Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact email@example.com with any questions.
We reviewed papers that compared intraspecific variation in territoriality vs. alternative forms of spatial or behavioral organization with three goals: (1) to discover which ecological variables act as determinants of territorial behavior and how they might act; (2) to extract and evaluate predictions and evidence for determinants of territoriality and (3) to suggest ways for future studies to build upon what the review revealed. Twenty ecological variables have been predicted, correlated with or experimentally demonstrated to relate to territoriality within vertebrate species. These variables include several characteristics of food: quantity, predictability, distribution, quality, renewal rate, type, density and assessibility. Other variables include nonfood resources, population density, habitat features, mates, space, refuges/spawning/home sites, predation pressure, host nests (for brood parasites) and energy availability. We suggest several reasons why food resources are cited most often, including their biological significance, ease of study and publishability of negative results. Certain groups of animals lend themselves to certain methods of study and, therefore, constrain the variables measured. Many variables are the subjects of apparently contradictory reports, i.e., some papers report that an increase in a given variable increases territoriality and others report that a decrease in the variable increases territoriality. After summarizing these reports we hypothesized U-shaped relationships between the ecological variables and behavior that could accommodate all these findings. However, these hypotheses cannot be tested rigorously by most current studies because of methodological limitations. We recommend a shift to quantification of intraspecifically varying spacing systems combined with simultaneous quantification of several ecological variables. Relative importance of different determinants of particular spacing systems can be revealed via multiple regression analysis. Hypothesized causal pathways, in which one ecological variable determines another variable that, in turn, determines territoriality, can be tested by path analysis.
Rates and timing of bird passage in the proposed Norris Hill Wind Resource Area (NHWRA) and vicinity in southwestern Montana were investigated using two marine surveillance radars between August 1995 and August 1996. The scanning radar array displayed movements in a horizontal plane within 360° while the vertical radar displayed altitudes of birds in and out of the NHWRA to the east and west. Radars were also used to record raptor movements within NHWRA in summer. Spatio-temporal profile of migration was determined by adjusting observed numbers of events by detection probability by radar, derived from point- and line-transect bird sampling techniques. Autumn migration was more protracted than vernal migration. Altitude of birds flying in and within 2 km east and west of NHWRA averaged 209 m in autumn and 388 m in spring. Higher altitudes in spring were a function of birds ascending after leaving Ennis Lake, whereas birds were descending to visit the lake in autumn. More birds passed over valleys and swales than high points. Passage rate decreased with declining barometric trend in autumn (headwinds), but the reverse was true in spring (tailwinds).
Recent technological advances have made wind power a viable source of alternative energy production and the number of windplant facilities has increased in the United States. Construction was completed on a 73 turbine, 25 megawatt windplant on Buffalo Ridge near Lake Benton, Minnesota in Spring 1994. The number of birds killed at existing windplants in California caused concern about the potential impacts of the Buffalo Ridge facility on the avian community. From April 1994 through Dec. 1995 we searched the Buffalo Ridge windplant site for dead birds. Additionally, we evaluated search efficiency, predator scavenging rates and rate of carcass decomposition. During 20 mo of monitoring we found 12 dead birds. Collisions with wind turbines were suspected for 8 of the 12 birds. During observer efficiency trials searchers found 78.8% of carcasses. Scavengers removed 39.5% of carcasses during scavenging trials. All carcasses remained recognizable during 7 d decomposition trials. After correction for biases we estimated that approximately 36 ± 12 birds (<1 dead bird per turbine) were killed at the Buffalo Ridge windplant in 1 y. Although windplants do not appear to be more detrimental to birds than other man-made structures, proper facility siting is an important first consideration in order to avoid unnecessary fatalities.
The muskrat (Ondatra zibethicus) is a wetland mammal whose disturbance activities include grazing, burrowing and lodge construction. We evaluated the effects of these disturbances on plant biomass, species richness and diversity, stem density and potential net nitrogen mineralization and nitrification rates in a freshwater tidal marsh on the Hudson River in New York. We hypothesized that muskrats increase floristic richness and diversity by decreasing the biomass of narrowleaf cattail (Typha angustifolia) and that muskrats increase potential net nitrogen mineralization and nitrification rates through aeration and reduced plant uptake because of herbivory. Because muskrats commonly build lodges on or close to creek banks, we separated the disturbance effects of muskrats from the disturbance effects of the creek bank by sampling quadrats along transects placed perpendicular to creek banks at lodge sites. Muskrats decreased biomass, particularly of cattail, but had no measurable effect on stem count, species richness or species diversity. Muskrats increased potential net nitrogen mineralization and nitrification rates; however, this effect was limited to active sites. Creek bank disturbance increased stem count but had no effect on the other variables. Although muskrats did not significantly affect floristic diversity in this study, their disturbance activities did influence soil nitrogen dynamics, which is an important component of wetland function.
Home range size of six swamp rabbits in south-central Arkansas was estimated by radio-telemetry from February 1991 through March 1992. The average home range size was significantly larger than previously reported estimates. This difference is partly attributable to the large number of observations per rabbit in our study, but may also be explained by our inclusion of numerous locations of swamp rabbits during periods of deep inundation. All of the individual rabbits tracked used different areas when the study site was flooded. These results provide the first quantitative description of the response of swamp rabbits to flooding.
We determined the relative abundance, days of surface activity and indices of species diversity, evenness and richness for amphibians inhabiting three differently managed forests surrounding a Carolina bay in South Carolina following restoration. We collected animals daily for 3 y (Oct. 1993–Sept. 1996) using drift fences with pitfall traps in three forest types: loblolly pine (Pinus taeda), slash pine (P. elliotti) and mixed hardwoods (predominantly oak, Quercus spp. and hickory, Carya spp.). Captured animals were marked and recaptures were recorded but not included in statistical analyses, except in our evaluation of activity. We compared results to those of a more limited study conducted before restoration.
Amphibians were significantly more numerous and more active in the mixed hardwood forest than in the pine forest types. However, the hardwood forest had the lowest species diversity in 2 of the 3 y of the study. The slash pine habitat had the highest diversity in all 3 y and for the 3 y combined. Because the evenness index (J′) values differ in step with the species diversity index (H′) it appears that the evenness component of diversity, rather than the richness component, is what is determining H′ variation. A summer subset of these data and summer data from an earlier study of 1977–1978 is in marked contrast with yearlong patterns. For our summer data each forest type had the highest H′ value in one of the years of the study and again the J′ values parallel the differences in H′.
Large numbers of southern toads (Bufo terrestris) reduced evenness, and therefore species diversity, for all three habitats particularly the mixed hardwoods where this species was especially abundant. Proportionally lower numbers of B. terrestris in the summer samples increased J′ and H′ indices. Overall lower abundance and H′ values in the summers of 1994–1996 compared with 1977–1978 may be the result of habitat alteration during the restoration of the Carolina bay.
The reproductive behavior and spawning microhabitat of the flagfin shiner, Pteronotropis signipinnis, was described from aquarium observations, instream observations and microhabitat specific seining collections. Based upon aquarium observations, P. signipinnis is a broadcaster and exhibits a spawning clasp. Although spawning was never observed in nature, a high frequency of spawning related behavioral acts was observed in shallow, densely vegetated habitats (“vegetated riffles”). The spatial distribution of males and females with gonads in advanced stages of development was additional indirect evidence that vegetated riffles were an important microhabitat for reproduction. The physical characteristics of vegetated riffles may enhance the males' ability to clasp females, increase the survival of eggs and provide refuge from predation for spawning adults. Behavior related to foraging was frequently observed in “vegetated runs”, indicating that P. signipinnis relies upon different habitat types to complete its life cycle and meet its resource needs.
General Land Office (GLO) survey notes (1840–1856), current land cover generated from Landsat TM Imagery (1991) and the Forest Inventory and Analysis plots (1991–1992, US Forest Service) were used to examine changes in forests of the Luce District in Upper Michigan over the past 150 y. Historical changes in two subdistricts, Grand Marais and Seney, were also analyzed. Interpretation of GLO notes showed that the presettlement landscape was a mixed conifer matrix (39% of total area), interspersed primarily with northern hardwoods (29%), wetlands (14%) and fire-susceptible pinelands (13%). Estimates of pre-European settlement stand density ranged from 81 trees/ha in open lands to 408 trees/ha in northern white cedar stands (Thuja occidentalis), and estimates of basal area ranged from 3.5 m2/ha in wetlands to 27.7 m2/ha in mixed hardwood/conifer forests. Notable changes in species composition over the last 150 y are the increase of red maple (Acer rubrum; 14%) and the decline of tamarack (Larix laricina; −11%), hemlock (Tsuga canadensis; −7%), white pine (Pinus strobus; −6%), beech (Fagus grandifolia; −5%) and yellow birch (Betula alleghaniensis; −5%). Contrasts between the two subdistricts, Grand Marais and Seney, reflect the influence of the integration of climate, physiography and disturbance regime. Overall presettlement vs. present-day tree diameter distributions differed between the two time periods. Differences in the diameter distributions among individual tree species are related to their growth rates and life expectancies. The diameter distributions of short-lived species are similar between the two time periods. Most species have diameter distributions with more small trees today than in presettlement forests, especially long-lived taxa such as hemlock and white pine.
The relationship of herbaceous plant diversity to overstory composition and stand structure in the mixed aspen forest of northern Minnesota was investigated on 23 study sites that contained aspen in monoculture or in mixture with boreal conifers or northern hardwood species. On each site overstory species were placed into species groups: conifers, aspen and hardwoods other than aspen. Each site was then placed in one of three cover-type groups based on proportion of the overstory species groups: Aspen (>0.9 basal area in aspen), Aspen-Conifer (>0.15 basal area in conifer species) and Aspen-Hardwood (>0.15 basal area in hardwood species other than aspen). The relationships between diversity of herbaceous vegetation and the following factors were tested: (1) overstory composition, defined as the proportion of basal area by species group in the overstory and (2) stand structure. Stand structure was described by the vertical position and horizontal arrangement of balsam fir within the stand. In addition, relationships were tested with respect to other stand structural features such as shrub height and cover, average amount of plant material intercepted within the vertical profile and an index of plant occupancy within the vertical profile (modified Foliage Height Diversity Index-FDH).
Understory herbaceous diversity (H′) and proportion of aspen basal area were significantly positively related whereas understory herbaceous diversity was significantly negatively related to proportion of hardwood basal area and not related to proportion of conifer basal area. Mixtures of overstory tree species provided a range of stand structures that can be represented by shrubs, subcanopy trees or the overstory trees. In the three cover-type groups different structural components were related to herbaceous diversity indicating that (1) overstory composition and stand structure interactively influence understory diversity patterns and (2) it is difficult to characterize stand structure for the range of stand conditions with a single measure. Increased diversity of structure (modified FHD) in the Aspen-Conifer group is negatively related with diversity (H′) of the herb layer. Composition of herbaceous species varied depending on presence or absence of conifers in the overstory. These patterns may be influenced by the interaction of a variety of resource levels and climate conditions, which, in turn, are controlled by factors such as tree architecture or shade tolerance of overstory trees.
