Lifetime reproductive success and composition of the home range in a large herbivore.

The relationship between individual performance and nonrandom use of habitat is fundamental to ecology; however, empirical tests of this relationship remain limited, especially for higher orders of selection like that of the home range. We quantified the association between lifetime reproductive success (LRS) and variables describing lifetime home ranges during the period of maternal care (spring to autumn) for 77 female roe deer (Capreolus capreolus) at Trois-Fontaines, Champagne-Ardenne, France (1976-2000). We maintained population growth rate (adjusted to account for removals of non-focal animals) near rmax, which enabled us to define the fitness-habitat relationship in the absence of density effects. Using a negative binomial model, we showed that a roe deer's incorporation into its home range of habitat components important to food, cover, and edge (meadows, thickets, and increased density of road allowances) was significantly related to LRS. Further, LRS decreased with increasing age of naturally reclaimed meadows at the time of a deer's birth, which may have reflected a cohort effect related to, but not entirely explained by, a decline in quality of meadows through time. Predictive capacity of the selected model, estimated as the median correlation (rs) between predicted and observed LRS among deer of cross-validation samples, was 0.55. The strength of this relationship suggests that processes like selection of the site of a home range during dispersal may play a more important role in determining fitness of individuals than previously thought. Individual fitness of highly sedentary income breeders with high reproductive output such as roe deer should be more dependent on home range quality during the period of maternal care compared to capital breeders with low reproductive output. Identification of the most important habitat attributes to survival and reproduction at low density (low levels of intraspecific competition) may prove useful for defining habitat value ("intrinsic habitat value").

Streptococcus equisimilis infection in striped skunks (Mephitis mephitis) in Saskatchewan.

Three radio-collared striped skunks (Mephitis mephitis) found dead during a field study of winter ecology of striped skunks near Willowbrook, Saskatchewan, Canada were examined. Streptococcus equisimilis was identified as the primary agent causing necrotizing purulent pneumonia in one skunk and suppurative meningoencephalitis in another. Both Streptococcus equisimilis and Streptococcus canis were isolated from lesions of purulent myocarditis and pyothorax in the third skunk. These are apparently the first reported cases of S. equisimilis infection in striped skunks and suggest that this opportunistic pathogen may be a significant cause of mortality under some conditions.

Genetic structure of the world's polar bear populations.

We studied genetic structure in polar bear (Ursus maritimus) populations by typing a sample of 473 individuals spanning the species distribution at 16 highly variable microsatellite loci. No genetic discontinuities were found that would be consistent with evolutionarily significant periods of isolation between groups. Direct comparison of movement data and genetic data from the Canadian Arctic revealed a highly significant correlation. Genetic data generally supported existing population (management unit) designations, although there were two cases where genetic data failed to differentiate between pairs of populations previously resolved by movement data. A sharp contrast was found between the minimal genetic structure observed among populations surrounding the polar basin and the presence of several marked genetic discontinuities in the Canadian Arctic. The discontinuities in the Canadian Arctic caused the appearance of four genetic clusters of polar bear populations. These clusters vary in total estimated population size from 100 to over 10 000, and the smallest may merit a relatively conservative management strategy in consideration of its apparent isolation. We suggest that the observed pattern of genetic discontinuities has developed in response to differences in the seasonal distribution and pattern of sea ice habitat and the effects of these differences on the distribution and abundance of seals.

Determinants of Home Range Size for Polar Bears (Ursus maritimus).

The mean home range size of female polar bears (Ursus maritimus; 125 100 km2 ± 11 800; n = 93) is substantially larger than the predicted value (514 km2 ) for a terrestrial carnivore of similar weight. To understand this difference, we correlated home range size and sea ice characteristics. Home range size was related to (i) the ratio of land vs. sea within a given home range (42% of explained variance), and (ii) seasonal variation in ice cover (24%). Thus, bears using land during the ice-free season had larger home ranges and bears living in areas of great seasonal variation in ice cover also had larger home ranges. In another analysis we investigated how variation in a bear's environment in space and time affects its choice of home range. We found that polar bears adjusted the size of their home range according to the amount of annual and seasonal variation within the centre of their home range. For example, polar bears experiencing unpredictable seasonal and annual ice tended to increase their home range size if increasing home range size resulted in reducing variation in seasonal and annual ice. Polar bears make trade-offs between alternate space-use strategies. Large home ranges occur when variable ice cover is associated with more seals but also a more unpredictable distribution of those seals.

Postnatal growth and development in semi-captive muskrats, Ondatra zibethicus.

