摘要:

Growth of upper canine teeth of male Antarctic fur seals (Arctocephalus gazella) which died of natural causes at Bird Island, South Georgia, was quantified from measurements of annual layers in longitudinal sections of teeth. Mean age at death was 7.69±0.07 years and this showed a small but significant increase through the period when samples were collected (1972/73–1988/89). There were significant correlations between morphometrics of teeth and those of seals, suggesting that tooth growth provided an indication of body growth. Tooth growth rate was lowest in seals which died early (age 4 years) and increased with age at death. Changes in the growth pattern of teeth suggested that fur seals which became sexually mature early also died early. Tooth growth layers deposited in each calendar year were compared with the expected layer depth based on a linear relationship between layer depth and age at which each layer was deposited. There was significant variation in the depth of tooth growth layers deposited in different years, suggesting that growth was greater in some years than others. No trends in cohort strengths were detected, but particularly poor years for growth were closely related to years in which reproductive performance was also observed to be low. Variations in growth from 1967/68 to 1987/88 were correlated significantly (P<0.008) with the Southern Oscillation Index of climatic variati

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02630.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

This study compares and contrasts variations of enamel fold pattern on the crowns of the molars of subterranean mole rats (Spalax) belonging to two superspecies,S. ehrenbergiandS. leucodon, and involving about 20 chromosomal species, distributed parapatrically and ranging on different soil types. The sample studied involved 397 skulls, subdivided as follows: 280 ofS. ehrenbergifrom Israel, representing the four chromosomal species 2n = 52, 54, 58 and 60; 59 ofS. ehrenbergifrom Egypt, Lebanon, Syria, Jordan and Turkey; 58 ofS. leucodonfrom Turkey.In making the comparisons it was necessary to take into account the marked changes of molar pattern that take place as a result of wear.There is a reasonably good agreement between differences of molar pattern and genetic and immunological distances. The species in Israel and Egypt form a compact group, clearly differentiated from Turkishleucodon; ehrenbergifrom Turkey and Syria are intermediate, in accordance with their geographical distribution.In Israel, differences associated with soil type are at about the same level as differences between species. Local populations show a higher level of diversity, and in a number of cases neighbouring populations differed significantly, sometimes over very short distances. Population differences within species are generally associated with differences of soil and vegetation, indicating the influence of natural selection. There are also differences across species boundaries, implying a phylogenetic (heritage) effect. The nature of the adaptive link between molar pattern and soil is unknown: possible factors are contamination of the food by soil, and toughness of the food which necessitates changes of enamel fold length to improve grinding efficiency.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02631.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

An analysis of the mechanism of the jumping organ of the cylindrical springtailTomocerus longicornisand the globular springtailDicyrtoma ornatais presented based on morphological examination and high‐speed photography. Both species have a click mechanism involving deformation of the abdominal sclerites. Morphological and photographic evidence supports the hypothesis that eversion of the springing organ involves a hydroelastic mechanism based on haemocoel pressurization and increased tension in the abdominal sclerites. A computer model was used to analyse jump kinematics and energetics. This model accounts for the spin observed during jumping and shows how body planform (e.g. cylindrical versus globular) and tail length can influence direction, height, range and rate of spi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02632.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A mechanism which enables flying foxes to lock their hind limb digits and thumbs in flexion is described. The deep digital tendons of the hind limbs have roughened fibrocartilage surfaces. The adjacent flexor tendon sheath supports ridges which interact with the rough tendon surface, temporarily ‘locking’ the two structures together. This tendon locking mechanism is of importance as it enables bats to reduce the energetic cost of hanging from branches. It does this by reducing, or eliminating, the need for digital flexor muscle activ

