摘要:

Males of king penguins(Aptenodytes patagonicus)naturally fast during one month at the beginning of their breeding cycle in the sub‐Antarctic islands. Previous qualitative data have shown that this species adapts to prolonged fasting by mobilizing fat stores and minimizing protein loss and that this strategy ends with a progressive increase in protein utilization. In the present study, the quantification of nutrient utilization from body composition of captive birds indicates that, during the phase of protein conservation, 93% of the energy produced derives from the oxidation of fat stores, body protein accounting for the remainder (7%). Tissue composition analysis shows that integument (feathers, skin and subdermal fat) is the main lipid source (65% of the fat loss) during this period, and that pectoral muscles provide the majority of body protein (57% of the total loss). If the fast is prolonged until a body mass below 10 kg is reached, there is a progressive four‐fold increase (from 1 68 to 6.50 gN/24h) in nitrogen excretion, together with a progressive exhaustion of fat stores. This shift in fuel metabolism is not a direct consequence of total lipid depletion, because 22% of the initial fat content still remains when proteins are no longer spared. During this later metabolic phase, protein is not only provided by pectoral muscles (71% of the loss), but also by hindlimb muscles (13%), and there remains only 2% of the initial amount of lipid in the integument at the end of the fast. Total energy expenditure is close to the fasting basal metabolic rate during the phase of protein conservation (2.52 W/kg), but it increases by 33% (3.36 W/kg) during the phase of protein wasting. This difference is probably due to a rise in locomotor activity, that is interpreted as reflecting a stimulation of food foraging behaviour before the lethal depletion of nutrient reser

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06052.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

This paper describes the factors affecting body mass at weaning and by hibernation of young fat dormice(Glis glis)We studied a free‐living population in 1991 and 1992 in a mixed forest where 100 nest‐boxes were placed. In the two years, 128 females used the nest‐boxes to give birth and rear their litters and more than 900 dormice have been individually marked. Body mass of young at weaning was positively correlated to body mass of the mother in both years and to birth date in 1991, while litter size was negatively correlated to body mass of the young in 1992 only, when birth took place about two weeks later than in 1991. On the contrary, by the time of hibernation, young born later weighed significantly less than those born earlier in the season, and heavier young at weaning remained heavier by hibernation, while maternal body mass and litter size did not significantly affect body mass of young at this stage. Body mass of the mother was negatively related to the date of parturition and early breeding females lost weight during lactation, while females that bred later did not. It seems, therefore, that early breeding carries a cost that only females in good condition can afford. It appears that females may follow two strategies: those in poor body condition will delay pregnancy so that lactation occurs when environmental feeding conditions are at their best; those in good condition will breed earlier, since they can afford to lose weight during lactation. Their young will have more time to grow before hibernation and the mothers themselves will have a longer period of time for restoring their fat res

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06053.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The Damaraland mole‐rat,Cryptomys damarensis, is a highly social subterranean rodent that exhibits reproductive suppression. Inhibition of reproduction occurs in colonies of the Damaraland mole‐rat such that only one female and one or two males are reproductively active. A strict breeding system is set up in which the sole reproductive female initiates courtship and selects her mate who is paired with her throughout the year.The present study has shown that inC. damarensiscolonies, both adult and juvenile non‐reproductive females are anovulatory and have low concentrations of oestrogen, 2.2 ± 4.6 nmols/mmol creatinine (n = 133) throughout the year. In contrast, the reproductively active female has elevated concentrations of oestrogen during pregnancy, 95.0 ± 151.O nmols/ mmol creatinine (n = 17). The non‐reproductive females are rendered at least temporarily infertile in that, instead of the secondary follicles maturing and ovulating, they develop into luteinizing follicles. This suppression of ovulation is maintained for as long as there is a reproductive female in the colony. These data support the behavioural findings that non‐reproductive females are never involved in courtship or copulatory behaviour nor do they solicit male colony members. Thus a socially induced suppression of reproductive physiology is apparent in females.In the male Damaraland mole‐rat, suppression of reproduction is due entirely to an inhibition of reproductive behaviour. The mean urinary concentration of testosterone of the reproductive male was 3.8 ± 3.7 nmols/mmol creatinine (n = 25) and that of the five non‐reproductive males 4.4 ± 5.3 nmols/mmol creatinine (n = 114). All male mole‐rats are capable of undergoing spermatogenesis and thus are physiologically capable of fertilizing the reproductive female.It appears, therefore, that reproductive suppression amongst non‐reproductive female mole‐rats is more profound than that which occurs in non‐reproductive males. The latter are apparently restrained from sexual activity by being subordinate to the reproductive male(s), excluded from the pair bond and by being the progeny of the reproductive animals. Thus a predominantly behavioural control mechanism would be in for

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06054.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A total of 297 common dolphin(Delphinus delphis)stomachs was used for these diet analyses. All originated from common dolphins incidentally captured in Natal, where their occurrence is strongly associated with an annual, northward fish migration, the sardine run, along the east coast. Thirty‐six fish and four cephalopod prey species were identified. Though 86.9% by weight of the diet was made up of only five prey species, common dolphins appear to feed opportunistically, their diet reflecting local prey abundance and availability. Prey were primarily small, easily‐caught, pelagic shoaling species, with the main prey being South African pilchard(Sardinops ocellatus).Although pilchard dominated the diet between 1974 and 1992, there were marked annual and seasonal fluctuations in dietary composition, reflecting changes in prey availability and abundance. There were clear differences in the contribution of particular prey species to the diet of different sex and size groups, with strong evidence for resource partitioning between groups. The influence of the annual ‘sardine run’, and the fish predators associated with it, on the diet, feeding biology and distribution of common dolphins is di

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06055.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The anatomy of the gastrointestinal system of Northeastern Atlantic minke whales(Balaenoptera acutorostrata)was investigated. The stomach consisted of four compartments. The first chamber, or forestomach, was non‐glandular and was lined with a keratinized stratified squamous epithelium. The tissue wet weight of the forestomach represented 10.4 ± 2.2% (n = 3) of the total gastrointestinal tract (GI‐tract). When maximally expanded with water, the forestomach contained from 68–321 litres (n = 3), while forestomach contentsin situranged from 5–80 litres (n = 12), with a pH of 6.43 ± 0.28 (n = 12). An orifice, with a relaxed diameter of 27.8 ± 100cm (n = 8), separated the forestomach from the fundic chamber. The mucosa of the fundic chamber possessed gastric glands comprising parietal and chief cells. The contents of this chamber had a pH of 5.26 ± 1.02 (n = 12). The tissue wet weight represented 13.5 ± 1.9% (n = 3) of the total GI‐tract, and when maximally expanded with water, the fundic chamber contained 63–100 litres (n = 3).In situcontents of this chamber ranged from 2–25 litres (n = 12). A connecting channel, with a relaxed orifice diameter of 7.3 ± 3.7 cm (n = 8), joined the fundic chamber and the pyloric chamber. The mucosa of the pyloric chamber contained mucous glands only and no primary glands of digestion. The contents of the pyloric chamber had a pH of 3.60 ± 0.97 (n = 12). The tissue wet weight represented 2.8 ± 0.1% (n = 3) of the total GI‐tract, while the maximally expanded pyloric chamber contained 18–39 litres (n = 3). The pyloric sphincter, with a relaxed diameter of 3.6 ± 0.5cm (n = 8), terminated the stomach. The small intestine began with a duodenal ampulla, lined with mucous glands similar to those in the pyloric chamber. The contents of the duodenal ampulla had a pH of 3.24 ± 0.79 (n = 12). The tissue wet weight represented 1.4 ± 0.2% (n = 3) of the total GI‐tract, and its maximally expanded volume was 8–30 litres (n = 3). The tissue wet weight of the small intestine, caecum and colon represented 61.9 ± 1.3 (n = 3), 0.82 ± 0.48 (n = 3) and 8.7 ± 2.1% (n = 3) of the total GI‐tract, respectively. The lengths of the small intestine, caecum and colon were maximally 36, 0.4 and 4 m, respectively. The forestomach somewhat resembles that of ruminants, but the overall size of the stomach is small, and the length of the

