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No description available.

No description available.

No description available.

No description available.

Agonistic behaviour was investigated by means of staged encounters in three species and two subspecies of deserticolous rodents of the genus Gerbillurus Indiviuals of the species G.paeba paeba, G.paeba exilis, G. tytonis, G. setzeri, and G. vallinus were used in intraspecific and interspecific encounters. Intraspecific territoriality was tested in animals of the same sex G.paeba paeba, G. tytonis, and G. setzeri Analysis of agonistic behaviour permitted identification of four groups of behaviours in most classes of intraspecific encounters. These were "exploratory and solitary", "aggressive", "submissive", and "sexual" behaviours. Males of four species were less aggressive than females in same-sex encounters, and were dominated by females in different-sex encounters; the reverse was observed in G. setzeri. Male G. tytonis and G. setzeri were more tolerant of conspecifics in the territoriality apparatus than females were. In G. tytonis-G.p. paeba encounters a hierarchy emerged: female G.. tytonis were most aggressive, followed by female G.p. paeba, male G. tytonis, and finally male G.p. paeba. In areas of syntopy, G. tytonis displace G.p. paeba through aggressive interactions. A reduction in the level of aggression was exihibited in G.p. paeba-G. setzeri and G. tytonis-G. interactions. This result may reflect the phylogenetic divergence and selection of a different habitat by G. setzeri. G. vallinus dominated G.p. paeba, a result which may have been influenced by past experience and body size, since these two species are syntopic and G. vallinus is larger than G.p. paeba. Cluster analysis of behaviour profiles of different species and sexes revealed two groups, which agree partially with the karyology of the genus. G.p. paeba and G. tytonis formed one cluster, while G. setzeri and female G.p. exilis formed a second group. Male G.p. exilis and G. vallinus were less closely related to both groups. It is suggested that several stages in the process of speciation are represented in species of this genus . A range of social types is exhibited from solitary (G.p. paeba and G. tytonis) through semi-tolerant (G. setzeri and G. tytonis) through semi-tolerant (G. setzeri and female G.p. exilis) to tolerant (male G.p. exilis and G. vallinus). Habitat has a strong influence on social type. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg.

The effects of response-independent mirror presentation schedules on the swimming behaviour of Betta splendens were studied in two experiments. In experiment 1, four fish received alternating baseline (no mirror) and fixed-time (FT) 2-min or variable-time (VT) 2-min mirror presentation conditions. Two fish consistently showed increased rates of mirror-side lap-swimming (MSLS; a back-and-forth swimming pattern) and decreased distance from the mirror during the inter-stimulus intervals (ISIs) of FT and VT sessions, and during baseline sessions that followed FT and VT phases. Data from one fish indicated that a VT schedule might increase both proximity to the mirror and MSLS rates that have decreased on FT. Therefore, in experiment 2 three fish from experiment 1 received alternating FT and VT conditions. Proximity to the mirror and MSLS rates increased during VT phases relative to FT phases in two fish, though effects were small and did not occur across all alternations. Additional findings were that MSLS during ISIs tended to increase within FT phases, that MSLS generally occurred either at a steady rate within ISIs or showed a scalloped effect, that mirror presentations produced approach to the mirror side that persisted during ISIs and subsequent baseline phases, and that mirror-side distance during the mirror presentations was less than during the ISIs. Although the findings were not consistent across all fish, they were replicated a number of times within at least two of the fish. The findings are discussed in terms of adventitious operant conditioning, respondent conditioning, and the behaviour systems approach. The results of this study increase the generality of response-independent schedule effects on locomotive behaviour.

The fate of farmed fish after escape is poorly understood. The extent to which these fish might impact freshwater ecosystems is dependent upon their survival and distribution in the wild. I simulated small- and large-scale escape events from two commercial aquaculture operations in Lake Huron over 2 years. I combined the use of telemetry (120) and Floy (1000) tags to determine the fate of escaped farmed rainbow trout (Oncorhynchus mykiss). Once released, escapees dispersed rapidly, showed low site fidelity (~15% after 3 months) and were capable of long distance movements (up to 360 km). Rainbow trout experienced low survival (~50%) but maintained high growth rates both at and away from the farms. The results of this study provide a strong basis for understanding the potential risks that farmed fish may pose to the Lake Huron fish community and ecosystem in an escape event.

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No description available.