Showing papers in "Journal of Mammalogy in 1990"

Comparative Responses of Five Arboreal Marsupials to Tropical Forest Fragmentation

Abstract: I used data from 160 spotlighting censuses to compare responses of five species of arboreal marsupial folivores to fragmentation of tropical rainforests in NE Queensland, Australia. Data from 1,062 mammal detections in 1986–1987 revealed a strong gradient in extinction proneness. Most vulnerable were lemuroid ringtail possums ( Hemibelideus lemuroides ), which declined by >97% in abundance in forest fragments and secondary regrowth. Herbert River ringtail possums ( Pseudocheirus herbertensis ) and Lumholtz's tree-kangaroos ( Dendrolagus lumholtzi ) exhibited negative but intermediate responses to fragmentation, whereas coppery brushtail ( Trichosurus vulpecula ) and green ringtail ( P. archeri ) possums were least affected, relative to populations in unfragmented rainforest. A multiple-regression model incorporating log10 fragment area and two measures of fragment isolation explained 82% of the variation in arboreal species richness in 10 fragments ranging from 1.4 to 590 ha. “Corridors” of secondary vegetation helped ameliorate effects of fragmentation for some species. The most useful indicator of extinction proneness was the relative abundance of a species in forest regrowth, not its initial rarity in unfragmented rainforest. The ability of these folivores to use regrowth appeared to depend upon their denning requirements, diet, and degree of arboreality.

Feeding Ecology of Red Foxes (Vulpes vulpes) in the City of Oxford, England

Abstract: The diet of red foxes ( Vulpes vulpes ) inhabiting the city of Oxford, England, was analyzed from 1,939 feces collected October 1980–February 1984. The dry weight of undigested remains comprised scavenged food (37%), earthworms ( Lumbricus terrestris , 27%), mammals (16%), fruits (9%), birds (8%), other invertebrates (2%), and domestic stock (1%). No single category of food occurred in more than 50% of the samples. Eighty-one types of food were indentified, including five orders of birds, 14 species of small mammals, and 14 species of fruits. The composition of the diet varied monthly and seasonally. Small mammals peaked in late winter, lagomorphs in April, and birds in June; fruits constituted a large proportion of the diet in autumn. Occurrence in feces of fruits, Passeriformes, Coleoptera, and invertebrate larvae correlated strongly with seasonal variations in indices of the abundance of these prey, suggesting that they were taken in proportion to their availability. Columbiformes, lagomorphs, and rodents showed no such direct relationship, indicating that foxes selected for or against these foods in some way not directly related to their abundances as censused.

Sexual Dimorphism in Size, Relative Size of Testes, and Mating Systems in North American Voles

Abstract: Sexual body-length dimorphism and relative size of testes were compared among 16 species (25 subspecies) of North American Microtus and Clethrionomys by use of data collected from museum specimens. Species with polygynous mating systems and territorial males had the greatest degree of sexual size dimorphism with males larger than females, and relatively small testes. Promiscuous species tended to show little or no sexual size dimorphism and relatively large testes. Species considered monogamous had no size dimorphism, and also had large testes. These data support the hypothesis that sexual dimorphism in size is correlated with the intensity of intrasexual competition for mates. However, the hypothesis that species with single-male breeding systems (single-male polygyny and monogamy) have relatively smaller testes than species with mating systems characterized by a high potential for sperm competition (promiscuity) was supported only for polygynous species.

Energetics and Water Flux of Free-Ranging Big Brown Bats (Eptesicus fuscus) during Pregnancy and Lactation

Abstract: We used doubly labeled water to measure carbon dioxide production and water flux during pregnancy and lactation in free-ranging big brown bats, Eptesicus fuscus. Mean (± SE ) carbon dioxide production was 1,749 ±144 ml/day during pregnancy ( n = 16) and 2,770 ±351 ml/day during lactation ( n = 5). Including estimates of tissue production and milk export, we calculated that the average requirement for assimilated energy was 48.9 and 105.1 kJ/day for pregnant and lactating females, respectively. About 2% of the total energy required during pregnancy was placed into fetal tissue; milk energy accounted for 28% of the energy assimilated during lactation. Daily water flux was 8.47 and 17.07 ml/day for pregnant and lactating females, respectively. We calculated that E. fuscus obtained >66% of its water preformed in the diet, but 20–22% of daily water intake was from drinking. Urinary water was the largest component of water efflux during pregnancy (72%) and lactation (56%); water exported in milk represented 22% of daily water efflux during lactation. Calculated evaporative losses for free-ranging E. fuscus were half those predicted from laboratory measurements.

Use of Riparian and Upland Habitats by Small Mammals

Abstract: Mark-recapture was conducted from 1981 through 1983 in the Cascade Range of Oregon to examine the use of riparian and upland habitats by small mammals. Both number of individuals and species richness were greater in riparian than in upland areas. Because of the occurrence of several less-commonly captured species in riparian locations, species evenness was greatest in the upland. Among Insectivora, Sorex monticolus and S. trowbridgii were captured most often on riparian sites. Among insectivores adult males weighed more in riparian zones. Three rodents ( Peromyscus maniculatus, Microtus oregoni , and Zapus trinotatus ) were captured more frequently in riparian habitats; two rodents ( Tamias townsendii and Clethrionomys californicus ) were captured more frequently in upland habitats. Among all rodents, except Z. trinotatus , adult males weighed more in riparian areas. Mustela erminea was captured more frequently in riparian sites. Eight species had greater numbers of adults in breeding condition in riparian than in upland habitats. Conversely, six species had greater numbers of juveniles in the upland. Data from several species, including T. townsendii, P. maniculatus, Z. trinotatus , and Glaucomys sabrinus , indicated that riparian habitats act as a species source and upland areas act as a dispersal sink.

Foraging Behavior and Habitat Use by a Gleaning Bat, Myotis myotis (Chiroptera: Vespertilionidae)

Abstract: I used radiotelemetry to study habitat use and foraging activity of 27 Myotis myotis from a nursery colony in Bavaria (West Germany) from May to August 1987 and June to August 1988. Adults spent most of the night flying in individual but nonexclusive areas and showed high specificity for forested habitats. Pregnant females had the longest foraging times. On cold and rainy nights, foraging time was reduced and bats of both sexes and all reproductive classes often used alternate day roosts. Radio-tagged juveniles progressively increased time and distance away from the nursery roost and foraged independently from their mothers. Carabid beetles were the most abundant prey (sampled on 12 nights), but their availability was not affected by weather.

Patterns of Lipid Content and Stratification in the Blubber of Fin Whales (Balaenoptera physalus)

Abstract: The lipid content and layering structure of the blubber of 82 fin whales ( Balaenoptera physalus ) caught off Spain were studied in relation to individual biological attributes. The lipid content of the external blubber stratum is stable and shows no apparent variation with age, reproductive status, or day of capture in either sex. This indicates that this stratum does not play a significant role in the dynamics of fat storage in fin whales. The internal stratum, in contrast, is variable, clearly reflecting the nutritive reserves of individuals. The mid-stratum is a transition between the external and internal layers. Reproductive categories are discriminated best by the mean of the values of the three layers than by any of them used independently. For this reason, this mean is proposed as the best index of condition for fin whales. Reproductive status is the main factor determining variation in lipid content of blubber in females, but is meaningless in males. Ranking of blubber fatness for the reproductive categories is: pregnant females > males = immature females > resting females > lactating females. These dissimilarities are explained by the energetic, migrational, and physiological characteristics of the different population components. In males, lipid content of blubber decreased significantly with age, whereas in immature females it increased with age. In both sexes, lipid reserves accrued from early May until mid-August, but tended to decrease afterwards, following variations in food availability. The nutritive condition of lactating females improved during late lactation probably because of increasing food consumption and decreasing energetic demands of suckling young.

Rates of seed harvest by two species of gerbilline rodents

Abstract: We measured rates of seed harvest by two coexisting rodent species, Gerbillus allenbyi and G. pyramidum , in the laboratory. Both species experienced diminishing returns to harvest rate with increasing foraging time. G. pyramidum had a significantly lower handling time, which may result in an advantage over G. allenbyi in foraging efficiency at high densities of seeds. The smaller-bodied G. allenbyi had a slightly but not significantly higher rate of encountering seeds, which may give this species an advantage in foraging at low densities of seeds.

Density-related home-range size and overlap in adult field voles (Microtus agrestis) in southern Sweden

Abstract: Home-range dynamics and the relation between population density, home-range size, and spacing pattern in a Microtus agrestis population were examined in a 2-year-long mark-recapture study. Home-range size varied with vole density. At high densities during the nonbreeding season, ranges were half the size of those measured at low densities. Home ranges during the breeding season were considerably larger than those established during the nonbreeding season with high densities, but did not differ in size from those in the nonbreeding season with low densities. Ranges of males generally were larger than those of females. Established voles generally stayed in the same restricted area throughout winter. At low densities, males showed a tendency to change home ranges. With onset of breeding in spring, overwintered individuals usually settled in areas adjacent to their winter ranges. Adult females became distributed according to a territorial pattern in spring, whereas ranges of males still overlapped extensively during the early part of the breeding season. During the nonbreeding season, vole ranges overlapped extensively, especially at high densities. There was, however, no evidence of group structure with aggregation behavior in any of the sexes.

Internal structure of home ranges of black bears and analyses of home-range overlap

Abstract: Eight black bears ( Ursus americanus ) outfitted with motion-sensitive transmitter collars were radiotracked from May through December 1984 in the Pisgah Bear Sanctuary in the mountains of western North Carolina. Activities and movement patterns within areas of overlap among neighboring bears were analyzed to determine whether neighbors exhibited spatial or temporal avoidance. The distributions of locations within home ranges were clumped but bears did not use specific areas for specific activities. Home ranges overlapped extensively, and even core areas (areas of high-intensity use) overlapped. Neighboring bears often used areas of overlap for the same activities and at the same time. The clumped or patchy use of areas within home ranges requires analyses that emphasize internal structure of home ranges and not merely outlines or total-area measures.

Responses of Red Squirrel (Tamiasciurus hudsonicus) Populations to Supplemental Food

Abstract: In this study I determined the responses of red squirrel (Tamiasciurus hudsonicus) populations to long-term supplemental food and tested the hypothesis that squirrel populations are limited by available food. Squirrel populations were sampled by live trapping on replicate study areas in mature coniferous forest near Prince George and in the Cariboo, British Columbia from June 1983 to June 1986. The Average abundande of squirrels in fed populations was 3-4 times higher than in controls during the 2 years of supplemental feeding. More adults were recruited into feld than into control populations. The fed population had longer breeding seasons and some females may have had two litters copmpared with only one in the controls. There were no consistent differences in survival between control andfed populations. Population densities declined slowly after the food was withdrawn from the experimental areas, and population declined slowly after the food was withdrawn from the experimental areas, and population characteristics gradually approached those of the control. Food limits population size in the red squirrel and is likely a driving factor in population fluctuations

Dental Age Classes in Marmosa incana and Other Didelphoids

Abstract: The tooth eruption and replacement sequence in Marmosa incana does not follow that described by Tyndale-Biscoe and Mackenzie (1976) for Didelphis marsupialis ; therefore, a modified system of dental age classes is proposed. Whereas, in Didelphis the first or deciduous molar (herein referred to as dP3) is shed and P3 erupts before the appearance of M4, in M. incana dP3 is retained until M4 is functional; four molariform teeth, therefore, are present at all times from class 4 onward. The same sequence occurs in many species of Marmosa (sensu lato), Monodelphis , and Caluromys , whereas the Didelphis pattern is followed by species of Philander, Chironectes, Lutreolina , and the microbiotheriid Dromiciops . The sequence in Metachirus is somewhat ambiguous. A possible inference is that Marmosa and Monodelphis belong with Caluromys in a monophyletic group, rather than with the other didelphids.

Patterns of mammalian species richness in relation to temperature, productivity, and variance in elevation

Abstract: In Texas, the relationship between environmental factors and species richness of all mammals, bats, rodents, and carnivores was investigated by multiple-regression methods. Variance in elevation was a strong, positive predictor of species richness for all mammals, bats (Chiroptera), and rodents (Rodentia). It was a significant but weak predictor for carnivores (Carnivora). Productivity had significant, negative regression coefficients for all mammals, bats, and rodents. Productivity was positive, significant, and relatively stronger for carnivores. Species richness of all mammals, rodents, and carnivores may follow a hump-shaped curve along a gradient of increasing environmental productivity. Mean-annual temperature range was significant with a negative sign for carnivores and with a positive sign for rodents. Mean intermonthly variability of precipitation had a positive and significant relationship to carnivores, but significant, negative coefficients for bats and rodents. Variation in all mammals and carnivore species richness, and in all mammals and bat richness, was significant, with positive signs, for maximum and minimum temperatures, of record, respectively. All mammals, bat, and rodent richness varied significantly, with negative signs, with the coefficient of variation of mean January temperature. Overall, the climatic-variability indices exhibited only weak control over density of mammalian species. With the exception of productivity their influence on current ecological hypotheses of species richness was complex. Statistical support, contradiction, and statistical lack of significance depended upon the particular combination of environmental factors and taxa under consideration. Results suggest that current ecological hypotheses of species richness often function in directions not concordant with predictions and are not satisfactory as general explanations of biotic richness for these vertebrate groups.

