Showing papers by "University of Stirling published in 1983"

Optic-Flow and Cognitive Factors in Time-to-Collision Estimates

Abstract: Time-to-collision (Tc) estimates were obtained from twenty-four subjects who viewed film clips for varying lengths of time. The film clips showed the view from a moving car travelling towards a stationary target car, but ended 100 m before reaching the target. Viewing time varied from 2 to 6 s, approach velocity from 40 to 100 km h-1, and Tc from 3.6 to 9.0s. It was hypothesised that, if time were needed to calculate Tc, the accuracy of Tc estimates would increase with viewing time up to some maximum. However, the results showed no effect of viewing time, and this was taken to indicate that estimates were based upon information directly available from the changing optic array at the eye of the observer. A significant velocity effect was found, accuracy increasing with velocity. Since velocity was inversely correlated with Tc, this probably implies that accuracy decreases with increasing Tc. Sex differences were found, with males giving higher and more accurate estimates than females. The relevance of these findings to the nature of Tc information is discussed.

Social organization of savanna-dwelling chimpanzees, Pan troglodytes verus , at Mt. Assirik, Senegal

Abstract: A community of chimpanzees at Mt. Assirik in south-eastern Senegal subsists in a hot, dry and open environment. This wide-ranging, savanna-living group provides an opportunity for comparisons of social organization with other population elsewhere in Africa living in forest and woodland. The group numbered about 28 over the four-year study, and its composition by age and sex was typical. The average size of parties (i.e., temporary sub-groups) did not differ from other populations. However, a high proportion of the group tended to remain together in such parties. The composition of parties resembled that found elsewhere, but some differences emerged between the wet and dry seasons. Larger, mixed parties containing adult males were much more common in open, non-forested habitats than were solitary individuals or parties without adult males. Large parties tended to form for travelling, especially for rapid movement over long distances. Such aspects of social organization seem unlikely to be related to the availability of food in any simple way. Instead, they seem to be adaptations to threat from predators and patchily distributed food, water and nesting sites. This results in occasional bivouacs and mass-migrations from one part of the home-range to another, especially in the dry season.

Short-Term Visual Memory

Abstract: Serial position effects in visual memory are presented as evidence for a short-term memory for visuo-spatial information that is not plausibly explained in terms of either verbal or sensory representations. This is called visualization, and is distinguished from long-term visual memory. Cases of head injury are reported in which long-term memory is affected but not visualization. In contrast with this, mental arithmetic interferes with visualization but not with long-term memory. Further studies are reported that throw doubt on the earlier explanation of this interference in terms of competition for a central executive or strategic coordinator. The significance of these findings is discussed in relation to a proposal for classifying the main kinds of information represented in higher visuo-spatial cognition.

Hybrid solar/combustion powered receiver

Abstract: An improved hybrid solar/combustion powered receiver, for use e.g. with a hot gas engine, the receiver being of the type having a housing and an aperture for admitting solar radiation to the cavity defined by the housing. The improved receiver includes a heat exchanger within the cavity and having the tubes tangentially spaced; multiple burners for providing a combustion gas flow path during combustion powered operation between and around the portions of the tubes upon which solar radiation impinges; and a fused silica, internally mounted window to seal the aperture against combustion gas leakage out of the receiver.

Animal foods in the diets of wild chimpanzees (Pan troglodytes): Why cross-cultural variation?

Abstract: The common chimpanzee (Pan troglodytes) in nature is an omnivore, i.e. it eats animals as well as plants. Six long-term field studies reveal differences in diet amongst populations of chimpanzees in east, central and west Africa. Specific comparisons can be made for social insect (ants, bees, termites) and mammalian (primates, ungulates) prey. Most of the differences can be explained in terms of environmental influences: presence or absence of prey species, abundance and distribution of prey, range of potential prey secies, competing predators, characteristics of habitat, human interference. However, other differences appear to reflect true social customs, independent of the bio-physical environment, and therefore can be termed cross-cultural.

Chimpanzees of Sapo Forest, Liberia: Density, nests, tools and meat-eating

Abstract: Two months were spent surveying for chimpanzees (Pan troglodytes verus) in the Sapo Forest, eastern Liberia. The population density, as estimated from the number of nests found on transects, appears lower than that in other forest sites. Nests were more similar to those of other forest-living chimpanzees than of a savannah population. Most nests were found in areas of primary forest. Evidence was found of the chimpanzees using stones as hammers to break open four species of nut; there may be differences in materials and techniques used in this behaviour between Sapo chimpanzees and those in Tai Forest, Ivory Coast. Analysis of faeces revealed that Sapo chimpanzees eat meat.

The adhesion of Vibrio anguillarum to host tissues and its role in pathogenesis

Abstract: . Vibrio anguillarum was shown to adhere to excised sections of rainbow trout gut in numbers which were a function of the concentration of bacterial cells and the time for which the tissue was exposed. Using a standardized method for assaying adhered bacteria the course of infection with vibriosis in rainbow trout was studied. It is suggested that the gut may be an important site of bacterial multiplication in slowly developing infections of mature fish. Bacteria adhere to gut sections of fish protected by vaccination substantially less than to sections from non-vaccinated fish.

Factors influencing the uptake of 14C‐labelled Vibrio anguillarum vaccine in direct immersion experiments with rainbow trout, Salmo gairdneri Richardson

Abstract: The factors influencing the uptake of a 14C-labelled Vibrio anguillarum vaccine in direct immersion experiments with rainbow trout, Salmo gairdneri were studied. Immersion times of longer than 10 s did not increase vaccine uptake. A pre-immersion dip in a hyperosmotic solution had no effect on uptake, even at lower vaccine bath concentrations. It appeared that the head end of the fish was implicated in uptake. Vaccine uptake decreased at lower temperatures, whereas the use of an adjuvanted vaccine and a soluble vaccine preparation led to increased uptake. Larger fish took up more vaccine.

Energetics and Growth Patterns of Three Tropical Bird Species

Abstract: --Energy budgets and growth data are presented for nestlings of three species of tropical insectivores: White-bellied Swiftlets (Collocalia esculenta), Blue-throated Bee-eaters (Merops viridis), and Pacific Swallows (Hirundo tahitica). A comparison with temperate nestlings, matched for body size, shows that the peak energy demand in our tropical sample averaged around 60% of temperate counterparts. We attribute savings to slow growth rates, reduced thermoregulatory requirements, a low resting metabolism (in swallows only), asynchronous hatching (in bee-eaters), and low nestling activity levels. Patterns of energy storage as lipid in nestlings of the three species were similar to the pattern in temperate swallows (Hirundinidae) and swifts (Apodidae), with those species feeding at the greatest heights, and hence on the most unpredictable supplies, storing the most fat while in the nest. Received 1 February 1982, accepted 16 November 1982. BIRDS that breed in the tropics usually have small clutches (Moreau 1944; Lack and Moreau 1965; Cody 1966, 1971; Skutch 1976), and their nestlings grow slowly (Ricklefs 1976, Oniki and Ricklefs 1981). Many nests may be lost to predators (Skutch 1967, Lack 1968, Ricklefs 1969), but, if the nest is successful, then care of fledglings is often prolonged (Fogden 1972, Skutch 1976). It has proved difficult to provide a unifying explanation for these trends, but short days (Hesse 1922, Lack 1954, Royama 1969) and poor nutrition (Snow 1976, Foster 1977) may be contributory extrinsic factors limiting clutch sizes and growth rates. Equally, high adult survival and poor offspring survival may favor low levels of reproductive effort (Williams 1966, Cody 1971, Charnov and Krebs 1974). It is usually assumed in discussions of avian reproductive rates that the number of eggs or young (at least within taxa, matched for body size) is a valid comparative unit and that resource demands are related mainly to brood size and the duration of parental care. The individual nestling's requirement is thus perceived as relatively constant, variability in the parents' propensity or capacity for gathering food being the main limiting factor. Food requirements for breeding in the tropics, however, may be less than those for temperate birds. For example, BMR (basal metabolic rate) among adults is lower in many tropical birds (Weathers 1979, Hails in press), and a similar trend was evident in a sample of nestling passerines (Ricklefs 1976). Thermoregulatory demands, 425 too, will usually be less, and additional energy savings may follow from reduced activity by nestlings in some tropical species (Snow 1976). In this study we examined the effect of economic factors on the overall energy demands of some tropical nestlings. By looking at three insectivorous pecies, we avoided many problems with nutrient deficiency, such as may apply with frugivores (Foster 1977, 1978). We made comparisons with temperate species, which are nourished almost exclusively on nutritionally rich foodstuffs, including granivorous species that generally take insects to the brood.

Brief report: Chimpanzees, tools, and termites: New record from Gabon.

Abstract: Wild chimpanzees (Pan troglodytes) in northeastern Gabon use tools made of vegetation to obtain termites (Macrotermes? nobilis) for food. They mostly use probes in termite fishing, as recorded elsewhere in eastern and far western Africa. This is the first record of termite fishing by the central west African race of chimpanzees. There are signs that they also use stouter tools, perhaps to perforate the mounds of the termites. These new findings further complicate the status of material culture in this species of ape in nature.

Mortalities of Salmo gairdneri exposed to cultures of Gyrodinium aureolum

Abstract: Rainbow trout were exposed to five different concentrations of a unialgal culture of Gyrodinium aureolum in laboratory tanks. All the concentrations used proved lethal within 24 h. The gills of the dead fish showed no mechanical occlusion by the algae but all displayed marked histological changes characterized by necrotic degeneration and disintegration of the lamellar epithelium.

Susceptibility and immunity to Vibrioanguillarum in post-hatching rainbow trout fry, Salmogairdneri richardson 1836

Abstract: Rainbow trout fry were tested for their susceptibility to experimental infection with Vibrio anguillarum, and their ability to mount an immune response against it, from the age of 2 weeks post-hatch onwards. Bath challenges were ineffective in inducing vibriosis until 6-8 weeks post-hatch, and then only low levels of specific mortality ensued, even at very high doses. However, at the earliest age tested, 7 weeks post-hatch, the fry were susceptible to infection by an intraperitoneal injection with live organisms. Protective immunity was evident in fry vaccinated by direct immersion as early as 2 weeks post-hatch (at an average weight of 0.14g), when tested by intraperitoneal challenge. By the time the fry reached 0.5g (10 weeks after hatching), protection levels had reached 50% for direct immersion vaccination and 100% for intraperitoneal vaccination. An oral vaccination, from first feeding onwards, proved ineffective in inducing immunity. The results are discussed in relation to the onset and maturation of immunological competence in rainbow trout.

Territorial behaviour in the green monkey, Cercopithecus sabaeus: Seasonal defense of local food supplies

Abstract: Territorial behaviour among green monkeys (Cercopithecus sabaeus) was studied for 15 months in Senegal, West Africa. Intergroup relations were quantified, as well as the distribution and availability of resources in the heterogeneous habitat. Intergroup encounters varied seasonally in their location and frequency. Green monkeys did not specifically engage in territorial ‘patrols’, bur rather, areas of range-overlap with neighbouring groups were exploited for specific resources they contained. Neighbours showed flexible responses to seasonally variable competition for these resources. Four types of encounter were quantified, varying in intensity and duration, with descriptions of the ecological context underlying each: chance, ritual, one-sided, and intense encounters, varying according to the relative net benefit to each group to defend specific resources. This depended on the relative availability and distribution of these resources, and the degree to which they could be depleted. Comparisons were made with other populations of C. aethiops. A higher frequency of encounters was associated with higher population density at one site, and with monkeys living in ranges small enough to be economically defendable.

Responses to mirror image stimulation and assessment of self-recognition in mirror- and peer-reared stumptail macaques

Abstract: Ten stumptail macaques (Macaca arctoides), varying in experience of conspecifics and mirrors from no experience to extensive experience throughout infancy, were tested for reactions to mirror image stimulation. Monkeys reared only with mirrors or only with one other monkey were highly responsive to their reflections, exhibiting mostly positive behaviour. Monkeys with experience of both a fully accessible cagemate and mirrors were intermediate in responsiveness, while monkeys reared with mirrors but given experience of a live conspecific behind a transparent partition responded least of all to the mirror. Monkeys reared with no experience of conspecifics at all were the most responsive. Rearing experiences influence reactions to social stimuli such as mirror image stimulation, and considerations of the novelty and complexity of the stimuli are important. Despite the most extensive exposure to mirrors yet reported, none of the monkeys showed any evidence of self-recognition.

Immunization of rainbow trout, Salmo gairdneri Richardson, against vibriosis: comparison of an extract antigen with whole cell bacterins by oral and intraperitoneal routes

Abstract: . An extract vaccine against Vibrio anguillarum was compared with other vaccine preparations when administered to rainbow trout intraperitoneally or orally on food. Intraperitoneal vaccination resulted in virtually 100% protection within two weeks whereas oral vaccination gave a maximum protection of 50–70% after eight weeks. When administered intraperitoneally the extract performed better than formalin killed cells but when administered orally formalin killed cells were better. The addition of alum as adjuvant enhanced the response to antigen administered by both routes. Serum agglutinin litres after oral vaccination were low and variable but after intraperitoneal injection they reached a consistent peak of 64. As the response to oral vaccination was so low it was not possible to relate agglutinin titre to protection in a quantitative relationship.

Trade and Politics Behind the Slave Coast: the Lagoon Traffic and the Rise of Lagos, 1500–1800

Abstract: The rise of Lagos, which became the principal port of the ‘Slave Coast’ at the end of the eighteenth century, can only be understood by reference to the interaction between the European Atlantic trade and the indigenous canoe-borne trade along the coastal lagoons. European traders in the sixteenth century used the Lagos channel and the lagoon to approach the Ijebu kingdom, where slaves and cloth were purchased, but this trade lapsed in the seventeenth century. The Lagos settlement originated as a fishing hamlet, but was occupied as a military base by Benin around the end of the sixteenth century. Benin expansion to the west may have been designed to prevent European trade with Ijebu, in the interests of a Benin monopoly. Lagos remained formally subject to Benin until the nineteenth century, but the decline of Benin power in the eighteenth century left it effectively independent. European sources of the seventeenth and early eighteenth centuries attest trade in cloth and slaves passing along the lagoons through Lagos to Allada and Whydah in the west. Although this pattern of trade has been assumed to date back to pre-European times, it was more probably a consequence of the European presence, and more specifically of the westward drift of European interest along the coast from Benin after the sixteenth century. European traders began to show an active interest in the lagoon trade to the east of Allada in the early eighteenth century, and again began to explore the possibility of using the Lagos channel to bapproach the inland lagoons. Lagos developed as an Atlantic port from the 1760s, exporting slaves and Ijebu cloth, but its importance was limited by its remoteness from any major source of slaves. Its emergence as a major port in the late eighteenth century was due to the disruption of slave shipments from ports further west by military pressure from Dahomey, which led to the diversion of slave supplies eastward along the lagoons for shipment from Lagos.