摘要:

AbstractThe use of placental scar counts in determining litter size and pregnancy rate among Red foxes (Vulpes vulpesL.) is reviewed. There is no experimental material to test the validity of the method, although many authors have discussed it. Recent workers have (1) included uteri from vixens killed later in the season and, (2) become more concerned about effects of resorptions and/or abortions on scar counts, as well as the possibility of scars persisting from earlier pregnancies. In the present study, scar counts overestimated numbers of persisting corpora lutea to a higher degree in old vixens than in yearlings; and scars were shown to fade over winter. Estimates of frequency of breeding among females, based on various combinations of placental scars of different shades, and on date of death, are discussed. The relation between number of scars of different shades, date of death and known minimum litter size in three wild and one captive vixen is compared with the foregoing. Counts of all scars evidently overestimate litter size at birth and breeding frequency, probably because some scars originate at resorption sites and others persist from earlier pregnancies. Only dark scars should be counted early in the season, but those of increasingly lighter shade should be included as winter progresses. A guide to counting placental scars over winter is presented.

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe food of foxes in suburban London was examined using stomach contents and den litter analysis. A great diversity of food was taken. Adult foxes killed nearer to the city centre were found to eat significantly fewer earthworms, domestic pets and wild mammals, but more scavenged food items, than foxes killed closer to the suburban fringe. Cubs killed closer to the city centre ate significantly fewer earthworms and insects, and more pet birds, pet mammals and scavenged food items than cubs killed nearer the periphery of the suburban area. Although seasonal trends in food selection were apparent, they were not as pronounced as those observed in studies of rural foxes. At no time of the year did a single food item predominate in the diet of adult foxes. Passeriformes were the most important single food item in the diet of young cubs, but there was no correlation between the number of Passeriformes eaten and their abundance, nor between annual changes in the abundance of small birds and mean fox birth litter size and productivity. Most foxes examined were in good body condition; there was no seasonal variation in body weight, although fat content did vary seasonally. A complementary survey in Bristol on losses of domestic pets to foxes revealed that 07% of pet cats and 80% of other pets kept outdoors were killed in a year. Damage to garden Crops was negligible.

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractField data on several social terrestrial carnivores, relevant to the function of social hunting, are reviewed in relation to the hypotheses that this function is (1) the ability to catch and kill stronger and faster prey, (2) the ability to cope effectively with interference competition from other carnivores at the kill, (3) unrelated to hunting and competing for food. Hypotheses (2) and (3) are found to comply with the data more often than the widely‐accepted hypothesis (1). This conclusion affects the question of when and how big game hunting favours sociality in a carnivorous species.ZusammenfassungDie biologische Bedeutung sozialen Jagens beigrösseren LandraubtierenNicht jeder Vorteil, den ein Merkmal seinem Träger bringt, ist gleichzeitig die biologische Bedeutung oder Funktion (im engeren Sinn) dieses Merkmals. Aus der Erörterung des Unterschiedes zwischen Vorteil und Funktion im Hinblick auf die Funktion des sozialen Jagens ergab sich die Hauptfrage dieser Arbeit: Welche Anforderungen der Umwelt bewirken, dass Jagdgruppen so gross sind, wie man sie antrifft, und nicht kleiner?Am in der Literatur vorhandenen Datenmaterial von 9 Raubtierarten (Löwe, Gepard, Fleckenhyäne, Hyänenhund, Wolf, Dhole, Gold‐ und Schabrakenschakal und Koyote) wurden die folgenden drei Hypothesen kritisch geprüft: (1)Jagdhypothese:Grössere Gruppen dienen dem Finden, Fangen oder Überwältigen stärkerer oder schnellerer Beute. (2)Konkurrenzhypothese:Grössere Gruppen dienen der wirkungsvolleren Verteidigung oder dem rascheren Auswerten der toten Beute angesichts der inner‐ oder zwischenartlichen Konkurrenz. (3)Nebeneffekthypothese:Die Selektionsfaktoren, die grössere Gruppen begünstigen (z.B. Konkurrenz urn Geschlechtspartner, Raubfeindvermeidung, Bewachen der Jungen) haben nicht direkt mit Jagd oder Nahrungsaufnahme zu tun.Entgegen einer verbreiteten Ansicht erwies sich die Jagdhypothese nur selten und nur für kleine Gruppen von 2–3 Individuen als die wahrscheinlichste (Gnukalbjagd der Hyänen; Goldschakal; s. Tabelle 4). Das gegenwärtige Datenmaterial spricht öfter für Konkurrenz‐bewältigung als die Funktion des sozialen Jagens (Löwen; Hyänen z.B. bei Zebrajagd; Hyänenhund; Schabrakenschakal; Koyote), während bei Löwenmännchen‐, Gepardmännchen‐gruppen und Wolfsrudeln am ehesten die Nebeneffekthypothese zutrifft. Die Funktion des sozialen Jagens kann je nach dem sozialen Kontext (Löwe), dem Beutetyp (Hyäne) oder den ökologischen Bedingungen eine andere sein und ist nicht unbedingt ein Charakteristikum der betreffenden Art.Eine solche Analyse der Selektionsfaktoren, die die Sozialstruktur der Raubtiere formen, kann ausserdem Hinweise auf die Evolution sozialer Verb

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractIn a survey of western France during October‐November 1980, signs of otters were found at 46 (15%) of the 315 sites investigated. Otters were largely restricted to four areas, three of these being in the uplands (of Brittany, the Massif Central and the Pyrenees) and one in the coastal lowlands (of the Landes‐Gironde). The average number of signs found per successful site was 1 6, significantly lower than for Scodand and Ireland but similar to the figure for England. The percentage of positive sites and the scattered nature of the signs in western France was also broadly comparable witJi the English situation. This is surprising since most of the factors which adversely affect otters appear to be less oppressive there dian in England. Only water pollution is noticeably more extreme and this seems to offer the best, overall explanation for the nature of the decline in the area stud

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Book reviewed in this article:HORMONAL CONTROL OF LACTATION By A. T. Cowie, I. A. Forsyth&I. C. Hart.FEVER, ITS BIOLOGY, EVOLUTION and FUNCTION By Matthew J. KlugerWHALES By W. Nigel Bonner, Blandford Press, PooleTHE RED FOX Bv H. G. Lloyd, Batsford Ltd. London.IRISH WHALES and WHALING By James FairleyTHE BACK GARDEN WILDLIFE SANCTUARY By Ron Wilson.TAXIDERMY‐A COMPLETE MANUAL By J. C. Metcalf.THE POPULATION ECOLOGY OF CYCLES IN SMALL MAMMALS By J. P. Finert

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY