Patterns Of Space Utilization Research Articles

Predicting Spatial Patterns of Plant Recruitment Using Animal-Displacement Kernels

For plants dispersed by frugivores, spatial patterns of recruitment are primarily influenced by the spatial arrangement and characteristics of parent plants, the digestive characteristics, feeding behaviour and movement patterns of animal dispersers, and the structure of the habitat matrix. We used an individual-based, spatially-explicit framework to characterize seed dispersal and seedling fate in an endangered, insular plant-disperser system: the endemic shrub Daphne rodriguezii and its exclusive disperser, the endemic lizard Podarcis lilfordi. Plant recruitment kernels were chiefly determined by the disperser's patterns of space utilization (i.e. the lizard's displacement kernels), the position of the various plant individuals in relation to them, and habitat structure (vegetation cover vs. bare soil). In contrast to our expectations, seed gut-passage rate and its effects on germination, and lizard speed-of-movement, habitat choice and activity rhythm were of minor importance. Predicted plant recruitment kernels were strongly anisotropic and fine-grained, preventing their description using one-dimensional, frequency-distance curves. We found a general trade-off between recruitment probability and dispersal distance; however, optimal recruitment sites were not necessarily associated to sites of maximal adult-plant density. Conservation efforts aimed at enhancing the regeneration of endangered plant-disperser systems may gain in efficacy by manipulating the spatial distribution of dispersers (e.g. through the creation of refuges and feeding sites) to create areas favourable to plant recruitment.

Altered behaviour in spotted hyenas associated with increased human activity

AbstractTo investigate how anthropogenic activity might affect large carnivores, we studied the behaviour of spotted hyenas (Crocuta crocuta) during two time periods. From 1996 to 1998, we documented the ecological correlates of space utilization patterns exhibited by adult female hyenas defending a territory at the edge of a wildlife reserve in Kenya. Hyenas preferred areas near dense vegetation but appeared to avoid areas containing the greatest abundance of prey, perhaps because these were also the areas of most intensive livestock grazing. We then compared hyena behaviour observed in 1996–98 with that observed several years earlier and found many differences. Female hyenas in 1996–98 were found farther from dens, but closer to dense vegetation and to the edges of their territory, than in 1988–90. Recent females also had larger home ranges, travelled farther between consecutive sightings, and were more nocturnal than in 1988–90. Finally, hyenas occurred in smaller groups in 1996–98 than in 1988–90. We also found several changes in hyena demography between periods. We next attempted to explain differences observed between time periods by testing predictions of hypotheses invoking prey abundance, climate, interactions with lions, tourism and livestock grazing. Our data were consistent with the hypothesis that increased reliance on the reserve for livestock grazing was responsible for observed changes. That behavioural changes were not associated with decreased hyena population density suggests the behavioural plasticity typical of this species may protect it from extinction.

Estimation of short-term centers of activity from an array of omnidirectional hydrophones and its use in studying animal movements

A method for studying animal movements based on data from independent data-logging acoustic receivers is described. The method takes presence or absence data from multiple receivers arranged in an array and converts them to position estimates based on weighted means of the number of signal receptions at each receiver during a specified time period. The method is equivalent to a short-term center of activity rather than a precise estimate of location at a single time. The utility of the method was assessed using data from a study of neonate blacktip sharks (Carcharhinus limbatus). Periods between 5 and 60 min were tested to find the most appropriate interval for estimating positions. The results from the method agreed closely with a simulated shark track and data from actively tracked sharks. The median distances between successive locations from the mean-position algorithm were between 28% and 42% of those from active tracking because of the center-of-activity nature of the method. The results presented demonstrate that the technique provides a useful method for investigating long-term movement patterns, space utilization patterns over broader areas, and home range.

Teneur azotée des ressources et choix trophiques du Mulot sylvestre (Apodemus sylvaticus) dans un système oligotrophe

The nitrogen content of plant tissue is an essential factor for the growth and survival of many wild phytophagous vertebrates. We tried to analyse the trophic choices of the wood mouse (Apodemus sylvaticus) in relation to the nitrogen content of various plant organs in a heathland, a common ecosystem in Brittany. Patterns of plant resources utilisation observed in this ecosystem show that this rodent species always selects concentrated resources, namely energy- or nitrogen-rich plant tissues. In other respects, the ingestion of animal prey in quantities varying according to the availability of highly nutritious plant resources is another adaptive response to this selection pressure. This strategy of nitrogen allocation based on seed and insect eating is compared with those observed in various other small rodents and correlations with their demographic and space utilization patterns are discussed.

The effect of early experience on aggression in two territorial scorpaenid fishes

The impact of population density and shelter availability on the development of aggressive behavior in two species of rockfishes, the black and yellow rockfish, Sebastes chrysomelas, and the gopher rockfish, Sebastes carnatus, were examined in this study. Adults of these species are typically territorial though other patterns of space utilization are observed. Dominance does not appear to account for these patterns. Since the level of aggressiveness seems to vary between groups, differences in early experience might play a role in determining adult behavior patterns. Laboratory experiments were performed on juveniles captured prior to settlement in which the aggressive tendencies of individuals were assessed by focusing on the development of displays toward a mirror image over a six month period. The results of this study suggest that the repertoire of agonistic behaviors used by adults is available to juveniles though seldom seen in the field. Increased population density and the availability of a shelter increase aggressiveness in S. carnatus and the effects of density were not reversible over the course of the experiment. The behavior of S. chrysomelas was less influenced by the manipulations.

Seasonal Shifts in Body Temperature and Use of Microhabitats by Galapagos Land Iguanas (Conolophus Pallidus)

Seasonal differences in the body temperatures (Tb) of free—ranging Galapagos land iguanas (Conolophus pallidus) were detected by temperature sensitive telemetry transmitters. Midday Tb's of iguanas average 4.4°C lower in the Garua (cool) season than in the Hot season. Measured Tb's and those predicted from biophysical models permitted the following conclusions: (1) lower Tb's during the Garua season represent an active shift in thermoregulation by the iguanas rather than a passive result of a cooler season; (2) the average midday Tb selected by the iguanas in either season is the Tb that allows maintenance of a constant Tb for the longest possible portion of the day; (3) by exploiting the warmer microclimate created by a cliff face, the iguanas are able to maintain a constant Tb for a full hour longer than they could elsewhere in their home range. Census data demonstrated that the iguanas exploited the warmer microclimate created by the cliff extensively during the Garua season, and the cliff face was visited by the iguanas relatively infrequently during the Hot season. Thus, the exploitation of the microclimate created by the cliff results in seasonal differences in the pattern of space utilization within the home ranges of the iguanas. Within the Garua season the iguanas moved away from the cliff more often on sunny days than during cloudy days. It is concluded that the physical environment is an important determinant of patterns of space utilization both within and between seasons.

Alternative space futures: The next quarter-century

Space developments do not exist in a vacuum! The shape of future space activities will depend on a combination of social, economic and political forces, creating the determinants for different patterns of space utilization. Forecasts of alternative space futures can therefore be explored by integrating different scenarios of world development and space trends. Here, alternative world trends are related to the underlying dynamics of space development, in terms of the economic, military and scientific utilization of space. The importance of space as a political issue is thus emphasized, in that the outcomes of policy choices to be made both now and in the future will help shape the social and economic contexts in which space technology will be used in the decades ahead.

Predation and space utilization patterns in a marine epifaunal community

The relative abundance patterns of several sessile epifaunal species occurring subtidally on large artificial substrata (pilings) were examined under experimental conditions involving the manipulation of densities of the echinoid Arbacia punctulata (Lamarck). The foraging activities of this predator could denude the substratum of most species with notable exceptions including the colonial hydroid Hydractinia echinata Fleming and the sponge Xestospongia halichondroides (Wilson). Moreover, these were the only two of the twenty most common species which did not significantly change in relative abundance over the experimental period. Both species had low recruitment rates and were commonly associated with substrata which had been submerged for several years. Neither species aggressively interacted with adjacent spatial competitors but instead, appeared to employ a defensive space utilization ‘strategy’. Provision of unoccupied substrata by Arbacia was apparently the major factor favoring both recruitment and growth of Hydractinia, which covered up to 30% of the area on the oldest pilings. More recently submerged substrata were covered by species such as Schizoporella errata (Waters) which had a much higher recruitment rate but was commonly overgrown by several other species. Recruitment rate, competitive ability, and vegetative growth are discussed in terms of the size of the substratum and the possibility of biased sampling in fouling studies. The widespread introduction of large artificial substrata into the natural environment has considerably altered the structure of the natural habitat and constitutes a potentially important selective force for changes in settlement preferences, especially among species such as Hydractinia which persist and become abundant on these substrata.

Patterns of agonistic interaction and space utilization by agoutis ( Dasyprocta punctata)

Field observation revealed that, in the months of food scarcity, normally solitary and minimally interactive agoutis (Dasyprocta punctata) aggregate at rich feeding sites and form dominance hierarchies. An individual agouti's position in such a hierarchy is uncorrelated with its previous frequency of utilization of the feeding site. The results are discussed as an example of plasticity in mammalian social organization in response to exogenous and endogenous variables. The type of social organization exhibited by subpopulations of many mammalian species in their natural habitats has been found to vary as a function of environmental conditions (see for examples; Rowell, 1969; Wilson, 1975). The present studies were undertaken, first, to provide a description based on direct observation of the normal pattern of space utilization and social interaction of a wild rodent population and, second, to determine the effects of variation in resource distribution on those patterns of interaction observed. The subject species, the agouti (Dasyprocta punctata), is a particularly suitable rodent for such studies because of its diurnal pattern of activity (Smythe, 1970), relatively large size (2-4 kg), small home range (2-3 hectare, Smythe, 1970), surface dwelling habits, and the relative ease with which individuals become habituated to the presence of human observers within their home ranges (Galef and Clark, 1976). Observations of agouti behavior were carried out in the Allee Creek ravine immediately adjacent to the Smithsonian Institution field station on

Space utilization of Peromyscus: Social and spatial factors

Space utilization of Peromyscus maniculatus bairdi and P. leucopus noveboracensis was studied in laboratory enclosures. After 1 week, individuals were given access to twice as much space for an additional week. The new area was either vacant or was occupied by a similarly experienced conspecific of the same or opposite sex. Patterns of space utilization and reaction to the doubling of space were species specific. Each species displayed specific patterns of social behaviour and only P. maniculatus reproduced. Both species exhibited similar patterns of space utilization in the presence of another individual. Social regulation of space utilization did not result from territorial defence of mutually exclusive areas, but from the initial mutual avoidance of two individuals.

Organization of the New England Rocky Intertidal Community: Role of Predation, Competition, and Environmental Heterogeneity

Organization of the New England Rocky Intertidal Community: Role of Predation, Competition, and Environmental Heterogeneity

Patterns of space utilization and group interactions among free-rangingMacaca mulatta

Patterns of space utilization and group interactions were studied using four social bands of free-ranging rhesus macaques at La Parguera, Puerto Rico. There were 0.26 group interactions/hr. of observation; 90% of the observed encounters occurred at feeder stations. Nineteen percent of the interactions involved actual fighting between monkeys from opposing social bands, 58% involved visual and/or vocal threats, 20% were group displacements without aggression and on 3% of the occasions the two groups mixed amicably. Group size was an important factor affecting both the dominance position of the social group and the group's use of space; larger groups were dominant, moved freely about the island, and used less of the total space than smaller lower-ranking troops. Smaller troops were continually forced to move about the island. A new troop of intermediate size added to the island colony provided an experimental test and validated these conclusions regarding group size, dominance and use of space. Patterns of space utilization for each group shifted seasonally, annually, and possibly in response to the addition of the new social troop.