We studied postnatal growth and preweaning development of muskrats under semicaptive conditions in a temperate environment. The principal objectives were to quantify weaning age and investigate potential effects of sex and parturition date on growth rate. We also tested a previous hypothesis that juvenile muskrats inhabiting temperate environments exhibit a winter growth diapause. Developmental attributes varied significantly among 6 litters (n = 31 individuals), except for age at eye opening (median = 15 days). Analysis of arithmetic growth (g/day) indicated that muskrats were weaned between 26 and 28 days of age. The Gompertz equation was used to estimate asymptotic mass, growth rate constant, and age at inflection for 25 individuals from 5 litters. There were no sex differences in growth parameters after controlling for the effect of parturition date. The growth rate constant was positively correlated with parturition date. Consequently, juveniles attained similar asymptotic mass in autumn irrespective of birth date. Although most of the compensatory growth was attributed to the postweaning period, a significant portion occurred during lactation which suggested that females were investing more in offspring born later in the breeding season. Juvenile muskrats exhibited a winter growth diapause from October through April and did not attain adult body mass until 14-18 months after birth. We briefly discuss these life history traits in relation to habitat selection in muskrats.

Winter foraging by muskoxen: a hierarchical approach to patch residence time and cratering behaviour.

We examined the temporal and spatial patterns of feeding behaviours of muskoxen during winter in the High Arctic. Pawing motions (to uncover forages beneath snow cover) were strongly aggregated into temporal bouts. Similarly, feeding stations (areas exploitable without motion of the forelegs) were aggregated into spatial patches. Muskoxen responded to greater snow accumulation at feeding sites by increasing the rates of pawing, rates of pawing bouts, number of pawing strokes per bout, and station residence times. Patch residence times showed little relationship to snow or forage abundance because, as muskoxen increased station residence times, they decreased the number of stations per patch. Muskoxen displaced one another from feeding stations more frequently as snow thickness and group size increased. Time spent at feeding stations was positively correlated to travel costs, in accordance with the marginal value model of patch residence. The model was not supported, however, at the scale of the feeding patch. The results indicate that behavioural responses of muskoxen to foraging conditions differ across scales.

Use of DNA fingerprinting to determine parentage in muskrats (Ondatra zibethicus).

The detection of high levels of genetic variability by DNA fingerprinting probes has allowed researchers to accurately assess relatedness. Multiple-mating strategies are characteristic of the mating systems of small mammals. As such, techniques that provide an accurate indication of how individuals are related genetically is of great importance to assess the mating system of a species. In this study, we applied the DNA fingerprinting technique to captive and wild muskrats (Ondatra zibethicus) to determine its usefulness for parentage analysis in wild populations. We found that DNA digested with the restriction enzyme Hae III and probed with Jeffrey's minisatellite 33. 15 identified a large amount of polymorphism in both groups of muskrats. The DNA fingerprinting technique correctly assessed parentage within the captive group. In the wild population, paternity was assigned between two adult males based on diagnostic fragments and similarity of banding patterns. The likelihood that paternity could be misassigned to a full sibling was high in this free-ranging population. However, because natal dispersal in muskrats is male biased, it is unlikely that two brothers would associate with the same female.

Density-dependent habitat selection in muskrats: a test of the ideal free distribution model.

Two predictions of the ideal free distribution model, a null hypothesis of habitat selection, were examined using free-ranging muskrats. We rejected the prediction that the proportion of the animals found in each of five habitats was independent of population size. Data on over-winter occupancy of muskrat dwellings tend also to refute the prediction of equal fitness reward among habitats. Habitat type and water-level had a profound effect on the suitability of a site for settlement. We concluded that the observed pattern of muskrat distribution followed more closely an ideal despotic distribution where some individuals benefited from a higher fitness because of resource monopolization. Current theories of density-dependent habitat selection, which assume an ideal free distribution, would not apply to muskrats and possibly to many other mammal species.

Characterization of new bacterial transformation products of 1,1,1-trichloro-2,2-bis-(4-chlorophenyl) ethane (DDT) by gas chromatography/mass spectrometry.

The microbial transformation of DDT, DDD and DDE was studied in Gram-negative strain B-206 and a number of phenolic metabolites were identified as the trimethylsilyl derivatives in the bacterial extracts by gas chromatography/mass spectrometry. The major metabolites of DDT were DDD, DDE, DDMU, 1,1,1-trichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethane, 1,1,1-trichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-hydroxyphenyl) ethane, and 1,1,1-trichloro-2,2-bis-(2-hydroxy-4-chlorophenyl) ethane. Conversely, DDD was mainly degraded into DDE, 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethane and 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-hydroxyphenyl) ethane. Finally, DDE was transformed into DDMU, 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethylene, 1,1-dichloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'hydroxyphenyl) ethylene and 1-chloro-2-(2-hydroxy-4-chlorophenyl)-2-(4'-chlorophenyl) ethylene. The phenolic metabolites exhibited [M - TMSCl]+., [M - HCl - TMSCl]+. and/or [M - HCl - TMSCl - Me]+ fragment ions which reflect the presence of an ortho hydroxyl group in these molecules. Other mass spectral features used to determine their structure are presented and a metabolic scheme accounting for their formation is proposed.

Microbial biodegradation of 4-chlorobiphenyl, a model compound of chlorinated biphenyls.

The biodegradation products of 4-chlorobiphenyl were analyzed in an Achromobacter sp. strain and a Bacillus brevis strain. Both strains generated the same metabolites, with 4-chlorobenzoic acid as the major metabolic product. Our results corroborate previous observations whereby most bacterial strains degrade the chlorobiphenyls via a major pathway which proceeds by an hydroxylation in position 2,3 and a meta-1,2 fission. However, we also detected several metabolites whose structure suggests the existence of other routes for the degradation of chlorinated biphenyls.

Bacterial nitration of 4-chlorobiphenyl.

In the course of a study dealing with the biodegradation of 4-chlorobiphenyl by strain B-206, we noticed that the gram-negative bacterium accumulated different metabolic intermediates depending on the nitrogen source of the medium. Hence, in the presence of nitrate, strain B-206 produced four compounds which were identified as 2- and 4-hydroxy-4'-chlorobiphenyl and 2- and 4-hydroxy-mononitro-4'-chlorobiphenyl. The accumulation of these compounds in the culture medium indicated the presence of a monooxygenase in strain B-206 leading to the production of arene oxide intermediates. The possible transformation of 4-chlorobiphenyl to an arene oxide by this bacterial strain is a matter of concern because of the high reactivity of these arene oxides with biological material.

Amaranth suppresses the mutagenicity of 2-acetylaminofluorene by lowering the concentration of NADPH in top agar.

Addition of 1 mg amaranth (FD&C Red No. 2) to the top agar of Salmonella/S9 assay plates decreased the yield of revertants induced by 20 micrograms 2-acetylaminofluorene (AAF) by over 50% and additional amaranth completely eliminated the mutagenic response. Similar suppression of AAF mutagenicity was seen with sulfonazo III, another azo dye. The suppressive effect of amaranth was greatest at low S9 concentrations and decreased as the amount of S9 was increased. When N-hydroxyacetylaminofluorene (N-OH-AAF) was used as mutagen, amaranth had little or no effect on either the number of revertants obtained or the S9 optimum. Similarly, 1-naphthylamine-4-sulfonic acid (a reduction product of amaranth) did not significantly affect the mutagenicity of AAF. The rate of metabolism of [14C]AAF by the S9 preparations was shown to be markedly decreased by amaranth, as were the levels of both the phenolic metabolites and of N-OH-AAF. Thus, it appeared that amaranth acts by blocking the conversion of AAF to N-OH-AAF and that this effect is caused by the amaranth itself and not by its constituent amines. Further experiments indicated that amaranth greatly decreased the levels of NADPH formed in reaction mixtures comparable to S0 mix in top agar and that such reaction mixtures also metabolized amaranth to colourless compounds. It appears likely that in top agar, NADPH reacts with amaranth at a fast enough rate to limit severely the level of the reduced co-factor (which must be formed from NADPH+ by the action of endogenous glucose-6-phosphate dehydrogenase) and thus decreases the rate of activation of mutagens by other NADPH-dependent processes.

Metabolism of 1-nitropyrene and formation of DNA adducts in Salmonella typhimurium.

1-Nitropyrene is slowly reduced by intact cells of Salmonella typhimurium to yield 1-aminopyrene and N-acetyl-1-aminopyrene plus six unidentified minor products. When the bacteria are exposed to tritiated 1-nitropyrene, increasing amounts of radioactivity become bound to DNA as the nitropyrene is metabolized. Enzymatic hydrolysis of the labelled DNA yields low molecular weight labelled compounds which probably represent nucleoside adducts formed by the reaction of nitropyrene metabolites with DNA. Results with appropriate mutant strains indicate that bacterial nitroreductases are involved in activating nitropyrene to a reactive intermediate that binds to DNA and that nitropyrene adducts in DNA are subject to excision repair.