Dispersal Of Mammals Research Articles

Small Mammal Distributions in Riparian and Adjacent Habitats of Grand Teton National Park, Wyoming

Riparian ecosystems are among the most productive biological systems providing food, water, shade, and cover for wildlife (Thomas et al. 1979a). Furthermore, they may display a greater diversity of plant and animal species and vegetative structure than adjacent ecosystems (USDI 1986). Thomas et al. (1979a) provide a descriptive definition which characterizes riparian ecosystems by the presence of trees, shrubs, or herbaceous vegetation that require free or unbound water, or conditions that are more moist than those of the surrounding areas. They suggest that more wildlife species depend entirely on or spend disproportionally more time in riparian habitat than any other. Although the importance of riparian vegetation to wildlife has been apparent since the 1970's, its overall importance to vertebrate species has not been widely studied, especially in the western United States (Patton 1977). Elsewhere, there is a paucity of information on the ecological role of small mammals in riparian areas. Because small vertebrate species may serve as an especially important link in the food chain of threatened, endangered, or reintroduced species, and because small mammal species seem to be compacted in environmentally diverse areas, analysis of riparian vertebrate communities should provide important insights in mechanisms of habitat subdivision and utilization. Clearly, riparian areas contain a greater variety of species than adjoining forest or upslope habitats (Cross 1985). The effect of patch shape on the number of species occupying riparian habitats also has received limited attention (Patton 1975). Because riparian habitat consists of a narrow patch, the elongated shape of riparian areas produces a low interior-to­high-edge ratio which may facilitate or enhance ecological processes, especially the production and dispersal of small mammals. Unfortunately, no documentation exists about patterns of mammalian movement along stream corridors (Forman and Godron 1986). Thus, the importance of the relative use of the edge, riparian, and upland areas by small mammals needs to be investigated, especially in forested mountain land, where riparian areas tend to have smaller areal extent and economic value than upslope vegetation (Swanson et al. 1982). The principle objective of our study was to determine if consistent environmental and landscape features could be found in western riparian, edge, and upland communities, and if these features affected residency of small mammals in Grand Teton National Park. Three independent study sites were studied from June, 1991 through October, 1991 in preparation for a proposed long-term analysis of the role of riparian areas in production of small mammals.

Magnetic Stratigraphy of Cenozoic Terrestrial Sediments and Mammalian Dispersal

The existing literature on the correlation of the magnetic polarity timescale to vertebrate mammalian chronology for the Cenozoic is reviewed for all continents except the Soviet Union. The magnetostratigraphic data from North America is the most complete, followed by the Indian sub-continent. Ten criteria for rating magnetostratigraphic studies are established, and the papers reviewed are rated from 1-10, with 10 being the maximum score. The timing of mammalian dispersal is examined against the background of information from magnetostratigraphic studies allied with radiometric dating. North American Land Mammal ages are partly defined on immigrant taxa and the boundaries of the NALMA are based on dispersal events. It has been suggested that dispersal and evolutionary episodes observed in Siwalik sediments were correlative to sea level change deduced from data from benthic Foraminifera. To test this possibility in the general case, dispersal events into North America were determined by using updated values of the boundaries of the NALMA. These boundaries (dispersal events) were compared to the master sea level curve from analysis of benthic Foraminifera. In a majority of cases the dispersal events correspond to inferred drops in sea level. Since dispersals proceed in both directions once a corridor is open, it follows that European Land Mammal ages will tend to be coincident with the North America Land Mammal ages. As close as can be determined this seems to be a correct inference for the Neogene of Europe.

Influence of Simulated Landscape Corridors on House Mouse (Mus musculus) Dispersal

The major objective of this study was to evaluate the influence of contrasting landscape corridors on population dispersal behavior of feral house mice (Mus musculus). Eight 0.1-ha enclosures were divided into two linear systems of four enclosures each. The two end enclosures of each system were planted in oats (Avena sativa). Two 1-m wide corridors connected the end enclosures. Corridors in one system consisted of strips of unmowed vegetation; corridors in the other system consisted of strips of unmowed vegetation plus a split-rail fence. Trials were conducted in early summer, late summer, autumn and winter. Significantly more mice dispersed in the corridors containing the split-rail fence during late summer and autumn, whereas equal numbers dispersed in both corridors in early summer and winter. Significantly more adult males dispersed than did adult females. Population density was not responsible for differences in dispersal rates observed between the two systems. Results suggest that both the vegetative and man-made corridor components influence the dispersal of small mammals within an agricultural landscape.

Effects of Fire on Hypogeous Fungi, Spore Dispersal and Dependent Flora Establishment in Soils

In our initial survey of dispersal of spores into areas disturbed by the 1988 Huckleberry burn, in the John D. Rockefeller Memorial Parkway, we focused on small mammal dispersal of hypogeous ectomycorrhizal fungi which had been touted as a primary means of dispersal (Trappe and Maser 1977, Ure and Maser 1982), and the recruitment and physiognomy of conifer seedlings germinating in the burned areas. Interestingly, the small mammals captured at the Huck burn sites were feeding on both epigeous and hypogeous, as well as, mycorrhizal and non-mycorrhizal fungi. The seedlings that had germinated in the burned areas were non-mycorrhizal until late in the season. These results are somewhat contradictory to hypotheses offered in the literature. For these reasons, additional objectives, such as including both hypogeous and epigeous ectomycorrhizal fungi, were established to examine the process of ectomycorrhizal colonization more closely.

Mammalian Dispersal Patterns: The Effects of Social Structure on Population Genetics

Journal Article Mammalian dispersal patterns: The effects of social structure on population genetics Get access Mammalian dispersal patterns: The effects of social structure on population genetics B. D. Chepko-Sad and Z. T. Halpin[eds.] 1987 University of Chicago Press, Chicago. Paper. xviii + 342 p. Daniel Simberloff Daniel Simberloff Department of Biological Science, Florida State University, Tallahassee FL 32306 Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 91, Issue 4, 1 November 1989, Pages 1014–1015, https://doi.org/10.2307/1368098 Published: 01 November 1989

Are small-scale landscape features important factors for field studies of small mammal dispersal sinks?

Interest in the influence of landscape features on animal movement has been widespread; however, few field studies of the emigration of small mammals from patches of habitat directly consider the effects of the small-scale landscape features. The simulation models of Stamps et al. (1987a, b) and Buechner (1987a, b) suggest that the size of a dispersal sink relative to the size of the source patch, the average distance traveled by dispersers in the sink, the ease with which dispersers cross the edge between the sink and a source patch, and source patch perimeter:area ratio may all be important influences on emigration rates. A review of field studies of small mammal dispersal into sinks suggests that in a substantial fraction of such studies the values of these factors fall within the ranges that the simulation models indicate have the greatest potential effect on emigration rates. New field studies of dispersal sinks that include a consideration of these factors are necessary in order to evaluate the magnitude of the impact of these factors on natural populations.

Mammalian Dispersal Patterns, eds. B. D. Chepko-Sade and Z. T. Halpinn [Review

Mammalian Dispersal Patterns, eds. B. D. Chepko-Sade and Z. T. Halpinn [Review

Population Biology Mammalian Dispersal Patterns: The Effects of Social Structure on Population Genetics B. D. Chepko-Sade Z. T. Halpin

Journal Article Population Biology Get access Mammalian Dispersal Patterns: The Effects of Social Structure on Population Genetics. Chepko-Sade B. D. Halpin Z. T., eds. University of Chicago Press, Chicago, 1987. 342 pp., illus. $19.95 (paper). Sarah Lenington Sarah Lenington Rutgers University, Newark, NJ 07102 Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 38, Issue 10, November 1988, Pages 715–716, https://doi.org/10.2307/1310890 Published: 01 November 1988

Examination of Socially Induced Dispersal in Sigmodon hispidus

Aggressive behavior within small-mammal populations may lead to dispersal of subordinates. Enclosures were used to test if dispersal in cotton rats (Sigmodon hispidus) resulted from group pressure; animals that crossed a 3-m mowed strip in 24 h were classified as dispersers. Animals were tested under two density treatments to identify dispersers, once when no other animals were present (16/ha) and once when three other animals were present in the enclosure (64/ha). The proportion of dispersers from the high-density enclosures was less than that from the single-animal enclosures, indicating that group pressure did not cause dispersal. Dispersal was not related to sex, season, or body mass, but was related to the reproductive condition of females. Reproductive females tended to be nondispersers. Behavioral data were collected by observing paired animals. Males that dispersed from the high-density treatment were more dominant than male nondispersers, suggesting that subordinates were not forced to disperse by more dominant individuals. Female dominance was not related to dispersal, but was confounded by reproductive condition. Several hypotheses include the assumption that social behavior plays a central role in dispersal of small mammals (Gaines and McClenaghan, 1980). Howard (1960) proposed that dispersal results from two separate processes: movement at about the time an animal attains puberty and movement in response to crowded conditions. Lidicker (1975) further refined Howard's ideas and included the suggestion that dispersal results from social subordination (Christian, 1970) to produce the presaturation-saturation dispersal hypothesis. Saturation dispersal occurs when populations are at or near their carrying capacity and social subordinates (juveniles, old animals, and animals in poor condition) are forced to disperse by aggressive social interactions. Presaturation dispersal occurs when conditions are not crowded. Individuals that disperse under these conditions are predicted not to be social subordinates, to be in good physical condition, and to have higher fitness than saturation dispersers. Stenseth (1983) proposed that the term nonadaptive dispersal refer to dispersers forced out of the pop- ulation and adaptive dispersal refer to presaturation dispersal. Dispersal under the genetic- behavioral polymorphism hypothesis (Chitty, 1967; Krebs, 1978; Morris, 1984) also results from social subordination. The proportion of aggressive genotypes increases during the increase phase of a cycle resulting in increased dispersal of subordinates in response to aggression. Different types of dispersers are not components of the social-fence hypothesis (Hestbeck, 1982, 1986). This hypothesis contains the postulate that spacing behavior results in dispersal from central populations into low-density neighboring populations, but, as density increases, aggression within the neighboring populations prevents dispersal from the central population. Although not directly developed for small-mammal populations, the social-cohesion hypothesis (Bekoff, 1977) also incorporates social behavior. Under this hypothesis, dispersal patterns of social mammals (pri- marily canids) are related to the development of strong social ties with littermates. Dispersal resulting from weak social ties occurs among the most dominant and also the most subordinate individuals because dominant individuals are avoided whereas subordinates avoid their litter- mates. Tests of these alternative hypotheses for a species require empirical documentation of details of the relationship between social interactions and the process of dispersal, but such documentation is rare. When the importance of social interactions has been demonstrated in a population, their relation to dispersal can be explored. Several investigators suggested that aggression is an im- portant component of the population dynamics of the hispid cotton rat, Sigmodon hispidus

Reasons for leaving home

Mammalian Dispersal Patterns: The Effects of Social Structure on Population Genetics. Edited by Diane Chepko-Sade and Zuleyma Tang Halpin. University of Chicago Press:1987. Pp.342. Hbk $55, £43.95; pbk $19.95, £15.95.

Late Cenozoic mammals from central Mexico

ABSTRACT Historically, the knowledge of late Cenozoic mammals from central Mexico has been slow in developing. Most early studies did not include stratigraphic controls or meaningful correlations. At present the geology is incompletely known at most fossil-yielding localities. However, research in the past several years, especially in the State of Guanajuato, has provided much needed stratigraphic control relevant to collected fossils. Of the eleven faunas identified in this paper, only the Cedazo (Pleistocene), Las Tunas, Rancho El Ocote, Coecillo, and Rancho Viejo (Pliocene) have this control. These faunas, then, with several taxa reported here for the first time, are considered most important. They provide significant information about changing climates, a trend from humid, warm conditions in the Pliocene to drier and cooler conditions in the Pleistocene, and mammalian dispersals. Most fossils can be derived from North American ancestors; however, South American constituents can be identified beginning in Hemphillian time with the occurrence of sloths, Megalonyx and Glossotherium (Rancho El Ocote). By the late Pleistocene, ten South American genera occur in central Mexico.

Mammalian Seed Dispersal of Pignut Hickory during Three Fruiting Seasons

Seed removal by mammalian predator—dispersers was monitored weekly for Carya glabra (Juglandacea) in an aok—hickory forest of southern Michigan during three fruiting seasons. It was expected that dispersal patterns would be influenced by annual variation in seed crop size. The prediction is that large crop size enables some seeds to escape predation through satiation of dispersal agents. Within a given year, neither size of crops for individual trees nor average weekly nut fall significantly affected weekly proportion of hickory nuts removed. However, among years, proportional disappearance of nuts was slowest during the year with highest seed prodution. During all three seasons, animals removed only a small percentage for nuts, but this pattern was not the results of satiation. Instead, it is more likely due to selective removal of viable nuts. Because virtually all viable nuts were removed from the parent tree, it is concluded that dispersal in hickories is effective in preventing seedling establishment under the parent tree. However, it might be at the cost of high seed predation. Although predator satiation before dispersal was not demonstrated even during the highest seed—producing year, it is possible that postdispersal satiation may have occurred. Results of this study illustrate a relationship between seed production and seed removal that may be found in other nut—producing trees.

A seasonal analysis of small mammal populations on woodlot islands

Ten woodlot islands (surrounded by cornfields) which varied in size and isolation were sampled on a seasonal basis during 1976–1977 to study patterns of small mammal dispersal. The number of small mammal species, density of Peromyscus leucopus, and sex and age ratios of P. leucopus fluctuated on a seasonal basis. During each season island isolation was inversely related to the number of small mammal species and density of P. leucopus. Both island size and isolation were significantly related to density of P. leucopus during the fall. During the winter and spring trapping periods, all P. leucopus on the islands were males. The proportion of males on the islands during the summer and fall was positively related to island isolation. The proportion of adult P. leucopus on the islands was inversely related to isolation during each trapping season.

Absence of ptilodontoidean multituberculates from Asia and its palaeogeographic implications

Gobibaatar parvus Kielan-Jaworowska 1970, formerly the only representative of the Ptilodontoidea in Asia, is recognized to be a junior synonym of Kryptobaatar dashzevegi Kielan-Jaworowska 1970 and allocated to the Taeniolabidoidea. Members of the Ptilodontoidea are thus currently unknown in Asian faunas. Chulsanbaataridae Kielan-Jaworowska 1974 is a junior synonym of the Eucosmodontidae Jepsen 1940. The absence of Ptilodontoidea in Asia gives further support to the theory of one-way Late Cretaceous dispersal of mammals from Asia to North America. The Marsupialia and Ptilodontoidea originated in the New World and never reached Asia, whereas the Taeniolabidoidea and Eutheria originated in Asia and dispersed to North America during the Late Cretaceous.

Mammalian Dispersal and the Ontogeny of Individual Behavioral Phenotypes

Explanations of dispersal mechanisms in mammals that have stressed the importance of aggression by dominant (?) individuals as the immediate cause of the dispersal of less aggressive (more subordinate?) individuals are insufficient for explaining recent data collected on a variety of mammals. In fact, avoidance of social interaction at the time of dispersal is more characteristic of some species in which individuals emigrate. Studies that have investigated genetic correlates of dispersal in rodent populations that undergo regular cycles are few and have not provided any causative explanations. In various canids and rodents, behavioral interactions at the time of dispersal do not appear to provide the necessary stimuli for dispersal. These observations suggest that knowledge of the behavioral interactions that occur before dispersal may provide a key to understanding both interspecific and intraspecific differences in social organization and dispersal patterns. It is suggested that individuals who have t...

The Effects of Roads on Populations of Small Mammals

Little is known about the effects of roads on populations of animals. Pienaar (1968) summarized the possible effects of roads on organisms in a national park, but most workers have been concerned with mortality of animals along roadways (e.g. Simmons 1938; Knobloch 1939; Haugen 1944; McClure 1951; Hodson 1966; Evenden 1971; Bellis & Graves 1971). Roads affect many mammals by facilitating access to food or by increasing the food supply, but they may lead to damaging or fatal accidents. Bellis & Graves (1971) reported that Odocoileus virginiana* often fed on grassy road shoulders and as a result were frequently hit by vehicles. Taylor (1971) related the numerous skeletal fractures in east African viverrids to their habit of catching prey along roadways. In contrast, road verges provide a ready supply of grass and this has allowed some microtines to flourish and even expand their ranges (Baker 1971). In other cases, road verges provide important habitats for conservation of plants and animals (Anon. 1966; Kabat & Thompson 1963; Joselyn, Warnock & Etter 1968). However, roadside soil and vegetation are often contaminated by lead and other heavy metals used as additives in gasoline (Lagerwerff & Specht 1970; Smith 1971) and vegetation may be severely injured by high levels of sodium chloride (Hofstra & Hall 1971). Roads and railways have been found to inhibit the movements of feral Rangifer tarandus, but not those of domestic R. tarandus (Klein 1971). Studies of the effects of roadways on the dispersal of mammals are lacking although Buckner (1957) reported some data for Clethrionomys gapperi. This study documents the effects of roadways on the movements of small and mediumsized mammals (small mammals less -than 700 g; medium-sized mammals 700 to approx. 14 000 g) obtained from capture-recapture studies and from direct observation of roadways. The term road 'clearance' used in this paper, refers to the distance an animal had to move between forest margins to cross the roadway. Clearance may be equivalent to right-of-way, but this is not always the case.

Distribution of Recent Mammals Along the Pacific Coastal Lowlands of the Western Hemisphere

Coastal lowlands on the western side of the Americas are irregularly narrow and squeezed between the shoreline and adjacent montane country. The 407 species belonging to 189 genera (marine and insular forms excluded) that are recorded as living on this coastal strip are best arranged in sectors north to south as follows: in Nearctica, the Tundran (67°N to 61°N) with 25 species; the Coniferan (61°N to 38°N) with 92 species; the North Eremian (38°N to 26°N) with 114 species; and in Neotropica, the North Subtropical (26°N to 16°N), a temperate-tropical transition with 109 species; the Tropical (16°N to 7°S) with 267 species; the South Eremian (7°S to 29°S) with a minimum of 18 species; the Nothofagian (29°S to 55°S) with 35 species; and the Patagonian (50°S to 55°S) with a minimum of 10 species. Northern sectors in Nearctica, somewhat comparable ecologically to southern sectors of Neotropica, are endowed with from two to six times as many species as the latter. Factors accounting for the paucity of species in southern sectors include (a) the progressive reduction of species as living space in continental South America dwindles in a southward direction, (b) the extreme narrowness of lowlands along much of the South American coast and (c) the abrupt insertion of sparsely-inhabited deserts (South Eremian Sector) in an otherwise latitudinally favorable environment of South America blocking north-south movements and preventing intermingling of tropical and temperate species, as has occurred in coastal North America. Holarctic species are conspicuous in the Tundran Sector but diminish rapidly to the southward, although 5 Holarctic genera are represented in Southern Chile. Our current knowledge of the distribution of Pacific coastal mammals indicates that their lowland habitats must be beset with assorted kinds of barriers to deter north-south dispersal of most mammals so that more than one-half (62 per cent) of the species are known only from single sectors. Consequently, mammalian affinities may be with inland faunas, in the Cordillera or the Atlantic coastal lowlands, rather than to sectors either north or south along the Pacific coast.

Mammalian Dispersal in Relation to an Artificial Land Bridge

Mammalian Dispersal in Relation to an Artificial Land Bridge