Leucistic Antarctic fur seals at Bouvetøya

One leucistic and one partially leucistic Antarctic fur seal Arctocephalus gazella were seen at Bouvetøya during the 1996/97 austral summer. Both likely came from South Georgia, where this colour morph is common. No individuals of this colour morph were sighted during three subsequent expeditions to Bouvetøya. The prevalence of this colour morph in the abundant populations of the Scotia Arc may be due to founder effect, as at least one leucistic animal was present at South Georgia when the Antarctic fur seal was close to extinction.     

Ascent exhalations of Antarctic fur seals: a behavioural adaptation for breath-hold diving?

Novel observations collected from video, acoustic and conductivity sensors showed that Antarctic fur seals consistently exhale during the last 50-85% of ascent from all dives (10-160 m, n > 8000 dives from 50 seals). The depth of initial bubble emission was best predicted by maximum dive depth, suggesting an underlying physical mechanism. Bubble sound intensity recorded from one seal followed predictions of a simple model based on venting expanding lung air with decreasing pressure. Comparison of air release between dives, together with lack of variation in intensity of thrusting movement during initial descent regardless of ultimate dive depth, suggested that inhaled diving lung volume was constant for all dives. The thrusting intensity in the final phase of ascent was greater for dives in which ascent exhalation began at a greater depth, suggesting an energetic cost to this behaviour, probably as a result of loss of buoyancy from reduced lung volume. These results suggest that fur seals descend with full lung air stores, and thus face the physiological consequences of pressure at depth. We suggest that these regular and predictable ascent exhalations could function to reduce the potential for a precipitous drop in blood oxygen that would result in shallow-water blackout.     

Does kin selection influence fostering behaviour in Antarctic fur seals (Arctocephalus gazella)?

A recent observation that female Antarctic fur seals foster pups born to related females raises the fascinating possibility that kin selection may promote altruistic behaviour even on a crowded breeding beach, where individual interactions are frequent and complex. However, the use of genetic markers to identify small numbers of unusually highly related individuals is fraught with difficulty due to the likely presence of genotyping errors and related problems. Consequently, we examined an enlarged dataset where errors had been reduced to an absolute minimum by a combination of close scrutiny and repeat genotyping. We find no support for the idea that females preferentially suckle pups born to female relatives. Instead, the previously reported pattern can be explained by a combination of genotyping errors and de novo mutations. Our study emphasizes the need for caution when interpreting rare events that occur at a rate approaching that expected for normal genotyping errors.     

Population changes of Antarctic fur seals at Nyrøysa, Bouvetøya

Antarctic fur seal Arctocephalus gazella pup production at Nyrøysa, Bouvetøya was estimated to be approximately 15,000 per annum during each of four summers from 1996 to 2002, indicating a total population of about 66,000. While the Bouvetøya population is the second largest for this species, pup production at this site still accounts for only 2.4% of the global total. This population experienced a mean annual rate of increase of 30.6% for the period 1989–1996, perhaps due, in part, to significant immigration, but has been stable since 1996. Historical accounts of significant numbers of animals being present towards the end of the period of sealing (C.1800–1930), indicate that the geographic isolation and inaccessibility of this site may have resulted in the Bouvetøya population being one of three populations that survived a series of periods of extreme exploitation of this species.     

Intraspecific differences in the diet of Antarctic fur seals at Nyrøysa, Bouvetøya

Intraspecific differences in the diets of many species of pinnipeds are to be expected in view of the great differences in morphology, life history and foraging behaviour between the sexes of many species. We examined the diet of the Antarctic fur seal population at Bouvetøya, Southern Ocean, to assess intersexual differences. This was made possible by the analysis of prey remains extracted from scats and regurgitations collected in areas used primarily by one or the other sex. The results indicate that both males and females feed primarily on Antarctic krill Euphausia superba with several species of fish and squid being taken, likely opportunistically given their prevalence. Significant differences were identified in the frequency of occurrence of otoliths in scats and the percentage numerical abundance of the major fish prey species in the diet. Adult males ate a smaller quantity of fish overall, but ate significantly more of the larger fish species. The greater diving capabilities of males and the fact that they are not limited in the extent of their foraging area by having to return regularly to feed dependant offspring may play a role in the differences found between the diets of males and females. Additionally, females might be more selective, favouring myctophids because they are richer in energy than krill. The absence of major differences in the diet between the sexes at this location is likely due to the high overall abundance of prey at Bouvetøya.     

The diet of Antarctic fur seals, Arctocephalus gazella, at King George Island, during the summer–autumn period

The diet of non-breeding male Antarctic fur seals, Arctocephalus gazella, was investigated at Stranger Point, King George Island, by scat analysis from February to April 1996. Overall, krill and fish were the most frequent prey, occurring in an average of 97% and 69% of samples (n=128), followed by cephalopods (12%). Myctophids constituted almost 90% of the fish predated, with Electrona antarctica and Gymnoscopelus nicholsi being the most abundant and frequent species consumed. All fish taxa identified were krill-feeding species suggesting that seals foraged primarily on krill and opportunistically on fish species associated with krill swarms. A seasonal change observed in the relative proportions of the different fish prey taxa indicates that fur seals spent more time foraging over the shelf in summer and off the shelf in autumn. During the study period, commercial fishing in the area was not based upon any of the fish identified in this study.     

Reemergence of Guadalupe fur seals in the U.S. Pacific Northwest: The epidemiology of stranding events during 2005–2016

Guadalupe fur seals (GFS), Arctocephalus philippii townsendi, an U.S. Endangered Species Act threatened pinniped, have recently reappeared in their historic range along the western seaboard of the continental United States. Starting 2005 through 2016, 169 GFSs stranded in Washington and Oregon, involving two designated unusual mortality events. The circumstances surrounding GFS strandings, mortality, and their increased presence in Oregon and Washington were analyzed during this study. Detailed necropsies, histopathology (n = 93), and epidemiological analysis found three main causes of death (COD): emaciation (44%), trauma (29%), and infectious disease (19%) and the factors associated with overall strandings and emaciation. Trauma included many cases found associated with fisheries interactions and clustered near the mouth of the Columbia River, where high levels of commercial fishing occur. The most common pathogens found associated with disease were Toxoplasma gondii, Sarcocystis neurona, and gastrointestinal helminths. Seasonality and upwelling were associated with higher stranding numbers regardless of COD. Seasonal migration into the region, coinciding with postweaning, suggests young GFSs are in search of prey and habitat resources. Reemergence of GFSs is likely due to conservation efforts, which have been critical for species recovery in the region. Continued monitoring is needed as this vulnerable species continues to rebound.     

Lunar cycles in diel prey migrations exert a stronger effect on the diving of juveniles than adult Galápagos fur seals.

In our study of the development of diving in Galápagos fur seals, we analysed changes in diving activity and body mass trends over the lunar cycle. Based on previously observed lunar cycles in colony attendance patterns, we hypothesized a greater impact of prey migrations of deep scattering layer organisms on younger fur seals. Using electronic dive recorders, we determined that seals dived less and deeper on moonlit nights than at new moon, and incurred body mass losses. These changes in foraging over the lunar cycle correlate with the suppression of the vertical migration of prey by lunar light. All effects were more pronounced in juveniles than adult females, with greater relative mass loss during full moon, which must (i) negatively affect long-term juvenile growth rates, (ii) lengthen periods of maternal dependence, and (iii) contribute to the lowest reproductive rate reported for seals. This underlines the importance of studying ontogeny in order to understand life histories, and for determining the susceptibility of animal populations to fluctuations in food availability.     

Are seals frequently infected with avian influenza viruses?

Influenza A virus isolates of the H4N5 subtype (which has previously been detected only in birds) were recovered from harbor seals dying of viral pneumonia on the New England coast from June 1982 through March 1983. When these isolates were compared with other mammalian and avian viruses in serological assays and RNA-RNA competitive hybridization, it was found that the seal viruses were most closely related antigenically and genetically to recent avian virus strains and were readily distinguishable from mammalian viruses, including H7N7 isolates recovered from seals in 1980. Unlike any previous isolates from mammals, these recent seal viruses replicate in the intestinal tracts of ducks, a characteristic of avian viruses. The association of avian viruses with influenza outbreaks in seals suggests that transmission of avian viruses to seals is occurring in nature. Potentially, this may be an example of the adaptation of avian viruses to mammals, which would represent an intermediate step in the evolution of new mammalian strains.     

调控子fur影响霍乱弧菌生物膜的形成

目的:铁摄取调节蛋白Fur,其在细菌体内维持铁代谢稳态中担任着抑制剂和激活剂的双重角色,已有研究证实Fur还是霍乱孤菌的毒力调控子.研究证实生物膜的形成和游动性与霍乱弧菌的毒力相关,因此我们通过一系列表型实验分析Fur蛋白对霍乱弧菌生物膜形成影响,并预测依赖Fur与霍乱弧菌致病相关的基因,为后续研究做准备.方法:基于自杀质粒缺失霍乱弧菌的Fur基因,并构建相应回补株及蛋白表达株;通过表型实验,比较霍乱弧菌野生株和fur突变株在细菌运动能力、生物膜形成.结果:成功构建霍乱弧菌fur缺失株,回补株和蛋白表达株,His-Fur蛋白在上清液表达.表型实验表明fur突变株的菌株游动性降低,生物膜形成能力增强.结论;因此我们得出Fur可能与其它调控子一起,调控霍乱弧菌的表多糖,TCP和鞭毛蛋白的合成,从而抑制霍乱弧菌生物膜的合成.转录调控子Fur直接或间接调控一些与环境生存和致病相关的基因,对霍乱弧菌的传播、侵染、定殖等过程发挥作用奠定了基础.     

Effects of environmental conditions on predator–prey interactions between white sharks (Carcharodon carcharias) and Cape fur seals (Arctocephalus pusillus pusillus) at Seal Island, South Africa

Effects of environmental factors on frequency and success rate of 2,546 natural predatory attacks by white sharks, Carcharodon carcharias, on Cape fur seals, Arctocephalus pusillus pusillus, were studied over an 8-year period at Seal Island, South Africa. Attacks occurred primarily during winter months (June–August). Attack frequency increased significantly during northerly winds, during high tides, and within 400 m of the island, but predatory success rate decreased with proximity to the island. Attacks occurred over a depth range of 5–31 m, with significantly more occurring at depths of 26–30 m. Attack frequency and success rate increased significantly at low light levels. These results are compared with published effects of environmental factors on white shark predation frequency at the Farallon Islands, California, and discussed in terms of the Predation Cycle. Suggestions for future work at this site are offered.     

Oedipus complex in an Antarctic fur seal pup?

We present the first evidence of a possible case of the Oedipus complex in a non-primate. An Antarctic fur seal pup, Arctocephalus gazella, unsuccessfully directed what appeared to be copulatory behaviour towards its own mother on several occasions. A herding sub-adult bull chased the pup from the female, which strengthens our suggestion that it was copulatory behaviour we witnessed. This seemed to constitute innocent sexual play with elements of the Oedipus complex rather than coercion because the female was not stressed nor did the pup possess the physical strength to coerce the female.     

Is the fur gene of Rhizobium leguminosarum essential?

Using primers corresponding to conserved regions of the bacterial regulatory gene fur, a homologue of this gene from the genome of Rhizobium leguminosarum biovar viciae, the nitrogen-fixing symbiont of peas, was isolated and sequenced. The fur gene is normally expressed constitutively, independent of the presence of Fe in the medium, but in one Rhizobium strain it was transcribed at a low level. Attempts to isolate a fur knockout mutant failed, suggesting that the gene is essential for free-living growth. In other bacteria, certain fur mutations confer manganese resistance; however, none of the manganese-resistant mutants of R. leguminosarum which we isolated was corrected by the cloned fur gene. When the cloned R. leguminosarum fur gene was introduced into a fur mutant of Escherichia coli, it caused some Fe-dependent reduction in the amount of siderophore, indicating that it can function heterologously.     

Do monk seals exert top‐down pressure in subphotic ecosystems?

Patterns of subphotic fish assemblages on seamounts in the Northwestern Hawaiian Islands were identified and compared for potential structuring influences, including the bottom-up effects of regional oceanic productivity and top-down predation pressure exerted by visiting monk seals ( Monachus schauinslandi ). Patterns in fish size, density, and biomass were evaluated at the deep extreme (350–500 m) of the seals feeding range to avoid confounding effects of diverse shallow habitats ( e.g. , coral reefs). Fish number and size were used to calculate biomass density of the seamount fish assemblages that were then compared to the independent variables of summit depth, substrate type, relief, oceanic productivity, distance to seal colonies, and seal colony population. Only the variables of distance to seal colony and seal colony population were retained in a multiple regression model that explained 31% of the variance. Despite the presence of obvious regional differences in oceanic productivity, the overall patterns in the subphotic fish assemblages are better explained by the top-down hypothesis of predation pressure from monk seals.     

Diving seals: are they a model for coping with oxidative stress?

The diving lifestyle of seals depends upon cardiovascular adjustments that result in frequent vasoconstriction of numerous organs. With the first post-dive breath, reperfusion allows for eliminating accumulated carbon dioxide (CO(2)) and reloading oxygen (O(2)) stores. Reintroduction of oxygenated blood raises the potential for production of reactive oxygen species (ROS) and the possibility that they may overwhelm the antioxidant defenses. This study addresses the question of possible adaptive responses that allow ringed seal (Phoca hispida) tissues to tolerate repeated cycles of ischemia and reperfusion, and thus protect them from oxidative insult. We obtained samples of ringed seal heart, muscle and kidney through the cooperation of native subsistence hunters at Barrow, Alaska. Samples were subjected to oxidative stress by addition of xanthine oxidase. Production of superoxide radical (O(2)(.-)), lipid peroxidation (as determined by the presence of thiobarbituric acid reactive substances, TBARS) and antioxidant capacity (AOX) were quantified by spectrophotometric analysis. Similarly treated pig tissues were anticipated to be more susceptible to oxidative stress. Contrary to expectations, pig tissues revealed less O(2)(.-) and TBARS compared with ringed seal tissues. These results show that ringed seal muscle, heart and kidney can be induced in vitro to generate ROS, and suggest that the living seal's protective defenses may depend upon O(2)(.-) production, similar to the protective effect of experimental preconditioning, or on enhanced intermediate scavenging, as evidenced by the larger AOX found in ringed seal tissues.     

Eat now,pay later? Evidence of deferred food-processing costs in diving seals

Seals may delay costly physiological processes (e.g. digestion) that are incompatible with the physiological adjustments to diving until after periods of active foraging. We present unusual profiles of metabolic rate (MR) in grey seals measured during long-term simulation of foraging trips (4-5 days) that provide evidence for this. We measured extremely high MRs (up to almost seven times the baseline levels) and high heart rates during extended surface intervals, where the seals were motionless at the surface. These occurred most often during the night and occurred frequently many hours after the end of feeding bouts. The duration and amount of oxygen consumed above baseline levels during these events was correlated with the amount of food eaten, confirming that these metabolic peaks were related to the processing of food eaten during foraging periods earlier in the day. We suggest that these periods of high MR represent a payback of costs deferred during foraging.     

Feast or famine: evidence for mixed capital–income breeding strategies in Weddell seals

Evolved patterns of resource expenditure for reproduction have resulted in a life history continuum across species. A strictly capital-breeding strategy relies extensively on stored energy for reproduction, whereas income breeding uses energy acquired throughout the reproductive period. However, facultative income breeding has been shown in some classically capital-breeding animals, and was originally thought to provide a nutritional refuge for smaller females incapable of securing sufficient reserves during pre-partum foraging. We examined milk composition and milk output for the Weddell seal to determine to what degree lactation was aided by food intake, and what factors contributed to its manifestation. Milk composition was independent of maternal post-partum mass and condition, but did change over lactation. Changes were most likely in response to energetic and nutritional demands of the pup at different stages of development. During early lactation, females fasted and devoted 54.9% of total energy loss to milk production. Later in lactation 30.5% more energy was devoted to milk production and evidence suggested that larger females fed more during lactation than smaller females. It appears that Weddell seals may exhibit a flexible strategy to adjust reproductive investment to local resource levels by taking advantage of periods when prey are occasionally abundant, although it is restricted to larger females possessing the physiological capacity to dive for longer and exploit different resources during lactation. This supports the assumption that although body mass and phylogenetic history explain most of the variation in lactation patterns (20–69%), the remaining variation has likely resulted from physiological adaptations to local environmental conditions. Our study confirms that Weddell seals use a mixed capital–income breeding strategy, and that considerable intraspecific variation exists. Questions remain as to the amount of energy gain derived from the income strategy, and the consequences for pup condition and survival. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Inter-sexual differences in Antarctic fur seal pup growth rates: evidence of environmental regulation?

We investigated the variation of Antarctic fur seal (Arctocephalus gazella) pup growth rates in response to sex, breeding season and duration of both maternal foraging trip and attendance bouts. Data were collected during five consecutive rearing seasons at Cape Shirreff, the most important breeding colony in the South Shetland Islands, Antarctica. Our results showed significant interannual and sexual variations in pup growth rates. Male pups grew significantly faster than female pups during 2000, 2001, 2002 and 2004 seasons, whilst during 2003 no difference was found. The interannual variation in pup growth rates was correlated with the interannual fluctuation in maternal foraging trip and attendance bouts. There was a significant effect of pup sex and maternal foraging trip duration on pup growth rates, which varied between years having foraging trip duration a major effect during 2003, when females spent more time at sea and interestingly on that year there were no sexual differences in pup growth rates. The effect of attendance bout on pup growth rates was not significant. Diet analysis showed that Antarctic krill (Euphausia superba) was the most frequent prey item during the study period. Analysis of krill size distribution showed a significant difference in krill length, during 2003, when A. gazella preyed upon the smallest sizes of krill. In this study, sex was the most important factor on pup growth rates, but when prey availability seemed more limited, there are longer foraging trips and shorter attendance bouts the sex factor became less significant.     

Effects of the lunar cycle on the Galápagos fur seal,Arctocephalus galapagoensis

Summary During the 1977 and 1979 reproductive periods of the Galápagos fur seals a census taken in the mornings and evenings at Cabo Hammond, Fernandina, showed a marked, synodic lunar rhythm in numbers of animals ashore. About twice as many fur seals were ashore at full moon than at new moon. By use of two independent Fourier analysis methods, the curve of the morning counts is shown to lag 15°–20° of the lunar month behind the curve of the evening counts. The lunar effect is demonstrated for males, females, and immatures. The rhythm is also seen is demonstrated for males, females, and immatures. The rhythm is also seen in attendance data from 13 individually marked females, all but one nursing young. Reproductive events show the lunar rhythm much less markedly than do numbers ashore. This and the clear rhythm in immature numbers make it very likely that the rhythm is a year-round phenomenon, independent of reproduction.There is no reason to assume that fur seals stay on land during moonlit nights especially for social interaction. It is then hypothesized that fur seals avoid moonlight at sea. If so, the peak of numbers ashore at full moon and the negative phase angle difference of the evening curve against the morning curve can be explained with the shift, and the varying duration and brightness, of the moonlit part of the night over the lunar cycle. Two hypotheses which might account for this moonlight avoidance are discussed: (1) predator (shark) avoidance and (2) varying feeding efficiency of the fur seals due to the influence of moonlight on the vertical distribution of prey.