaceuticals in aquatic systems—impacts through behavioural alterations

The study of animal behaviour is important for both ecology and ecotoxicology, yet research in these two fields is currently developing independently. Here, we synthesize the available knowledge on drug-induced behavioural alterations in fish, discuss potential ecological consequences and report results from an experiment in which we quantify both uptake and behavioural impact of a psychiatric drug on a predatory fish (Perca fluviatilis) and its invertebrate prey (Coenagrion hastulatum). We show that perch became more active while damselfly behaviour was unaffected, illustrating that behavioural effects of pharmaceuticals can differ between species. Furthermore, we demonstrate that prey consumption can be an important exposure route as on average 46% of the pharmaceutical in ingested prey accumulated in the predator. This suggests that investigations of exposure through bioconcentration, where trophic interactions and subsequent bioaccumulation of exposed individuals are ignored, underestimate exposure. Wildlife may therefore be exposed to higher levels of behaviourally altering pharmaceuticals than predictions based on commonly used exposure assays and pharmaceutical concentrations found in environmental monitoring programmes.     

Fence effects on the behavioural responses of South American fur seals to tourist approaches

Animals that breed in coastal colonies, such as pinnipeds, usually attract tourism, which can negatively affect their resting and breeding behaviour if not managed properly. One strategy to reduce human disturbance is to set up fences, but little is known about their local effectiveness. Our purpose was to assess the behavioural responses of South American fur seals (Arctocephaalus australis) towards tourist approaches before and after the implementation of fences in Cabo Polonio colony (Uruguay). We found that human disturbance levels were similar between years and that the presence of a fence reduced (1) overall fur seal responses to tourists by 60%, (2) the most intense behavioural responses (threat, attack, leaving the colony) by more than half, (3) the responses to large tourist groups (>2 people), which were the most disturbing, (4) the responses to closer (<10 m) tourist approaches, and (5) the responses involving more intrusive tourist behaviours (running, shouting, hand waving). Overall, we showed that after the erection of the fence not only human–wildlife interactions were reduced but also the most stressful fur seal behavioural responses. Although further studies are necessary, our results suggest that the implementation of fences can be a simple and affordable means of minimising human disturbance effects on pinnipeds at local levels (e.g., within colonies), particularly if combined with other strategies (e.g., changes in tourist attitudes).