摘要:

The fish eagles along 32 km of shoreline were counted regularly from a launch. The territory size was found to be 0.6 km of shore with a density of 3.5 eagles per km. A single aerial count along 323 km of shore returned a density of 1.9 eagles per km with a territory size of 1.0 km of shore. The distribution of fish eagles is related to the relative availability of trees as perches and probably also to the abundance of fish. The quantity of fish taken by the fish eagles is shown to be negligible compared either with the total production or with the yield harvested by man.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01386.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

This study was based on a collection of 110 Roe deer jaws from Thetford Chase, Norfolk. The cementum of these deer contained broad white cellular bands rich in cementocytes, separated by thin dark layers of acellular material. These bands were clearly defined, of even thickness and appeared to be laid down each summer and autumn. Examination of nine known‐age jaws suggested that the number of white bands in the cementum gave an accurate indication of an animal's age.Tooth wear appeared to be a less reliable ageing technique owing to the variable attrition encountered between animals of the same age clas

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01387.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Information has been collected from various sources on spawn site selection and colony size of the frog (Rana temporaria) and the toad (Bufo bufo). Details are tabulated for 764 frog breeding sites in Britain and in the Republic of Ireland and for 139 toad sites in Britain (the toad does not occur in Ireland). Both species tend to breed in whatever types of site are most available. In Britain the garden pond has steadily increased in importance for both species since 1950. Frogs usually spawned in shallow water, 266 reports out of a total of 588 (45%) referring to water up to six inches (15 cm) deep. Toads tended to spawn in deeper water, 48 reports out of 82 (59%) mentioning water 7–18 inches (18–46 cm) in depth. Median depths were: frog, seven inches (18 cm); toad 13 inches (33 cm). Information on colony size was assimilated for 574 frog colonies and 86 toad colonies. Colonies in gardens were smaller than those in other types of site. Relatively fewer large frog colonies (≡100 animals) were found to occur in London than elsewhere in Britain, and British colonies were generally larger than those in Ireland. Colonies of 100 or more individuals were recorded relatively more frequently for toads than for frogs. By combining information on choice of site and colony size, rough estimates can be derived of the percentage of frogs and toads breeding in gardens and other types of site. For instance, in the London area in the 1960s perhaps 20–25% of the frogs bred in gardens and private grounds. The ecological significance of these observations is di

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01388.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

An elastic longitudinal ligament stretched under considerable tension lies within the dorsal aorta of Rainbow trout.Experiments with mechanically simulated swimming movements in an artificial model demonstrate that such a ligament can act as a pump mechanism. The output of the pump increases with tail beat frequency up to a certain point where the mechanism tends to break down. Investigations on the trout dorsal aorta show that pump breakdown probably takes place at relatively low output pressures.Fundamental blood flow considerations indicate that a fully effective dorsal aorta pump over the full range of swimming speeds is undesirable. It is concluded that the dorsal aorta ligament can act as a pump which automatically increases circulation during swimming particularly to the body musculature. The output pressure is small but may be of significance in causing reflex increase in cardiac output.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01389.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Female budgerigars provided with nest boxes and exposed to male vocalizations were kept on light regimes involving 6 h of light and then a further 2 h of light starting 8, 12, 16, 17 or 18 h after the initial dawn. A higher proportion of females laid when the second light period started 6 h after the first one, than when it started earlier or later. That the effect was not due merely to the males vocalizing more on this light regime than on others was shown by substituting for the males taped vocalizations played during the light periods. It remains possible that females are more responsive to those vocalizations instead of/as well as to light at some points of the circadian cycle than others.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01390.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The playful behaviour of laboratory rats (Rattus norvegicus) was investigated in litters of five individuals with the mother present; parallel observations were made on mice (Mus musculus). Seven mixed litters containing four young rats and a young mouse fostered at birth were also observed.Solitary play was recorded in both species and took a similar form but social play was only observed in rats. In rats, solitary play frequently preceeded social play.The behavioural elements involved in the social play ofRattus norvegicuswere described, and the majority of these were the playful equivalent of adult agonistic behaviour elements. These social play elements were found to be organized into definite sequences which differed from those of adult aggression. Each behavioural element was found to act as a social releaser.Young mice did not respond playfully to social play from a rat litter mate; mice were less attractive to rats as playmates in comparison with fellow rats.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01391.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Univariate and multivariate study of 22 dimensions describing overall body proportions in 34 primate genera, has shown that these quantities effect a separation between the principal taxonomic divisions of the Primates: Prosimii, Ceboidea, Cercopithecoidea and Hominoidea. The last three do not, however, link to form a single unit, and the separation between the Ceboidea and Cercopithecoidea is imperfect. Some grouping within these major divisions appears, in certain aspects, to be of functional (locomotor), rather than of purely taxonomic, significance. For instance, within the Prosimii, the generaMicrocebus, GalagoandTarsius(the two latter being saltatory forms, while leaping is a component of the locomotor pattern of the first) are associated, while within the apes, the Asiatic formsHylobates, SymphalangusandPongo(all brachiators) tend to be grouped, as also do the African formsPanandGorilla(both, to a large extent, secondarily terrestrial in habit).The measures especially prominent in effecting this pattern of discrimination are: relative foot length, relative lower limb length and length of foot relative to lower limb length.Similar, if less clearly defined results emerge if groups of dimensions relating to individual body regions (forelimb, hindlimb, head and trunk) are analysed separately.The apparent failure of compounds of the measures of the limbs to give an anticipated close reflection of locomotor function stems possibly from the fact that the available dimensions are of an overall nature rather than a reflection of specific biomechanical functions. Such sub‐division, according with locomotor pattern as seems to emerge from this study, appears, in fact, to be little more than that implied in current taxonomic schemat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01392.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Variations in the fine structure of the flask cells of frog epidermis are described. Some flask cells have apical ridges with an alveolar layer of material under the cell membrane; others may have adjacent apical ridges sealed together by fusion of the outer leaflets of the cell membrane. The apical membrane of the flask cells and of the second tier epithelial cells (replacement or first reactive cells) is visibly different from the membranes on the lateral and basal aspects. Other variations in the appearance of flask cells may depend on their individual age, or on the stage of the moult cycle. The events of moulting can be divided into preparation, separation, sloughing and differentiation phases. During the preparation phase the flask cell apices disintegrate, and they are covered over by the adjacent replacement cells, which will later keratinize during the separation phase. New tight junctions are formed in the outer layers of the epidermis. Desmosome release frees the slough during the separation phase, before it is actually shed. During the differentiation phase the flask cells develop new apical ridges. The fine structure of the flask cells is compared with that of the mitochondria rich cells of the bladder epithelium, and with mitochondria rich cells which have been found in the palatal epithelium; the flask cells are considered not to be homologous with these other types. There are no comparable cells in the corneal epithelium. Possible functions of the flask cells are considered; some previous hypotheses can now be discounted. An attempt is made to integrate the phases of the normal moult with the variations in active sodium transport and water flux reported from isolated skin treated with aldosterone. It is suggested that the flask cells may transmit a hormonal stimulus causing release of the slough, but that they are not concerned in the effects on sodium transport, which can be explained by changes of the epithelial cells. The flask cells could however be involved in the transport of substances other than sodium.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1975.tb01393.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY