Signal Redundancy and Receiver Permissiveness in Acoustic Mate Recognition by the Tungara Frog, Physalaemus pustulosus

The tungara frog has an advertisement call with two structurallyand functionally distinct components: the whine is both necessaryand sufficient for species recognition, and addition of chucksfurther enhances call attractiveness. Only the fundamental frequencyof the whine contributes to phonotaxis; the upper harmonicsplay no role. Furthermore, only a small portion of the whine,within the first 0–100 msec, is necessary to elicit phonotaxis;there is some redundancy since either the 0–50 msec orthe 50–100 msec portion elicits a response. Most of theremainder of the whine's fundamental further enhances call attractiveness.Only the amphibian papilla in the peripheral auditory systemis involved in decoding the whine. In stark contrast, severalchuck variants, which stimulate either the amphibian papillaor the basilar papilla, and white noise are as effective inenhancing call attractiveness as is the normal chuck, showingthat either peripheral end organ can be involved in the perceptionof a more attractive call. Thus there is greater receiver specificityfor decoding stimuli in interspecific mate choice, and greaterreceiver permissiveness for decoding stimuli in intraspecificmate choice; it appears that intraspecific mate choice can takeadvantage of a greater array of neural pathways for call decodingthan can interspecific mate choice.     

EFFECT OF HOMOGENIZATION AND FAT CONTENT ON ORAL PERCEPTION OF LOW AND HIGH VISCOSITY MODEL CREAMS

Assessed under low-intensity red illumination, homogenized and thickened higher fat milk samples evoked higher sensory ratings of creaminess than did the unhomogenized or lower-fat milks that had not been thickened to the viscosity of double cream. Furthermore, perceptual ratings of fat content showed the same dependency on homogenization, higher fat and thickness and were entirely accounted for by the creaminess ratings. This indicates that assessors recognize the type of milk or cream most similar to a rated standard and infer its fat content on the basis of tactile patterns produced in the mouth by forces at the surface of small and even-sized dairy fat globules when bulk forces are produced by sufficient viscosity.     

Aerial systematic sampling applied to censuses of large mammal populations in Kenya

Four systematic sample censuses are described, one of elephants in Tsavo East National Park, and three of kongoni on the Athi-Kapiti Plains. Flight paths in the form of a regular grid with 5-km spacing were used. Distribution maps from each census are shown. A statistical test is described, which revealed the presence in two of the censuses of non-random features in the spatial distribution of the animals, on a scale large enough to interact with the sampling grid. It is recognized that this could lead to an inflated estimate of variance, as compared to that which would be obtained from a stratified random sample, but it is thought unlikely that any effect of this kind would be appreciable in practice.     

Preference of the cabbage root fly, Delia radicum (L.), for coloured traps: influence of sex and physiological status of the flies, trap background and experimental design

Abstract. Catches of Delia rudicum (L.) (Diptera: Anthomyiidae) were compared in water traps that reflected predominantly wavelengths shorter (violet and blue traps) and longer (green and yellow traps) than 500 nm.Traps were positioned in choice and no-choice situations against backgrounds of bare soil and weeds in the field and against backgrounds of brown and green paper in the laboratory.The physiological status of the flies was modified in the laboratory by denying them access to food sources and oviposition sites.
Males discriminated significantly more clearly than females between yellow and blue traps.The discrimination between yellow and blue traps was significantly more pronounced when the traps were presented in the choice than in the no-choice situation in both sexes.Green background (weeds and green paper) was highly preferred for landing and thus competed with the traps to such an extent that few flies were caught when non-preferred violet and blue traps were sited on green backgrounds.Flies seldom landed on the brown background (soil and brown paper) which resulted in the relative increase of catches in the non-preferred violet and blue traps.The preference for yellow traps was innate even in young flies with immature egg-follicles.Females that were ready to lay eggs, even those deprived of an oviposition site till the age of 8 days, also preferred yellow traps.In the no-choice situation, flies deprived of food landed with the same frequency in yellow and blue traps.Food deprivation, however, did not affect preference for yellow traps over the blue traps presented in a choice situation.