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06056.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Variation in habitat use was studied by radiotracking 11 polecatsMustela putoriusin two wetlands in western France. Habitat selection showed a clear seasonality. Marshes were the most exploited habitat in spring while woods were mainly used in the coldest months and meadows were frequented in summer and winter. An analysis of scats showed that diet correlated with habitat utilization. The proportions of bank volesClethrionomys glareolus, and meadow volesMicrotussp. were, respectively, related to the use of woods and meadows, while amphibians (mainlyRana dalmatinaandBufo bufo)were associated with marshes. Availabilities of rodents, assessed monthly by trapline success, were also significantly correlated to their occurrences. In contrast, no correlations were found between larger prey, such as brown ratsRattus norvegicusand rabbitsOryctolagus cuniculus, and any habitats or their abundance in the field. The occurrences of these prey and of some minor resources, such as shrews and birds, were correlated most with meteorological factors. The exploitation of marshes and amphibians increased when small rodents declined. Therefore, in the polecat, habitat selection was mostly influenced by trophic factors. Dietary diversity was greater in spring when food resources decreased, suggesting that polecats were optimal foragers. The study has emphasized that the polecat is a generalist feeder.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06057.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The early stages of development of three blenniid species,Aidablennius sphynx(6.7–15.8 mm BL),Coryphoblennius galerita(4.3–13.9mm BL), andLipophrys canevai(3.5–10.4 mm BL) are described from specimens collected in the western Mediterranean. The characteristics used for identification included meristic, developmental, morphological and pigmentation characters. Distinguishing characters of these species useful in differentiating them from other species of blenniids for which early stages are known in the Mediterranean are presented. Information on the occurrence of larvae and juveniles of these species off the Catalan coast (north‐western Mediterranean) is als

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06058.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

An investigation of the feeding habits and prey availability in a community of seven species of shrew (Insectivora: Soricidae) inhabiting the taiga of Central Siberia was carried out with the aim of quantifying levels of niche overlap and elucidating modes of ecological separation amongst these coexisting species. All species took a wide range of invertebrate prey, and overlap in the numbers of shared prey taxa was high, but differences in dietary composition of certain taxa reduced overlap between most species. Small species fed almost exclusively on small arthropods, mostly Araneae, Chilopoda and Coleoptera, while medium and large‐sized species took high proportions of oligochaetes. Prey were mostly taken in proportions approximately equal to their availability, although certain prey appeared to be selected. All shrews took prey in a range of sizes, and the high dietary occurrence of small invertebrates reflected their availability and high encounter rate in field samples. Dietary occurrence of small prey was negatively correlated, and large prey positively correlated, with body size of shrew. Smaller shrews were predominantly ground‐surface foragers while larger species were more subterranean, with body size and dietary occurrence of soil prey being positively correlated. Differences in prey size and foraging mode reduced niche overlap between shrew species of widely differing sizes. Each shrew species did not occupy a separate, well‐defined food niche. Instead, the community was sub‐divided into three functional groups: large and small species which tended towards specialization with relatively low levels of overlap, and intermediate, generalist species with higher levels of

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06059.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Interannual variation in aspects of the breeding biology of Antarctic prions was studied for three summers (1989–1992) at Bird island, South Georgia. Egg size, mass and incubation period remained constant. Laying, hatching and fledging were significantly delayed and less synchronous in 1991/92 (range of laying dates 51 days compared to 10–15 days in the two other seasons). This was due to an unusually cold and protracted winter, with ice blocking burrows into the spring, restricting availability of nest sites. Brooding lasted longer in 1991/92 but the overall fledging period was unchanged. Skeletal growth rates did not vary amongst years; growth in mass was slower in 1989/90 but fledging mass was similar in all three years. In 1989/90 and 1991/ 92 later hatched chicks grew (in mass) faster. The survival of chicks from hatching to fledging did not vary amongst years or with hatching date. Feeding frequency was similar between years, once allowance had been made for starlit nights. Thus late and asynchronous breeding in 1991/92 did not result in reduced breeding success either through predation or starvation.Crustaceans formed 98–99% of the mass of the identifiable portion of regurgitated food samples. Significant annual variation was found within these crustaceans with the presence of krill (least in 1990/91) being inversely related to that of amphipods and copepods. There was no relationship between diet composition and chick growth or survival. Other seabird species, lacking the morphological specialization for feeding on copepods and amphipods, had very low breeding success in 1990/91, when krill was s

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06060.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

There is much confusion concerning the identity of bullfrogs in southern Africa. Currently three subspecies are recognized, and introgression has been suspected. We demonstrate that in southern Africa there are two species:Pyxicephalus adspersuswhich has a long call, breeds during the day, and exhibits lek behaviour;Pyxicephalus eduliswhich is smaller, has a short call, breeds at night and does not exhibit lek behaviour.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb06061.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY