摘要:

Great skuas on Foula, Shetland have responded to a decline in the availability of sandeels since the late 1970s by increasing the proportion of other items in their diets. This change is correlated with the annual recruitment of sandeels in Shetland waters. Since 1983 there has been a 10‐fold increase in predation by great skuas upon other seabirds, as Furness&Hislop (1981) suggested might occur in response to a low availability of sandeels. Changes in diet have been accompanied by a 50% reduction in adult territorial attendance as adults increased their foraging effort, such that between 1987 and 1989 breeding adults were probably working as hard as they were able to. Despite this, breeding success was less than 40% in 1987 and less than 15% in 1988 and 1989. The major cause of breeding failure was predation of unguarded chicks by adults from neighbouring territories. The willingness of adults to expose their chicks to high predation risk is probably maintained because of a positive correlation between chick pre‐fledging growth and post‐fledging survival, which is expressed up to the age of two years and which will place a strong pressure upon adults to feed their chicks as well as possible. The high expenditure of effort by adults in 1987 and 1988 did not affect the weights of those birds incubating eggs in 1988 and 1989, but there was a slight (3%) decrease in egg size between the late 1970s and the late 1980s. Changes in the age structure of the breeding population and the absence in 1989 of 28% of adults colour‐ringed during incubation in 1988 suggest an increase in the rate of egress since the 1970s. These changes probably represent an increase in the long‐term costs of reproduction to adults at th

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04758.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The breeding biology of the macaroni penguin,Eudyptes chrysolophus, was studied over four years, 1976 and 1986–88, at Bird Island, South Georgia. Birds were migratory, being absent during winter (May to September). Arrival at the colony was highly synchronous between years: 14–23 October, over a 7‐year period. The pre‐breeding, incubation and chick‐brooding period was characterized by long fasts ashore, for 36 and 39 days in males and 41 days in females, alternating with long periods at sea. Within years egg‐laying was highly synchronous: 95% of clutches initiated within 4–6 days. Arrival date and mean egg‐laying date were later (by 3 days), and breeding population size lower (by 20%) in 1987, compared to other years. The incubation period was 35 days and comprised three long shifts, the first shared by the male and female, the second by the female and the third by the male. In 1986 and 1988 these were of 12, 12 and 9 days' duration, but in 1987 the first shift was significantly shorter: 9 days. Chicks creched at 23–25 days of age and fledged at 60 days of age. Neither chick age nor weight at creching or fledging varied between the years 1986–88. The breeding biology of macaroni penguins at Bird Island is compared with that of otherEudyptespenguins, and with the sympatric gentoo penguin,Pygoscelispupuu.There is little variation in breeding biology within the genusEudyptes, except in the length of time spent at sea prior to the annual moult. This is much shorter at Bird Island, probably reflecting a greater food availability compared to other localities. Inter‐annual variation in certain breeding parameters, e.g. laying date, breeding population size, is much greater in the gentoo penguin than in the macaroni penguin. The shorter breeding season, rearing of only one chick and proportionately lower chick fledging weight in macaroni penguins, may be linked to this specie

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04759.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Aggressive encounters between pairs of male mountain dusky salamanders(Desmognathus ochrophaeus)were staged in the laboratory in the absence of any obvious limited resource. We observed aggressive interactions which sometimes escalated to biting. Physical injuries were inflicted during some aggressive encounters; however, the consequences of injury for future fitness are uncertain. Several behaviour patterns used in contests apparently functioned as threat displays, and these sometimes ended contests before they escalated to biting. We could detect no significant influences of three types of asymmetries among males in determining the winners and losers of contests (body size, recent mating experience and familiarity with the testing arena). Three cases of ‘homosexual’ courtship were observed. Both intermale aggression and intermale courtship may be interpreted as forms of competition for ma

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04760.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

We investigated the efficiency of mass transfer in lactating harp seals through serial measurements on individual mother‐pup pairs during the whelping seasons of 1988 and 1989. We also compared the influence of longitudinal versus cross‐sectional sampling on estimates of the efficiency of mass transfer. Among longitudinally sampled pairs, pups grew at an average rate of 2·3 ± 0·5 (mean ± S.D.) kg/d (N = 20). The concomitant mass loss by females averaged 3·1 ± 0·8 kg/d (N = 19). The mean efficiency of mass transfer was 77·0 ± 13·6% (N= 19 pairs).Estimates of pup growth and female mass loss from regressions of cross‐sectional data were 2·0 kg/d and 3·1 kg/d, respectively. These values produce an estimate of 65% for the efficiency of mass transfer.Consistent with the high efficiency of mass transfer, harp seal females contribute less of their total body mass to nursing (c.28%) than most other phocids examined. The resulting energy savings may be important for females of an ice‐breeding species, which migrate a long distance shortly afte

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04761.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

In a number of species of seasonally breeding marsupial, the male is fertile throughout the year but there is a marked seasonal change in weight of the accessory sexual glands. In this study, body weight, prostate, epididymis and testis weights and plasma concentrations of testosterone, LH and prolactin and pituitary content of LH and prolactin were determined in male Bennett's wallabies shot at 1–2 month intervals over a period of 17 months. There was a highly significant increase in prostate weight which was coincident with the breeding season for this species. A small but significant increase in testis weight was also observed but epididymis weight remained unchanged. Plasma testosterone concentrations were significantly increased at a time coincident with the increase in prostate weight. Plasma prolactin and LH concentrations were low in most animals and remained unchanged during the study. In contrast, pituitary prolactin and LH contents showed highly significant changes, with increasing and peak hormone content preceding maximum prostate weight and plasma testosterone concentrations by several months. While these latter results suggest a role for prolactin and LH in the seasonal control of the reproductive organs in the male wallaby, a more intensive study of the pattern of secretion of these hormones and possibly more sensitive hormone assays are required to understand their relative roles in regulating the annual cycle of prostate growt

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04762.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