Colonization of a relatively undisturbed 1915 debris flow by an upper montane coniferous forest was examined in Lassen Volcanic National Park in northern California in 1987. Seventy 100-m2 circular plots were arranged in four transects across the flow and sampled to measure tree densities, heights, basal areas and ages. The composition of the forest changed from a mixture of Abies magnifica, Pinus monticola and P. contorta on steep slopes to a forest dominated by P. contorta on shallow slopes. This pattern is typical for these terrains at the 2000-m elevations of the flow. Age data and historical photographs indicated little successful colonization before the late 1930s and peak colonization rates about 1955. Height growth has generally been slow with most trees being >20-y-old but <2-m tall; however, some individuals, including some recent colonizers, have shown rapid growth. This variation among individuals suggests (1) that the earliest colonizers are not necessarily those which will eventually dominate the forest and (2) that opportunities to invade and occupy the canopy may extend for 30 y after the first successful colonization.
Pitcher's thistle (Cirsium pitcheri) is a federally listed monocarpic plant species endemic to the shoreline dunes of Lakes Huron, Michigan and Superior. Individual plants may require 4–8 y to mature, after which they flower and die. This life history and the lack of vegetative modes of reproduction make an understanding of seed and seedling ecology critical for preservation and restoration of Pitcher's thistle. We report conditions necessary to overcome seed dormancy and the effects of light, seed mass and depth of burial (0, 2, 4 or 8 cm) on seed and seedling success from laboratory experiments in controlled growth environments. Seeds of Pitcher's thistle are dormant when dispersed, but a combination of low temperatures and afterripening can break dormancy. Germination over 30% was obtained with at least 24 wk of low temperature moist stratification; 25% germination occurred after 6 mo of storage at room temperatures. Light suppressed germination of nondormant seeds. Although burial is required for germination, only 8% of seedlings emerged from a depth of 8 cm, associated with longer time to emergence. Achenes of this taxon lack endosperm; seedlings probably lack the reserves to overcome excessive burial. Logistic regression was used to compare the relative effects of the presence or absence of light, burial depth, seed mass and differences between populations from Michigan's upper and lower peninsulas. All three variables were significant predictors of germination and emergence when tested alone. Seeds from the upper peninsula were more likely to germinate, provided they were buried, although their probability of emergence decreased at greater burial depths. Although seeds from the upper peninsula were significantly heavier on average than those from lower peninsula populations, seed source was an even better predictor of seed and seedling success than seed mass. This suggests genetic differences among populations even within this geographically restricted endemic. Seeds of Pitcher's thistle can remain viable 1–2 y in the laboratory, suggesting this species can maintain a seed bank, although it is ephemeral. Seeds and seedlings of Cirsium pitcheri successfully exploit the dynamic nature of their dune habitats. Our results suggest that conservation efforts must consider seed storage conditions, genetic source of seeds and seed size, as well as maintenance of natural sand erosion and accretion regimes for preservation and restoration of this taxon.
The presence of hybridization among coexisting species of Quercus section Lobatae raises questions regarding the selection of mother trees to control seedling quality. Currently, trees are selected as a seed source on the basis of whole tree silvic characters. There are two sympatric red oak species in northern Wisconsin, Q. rubra L. (northern red oak) and Q. ellipsoidalis E. J. Hill (northern pin oak). We characterized 30 mother trees and their seedlings to assess the potential for selecting red oak seed sources based on silvic characters of the mother tree. Mother trees were selected based on whole tree silvic characters to represent Q. rubra L., Q. ellipsoidalis E. J. Hill and their putative hybrids. Mother trees were then characterized by leaf and acorn morphometric analyses and by isozyme profiles. One-year-old bareroot nursery seedlings raised from seeds collected from these mother trees were characterized by height, diameter and number of lateral roots. Height and diameter growth were also measured the year after planting these nursery seedlings. Multivariate analyses revealed two, rather than three, distinct mother tree groups: Q. ellipsoidalis and Q. rubra plus putative hybrids. Thus, whole tree silvics are not adequate for differentiating northern red oak and hybrids. However, analyses, particularly of leaf morphology, isozymes and seedling performance, provided evidence of a continuum between the two species, consistent with the existence of hybrids among the mother trees. Whereas Q. rubra and putative hybrids could not be distinguished, Q. ellipsoidalis trees were distinguished on the basis of whole-tree silvic characteristics, or by acorn, leaf or seedling morphological characteristics. Thus, Q. ellipsoidalis can be distinguished and removed from the publicly collected seed source to improve seedling quality.
Dogwood anthracnose is a disease caused by Discula destructiva, a fungus of probable exotic origin that is a serious threat to natural populations of Cornus florida in the eastern United States. This epidemic provides an interesting opportunity for the study of the ecology of a highly virulent pathogen and its host. We present evidence that dead dogwoods tend to have larger neighboring conspecifics than do living dogwoods, that smaller trees have higher levels of foliar infection than larger trees and that in trees of reproductive size, higher levels of anthracnose infection are associated with lower fruit production. In contrast to our data on mortality, proximity to conspecifics did not account for significant variation in the severity of foliar anthracnose infection among live dogwoods. These patterns of infection suggest that D. destructiva could severely impair the ability of this important component of the forest understory to regenerate itself.
In the early 1900s several hosts were identified for the black sandshell Ligumia recta. Recent attempts to propagate juvenile L. recta with two of the reported hosts (bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides) have produced inconsistent results and few juveniles. We conducted this study to determine which of the reported hosts or other fish hosts were the most suitable for glochidial metamorphosis. The duration of glochidial metamorphosis varied among seasons. Despite similar water temperatures, juveniles metamorphosed sooner and over a shorter period of time in the spring than early fall; the modal day of metamorphosis differed by 78 d. Relatively few juveniles were recovered from bluegill and largemouth bass in three trials. White crappie Pomoxis annularis and black crappie P. nigromaculatus were marginally suitable hosts. Although glochidia encysted on all hosts, >10× more juveniles metamorphosed on sauger Stizostedion canadense compared to other hosts tested.
The taxonomy, distributional history, present occurrence, life cycle, morphology of developmental stages and epizootiology of the heterophyid trematode Centrocestus formosanus (Nishigori, 1924) in Mexico are reviewed. This parasite was most likely introduced to Mexico with the importation of the first intermediate host, the thiarid snail Melanoides tuberculata, from Asia in 1979. Centrocestus formosanus was first recorded in 1985 as metacercariae in fry of the first generation of black carp Mylopharyngodon piceus imported from China and subsequently in other fish from a farm in central Mexico. Since that time the trematode has spread rapidly over a wide area which includes central Mexico and both the Atlantic and Pacific coasts. This rapid spread has apparently been enabled by previous propagation of M. tuberculata in Mexico. Metacercariae of C. formosanus occur encysted on the gills of fish. They have been found in 39 species of fish of the families Atherinidae, Characidae, Cichlidae, Cyprinidae, Eleotridae, Gobiidae, Goodeidae, Ictaluridae, Mugilidae and Poeciliidae from 11 Mexican states (Colima, Guanajuato, Hidalgo, Jalisco, Michoacán, Morelos, San Luis Potosí, Sonora, Tabasco, Tamaulipas and Veracruz). The heron Butorides striatus is the only known natural definitive host in Mexico. Further research towards better understanding of all aspects of the life cycle, transmission, host-parasite relationships and the effective control of C. formosanus in Mexico is necessary. It should also include monitoring of the present distribution of M. tuberculata and its infection with larval stages of C. formosanus. Much more emphasis should be given to histopathological studies to assess actual impact of the parasite on fish of different species and age classes. The spectrum of natural definitive hosts and their epizootiological importance in the transmission and maintenance of the parasite in Mexico should also be better documented. Adequate preventive and control measures should be applied in aquaculture, with emphasis given to prevention of movement of infected fish stocks.
