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Experience effects on mating have been implicated as important factors that can account for some of the variability in responses by prospective mates. Previous studies have demonstrated that sexual experience and learning can play significant roles in female choice; however, few studies have concentrated on experience effects in males. Using a partially sex-role reversed cellar spider, Pholcus phalangioides, in two laboratory experiments, we addressed the importance of male experience with (1) nonvirgin female cues associated with silk and (2) virgin females on a suite of male behaviors associated with mating. We discovered that males experienced with female silk and associated cues courted nonvirgin females for a longer duration than inexperienced males. Courtship latency and courtship duration had significant effects on mating success in trials involving inexperienced, but not experienced males. Female leg length affected the mating success of experienced, but not inexperienced males. Interestingly, no males mated twice when sequentially presented with two virgin females over a 24 h period, and most mated males (92%) failed to court the second female. Our findings suggest that male experience affects mating behaviors with both mated and virgin females and that males may be sperm limited.
Many research studies have focused on the interactions among larval anurans, but relatively little is known about competitive or predatory interactions among anurans following metamorphosis. The purpose of our study was to examine the effects of post-metamorphic green frogs (Rana clamitans) on post-metamorphic American toads (Bufo americanus) in the terrestrial environment as a model for understanding how interspecific differences in size at metamorphosis may influence terrestrial interactions. We examined if caged, uncaged or no green frogs affected survival, growth and hiding behavior of recently metamorphosed American toads in a replicated laboratory experiment. Green frogs did not appear to prey upon small American toads. However, by the end of the experiment American toad survival was lowest in treatments with uncaged green frogs; this result suggests that green frogs may outcompete American toads for food, but such impacts in nature may be limited or may have selected for spatial segregation in the terrestrial environment. Green frogs also increased hiding activity of toads at some times, which may in part explain the trend of reduced mass gained when toads were reared with green frogs. This study represents one of the first to examine interspecific interactions among anurans with complex life cycles in the terrestrial environment.
We examined the diets of two species of stream-dwelling North American crayfishes (Orconectes propinquus and O. rusticus) at eight sites in the Midwestern United States both by measuring natural abundances of stable isotopes of carbon and nitrogen and by quantifying gut contents. Our goals were to test the hypothesis proposed by others that crayfish are primarily carnivorous, and in particular, to examine the frequency of fish consumption by crayfishes. Stable isotope profiles indicated that both species of crayfish were omnivorous and had a trophic position between those of other invertebrate consumers and fishes. Isotope profiles demonstrated that lower quality foods such as leaf litter, periphyton and fine particulate organic matter made up a larger proportion of the diets of both species than did animal material and that fish comprised approximately 12% of the diet of both crayfishes; this percentage was less variable than that of other food types. Gut content analysis corroborated stable isotope results in finding a similar percent occurrence of fish matter in both species. Our results suggest that the consumption of fish by crayfishes is often underestimated or ignored.
Conservation of an imperiled plant species requires an understanding of its local occurrence and density in relation to habitat variation. Paronychia chartacea ssp. chartacea is a federally threatened species restricted to gaps in fire-maintained Florida rosemary scrub and to roadside sites that mimic scrub gaps. To assess the effects of time-since-fire and microhabitat on the occurrence and density of Paronychia populations, we conducted surveys of 119 scrub gaps and 16 roadside macroplots. In rosemary scrub, we found that the frequency of gap occupancy decreased with time-since-fire and that Paronychia occurrence and density were greater in the centers of large gaps than in small gaps or large gap edges. In roadside sites, the distance from adjacent rosemary scrub did not affect the presence of Paronychia, but density increased with distance from rosemary scrub vegetation. Paronychia densities in roadside sites were most similar to densities in recently burned rosemary scrub. Time-since-fire and microhabitat quality affect the occurrence and density of Paronychia and should be considered in management of Paronychia populations.
Brush pile creation is a common habitat management method used to attract wildlife. However, there is a paucity of data regarding effectiveness of brush pile creation and the indirect effects of brush piles on multi-species interactions. Here we document use of man-made brush piles by Texas ratsnakes (Elaphe obsoleta), examine mechanisms behind that use, and present results of a pilot study comparing avian nest success in areas with and without brush piles to determine if predator attraction to brush piles negatively affects the surrounding bird community. Radio-tracked snakes were found in brush piles 10% of the time, despite brush piles comprising less than 0.2% of the habitat by area. More abundant small mammals and more moderate temperatures in brush piles than in surrounding habitats could explain snakes' attraction to brush piles. Nest success of birds was similar in areas with and without brush piles in the year following brush pile creation. Because it may take substantially longer than 1 y for snake use to reach its maximum, however, it is premature to conclude that brush piles do not affect birds nesting in adjacent habitat. Given the apparent prevalence of brush pile creation, and the demonstrated preference of brush piles by ratsnakes, further research to document the consequences of brush pile creation is warranted.
Ammocrypta clara Jordan and Meek (western sand darter) occurs primarily in the western portions of Mississippi River system, but also has been reported from a Lake Michigan drainage and a few eastern Texas Gulf Slope rivers. Additional range records depict a semi-disjunct distribution within the Ohio River drainage, including collections from Wabash River in Indiana, the Cumberland, Green, Kentucky and Big Sandy rivers of Kentucky, and the upper Tennessee River in Tennessee and Virginia. This paper documents the occurrence of A. clara from the upper Ohio River drainage within the lower Elk River, West Virginia, based on collections from 1986, 1991, 1995, 2005 and 2006. The Elk River population, consistent with those of other Ohio River drainages, has slightly higher counts for numbers of dorsal-fin rays, scales below lateral line and lateral line scales when compared to data from populations outside of the Ohio River drainage. Modal counts of meristic characters are similar among populations, except for higher modal counts of lateral line scales in the Ohio River population. The discovery of the Elk River population extends the range distribution of A. clara in the Eastern Highlands region, documents wide distributional overlap and additional sympatry with its sister species, A. pellucida (eastern sand darter), and softens support for an east-west Central Highlands vicariance hypothesis for the present distribution of A. clara and A. pellucida.
Gonadal condition of the cyprinid stream fish Notropis telescopus (telescope shiner) was monitored from Feb. to Sep. to determine reproductive schedule. The study site was at the southern limit of species range in northeastern Alabama. Notropis species are multiple batch spawners with strong seasonality to gonadal size and condition. The number of maturing oocytes observed in ovaries was at a peak from Apr. to Jul., with strong majorities of oocytes at the most mature stages in Apr., May and Jun. Ripe and fully mature ovaries were found in fish collected in Apr., May and Jun. A pronounced peak in the gonadosomatic index (GSI) was found in Jun. for both males and females. The evidence points to an Alabama spawning season from Apr. to Jul., peaking in the middle of this season.
The life history and population demography of the endangered birdwing pearlymussel (Lemiox rimosus) were studied in the Clinch and Duck rivers, Tennessee. Reproducing populations of L. rimosus now occur only in the Clinch, Duck and Powell rivers, as the species is considered extirpated from the remaining portions of its range in the Tennessee River drainage. Females are long-term winter brooders, typically gravid from Oct. to May. Glochidia are contained in the outer gills and are released in association with a mantle-lure that resembles a small freshwater snail. Estimated fecundity, based on 8 gravid females collected from the Clinch and Duck rivers, ranged from 4132 to 58,700 glochidia/mussel. Seven fish species were tested for suitability as hosts for glochidia, and five darter species were confirmed through induced infestations: Etheostoma blennioides, E. camurum, E. rufilineatum, E. simoterum and E. zonale. Ages of L. rimosus shells were determined by thin-sectioning and ranged from 3 to 15 y in both rivers. Shell growth was higher and maximum size greater in males than females in both rivers. Shell growth was greatest in the Duck River. Densities of L. rimosus in the Clinch River were maintained at seemingly stable but low levels ranging from 0.07 to 0.27 m−2 from 2004–2007, and in the Duck River at similar but higher levels ranging from 0.6 to 1.0 m−2 from 2004–2006. In the latter river, abundance has increased since 1988, likely due to improved minimum flows and dissolved oxygen levels in water releases from a reservoir upstream.
While most studies of heterogeneity have focused on describing patterns of species or communities, few have focused on the relationships between biotic and abiotic environmental landscape-level gradients. Our study was designed to determine relationships between grazing (heavy, moderate, ungrazed), topographic position (upland vs. riparian), vegetation structure and the thermal environment (i.e., soil-surface temperatures) and determine the influence on landscape patterns of heterogeneity. Biotic and abiotic patterns of heterogeneity were evaluated by establishing 200-m transects that were centered on and perpendicular to a riparian zone so that spatial patterns of variability could be determined along each transect which transcends the maximum level of landscape heterogeneity. Vegetation cover and structure and soil-surface temperatures were recorded at 1-m intervals along the transect. Bare ground increased and leaf litter, grass cover, vegetation heights and angle of obstruction decreased with grazing intensity. However, mean soil-surface temperatures did not differ between grazing treatments. Tree canopy cover associated with riparian areas generally reduced soil-surface temperatures 20 C below that of upland temperatures. In fact, 96% of observations of riparian soil-surface temperature were ≤ 39 C, while 94% of upland soil-surface temperatures were ≥ 40 C regardless of grazing intensity. Vegetation characteristics and soil-surface temperatures were correlated (P < 0.05), but correlation coefficients were small because soil-surface temperature was highly variable. Grazing influenced patterns of landscape heterogeneity, but effects were inconsistent among biotic and abiotic variables. Although grazing had little influence on moderating mean soil-surface temperatures, results suggest that grazing intensity influences thermal heterogeneity at a variety of spatial scales. For instance, thermal heterogeneity (in moderately grazed treatments) is highest at smaller (lag distances ≤ 20 m) and larger (lag distances ≥ 48 m) spatial scales but was lowest at moderate scales (lag distances 22–45 m). For all variables, other than soil-surface temperature and forb cover, semi-variances of moderately grazed sites generally lie intermediate between heavy and ungrazed sites. Nearly all ungrazed vegetation characteristics, except leaf litter, fit a spherical model that reached a sill at a lag distance ≤ 20 m and became spatially independent thereafter, while heavily and moderately grazed sites typically fit an exponential model, indicating a high degree of continuity. Patterns of thermal variability (on uplands) are not related directly to any one vegetation variable, hence, landscape patterns based on vegetation parameters alone are of limited value since patterns of thermal variability are effected by the integration of vegetation and environmental variables within the ecosystem.
Current research suggests that female white-tailed deer (Odocoileus virginianus) will adopt sedentary breeding strategies in populations with an abundance of males and a more active mate-searching strategy in low-density or unbalanced herds. We used GPS collars to document the movements of 10 female deer during the breeding season at two Mid-Atlantic study sites that support high-density herds with nearly equal sex ratios. We calculated 95% and 50% seasonal and weekly kernel home ranges and the daily percentage of points located outside of the seasonal home range (SHR). Peaks in weekly home range size and in the percentage of points located outside of the SHR occurred between 7 Nov. and 9 Dec. (x ¯ = 22 Nov.) for eight deer. Past data from one of the study sites have indicated that most breeding activity occurs from 5–25 Nov. Peaks in the percentage of points outside of the SHR corresponded to brief (x ¯ = 24.0 h, sd = 18.2 h; range 8–68 h) excursions. On peak days, 46–100% (x ¯ = 68.3%, sd = 17.1%) of data points were located outside of the SHR. No other excursions were observed during the 17 wk study period. Our results suggest that female deer may travel outside of their home range during the breeding season even when presented with an abundance of potential mates; these data suggest females are engaging in a discrete form of mate selection.
The response of postparturient females to conspecifics at the natal den can provide insights into intraspecific dynamics, particularly the risk of infanticide. In solitary species, the risk of infanticide may be high and mothers are expected to secure dependent young in dens and tolerate little, if any visitation by males. We monitored 10 male raccoons (Procyon lotor) and 11 females from pregnancy through lactation that were equipped with proximity detecting collars during the neonate rearing period (Apr.–Jul.). Natal den trees were identified and proximity detectors were also attached to these trees to document the mother's movements and visitation by conspecifics. A total of 21 den trees (1–8 dens/mother) were used, yielding 337 den-nights of data. Besides those of the mother, 284 visits (0–2.9 visits/night) were recorded and dens were visited by three to 10 individuals. Time spent away from the den by the mother increased with litter age (F = 45.36, P < 0.001, R2 = 0.19). Females who moved their litters from the primary natal den tended to receive more (t = −1.99, P = 0.08, df = 8) male visits/night before their move, than females that stayed in the primary natal den. Males also visited natal den trees more often (t = 2.26, P = 0.05, df = 7) when a natal family was occupying the den tree than once the family had stopped using the den tree. We were unable to examine den trees that were abandoned by their mothers, but our data suggested that female raccoons are intolerant of adult males at natal dens while raising their litters. This may be a response to the risk of male-driven infanticide.
This study of dominant and subordinate led social groups of white-tailed deer (Odocoileus virginianus) was designed to investigate longevity and associations among members as well as the reproductive success that determines the durability of these groups. Characteristics of 25 dominant and 17 subordinate female led social groups of white-tailed deer were studied on three areas in Illinois. Group size for dominant led social groups ranged between 3.8 and 5.2 deer/y and for subordinate led groups only 2–2.5 deer. Dominant females survived significantly longer (8.2 y) then did subordinate females (5.4 y) and fawns born to dominants were significantly more sedentary after independence. Fawn recruitment (fawns alive at 1 y) was also significantly higher for fawns born to dominant females. Members of a dominant female's social group generally confined themselves to the home range of the dominant female but as they aged were seen less often with her. Dominant females occupied stable habitats free of environmental problems while subordinates occupied ranges with frequent natural and human induced disturbances. By association, fawns of dominant females inherit a stable home range that fosters improved longevity and successful fawn recruitment
We examined spatial distributions and resource partitioning among female mule deer (Odocoileus hemionus) and female North American elk (Cervus elaphus) during summer and winter in southeastern Idaho, USA. Our objective was to understand differences in distributions and habitat selection by these two species of large herbivores in a sagebrush-steppe ecosystem. We used multi-response permutation procedures to examine seasonal distributions of mule deer and elk. We compared animal locations with random locations on a GIS-based habitat map to examine habitat selection and importance. Both species were more widely distributed during summer than winter, when distributions of both species were more restricted. During winter, habitat selection differed among mule deer and elk in use of aspect; east facing slopes were selected by elk and west-facing slopes by mule deer. Mule deer also were located closer to roads than random locations, which may have resulted from avoidance of elk. We observed no differences in habitat selection between mule deer and elk during summer, although these large herbivores showed resource separation by strongly partitioning use of habitats. Conversely, both species used the shrub-steppe ecosystem during winter, but partitioned habitat mostly via use of aspect and distance to roads. Our research provides insights into niche partitioning between these large mammals.
Gray fox ecology is poorly understood within the longleaf pine ecosystem, despite the importance of these landscapes to conservation and biological diversity. During 2002–2006, we radio-monitored 42 gray foxes and estimated space use, habitat selection and survival within a managed longleaf pine forest. Sizes of home ranges and core areas were greater in winter than during other seasons, but were similar between males and females. Industrial agriculture field and residential areas were important to foxes when selecting home ranges, but hardwood forest stands were selected when establishing core areas and were consistently used more than other habitats. Despite being captured within the longleaf pine community, most foxes either consistently were found outside of this system in other habitats, or used habitats along the periphery of the longleaf pine system. Mean annual survival was 0.61, and human-induced factors (vehicle collisions and trapping) accounted for most (63%) fox mortalities. Longleaf pine forests did not appear to be important to gray foxes in this study, which is significant because natural ecosystems are often important for predator species. We provide evidence that sources of gray fox mortality are influenced by habitat selection patterns.
Recently collected fossils from the late Pleistocene (Rancholabrean North American Land Mammal Age) locality at Térapa, Sonora, México, represent 31 species of non-passerine birds. Twenty-three of the species (74%) are aquatic (grebes, pelican, cormorant, herons, ibis, stork, geese, ducks, rails), reflecting the lacustrine environment (marsh, lake) in which the fossils accumulated. The eight non-aquatic species (harrier, kite, two eagles, caracara, quail, killdeer and owl) suggest habitats from grassland to open woodland to desertscrub to tropical thornscrub. Three species are certainly extinct (the duck Anabernicula cf. A. oregonensis, eagle Buteogallus (Wetmoregyps) daggetti and owl Strix brea). Only the owl has been recorded previously in Sonora. A species of large stork (Ciconiidae sp., genus uncertain) probably is extinct as well. Previously unrecorded in Sonora is a kite Ictinia sp. Among the 26 other species (all extant), four have no modern records within 100 km of Térapa (the ibis Plegadis cf. P. chihi, Canada Goose Branta canadensis, Common Moorhen Gallinula chloropus and Purple Gallinule Porphyrio martinicus). Although the non-passerine fossil bird community at Térapa is dominated by aquatic species with broad latitudinal and longitudinal ranges, five of the eight species of landbirds do not occur north of the southwestern U.S. or northern México. The subtropical biogeographic affinities of the Térapa birds agree with those suggested for the associated reptile and mammal fossils.
Laughing gulls (Larus atricilla) are commonly found in many areas of North America and little is known about their diet, particularly in coastal-urban interfaces where gull-aircraft collisions can be a serious concern. The objective of this study was to describe and quantify the consumption of terrestrial invertebrates by laughing gulls at a coastal-urban interface in the northeastern United States. We examined the stomach contents of laughing gulls (n = 1053) collected during wildlife damage management operations at John F. Kennedy International Airport during the summers of 2003 and 2004. Terrestrial invertebrates consumed by laughing gulls represented 2 taxonomic phyla, 4 classes, 15 orders and 40 families. Beetles (Coleoptera) and ants (Hymenoptera) were the most common terrestrial invertebrates consumed by laughing gulls. We found evidence of temporal (i.e., monthly) variation in the frequency of occurrence of terrestrial insects in laughing gull diets. Laughing gull gender and age did not influence the frequency of occurrence of terrestrial insects in gull diets. Terrestrial environments (e.g., areas of turfgrass) appear to provide important foraging locations and food resources for laughing gulls in coastal-urban areas. This information is important for developing effective management approaches to reduce human-gull conflicts, such as gull-aircraft collisions at coastal airports.
Factors that affect movement of small mammals include vegetation structure, resource distribution, interspecific interactions and parasitism. The objective of this study was to assess the effect of bot fly (Cuterebra fontinella) parasitism on movement distance [estimated by mean squared distance (MSD)] of white-footed deermice (Peromyscus leucopus), using a repeated measures approach. Although there was no significant effect of infestation on MSD, there was a nonsignificant trend towards increased movement during infestation for females. In addition, there was no difference in MSD between individuals with single infestations and those harboring several larvae. These results are unexpected given the large size of the parasite relative to the host. Studies of fine-scale temporal movements within a single night could shed further light on the effects of infestation on movement.
Analyses of the annual seed set taken from 208 shrubs of Vaccinium corymbosum at six locations in eastern North American from 1978 to 1999, showed that at each location, a group of individual plants retained the same rank among the others in the number of viable seeds produced per berry from year to year, and that the top five percent producers in the group produced approximately 25% of the total seed production, while on the low end a group of about half the plants contributed < 10% of the total. The relationship between the cumulative proportions of seed set per plant against the cumulative proportion of producers is consistent throughout the six locations, with some evidence of clustering of locations. At all locations, the proportion of seeds produced per plant or equivalently the total seed production per plant over the sampling period has right skewed distributions. At each location, the same proportion of plants produces the same proportion of seeds. The total number of seeds produced at each location are closely fitted by Weibull distributions with shape parameters less than 1, indicating that the more seeds a given plant has produced the more likely it will produce in the future.
We report two new geographic distribution records for the Brook Stickleback (Culaea inconstans) in Nebraska. Both records are from Dawes County, the first from Dead Man's Creek and the other from Chadron Creek. These are the only records of C. inconstans from the WH1 sub-basin of the White River basin. This fish is apparently extending its range westward in the state.
Persistence and stability of the component helminth community of Rana boylii from Humboldt County, California was evaluated using two collections made 40 y apart (1964–1965 and 2004–2007). The component helminth community consisted of 13 species: one species of Cestoda (Distoichometra bufonis), six species of Digenea (Deropegus aspina, Glypthelmins quieta, Gorgoderina multilobata, Haematoloecus kernensis, Megalodiscus microphagus, echinostome metacercariae) four species of Nematoda, (Cosmocercoides variabilis, Hedruris sp., Rhabdias ranae, third stage Physalopterids) and two species of Acanthocephala (represented by centrorhynchid cystacanths and oligacanthorhynchid cystacanths). Twelve (92%) of the 13 species occurred in the 1964–1965 sample; nine (69%) of the 13 species were found in the 2004–2007 sample; eight (62%) of the 13 species occurred in both samples. Rana boylii is parasitized by generalist helminths that co-occur in other hosts. The aggregate of host species may be more important to parasite community stability than any single host species.
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