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PubMed1983

Optimization of Brownian search strategies.

What are the simplest search strategies that lead an animal to a particular target, what are their limitations, and what changes can be made to develop more effective strategies? To answer these questions a class of search strategies was examined that require an animal to have only a minimal capacity for spatial orientation; the effectiveness of such strategies in solving the following basic search problem was determined. The animal begins its search at a distance r0 (starting distance) from a spatially fixed target. It detects the target when it has approached it to within a certain distance a (the detection radius). The analysed class of search strategies has the following characteristics: C1. The animal uses the same search strategy in all regions it enters. Therefore it needs no information as to the actual location of the target. C2. Its search strategy is constant in time. The animal has only to detect whether it has reached the target or not. C3. Once the animal has chosen a direction, it continues in that direction for a certain distance. This is the only way in which the preceding parts of the search affect the animal's decision as to the direction in which it will search next. In the long term the animal's movement directions are independent, with no preference for any particular direction. Despite their extreme simplicity in application these "Brownian" search strategies are remarkably successful (Fig. 1). Indeed, if the search is continued long enough the target is certain to be found. The success of the search depends in part on the search duration (Fig. 2) or the search-path length S, the starting distance and the detection radius. On the other hand, an animal can have a decisive influence on its degree of success simply by adjusting the frequency with which it changes its walking direction to match its sensory abilities. That is, a not-too-short Brownian search (S much greater than r0) is most successful when the searching animal, between the points at which it changes direction, walks approximately straight for a distance equal to the detection radius (Figs, 3 and 4). A further increase in search effectiveness is possible only by turning to another class of search strategies. These, however, demand that the animal either have more information about the position of its target at the beginning of the search or be able to organize its search behavior even over fairly long periods of time.

Animals↗
PubMed1988

Ectoparasites of guinea fowl (Numida meleagris galeata Pallas) and local domestic chicken (Gallus gallus) in southern Guinea Savanna, Nigeria.

The ectoparasites of poultry in a southern guinea savanna zone were investigated by the examination of guinea fowl and local domestic chickens in the range and guinea fowl under intensive management. The prevalent ectoparasites of range guinea fowl and local chickens include seven species of lice Menacanthus stramineus, Menopon gallinae, Goniodes gigas, Goniocotes gallinae, Lipeurus caponis, Numidilipeurus tropicalis, Damalinia bovis; three mites Bdellonyssus bursa, Megninia cubitalis, Dermanyssus gallinae; two fleas Echidnophaga gallinacea, Ctenocephalides felis and two ticks Argas persicus and Ambylomma variegatum. Under intensive management, infestation by G. gigas, L. caponis and M. gallinae led to clinical signs, feather damage, reduced food intake and death.

Animals↗
PubMed1989

Formation and function of accessory nuclei in the oocytes of the bird louse, Eomenacanthus stramineus (Insecta, Mallophaga). I. Ultrastructural and histochemical studies.

In the oocytes of Eomenacanthus stramineus accessory nuclei arise by budding from the nuclear envelope. It is suggested that microtubules and the thick layer of the nuclear lamina are involved in this process. Newly formed accessory nuclei contain aggregations of fibrillogranular material. These aggregations are slightly Feulgen positive, RNA negative and stain positively with the Ag-NOR method. During later developmental stages one dense, RNA-positive inclusion appears in each accessory nucleus. These inclusions consist of an Ag-NOR-positive cortical layer and an Ag-NOR-negative core. The function of accessory nuclei in the species investigated is discussed in the light of these results.

Actins↗
PubMed1979

Biodegradability of Tioctilate.

The biodegradability of Tioctilate (octylthiobenzoate), a new pesticide, has been examined by means of 5 tests. The compound appears to be susceptible to microbial metabolism.

Aerobiosis↗
PubMed2002

Grooming site preferences determined by lice infection among Japanese macaques in Arashiyama.

I investigated the effect of the density of louse eggs (Pedicinus obtusus and P. eurygaster) on grooming site preferences in Japanese macaques (Macaca fuscata). Louse eggs were more often found on the outer side of the body (upper back, lower back, outer arms, and outer legs) than on the inner side of the body (chest, belly, inner arms, and inner legs). Japanese macaques were more likely to be groomed on the outer side than the inner side of the body by allogrooming and autogrooming. Such grooming site preferences correlated with the distribution of louse eggs but not with the areas of body parts. Thus, the ecology of lice might affect grooming behavior of Japanese macaques. Five hundred and fifty louse eggs were estimated to parasitize an adult female Japanese macaque. Considering the intrinsic rate of natural increase of lice, monkeys need to be groomed almost every day. This suggests that Japanese macaques need grooming partners and form social bonds with others for everyday grooming.

Animals↗
PubMed2002

Leaf-grooming by a wild chimpanzee in Mahale.

During the course of systematic observations of the leaf-grooming behavior by the chimpanzees (Pan troglodytes) of the Mahale Mountains National Park, Tanzania, I recovered a louse from a leaf "groomed" by an adult male chimpanzee after a typical leaf-grooming session. During the leaf-grooming session I observed a small object on his lower lip. He picked up a leaf, transferred the small object from his lip to the leaf, folded the leaf and crushed the folded side of the leaf with his thumb. I present this observation as further evidence of the "squashing ectoparasites" hypothesis for leaf-grooming.

Animals↗