Effects of Forage Availability on Home Range and Population Density of Microtus pennsylvanicus

Abstract: The hypothesis that territoriality of female meadow voles ( Microtus pennsylvanicus ) regulates population size was tested during four breeding seasons by using radiotelemetry to determine home range, dispersion, and use of vegetative cover in crownvetch ( Coronilla varia ) fields. The percentage of transient voles in the population was related directly to density. The percentage of transient females increased as nearest-neighbor distances between females decreased. Territory size for females was related inversely to available forage, supporting the hypothesis that territory size is a function of availability of food. I conclude that the quantity of forage is a factor in controlling population density.

Quantitative Habitat Associations of Small Mammals along an Elevational Transect in Temperate Rainforests of Chile

Abstract: Distribution and abundance of small mammals in temperate Andean rainforests are correlated with elevation. To interpret such patterns, we examined elevational variation in habitats and habitat use by small mammals. Elevation accounts for significant variation in 22 of 24 habitat metrics, reflecting the diminishing stature and more open canopies of higher-elevation rainforests. Principal-components analysis of habitat shows significant multivariate effects of elevation. Mammal species differ significantly in use of about half of the habitat variables, in ways generally consistent with morphology, behavior, and diet. Abundant species appear to occupy typical habitats along the transect, whereas rarer species are associated with more distinctive habitat types. Species overlap substantially in their use of habitats, but analyses of trap captures indicate that species are segregated at finer spatial scales. Spatial segregation at this scale may contribute to the coexistence of abundant species and congeners. Elevational variation in habitat and specific habitat associations provide a plausible explanation for correlations of mammalian distribution and abundance with elevation.

Comparison of ear-tagging and toe-clipping in prairie voles, Microtus ochrogaster

Abstract: Particularly with the recent interest in animal rights and renewed emphasis on humane treatment of research animals, mammalogist should be concerned about effects of marking techniques on free-living animals. The purpose of this study was to evaluate the effects of ear -tagging and toe-clipping on free living population of prairie voles

Winter Diets of Coyotes in Relation to Prey Abundance in Southern Texas

Abstract: Diets of coyotes ( Canis latrans ) and abundance of mammalian prey were estimated during 8 winters (1979–1986) in southern Texas. Lagomorphs ( Sylvilagus audubonii and Lepus californicus ) composed the greatest percentages of coyote diets (40–54%) in 6 of 8 winters; woodrats ( Neotoma micropus ) were staple prey; proportions of cotton rats ( Sigmodon hispidus ) in diets varied markedly in association with population irruptions; and small rodents and white-tailed deer ( Odocoileus virginianus ) were minor dietary components. The proportion of other minor prey items in coyote diets varied inversely with abundance of the five principal prey types. Although coyotes exhibited a general functional response to changes in abundance of prey types in the diverse prey community, evidence for selective feeding on cotton rats was revealed by regression analyses.

Geographic Variation and Taxonomy of Daubenton's Bat, Myotis daubentoni in Europe

Abstract: Multivariate analyses of 12 cranial and 15 dental measurements demonstrated that Myotis daubentoni increases in size from south to north. Geographic coordinates explained 53 and 43% of cranial and dental variation, respectively. The gradual clinal variation appears to be an example of Wright's (1943) isolation-by-distance model. The latitudinal clines in size are correlated negatively with temperature (as predicted by Bergmann's rule) and associated positively with moisture. Cranial variation, however, is more strictly associated with geoclimatic factors than is dental variation, which shows a more complex pattern. These results suggest that both climate (natural selection) and geographic factors (barriers to gene flow) contributed to differentiation in M. daubentoni . There also is a significant positive correlation between skull size of M. daubentoni and number of presumably competing species of Myotis at a given locality. Significant phenetic overlap exists among the three currently recognized subspecies of M. daubentoni in Europe. I, therefore, propose that M. d. nathalinae and M. d. volgensis be considered synonyms of M. d. daubentoni .

Gait selection in the brush-tail possum (Trichosurus vulpecula), the northern quoll (Dasyurus hallucatus), and the Virginia opossum (Didelphis virginiana)

Abstract: La demande de 3 especes de Marsupiaux a ete etudiee a l'aide d'enregistrement video et analysee image par image

Horns and Fighting in Male Spanish Ibex, Capra pyrenaica

Abstract: As adult body mass is reached fighting force is greater, consequently horn growth in male Spanish ibex ( Capra pyrenaica ) must compensate to minimize breakage. This is done by increasing the value of the second moment of the area at the base of horns, which keeps the maximum horn-bending stress low. Transverse horn ridges are apparently involved in helping to control the length of the lever arm, hence the bending moment, thus helping to minimize bending stress and torques about the occiput. In the rear-clash type of fight, the probability of horn breakage is highest, but horn-bending stress is minimized by clashing against the basal sections of horns. I hypothesize that the most frequent, and harmless, types of conventional fighting serve as reliable tests of the fighting ability of an animal. Contenders resist dangerous rear clashes by their body mass and absorb the energy of fighting and prevent skull rotation by contraction of their neck muscles.

Serial Changes in Metabolic Correlates of Hibernation in Female Black Bears

Abstract: Captive female black bears were immobilized and sampled at approximately 10-day intervals from September to March during 2 years (six bears/year) in Virginia. Ten of 12 bears hibernated for an average of 92 days. Rectal temperature declined ( P < 0.001) during hibernation to as low as 34.6°C. Average loss in mass for hibernators was 260 g/day and represented 23.1% of peak body mass. Urea : creatinine ratios differed ( P < 0.01) after hibernation between hibernators and active bears, declining to 7.2 ± 0.3 ( X ± SE ; 84 samples) during hibernation. Serum concentrations of total protein, urea nitrogen, creatinine, and bilirubin also differed ( P < 0.01) between groups after onset of hibernation. Urea : creatinine ratio was a good indicator of the hibernating state, but the sensitivity of serum-urea concentrations to diet suggests careful use of this ratio as a field index of hibernation.

Habitat Use by Sherman's Fox Squirrel (Sciurus niger shermani) in Florida

Abstract: The mean cumulative size of home ranges of Sciurus niger shermani was 42.8 ha for males and 16.7 ha for females during a 1-year period. Home ranges shifted position during a food shortage. Males moved long distances before and during the breeding season. Seed production of the two tree species in sandhill habitat was greater on low slopes, significantly so in turkey oaks ( Quercus laevis ). Longleaf pines ( Pinus palustris ) produced seeds in each of 2 years, half as many in the second as in the first. The crop of turkey oak acorns failed entirely in the 2nd year. Because acorns of live oak ( Quercus virginiana ) appeared to be a major food resource, best habitat for Sherman's fox squirrel may be along the edge of longleaf pine savanna and live oak forest. Low diversity and abundance of food resources and their variability in time and space may explain the large home ranges of this animal. Squirrels used leaf nests much more often than tree cavities. Nest counts are recommended for documenting the status of populations of Sherman's fox squirrels. Preservation and proper management of natural, old-growth longleaf pine forests is paramount for survival of this subspecies.

Encephalization Quotients and Life-History Traits in the Sirenia

Abstract: Relative brain size in the Sirenia is unusually small. Encephalization quotients are 0.27 for Florida manatees (Trichechus manatus) and 0.38 for dugongs (Dugongs (Dugong dugon). Estimates for Steller's sea cow (Hydrodamalis gigas) range from 0.12 to 0.19. These values are among the lowest known for recent mammals, and seemingly have changed little since the Eocene. A body plan specialized for the aquatic environment does not account for low encephalization quotients; values are substantially less than predicted based on cetacean or pinniped allometry. Life-history, ecological, and behavioral traits of the Sirenia are typical of relatively large-brained species. Low quality food and a low metabolic rate, however, are characterisitic of the Sirenia and other small-brained mammals. Acting through prolonged postnatal growth, selection also likely favored large body size in the Sirenia without a correlated increase in brain size

Diel Activity Pattern of a Diurnal Desert Rodent, Psammomys obesus

Abstract: L'activite diurne de P.o. est etudiee durant toute l'annee en relation avec des facteurs environnementaux (temperature, pluie) et comportementaux (activite sexuelle)

Effect of attacks by male Australian sea lions, Neophoca cinerea, on mortality of pups

Abstract: Attacks on pups by adult territorial males accounted for 19% of pup mortality during two breeding seasons. All observed attacks were on pups <2 months of age, and appeared to be the result of misdirected aggression. Injuries included puncture wounds, lacerations penetrating to the bone and internal organs, fractures, and dislocations.