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02633.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Resistance to desiccation was examined in six populations of the Israeli bush‐dwelling snailTrochoidea simulata, a desert species distributed mainly between the 100–200 mm isohyets.The present study revealed significant intraspecific differences in resistance to desiccation which are correlated with habitat and climatic gradients within the distribution range of the species. Populations from more arid sites were more resistant to desiccation and heat exposure than those from more mesic areas. However, the population from the Rift Valley (an extremely arid region) was surprisingly poorly resistant. Rates of population water loss under the controlled experimental conditions in the laboratory generally matched the calculated water losses during natural summer aestivat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02634.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Composition of the diet of fallow deer in the New Forest in southern England was determined on a monthly basis from faecal analyses. The deer were shown to be predominantly grazers: grasses accounted for approximately 70% of annual forage intake, with the remainder of the diet dominated by sedges, rushes, heather and broadleaved browse. Differences in dietary composition and diet quality could be shown between males and females where buck and doe groups occupied discrete home ranges. Differences between the male and female diets were also maintained in areas where the two sexes. while still socially segregated, occupied overlapping ranges. Males had higher quality diets in winter, while females consumed higher quality diets in spring and summer. These results are considered in the context of general theories of dietary difference between the sexes in dimorphic species of ungulates.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02635.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Aspects of community structure and organization are examined in an assemblage offive species of small carnivores (Family Viverridae). Comparative use of the spatial and temporal niches for each species is studied and used to interpret coexistence. The spatial niche segregates the assemblage into three groups, including a three‐species mixed‐forest group. This mixed‐forest group comprises a single‐species diurnal branch and a nocturnal branch. Segregation of the nocturnal branch may only be achieved through trophic diff

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02636.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Gekkonid lizards are shown to have well‐developed nasal chemical senses. It is argued that they are unique among squamates so far studied in the degree of their olfactory (as opposed to vomeronasal) development. This contention is supported by evidence from the brain, nasal capsule, tongue, and experimental studies of behaviour. Limited evidence suggests that olfaction functions in food‐finding and predator detection; vomerolfaction during investigation of novel stimuli and in reproduction. The conception of gekkonids as members of a ‘visual Ascalabota’ is not supported by these findings. Olfactory specialization makes geckos ideal subjects for tests of the Cowles and Phelan hypothesis of olfactory function and suggests that they might be better subjects than snakes for future studies of dual olfactory form, function and evolution in a nonmammalian

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02637.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Eleven small mammal species (nine rodents and two shrews) were recorded in 16 months of trapping in the Karkloof Forest, Natal. Total densities varied seasonally, ranging from 60.7 animals/ha in the dry autumn and winter to 29.1 animals/ha at the onset of the rains in spring and early summer. Peaks in breeding coincided with high body fat and water content in the five common species during summer: in winter, when body fat and water levels were low, there was no breeding. This may be related to poor food quality at this time. Annual changes in density, breeding season and juvenile recruitment ofRhabdomys pumilio, Mastomys natalensisandMyosorex variusare the same as recorded in conspecific populations from other habitat types and do not seem modified by the habitat stability of the forest environment. Of the five common species, onlyGrammomys dolichurus, one of the few forest‐associated small mammals in southern Africa, andGraphiurus murinusdemonstrated stable, K‐selectéd life‐history

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02638.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Post‐natal growth in the African elephant (Loxodonta africana) was described using three alternative mathematical models, and two age estimation schedules. Von Bertalanffy, Gompertz and Logistic equations all provided adequate models of post‐natal growth in a species for which age estimation methods are largely unsubstantiated. Gompertz and Logistic models overestimated pre‐weaning growth and underestimated adult size. Self‐accelerating growth is of short duration (one and three years in females and males, respectively), and we found no evidence of a secondary growth spurt in males. Males, nevertheless, continue to grow throughout their lifespan, while females reach asymptotic size at the age of 35–40 years. We found no evidence of differences in growth rate of males and females up to 10 years, and there does not seem to be differential investment in male and female offspring. Growth rates of captive elephants differ substantially from all wild populations studied and may not serve as adequate references for the revision of existing age estimation

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb02639.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY