Results and evaluation of a survey to estimate Pacific walrus population size, 20061

In spring 2006, we conducted a collaborative U.S.–Russia survey to estimate abundance of the Pacific walrus (Odobenus rosmarus divergens). The Bering Sea was partitioned into survey blocks, and a systematic random sample of transects within a subset of the blocks was surveyed with airborne thermal scanners using standard strip‐transect methodology. Counts of walruses in photographed groups were used to model the relation between thermal signatures and the number of walruses in groups, which was used to estimate the number of walruses in groups that were detected by the scanner but not photographed. We also modeled the probability of thermally detecting various‐sized walrus groups to estimate the number of walruses in groups undetected by the scanner. We used data from radio‐tagged walruses to adjust on‐ice estimates to account for walruses in the water during the survey. The estimated area of available habitat averaged 668,000 km² and the area of surveyed blocks was 318,204 km². The number of Pacific walruses within the surveyed area was estimated at 129,000 with 95% confidence limits of 55,000–507,000 individuals. Poor weather conditions precluded surveying in other areas; therefore, this value represents the number of Pacific walruses within about half of potential walrus habitat.     

TRENDS IN AGE STRUCTURE AND PRODUCTIVITY OF PACIFIC WALRUSES HARVESTED IN THE BERING STRAIT REGION OF ALASKA, 1952–2002

Pacific walruses ( Odobenus rosmarus divergens ) are harvested by subsistence hunters in Alaska as they migrate north through the Bering Strait in the spring. Harvest records and biological specimens have been collected from the Bering Strait communities of Little Diomede, Gambell, and Savoonga since the 1950s. Harvest levels in the Bering Strait region peaked in the late 1980s and declined thereafter; however, there was considerable variation in the size and composition of the harvests among communities and over time. The relationships among characteristics of the community harvests and the presence of temporal trends were investigated using generalized linear models. The proportion of females in the catch increased over time in all three communities, while the proportion pregnant among harvested females declined over the range of sample years. The ages of harvested walruses increased over time in all three communities through the 1980s, after which trends in age stabilized or began to decline. The age of first reproduction was significantly older for females sampled in 1975–1985 than for females sampled between 1952 and 1962 or 1992 and 1998. Factors thought to have influenced the size and composition of the catch over the past 50 yr include hunter preferences, harvest management regimes, environmental conditions, and changes in the population itself.     

Issues in determining factors influencing bacterial attachment: a review using the attachment of Escherichia coli to abiotic surfaces as an example

The emergence of an increasing number of antibiotic resistant human clinical bacteria has been a great cause of concern for the last decades. As an example, Staphylococcus aureus isolates in the hospital environment are becoming more and more resistant to antibiotics including vancomycin which is considered as a last line of defence in treatment of Staphylococcus aureus -resistant methicillin. On the other hand, food safety is threatened by development of pathogenic bacteria including Listeria monocytogenes, Campylobacter jejuni, Salmonella enteritidis, Escherichia coli O157:H7 and Staphylococcus aureus. The use of antimicrobial peptides such as glycopeptides, semi-synthetic peptides, bacteriocins including lantibiotics offers a hope to face these clinical and food microbiology concerns. Clinical approval of new chemotherapeutic agents requires a long period of time. Research on bacteriocins has demonstrated potential use to fight against undesired foodborne pathogens but the use industrial use of bacteriocins is limited. To date only lantibiotic nisin and in class IIa bacteriocin Pediocin PA-1 are legally used as food preservative in many countries. The present minireview is focused on divercin V41 (DvnV41), a class IIa bacteriocin naturally produced by Carnobacterium divergens V41. The last decade has been the witness of intensive investigations carried out on this cationic peptide tempting to answer multiple questions covering basic and applied aspects. DvnV41 has shown a wide spectrum of activity either alone or in combination with nisin and/or polymixins (synergistic effect). This outcome indicates that Cb. divergens V41 could potentially be used for safe and efficient prevention of L. monocytogenes growth in cold smoked salmon.     

Lipid trafficking between high density lipoproteins and Babesia divergens-infected human erythrocytes.

A two-fold increase in the amount of phospholipids was observed in Babesia divergens infected human red blood cells. In vitro incubation with [32P]-phosphorus and [3H]-glycerol demonstrated that B divergens has the ability to synthesize the phospholipid backbone. On the other hand, the low incorporation of [14C]acetate indicated the absence of a de novo fatty acid synthesis and suggested the necessity of an exogenous lipid source for the parasite. Several intra-erythrocytic growth cycles of B divergens could be achieved in vitro, using a serum-free medium supplemented only with fractions of human high density lipoproteins (HDL). At an HDL concentration of 0.5 mg/ml (protein concentration) and with a 1% starting parasitaemia, parasite growth was similar to that observed under standard culture conditions with 10% human serum, at least for the first 24 h, a time equivalent to three parasite erythrocytic life-cycles. Lipid transfer from HDL to the intra-erythrocytic parasites was demonstrated by uptake and exchange of fluorescent NBD-phosphatidylcholine (NBD-PC) loaded HDL at different temperatures. Kinetic experiments with [3H]-oleyl-PC-loaded HDL demonstrated a unidirectional transfer of lipids from radiolabelled HDL to the parasite; partial conversion of PC to phosphatidylethanolamine (PE) was also observed. In the semi-defined medium, the HDL fraction appeared to be the major source of lipids for the growth of B divergens in human erythrocytes.     

COMPARISON OF METHODS USED TO ESTIMATE NUMBERS OF WALRUSES ON SEA ICE

The US and former USSR conducted joint surveys of Pacific walruses on sea ice and at land haul-outs in 1975, 1980, 1985, and 1990. One of the difficulties in interpreting results of these surveys has been that, except for the 1990 survey, the Americans and Soviets used different methods for estimating population size from their respective portions of the sea ice data. We used data exchanged between Sovier and American scientists to compare and evaluate the two estimation procedures and to derive a set of alternative estimates from the 1975, 1980, and 1985 surveys based on a single consistent procedure. Estimation method had only a small effect on total population estimates because most walruses were found at land haul-outs. However, the Sovievr method is subject to bias that depends on the distribution of the population on the sea ice and this has important implications for interpreting the ice portions of previously reported surveys for walruses and other pinniped species. We recommend that the American method be used in future surveys. Future research on survey methods for walruses should focus on other potential sources of bias and variation.     

Historical sex-specific distribution of Atlantic walrus (<Emphasis Type="Italic">Odobenus rosmarus rosmarus</Emphasis>) in Svalbard assessed by mandible measurements

We developed a discriminant function based on measurements of known-sex mandibles of walrus from the Canadian Arctic collected between 1983 and 1998 and used it to explore the sex ratio in the catches of walrus in Tusenøyane, south-eastern Svalbard, during the nineteenth century. Canadian mandibles older than 5 years of age of known sex were classified into correct sex with 100% accuracy by using two measurements. Applying the same discriminant function to 80 mandibles from Svalbard older than 5 years of age classified 48 (60%) as males and 32 (40%) as females. It also classified 584 aged and un-aged mandibles from Svalbard 67% (390) as males and 33% (194) as females. Eight of the aged jaws (10%) and 41 (7%) of the un-aged jaws had probabilities of classification into sex <80%. We stress the importance of being cautious in applying a discriminant function developed from Canadian mandibles to classify the sex of old weathered mandibles from Svalbard. However, we believe our results indicate that female walrus were once more common in south-eastern Svalbard than they are now.     

IMMOBILIZATION OF WALRUS WITH ETORPHINE HYDROCHLORIDE AND ZOLETIL®

Abstract: The paper describes the use of the drugs Zoletil® and etorphine for the immobilization of walrus ( Odobenus rosmarus rosmarus ) for attachment of satellite telemetry equipment. Three animals weighing approximately 1,500 kg each were injected intramuscularly with Zoletil® at a dose between 1.4 and 2.2 mg/kg. One walrus died while the two others were adequately restrained. The induction time was between 14 and 29 minutes and the effect lasted for 75-220 min.
Thirty-eight animals of weight 900-1,500 kg were darted intramuscularly with etorphine at a dose between 3.3 and 8 mg/kg. Thirty-six were immobilized although one died later. The induction time for etorphine was two to ten minutes. The action of this drug was terminated with an injection of the antidote di-prenorphine.
The use of etorphine was accompanied by convulsive movements and apnoea while Zoletil® produced a gradual and smooth entry into and withdrawal from immobilization.     

WALRUS LIFE-HISTORY MOVEMENTS RECONSTRUCTED FROM LEAD ISOTOPES IN ANNUAL LAYERS OF TEETH

Putative life history movements of male Atlantic walrus ( Odobenus rosmarus nsmarus ) harvested at Sanirajak in northern Foxe Basin, Canada, were reconstructed by comparing Pb isotopes in tooth cementum growth layer groups (GLGs) to those in whole-cementum samples from other walrus of Foxe Basin and nearby areas. The analyses yielded three life history patterns including one, "prodigal sons," not previously recognized in large mammals. Isotope ratios in GLGs of "local" Sanirajak walrus were relatively constant over time and similar to the whole-cementum data for most walrus caught in northern Foxe Basin. An "immigrant" walrus acquired the local signal only in young adulthood. In two "prodigal sons," GLG Pb isotope ratios changed significantly from the local signature after weaning but returned to it in late maturity, shortly before being harvested. Possible recruitment and dispersal areas for the two types of outliers included regions in northern and eastern Hudson Bay, some 300–600 km distant. The return of mature males to their natal group after associating with other groups for several years, as seen in some of the walrus, may be more common among mammals than previously thought. However, without a reconsttuctive technique such as employed here, it could only be detected through long-term studies of known individuals and all the relevant social groups.     

Year‐to‐year changes in water level drive the invasion of Vochysia divergens in Pantanal grasslands

Abstract. In recent decades, cattle ranchers of the Pantanal of Mato Grosso, Brazil, have pointed to the accelerated spread of several herbaceous and woody plant species that invade natural and artificial pastures (campos). It has been speculated that overgrazing by an increasing number of cattle, lack of grazing in abandoned areas, or large‐scale changes in environmental conditions may be the reason for this invasion. This study focuses on ecological and ecophysiological aspects of Vochysia divergens (cambará), a flood‐tolerant tree that began spreading in the Pantanal during the last 30 years and is considered a very aggressive invasive plant. The study shows that the spread of cambará can be related to natural multi‐years wet periods. During multi‐years dry periods the species is reduced by the increasing impact of fires in the Pantanal. This points to the great importance of multi‐years climatic events on the vegetation cover of the Pantanal and indicates a very dynamic development in plant communities.