This paper attempts to describe the relationship between habit, body structure and form in five species of ground beetle representing five different tribes. The results support and broaden the basis for currently accepted ideas about the mode of life of Scaritini, Morionini, Licinini, Omophronini and Galeritini. It examines feeding mechanisms, leg structure and body form. In this study two types of feeding method are recognized: fluid or semi‐fluid feeding, as inScarites subterraneus, and mixed intake feeding. In the second method, food ingested varies from fluid, mush and recognizable arthropod fragments (Morion monilicornisandOmophron labiatum)to mainly fluids or semi‐fluids with some fragments (Diplochila majorandGalerita lecontet). All these species show morphological adaptations of their feeding mechanisms indicative of their feeding habits.Pro‐, meso‐ and meta‐femoral and tibial lengths and femoral width measurements have been made and correlated with body lengths; maximum running speeds and maximum horizontal pulling (= pushing) forces have also been made and correlated with body lengths.Galerita leconteiandOmophron labiatumhave long femora, whereas those ofDiplochila majorare somewhat shorter and those ofScarites subterraneusandMorion monilicornisare very short.Scarites subterraneushas relatively narrow femora although there is a trend towards a narrowing of the femora inMorion monilicornis.OnlyOmophron labiatumhas broad femora.Galerita leconteiandOmophron labiatumhave long tibiae whereasScarites subterraneusandMorion monilicornishave very short tibiae.Diplochila majorrepresents the mainstream of carabids, with tibial lengths lying between the two extremes. All five species show morphological adaptations of their locomotory apparatus indicative of their locomotory abilities.In this studyOmophron labiarumwas found to be particularly fast at high speed running (i.e. sprinting) whereasScarites subterraneuswas found to be relatively slow. OnlyScarites subterraneusshowed particularly strong pushing abilities whereasGalerita leconteiwas found to be weak at pushing.Omophron labiatum, Diplochila majorandMorion monilicorniswere found to have pushing abilities between the two extremes.Variations in height of the prothorax and hind body, the widths of the hind body, prothorax and metatergum, and the lengths of the metasternum, metatergum and wings are discussed and compared with body lengths in the five species. These various parameters have been displayed in the form of tables, and have been discussed in relation to the various habits of the five species. Certain trends were noted.OnlyDiplochila majorhas body proportions similar to those of mainstream cursorial carabids.Galerita leconteihas a shallow, narrow prothorax which may be correlated with its particular hunting habits.Scarites subterraneushas a somewhat cylindrical body form; the hind body is often narrower and flatter and the prothorax flatter than mainstream cursorial carabids. This kind of body form reduces friction and causes less obstruction when burrowing or moving in confined spaces.Morion monilicornishas a similar body form toScarites. Omophron labiatumis unique in having a very deep, wide prothorax and hind body. Its oval and streamlined body form ideally suits it for its unusual burrowi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04763.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The possibility of adaptations of mandibular salivary function to a diet of eucalypt leaves and for evaporative cooling was investigated in anaesthetized koalas. Salivary composition, at a range of flow rates up to maximum and during aldosterone administration, was measured in saliva evoked by intravenous infusion of carbamylcholine chloride. Maximum fluid secretion rates per gram tissue (230 ± 18·2 μl/min/g gland) were similar to mandibular glands of other species and about four times the rates/g gland reported for the parotid gland of koalas. Salivary concentrations of Na (6·1 ± 0·91 to 67·7 ± 3·51 mmol·l−1), Cl (7·2 ± 0·71 to 53·0 ± 2·82 mmol·l−1), HCO3(8·6 ± 0·81 to 19·4 ± 2·13 mmol·l−1) and the osmolality (26·7 ± 2·34 to 132·9 ± 5·47 mosmol.kg−1) were positively correlated with salivary flow rate. The concentrations of urea (1·87 ± 0·034 to 0·71 ± 0·099 mmol·l−1), K (13·0 ± 0·90 to 6·25 ± 0·482 mmol·l1‐), Mg (33·6 ± 2·53 to 10·1 ± 4·68 pmol·l−1), H+(246·2 ± 55·78 to 62·1 ± 8·01n̈mol·l−1) and PO4(3·46 ± 0·350 to 1·13 ± 0·044 mmol·l−1) were negatively related to flow rate. Total protein (411 ± 44·4 to 656 ± 146·4 mg·l−1) and total Ca (356 ± 45·2 to 467 ± 61·6 μmol·l−1) concentrations were not correlated with flow but were highly correlated with one another. With salivary amylase activity being absent and plasma amylase activity being very low indicating low production rates by other tissues, the koala is likely to have limited ability to digest starch. Intravenous infusion of aldosterone at 5 μg·h−1for 90 rnin followed by 50 μg·h−1for 105 min demonstrated that the gland responded rapidly to changes in endogenous mineralocorticoid levels. Mean salivary Na/K ratio before aldosterone administration was 6·9± 201, the ratio had fallen significantly (P<0·05) after 75–90 min infusion and had fallen to 0·71 ± 0·172 by the last 30 min of infusion.It was concluded that the mandibular gland of the koala, with its relatively high secretory capacity and its sensitivity to stimulation, would have the major influence on the composition of mixed saliva during low‐flow reflex secretion. Additionally, because the gland is responsive to acute changes in mineralocorticoids and produces a markedly hypotonic saliva

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04764.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Five individuals of four civet species were captured and followed by radiotelemetry in a mosaic of dry tropical forest in Huai Kha Khaeng Wildlife Sanctuary, Thailand. Observations were made on a fifth, arboreal species which was never captured. Radio‐collared civets used overall areas ranging from 3.1 to 17 km2with average monthly ranges from 0.72 to 5.4 km2. Average monthly ranges, home range centre shifts and activity radii showed a linear increase with weight and size of the individual, both within and between species. Despite individual differences, there were similar behavioural responses to extrinsic seasonal changes. Civets had activity levels of 50–55% and displayed nocturnal activity patterns. The four smallest civets used trees as resting sites extensively while the largest civet,Viuerra zibetha, was always located on the ground. Faecal analysis indicated that civets fed on at least 18 fruiting tree species as well as rodents, insects and crabs. At least one of the fruits found in civet faeces,Cassia fistula, was not eaten by other major frugivores in the area. The civets showed a preference for mixed deciduous and dry evergreen forest over dry deciduous dipterocarp forest, which had a lower abundance of known food items. The role that civets play as seed dispersal agents may help in the maintenance and structuring of tropical forest communit

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04765.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The diets of Natterer's batMyotis nattereriand the common long‐eared batPlecotus aurituswere investigated at a nursery colony of each species by analysis of droppings collected monthly from May to September. Respectively, 68% and 42% of the diets comprised items presumed to have been gleaned from foliage or other surfaces: diurnal insects, insects which rarely fly, and non‐flying arthropods. Such surfaces included the ground: centipedes were eaten by both bats, and the muscid,Scatophaga stercoraria, usually associated with cattle dung, was a common prey. Indeed, the prevalence of cattle‐farming around both of the bat roosts almost certainly contributed indirectly, in the form ofS. stercoraria, to a significant part of the Diptera consumed. The chief food ofM. nattereriwas the larger Diptera, but Trichoptera, Hymenoptera and Arachnida were also important. Lepidoptera, Coleoptera and Hemiptera were minor prey, with Dermaptera and Chilopoda taken occasionally. Diptera, closely followed by Lepidoptera, together accounted for nearly two‐thirds of the diet ofP. auritus.Also taken, in descending order of importance, were Trichoptera, Arachnida, Chilopoda, Coleoptera, Dermaptera, Hymenoptera and Hemiptera.Plecotus auritus, but notM. nattereri, was evidently able to take a few small insects such as aphids and lesser nematoceran

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04766.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Populations of Cuvier's, dama and dorcas gazelles were removed from the western Sahara to the Estacion Experimental de Zonas Aridas, Almeria, Spain, between 1970 and 1975. The life‐history records of all the females living between 1970 and 1988 were examined.Results show that fecundity is lower in young females than in middle‐aged females, and that juvenile mortality is higher in fawns of young females. The adult body length of Cuvier's and dorcas gazelles is affected by their early development but this does not apply to the dama gazelle. The adult body length and the birth weight are positively correlated with longevity in female Cuvier's and dama gazelles, but for the dorcas gazelle only birth weight is related to longevity. Juvenile survival and reproductive performance of the three gazelle species studied are not related to adult body length or birth weight.A high inbreeding coefficient reduces longevity in Cuvier's and dama gazelles but not in the dorcas gazelle. The effect of a high inbreeding coefficient is pronounced in the fecundity and juvenile survival of the female dama gazelle, less pronounced but evident in dorcas gazelle. The effects of inbreeding are minimal in Cuvier's gazelle and are evident only in the twinning rate. This result is surprising in view of the high inbreeding coefficient in Cuvier's gazelle relative to the other two species.As in many mammals, birth weights in the three species studied are closely related to the probability of survival during the first days of life. One of the causes of decreasing birth weight in male and female offspring of Cuvier's gazelles and in female offspring of dorcas gazelles is their inbreeding coefficient. The inbreeding coefficient of the mother also reduces the offspring's birth weight in both sexes of the dama gazelle, but there is no influence on offspring of Cuvier's or dorcas gazelles. On the other hand, only the birth weight of the male offspring of the dorcas gazelle is influenced by the birth weight of its mother. Mother's age and offspring birth weight are related for male offspring of Cuvier's and dama gazel

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04767.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY