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Isolated Individuals (isolated + individual)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Confusion Effect in a Reptilian and a Primate Predator

ETHOLOGY, Issue 8 2000
Carsten Schradin
The confusion effect is claimed to be one benefit of group living with respect to predator avoidance: it is more difficult for predators to capture prey that is surrounded by other conspecifics than to capture an isolated individual. So far, the predictions of the confusion effect have been tested mainly in aquatic predators. As the confusion effect is seen to be a general problem for predators, terrestrial predators of two different vertebrate classes were used to test it. The prey (mealworms and black beetles, Tenebrio molitor) was harmless and had no chance of predator avoidance. Thus, confounding effects of group defence and enhanced vigilance were controlled. Both leopard geckos (Eublepharis macularius) and common marmosets (Callithrix jacchus) took longer to catch one out of several prey compared to one single prey. Leopard geckos showed more fixations (changing of head position) when confronted with 20 mealworms than when confronted with only one mealworm, thus showing indications of being ,confused'. [source]

KILLER WHALE PREDATION ON SPERM WHALES: OBSERVATIONS AND IMPLICATIONS

MARINE MAMMAL SCIENCE, Issue 3 2001
Robert L. Pitman
Abstract In October 1997 we observed a herd of approximately 35 killer whales (Orcinus orca) attack a pod of nine sperm whales (Physeter macrocephalus) 130 km off the coast of central California. During the four hours we watched, adult female killer whales, including some with calves, attacked in waves of four to five animals in what was apparently a "wound and withdraw" strategy. Adult male killer whales stood by until the very end when one charged in and quickly killed a seriously wounded sperm whale that had been separated from the group. The sperm whales appeared largely helpless: their main defensive behavior was the formation of a rosette ("marguerite"-heads together, tails out). When the killer whales were successful in pulling an individual out of the rosette, one or two sperm whales exposed themselves to increased attack by leaving the rosette, flanking the isolated individual, and leading it back into the formation. Despite these efforts, one sperm whale was killed and eaten and the rest were seriously, perhaps mortally, wounded. We also present details of two other encounters between sperm whales and killer whales that we observed. Although sperm whales, because of various behavioral and morphological adaptations, were previously thought to be immune to predation, our observations clearly establish their vulnerability to killer whales. We suggest that killer whale predation has potentially been an important, and underrated, selective factor in the evolution of sperm whale ecology, influencing perhaps the development of their complex social behavior and at-sea distribution patterns. [source]

Psychological Predictors of Internet Social Communication

JOURNAL OF COMPUTER-MEDIATED COMMUNICATION, Issue 4 2002
Sarah A. Birnie
This study investigated the relationship of traditional social behavior to social communication via the Internet in a completely wired campus where every professor uses computers in classroom teaching, each residence is wired to the Internet, and every student is issued a laptop computer. It has been suggested that shy and socially isolated individuals communicate more on the Internet because it provides some protection from social anxiety. However, little research has empirically tested this assumption. In line with social network theory, we proposed, instead, that online social communication would complement or supplement the uses of face-to-face social contact resulting in a positive association between the two forms of social behaviors. We assessed the frequency and intimacy of traditional social behaviors, sociability, and shyness in 115 undergraduates (52 male, 63 female). These variables were then used to predict the frequency and intimacy of Internet social communication. Sociability and the frequency of traditional social behaviors were positively associated with the frequency of Internet social communication. The intimacy of traditional social behaviors was positively associated with the intimacy of Internet social communication. Overall, the findings supported the implications of social network theory in that online social communication appeared to complement or be an extension of traditional social behavior rather than being a compensatory medium for shy and socially anxious individuals. With relation to uses and gratifications theory, however, shyness was associated with increased intimate socializing over the Internet, indicating that traditional and Internet communication are not functionally equivalent. [source]

Palaeoecology Of A Late Devonian Back Reef: Canning Basin, Western Australia

PALAEONTOLOGY, Issue 4 2000
Rachel Wood
Back-reef ecologies within the celebrated mixed carbonate-siliciclastic Late Devonian (late Frasnian) Pillara Limestone of Windjana Gorge, in the Canning Basin, Western Australia, are re-interpreted as being dominated by microbial communities. Proposed microbialites are expressed as weakly-laminated, fenestral micrite, that show unsupported primary voids, peloidal textures, disseminated bioclastic debris, and traces of microfilaments. These grew as either extensive free-standing mounds or columns, often intergrown with encrusting metazoans, or thick post-mortem encrustations upon skeletal benthos. In some cases, microbial encrustations are inferred to have developed in protected cavities formed by progressive burial of the reef. The calcimicrobe Shuguria also shows a preferentially cryptic habit, encrusting either primary cavities formed by skeletal benthos, microbialite, or the ceilings of mm-sized fenestrae within microbialite. A further calcimicrobe, Rothpletzella, formed columns up to 0.3 m high in areas enriched by very coarse siliciclastic sediment. Stromatoporoid sponges with a diverse range of morphologies also formed in situ growth fabrics. Monospecific thickets of closely-aggregating dendroid stromatoporoid sponges (Stachyodes costulata), and platy-laminar forms (?Hermatostroma spp.) were common, as were remarkably large stromatoporoids (Actinostroma spp.) that grew as isolated individuals up to 5 m in diameter. Such sponges showed impressive powers of regeneration from partial mortality, and individual clones may have been capable of substantial longevities of up to 500 years. Actinostroma spp. showed highly complex growth forms including platy-multicolumnar (A. windjanicum), and a hitherto undescribed inferred whorl-forming foliaceous morphology (Actinostroma sp.) reminiscent of the modern photosymbiotic coral Acropora palmata. These complex morphologies formed abundant primary cavities, previously thought to be only rarely developed in association with stromatoporoids.key words: Late Devonian, Canning Basin, reefs, palaeoecology, microbialite. [source]

Variation in gametophyte dominance in populations of Chondrus verrucosus (Gigartinaceae, Rhodophyta)

PHYCOLOGICAL RESEARCH, Issue 4 2008
Alecia Bellgrove
SUMMARY We describe the abundance, including spatial and temporal variability, of phases of the isomorphic Chondrus verrucosus Mikami from Japan. Chondrus verrucosus occurred in a dense (,90% cover) and temporally stable bed on a small, isolated rocky outcrop (Oyakoiwa) in Shizuoka Prefecture. Small vegetative fronds were always much more abundant than large vegetative and fertile fronds over the spring to late summer periods in 1999 and 2000. Over the same period, fertile carposporophytic fronds were generally more abundant than fertile tetrasporophytic fronds, and fertile male fronds appeared infrequently at low densities. Using the resorcinol-acetal test, we determined the proportion of gametophytes and tetrasporophytes in three populations of C. verrucosus: Oyakoiwa and Noroshi (Shizuoka) in the summers of 1999 and 2000 and Kamehana Point (Miyagi) in autumn 2000. All populations had a significantly higher proportion of gametophytes than tetrasporophytes in both years, although gametophytic proportions were lower at Noroshi (,70%) than at Oyakoiwa (,80%) and Kamehana Point (,97%). However, examination of all isolated individuals sampled on Noroshi showed equal proportions of each phase in 1999, but gametophyte dominance (74%) in 2000. Differences in dispersal and spore production between phases are discussed as mechanisms potentially contributing to variation in gametophyte dominance. [source]