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81.
82.
S. Fuchs 《Behavioral ecology and sociobiology》1992,31(6):429-435
Summary The effect of variation in copulation duration on sperm precedence (P2) of the last male was investigated in a non-territorial libellulid using irradiated-male techniques and observations in a large field enclosure. Copulation duration varied between 6 min and more than 1 h (X = 23.19 min ± 12.74). In the clutch deposited immediately after the copulation, most copulation durations resulted in high sperm precedence for the last male. Several experimentally interrupted short matings still resulted in 100% precedence. However, most interrupted copulations of 10 min or less resulted in a low P2. After long, uninterrupted copulations, P2 remained high in clutches that were collected up to 9 days after the mating. After interrupted short copulations, P2 fluctuated or remained at a low level from the first clutch onwards. This indicates that sperm mixing probably starts within 24 h and that after a long copulation virtually no rival sperm is left in the female's sperm storage organs. As most natural copulations are long, complete removal of rival sperm seems to be common in S. danae. Only 3 f 17 variables investigated explained a significant amount of the variation in copulation duration. Copulations shortened with increasing temperature and for each additional mating of the male. The strongest effect however, was due to time of day: early morning copulations lasted longer than midday copulations. Adjustment of the copulation duration to the decreasing chance of obtaining additional matings was found to be the most likely of five explanatory hypotheses that were evaluated. 相似文献
83.
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85.
Christopher Patten MP 《The Environmentalist》1987,7(2):91-94
Summary Some of the environmental and developmental activities assisted by Britain's Programme of Overseas Aid are outlined. In particular, the article draws attention to a new booklet published by the Overseas Development Administration to mark the European Year of the Environment which, in the Minister's words, shows how through British aid, programme improvements are possible by a combination of sound scientific research and a sensitivity to people's needs.Mr Christopher Patten, Member of Parliament for Bath, is the UK's current Minister for Overseas Development. He also serves as Minister of State for Foreign and Commonwealth Affairs. The Minister may be contacted through the offices of the Overseas Development Administration, Eland House, Stag Place, London SW1E 5DH, UK. 相似文献
86.
Randolf Menzel Jacqueline Fuchs Leonard Nadler Benjamin Weiss Nicole Kumbischinski Daniel Adebiyi Sergej Hartfil Uwe Greggers 《Die Naturwissenschaften》2010,97(8):763-767
Honeybees use their visual flow field to measure flight distance. It has been suggested that the experience of serial landmarks
encountered on the flight toward a feeding place contributes to distance estimation. Here, we address this question by tracing
the flight paths of individual bees with a harmonic radar system. Bees were trained along an array of three landmarks (tents),
and the distance between these landmarks was either increased or decreased under two test conditions. We find that absolute
distance estimation dominates the search for the feeding place, but serial position effects are also found. In the latter
case, bees search only or additionally at locations determined by serial experience of the landmarks. 相似文献
87.
Although mate guarding as prevention of extra-pair copulation is common among birds, evidence for aggressive behaviour involving
physical contact related to mate guarding in passerines is scarce and cases of the presence of one partner directly influencing
the aggressiveness of the other are lacking. We investigated the intra-specific territorial behaviour of male meadow pipits
(Anthus pratensis; Passeriformes: Motacillidae) at the beginning of the breeding season by placing a pipit model accompanied by an intra-specific
song playback in the territory of socially paired males and compared the responses of males whose mates were physically present
during trials with those whose females were out of sight. The level of aggression of males was significantly higher in the
presence of the female; half of the males in this group physically attacked the model (the most intense and risky aggressive
behaviour). Physical attacks did not occur among males whose female was absent during the trial; response to the playback
by most of these males was only weak. This pattern may be related to the prevention of extra-pair copulation; if the risks
involved in the conflict are outweighed by potential loss of paternity, such aggressive mate guarding may pay off. The apparently
overlooked effect on the territorial behaviour of a partner’s passive physical presence during conflict should be further
evaluated because it may be important for the design and interpretation of results of behavioural experiments. 相似文献
88.
The stridulation of the giant pill-millipede genus Sphaerotherium from South Africa, one of only three groups of millipedes that produce sounds, was studied. One hundred one stridulation
series of a total of nine different species (Sphaerotherium dorsaloide, Sphaerotherium hanstroemi, Sphaerotherium mahaium, Sphaerotherium similare, Sphaerotherium punctulatum, Sphaerotherium convexitarsum, Sphaerotherium dorsale, Sphaerotherium rotundatum, and Sphaerotherium perbrincki) were analyzed. Stridulation sounds are produced only with a special field of ribs on the posterior surface of the posterior
telopod, which is actively moved over a field of sclerotized nubs on the inner margin of the anal shield. The Sphaerotherium male usually stridulates only when in contact with a female to initiate mating. This seems to prevent the female from volvating
into a ball or stimulate the female to uncoil when already rolled in. The sound analyzes revealed a broad frequency spectrum
in all stridulation sounds produced, without obvious differences in frequency distribution among species. However, the temporal
pattern of the stridulation varies greatly between species and seems to be species-specific, arguing for a species recognition
function of the stridulation during courtship behavior. A single species (S. punctulatum) was found to stridulate during mating while three species also show postcopulatory stridulation. Apparently, pill-millipedes
are not capable of acoustic perception, as no hearing organs are known, indicating that the communication is mainly based
on perception of temporal vibration patterns, and not of the acoustic signal itself. The need to overcome the rolling-in reflex
of the female is developed as a hypothesis why stridulation exists only in millipedes able to coil into a ball, and apparently
evolved four times independently in the superorder Oniscomorpha. 相似文献