Current theory predicts that males should guard prereproductive females if they will thereby achieve sperm priority and that the propensity of males to guard prereproductive females, and aggression exhibited by both sexes at this time, should be related to their density and sex ratio. Low female density should select for males to guard prereproductive females, but a female-biased sex ratio should weaken any propensity for males to guard them. Low density and a female-biased sex ratio should favor a low level of aggression by both males and females. We tested these predictions with a low-density, female-biased population of the crab spider Misumena vatia. During experimental introductions only 10% (n = 40) of the males guarded penultimate-stage females through their final molt to copulate with them, even though penultimate females seldom responded aggressively to males in these trials (10%). Nearly all males mated soon after they found newly molted adult virgin females (94%: n = 31). Males guarded only 8% (n = 39) of the penultimate females censused in the field, but each male mated with the female it guarded as soon as that female molted. Only 22% (n = 23) of trials with two males and a penultimate female resulted in more than momentary physical contact between the males, and none resulted in injury. Thus, both predictions were based on the sex ratio, but only one of the two associated with population density, were confirmed. These results suggest that sex ratio is more important than density in dictating precopulatory guarding and aggression. The strongly female-biased sex ratio of Misumena may explain why males guard pre-reproductive females less frequently and exhibit less aggression than males in a population of the closely-related Misumenoides formosipes.
Many amphipods (Crustacea: Amphipoda) exhibit sexual dimorphism in the size of a paired chelate appendage, the gnathopods. As with sexually dimorphic weapons and ornaments in other taxa, little is known of the evolutionary processes underlying species variation in the dimorphism. In this study I examined males of two ecotypes of freshwater amphipods in the genus Hyalella to determine (1) the degree and form of reproduction-mediated selection acting on gnathopod size, (2) the importance of fluctuating asymmetry in gnathopods for mating success and (3) differences between ecotypes in gnathopod size. I examined sexual selection arising from differential success in forming mating pairs and natural selection due to success in mating with larger, more fecund females. The two ecotypes differed in the pattern of selection acting on gnathopod size. The small-bodied ecotype did not experience significant selection on gnathopod size in either selection episode. In contrast, the large-bodied ecotype experienced significant sexual selection for increased gnathopod size (relative to overall body size) and experienced selection for smaller gnathopod size during the natural selection episode. Fluctuating asymmetry in gnathopods occurred at relatively low levels and was not related to pairing success in either ecotype. The two ecotypes differed significantly in gnathopod size relative to body size, with the small-bodied ecotype having gnathopods approximately 18% larger than those of the large-bodied ecotype. These results, together with previous results, suggest that gnathopod size is important in the mating success of males of the large-bodied ecotype, but not the small-bodied ecotype, and that ecotype differences in the level of the sexual dimorphism may have evolved for reasons unrelated to mating success.
Although belowground food webs have received much attention, studies concerning microarthropods in nondetrital food webs are scarce. Because adult oribatid mites often number between 250,000–500,000/m2 in coniferous forests, microarthropods are a potential food resource for macroarthropod and vertebrate predators of the forest floor. Although the contribution of microarthropods to aboveground food webs has received little attention, sufficient data concerning macroarthropods and vertebrate predators were available at the Savannah River Site (SRS, Aiken, South Carolina) to construct a food web model of the various trophic interactions. To supplement this analysis, literature of microarthropod predation by arthropods and vertebrates was reviewed. This information was incorporated with the existing data to produce a model for taxa occurring in coniferous forests at the SRS. Because of the diversity and natural history of microarthropod predators, both vertebrate and invertebrate, the resulting web is quite connected and includes transfers to many trophic levels. The diets of arthropods and vertebrates are variable; yet feeding patterns reflect the relative abundance of prey at a place and time. Also, many predators feed on members of their own group. These factors suggest that belowground transfers are deserved of more attention in these and other forest food webs where substantial numbers of detritus feeding invertebrates inhabit the soil/litter interface and are available as prey items. Moreover, this model can be generalized to describe the dynamics of arthropod and vertebrate communities in other coniferous forests. The functioning of terrestrial ecosystems is dependent upon the interrelationships between aboveground and belowground food webs, and transfers of biotic components of the decomposer subsystem to aboveground consumers connect the two subsystems. It is hoped that those consumers traditionally associated with foliage-based food webs be reconsidered, as they may be gaining a proportion of their nutrition from organisms in the detrital pathway.
The eastern woodrat (Neotoma floridana) is considered a generalist herbivore. Only anecdotal evidence suggests that eastern woodrats eat meat given the opportunity. We conducted trials to test whether the eastern woodrat would consume northern bobwhite (Colinus virginianus) under experimental conditions. We live trapped 27 eastern woodrats in the Flint Hills region of Kansas during Nov. and Dec. 1997. We assigned woodrats to either a control or one of two 108 h experimental treatments. We provided 9 control animals with laboratory rat chow ad libitum, 9 woodrats in treatment 1 with laboratory rat pellets ad lib. and a wild northern bobwhite carcass and 9 woodrats in treatment 2 with a bobwhite carcass only. Woodrats willingly consumed quail in both treatments. Control and treatment 1 woodrats maintained body mass, whereas animals in treatment 2 lost 17% of body mass. Consumption preferences changed temporally. Head and leg/feet of quail were consumed first, muscle second and organs last. We observed no difference in consumption preferences between treatments. We suggest the eastern woodrat may include meat in its food selection when seasonal food resources are limited.
Once territories become established residents often have a high probability of successfully defending their territories against intruders. This advantage often can be explained by intrinsic qualities (e.g., size, body condition, experience) that make residents superior competitors. In addition, residency status can confer an advantage that is independent of fighting ability. We used a laboratory experiment to examine the effect of residency status on aggressive behavior by adults of the Ozark zigzag salamander (Plethodon angusticlavius), a small terrestrial salamander found under rocks and logs on the forest floor. We controlled for intrinsic effects by testing each individual as both a resident and an intruder in random order. Males and females were tested in same-sex contests in separate experiments. Based on an index that incorporated the frequency of aggressive and submissive postures, both males and females were significantly more aggressive as residents than as intruders. Bites were performed by both males and females, occurring in 11 of 38 pairings overall, and also tended to be more frequent in residents than in intruders (P = 0.057). These data are consistent with the hypothesis that both males and females defend feeding territories and that residency offers an advantage that is independent of fighting ability in this species.
In August 1995 six rusty crayfish (Orconectes rusticus) colonized with zebra mussels (Dreissena polymorpha) were captured in small-meshed fyke-nets set as part of a fish sampling effort at Peter's Marsh and Long-Tail Point Wetland in lower Green Bay. The number of mussels per crayfish ranged from 16 to 431 and the length of the zebra mussels ranged from 1.2 to 12.0 mm with a mean of 3.6 mm. Mussels colonized virtually all areas of the crayfish bodies but the chelae, telson and uropods and thorax were most heavily colonized. Although it is possible that zebra mussels may have positive effects on crayfish populations through associated effects on water clarity, autotroph and invertebrate production, we are concerned that energetic costs or physical constraints caused by attached zebra mussels may be detrimental to crayfish in the Great Lakes.
Live-trapping was conducted to determine the influence of trap disinfection on trapping success. Deer mice (Peromyscus maniculatus) on most (83.3%, n = 6) grids were equally likely to be caught in traps recently (≤8 h) or previously (≥5 d) disinfected. Traps were as likely to recapture mice previously captured in the other treatment as mice previously captured in the same treatment.
Shortnose gar foraged on spent periodical cicadas floating on the surface during a mass coemergence of 13- and 17-y broods. The largest gar in each pool of an observed stream reach was positioned at the upstream pool lip. Ambient cicada drift was observed and increased feeding trials were used to investigate the observed pattern. The largest gar defended the upstream pool lip from other gar in the pool and consistently consumed more cicadas than any other single gar.