Shelter Selection Research Articles

Effect of age, injury, and predator odors or settlement and shelter selection by lobster Homarus amencanus postlarvae

Effect of age, injury, and predator odors or settlement and shelter selection by lobster Homarus amencanus postlarvae

Shelter preferences in the Mediterranean slipper lobster: effects of physical properties

The physical properties of shelter and biotic factors associated with shelter selection were studied in the Mediterranean slipper lobster Scyllarides latus (Latreille) in both the field and laboratory. In laboratory experiments, lobster significantly preferred a shaded cover or an opaque shelter to a transparent shelter of the same dimensions. No preference was exhibited by lobsters between a shaded transparent shelter and an opaque shelter. Lobsters also demonstrated a significant preference for shelters with more than one opening and for those that were in a horizontal as opposed to vertical position. They also tended to shelter together with other conspecifics. S. latus preference for horizontal dens with a small entrance, close to the substratum and with multi-openings were observed in natural and artificial reefs. Tendencies for cohabitation, shelter sharing with moray cels, and bringing clams to the shelter after night foraging, were also etected among field lobsters. No correlations between the various sheltering behaviors and sex or size of lobsters were found. It is suggested that these characteristics are anti-predator adaptations of S. latus which lack any morphology for active defense.

Variations in Disaster Evacuation Behavior: Public Responses Versus Private Sector Executive Decision‐Making Processes

Data obtained from 65 executives working for tourism firms in three sample communities permitted comparison with the public warning response literature regarding three topics: disaster evacuation planning, initial warning responses, and disaster evacuation behavior. Disaster evacuation planning was reported by nearly all of these business executives, although it was highly variable in content, completeness, and formality. Managerial responses to post-disaster warnings paralleled the type of complex social processes that have been documented within the public response literature, except that warning sources and confirmation behavior were significantly affected by contact with authorities. Five key areas of difference were discovered in disaster evacuation behavior pertaining to: influence of planning, firm versus family priorities, shelter selection, looting concerns, and media contacts.

Shelter Selection by Spiny Lobster Under Variable Predation Risk, Social Conditions, and Shelter Size

Shelter use patterns of den—dwelling Caribbean spiny lobster, Panulirus argus, appear to be regulated by predation risk. The risk of predation may be modified by (1) social structure, which alters the effectiveness of communal defense, and (2) the scaling between lobster size and shelter size, which enhances the protective capacity of the den. These hypotheses were tested with field enclosure experiments using artificial lobster shelters, which examined the effects of predation risk (i.e., presence or absence of a major predator, the nurse shark Ginglyostoma cirratum), spiny lobster size, social condition (i.e., presence or absence of conspecifics), and shelter size upon den choice by juvenile and adult P. argus. To corroborate the findings of the enclosure experiments we also quantified seasonal, size—specific abundance patterns of P. argus in the field by deploying artificial lobster shelters (casitas) of different sizes in two habitats that differed primarily in the potential for gregarious interactions: an inner—bay, sand seagrass flat with high lobster densities, and an outer—bay, seagrass bed adjacent to coral reefs with sparsely distributed lobsters. The experimental and observational field results were strikingly similar–social condition and the scaling of lobster size to shelter size jointly regulated den choice patterns of adult and juvenile Panulirus argus, particularly under high predation risk. When conspecific density and predation risk were low, lobsters resided primarily in shelters whose dimensions were scaled to their own; when conspecific density was high and predation risk was low, lobsters resided predominantly in large shelters offering the highest potential for gregariousness; when conspecific density and predation risk were high, lobsters shifted to gregarious habitation in smaller, scaled shelters; and, when predation risk was high and conspecific density was low, lobsters occupied smaller shelters. The frequency of gregariousness in the field was much higher at the inner—bay site, where lobsters were dense, than at the outer—bay site, where lobsters were sparse, even accounting for the difference in lobster density between sites. This study indicates that the density of conspecifics in a given habitat can enhance gregariousness in spiny lobsters, which in turn influences the relative impact of lobster size, shelter size, and predation risk upon den choice. In defining the critical determinants of den choice for P. argus, we also provide an empirical and conceptual framework for identifying how variation in the availability of resources, such as conspecifics and appropriately scaled refuges, influence the distribution and abundance of social, shelter—dwelling species.

Benthic invertebrate larval response to substrate characteristics at settlement: Shelter preferences of the American lobsterHomarus americanus

The factors controlling shelter selection by the first post-larval stage of the American lobsterHomarus americanus were studied in the laboratory in 1988 using an experimental approach. The relative importance of shelter size, light level within shelters, number of shelter entrances, and presence of algal-film cover in and around them were investigated. Post-larvae showed a strong preference for opaque versus transparent shelters. No difference in post-larval selectivity was observed either for shelters of different widths or heights or between shelters with different numbers of entrances. Post-larvae showed no preference for microhabitats colonized by microorganisms compared to others without colonization. The intensity of the response measured suggests a possible hierarchical organization of the different cues involved in shelter selection, the light level within the shelter apparently being the most important. Simple linear regression was used to assess the effect of shelter area on the number of post-larvae occupying a shelter. Up to four post-larvae were observed simultaneously in a shelter of 40 cm2 basal area, indicating that they can cohabit at settlement. The minimum shelter area necessary to the first post-larval stage was estimated to be about 3.25 cm2. The results are discussed with reference to recent hypotheses concerning the mechanisms controlling larval settlement in other benthic species with relatively weak mobility during the larval and the post-larval phases.

Shelter selection by a small mammal community in the wet-dry tropics of Australia.

The location of shelter used by nine species of small mammals released after capture during a mark-recapture study in tropical woodland and open forest was recorded whenever possible. A quantitative profile of such post-release behaviour by different species permits its incorporation into analyses of habitat selection. Characteristics of post-release behaviour also provide clues about the nature of predation pressure on various species. Arboreal species tended to select tree species with boles having camouflage potential. Small species used small holes. Scansorial species used the greatest range of sheltering sites. Average distance moved to shelter was inversely related to the mean density of a species.

Seasonality and shelter selection by the slipper lobster Scyllarides latus in the southeastern Mediterranean

Patterns of migration, abundance and shelter selection by Mediterranean slipper lobsters Scyllarides latus were studied in artificial shelters placed on the shallow continental shelf off the coast of Israel. Underwater censuses and tagging experiments over >3 yr indicated a seasonal pattern of adult lobster abundance in shallow water. Lobsters' appearance at the site was associated with low water temperature m winter. They disappeared from shallow water in the study area from mid-summer to late fall. Preliminary data of recaptured tagged lobsters suggest that they migrate northwards and to deeper water. Such long-term migration may be triggered by the high, and perhaps unfavorable, mid-summer temperature in the shallow coastal habitats. It is hypothesized that the continuous stay of slipper lobsters in deeper water through late fall may be a physiolo~cal/behavioral adaptation to molting occurring in this period. During their stay in shallow water lobsters tended to remain in the artificial shelters complex and its vicinity. They dwelt in shelters during the day and foraged at night, mainly for bivalves, of which some were brought back to dens before daylight. Analysis of lobster recruitment to artificial reefs of different design indicated preference for lower, horizontal dens with small apertures. Habitats rich w i t h such she!ters arc very limited aiong the ilat bottoms of the littoral southeastern Mediterranean. Since sheltering in such dens presumably reduces the risk of predation by diurnal predators, it is advantageous for lobsters to return to these preferred sites after short as well as long-term movements.

Laboratory observations of aggregative behavior of garter snakes, Thamnophis sirtalis: Roles of the visual, olfactory, and vomeronasal senses.

Two experiments were conducted to determine (a) whether male garter snakes (Thamnophis sirtalis) require a functional vomeronasal or olfactory system to return to previously preferred shelter locations and (b) the sensory modalities used by snakes to aggregate in the absence of previously deposited chemical cues. In Experiment 1, snakes with vomeronasal nerve lesions did not return to previously preferred shelter locations when tested individually. However, when tested with a group that included "control" animals, they returned to previously preferred shelters. The shelter-selection behavior of snakes with olfactory nerve lesions improved postoperatively, whereas the behavior of animals with sham lesions was unchanged. In Experiment 2, snakes were tested for aggregation in aquaria in which the substrate and other contents were cleaned between trials. After blindfolding or after olfactory nerve cuts, snakes aggregated at normal levels. When the snakes' vomeronasal ducts were sutured closed, aggregation scores were significantly depressed, although two of the three groups with vomeronasal duct sutures did aggregate just above chance levels. These studies indicate that use of chemical signals by garter snakes in shelter selection and aggregation is mediated by the vomeronasal system and that neither the olfactory nor the visual system is critical for these behaviors.

The Shelter‐Related Behavior of the Losbter, Homarus Americanus

Some of the relationships between a lobster (Homarus americanus) and the dimensions of its shelter have been examined. Field studies showed that lobsters generally occupied shelters in which the height was less than the width, and that there was a correlation between lobster size and shelter size. In the laboratory lobsters chose low profile shelters when given a choice of flat (height = ½ width) versus square (height = width) profile openings. Back doors were often present in the field, and laboratory experiments suggested that some sort of constriction before the rear opening was necessary to qualify it as a back door. The amount of time spent in eight opaque or transparent shelter under bright, dim, and dark illumination was measured. In bright and dim light with opaque shelter, lobsters spent significantly more time in a shelter than in the other treatments, showing darkness to be major factor in shelter selection. Shelters are excavated by pushing sand or gravel with the third maxillipeds in a bulldozing motion or by digging with the first two or three pairs of walking legs, followed by a vigorous fanning of the pleopods.

棲所に関するイセエビの習性について

During the daytime, Japanese spiny lobsters hide themselves in fissures and crevices of the rocky bottom, and shores with more of such shelters are better fishing grounds for the lobsters. At a good shelter, a “mizuki**” fisherman catches lobsters many times during the same season. In order to investigate the habit of shelter selection by the lobster, experiments were conducted, using a reserve pond and an aquarium. The experimental results are as follows. (1) Although the reserve pond and the aquarium had no suitable shelter, the lobsters in them were distributed in the daytime not at random but with preference depending upon the place. When several rocks were piled on the bottom for a shelter, many individuals gathered there. (2) The number of lobsters gathering in the artificial shelter of rocks was determined by its shape and construction, and by the total number of lobsters present in the aquarium. (3) When the size and construction of the shelter and the total number of lobsters were kept unaltered, the number of individuals gathering in the shelter became constant in a few days after the beginning of experiment, the rest of the animals getting settled at the most preferable parts of the aquarium. If some individuals were removed from the shelter under this condition, the decrement was filled up by recruitment from other places, and the previous number at the shelter was recovered within a few days. (4) When a shelter was constructed with several oblong rocks piled in such a way that holes of 10×l5×30cm were made among the rocks, the following relation was obtained between the total number of lobsters in the aquarium (x) and the number gathering in the shelter (y). y=a(x-A)b+A where, A, b and a are constants representing a limit within which all individuals gather in the shelter, a coefficient determined by the shape of the holes, and that determined both by b and the number of holes, respectively.