摘要:

The reliable detection of reproductive events in free‐ranging primates is usually not feasible because of the difficulty of obtaining physiological measures in the field. Utilizing a non‐invasive technique, urine was collected from wild Vervet monkeys in Amboseli National Park, Kenya. Measurement of pregnanediol‐3α‐glucuronide levels in urine of female Vervets, combined with behavioural observations, permitted accurate estimation of conception dates for individual females. Copulatory behaviour in Amboseli Vervets was unrelated to female hormonal cycles, and females copulated both before the initiation of ovarian function and during pregnancy. This study establishes new possibilities for integrative studies of the physiology and ecology of mammals in their natural

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03538.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Hypotheses relating the form and function of bivalve hinge and marginal dentition were examined using experimental manipulations of shell sculpture. Experiments were designed to estimate relative resistance proffered by these two sculpture types in the absence of the adductor‐ligamentum complex. Forces required to shear two species of bivalve molluscs (with altered sculpture) were measured in the plane of the commissure, using an Instron materials testing machine.Noetia ponderosa and Mercenaria mercenaria were chosen for their divergent morphology. Interpretation of results on the relative importance of hinge and commissure interdigitation in preventing shear suggests that crenulated margins, whether weakly or strongly elaborated, contribute little direct resistance to shear stress. By comparison, results for hinge dentition (taxodont or heterodont) support previous conclusions concerning their functional importance. For example, the ‘primitive’ taxodont hinge of Noetia withstood forces five times those for Mercenaria, which has a heterodont hinge type.Further observations and qualitative results are given comparing different hinge types and marginal modifications. Teeth pattern breakage for Noetia suggests that certain teeth may function differently, depending on the direction in which forces are applied. Search of the literature yielded no examples of predators capable of exerting sufficient forces to shear bivalve organisms. Though the data are not comprehensive, and are intended only to demonstrate relative differences in shell (sculpture) resistance to shear, much insight can be gained from these results for future st

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03539.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The development of the free‐swimming veliger ofAmphibolais followed from hatching to settlement, and the larval structures compared with those of post‐metamorphic juveniles and adult snails. Observations of living specimens and light‐microscope sections were combined with scanning electron microscopy to build up a composite picture of veliger structure.Four stages in the development of veligers are recognized, each being characterized by the appearance of organ systems such as the mantle cavity, larval heart, adult heart and kidney, and larval pallial gland. At or after metamorphosis, the larval systems (heart, kidney and pallial gland) disappear, and the developing adult organs move to the positions characteristic of adult snails.Organogenesis inAmphibolaveligers is compared with that of prosobranch and opisthobranch larvae, and with that of pulmonate larvae with direct development. The closest similarity is seen to be with opisthobranch vel

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03540.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The elastic properties of the forefeet of Donkeys, and of tendons removed from the feet, have been investigated in dynamic tests at a frequency chosen to simulate running. The elastic properties of the foot are explained in terms of the properties of individual tendons and check ligaments. The elastic strain energy stored in the foot, during a trotting step, is calculated to be only a little less than the optimum quantity which would minimize the work required of the muscles in this gait. Frictional and viscous energy losses were fairly small in the experiments on feet, and would probably be smaller in the intact animal.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03541.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The avian reproductive cycle is integrated and timed by a variety of environmental factors that include day length, availability of food, nest sites, presence of a mate, etc. However, reproduction can be delayed or disrupted by inclement weather and, until recently, the endocrine responses of avian species to storms were entirely unknown. This communication describes changes in endocrine state in free‐living male Song sparrows,Melospiza melodia,during gonadal recrudescence after a severe winter, and in response to storms in early spring and summer. Both the severe winter weather and an early spring snow storm delayed testicular development, and depressed circulating levels of testosterone. The sparrows did not appear to be stressed, however, since body mass and fat deposits were higher than in birds sampled during the previous spring after a less severe winter.A second storm occurred in late May and early June when Song sparrows were feeding young. Curiously, plasma levels of testosterone were not affected, but the sparrows did appear to be stressed since there was a significant decline in body mass, and a marked increase in circulating levels of corticosterone. These data suggest that the effects of inclement weather on reproductive function can vary in relation to the stage in the reproductive cycle when the storm strikes, and that the endocrine mechanisms underlying acclimatization to severe meteorological conditions are also differen

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03542.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Prolonged and severe periods of inclement weather can retard gonadal development in early spring or disrupt the breeding cycle in summer. Previous investigations on the endocrine responses of free‐living avian species to storms have been restricted almost entirely to males. This communication presents the endocrine responses of free‐living female Song sparrows,Melospiza melodia,during gonadal recrudescence after a severe winter, and during storms in early spring and summer. As in males, gonadal recrudescence was delayed by the severe winter weather, and this effect was exacerbated by an aseasonal snow storm in early spring. Unlike males, female Song sparrows did appear to be stressed by this snow storm, since body mass and fat deposit decreased, and plasma levels of corticosterone increased. A second storm in early summer did not, however, prove to be stressful to females, although males were apparently stressed by the same storm. At the time the early summer storm occurred, young had been fledged and were being fed mostly by the male. Females begin preparing for a second clutch of eggs and do not feed fledglings to the same extent as males. Thus it is possible that males are stressed by storms at this time, because they are feeding several young as well as themselves during a period of reduced availability of food, whereas females are feeding themselves only. These data suggest that, not only do the endocrine responses to inclement weather vary in relation to stage in the reproductive cycle when storms strike, but also that there are sex differences in those respon

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03543.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The Giant anteater(Myrmecophaga tridactyla)is one of the most specialized mammalian predators, subsisting exclusively on a diet of ants and termites. This study examines the feeding and food preference of captive and wild Giant anteaters in central Brazil. Eight species of mound‐building termites were offered to anteaters in the Brasilia Zoo. The anteaters showed marked preferences for some species over others. The overall pattern of preference did not correlate with prey size, prey nutritional quality or the soldier‐based defence type of the different prey species.Preferences of wild anteaters in Emas National Park, Goias State, Brazil for an equivalent set of termite species were then determined. The preferences of wild animals did not correlate with the preferences of captive ones. This discrepancy results principally from the fact that the conditions under which anteaters encountered prey in the captive trials were very different from the conditions under which prey were encountered in the wild. A Giant anteater incorporates three major factors in its decision to feed on a particular termite species: nutritional value, availability (or mound defence) and response to attack.The very short feeding periods that typify anteater feeding are caused by the rapidly decreasing prey value of the social insect colony following predator attack. The different types of defence exhibited by the different prey species all serve to cause this rapid decrease and thus limit, but do not prevent, predation.SummaryThe purposeofthis study was to investigate the relationship between the Giant anteater as a predator and termites as prey. Giant anteaters have long been known to eat only ants and termites, but little work has been done on which species are consumed and why those are chosen over others. In two‐way choice trials the present author offered captive Giant anteaters eight species of central Brazilian mound‐building termites.Myrmecophagapreferences were determined by the amount of time spent feeding on each termite species. The preferences of captive animals were then compared with the preferences of wild anteaters in Emas National Park, Brazil.Myrmecophagashowed marked preferences for some species of termites, both in captivity and in the wild. However, the ranking of prey species differed between the two situations. Most dramatically, one genus,Velocitermes, which was least‐preferred in captivity, was most‐preferred in the wild. By analysing the differences between wild and captive animals, it has been shown that three major factors seem to influence Giant anteaters food preferences: (1) the type of soldier‐based defence; (2) the type of mound defence or availability and (3) the nutritional value. Each of these factors can serve as a defence against anteater predation, and the different termite species incorporate these defences in different ways with different emphases.Giant anteaters feed on all prey species in a similar way: by feeding for short periods of time at many different locations. This pattern of feeding is forced on the predator by the nature of its prey defences, and is not a form of prudent predation as has been previously suggested.I would like to thank the following organizations for funding my research: Organization of American States, National Geographic Society, Harvard University, Sigma Xi and Friends of the National Zoo. The Brazilian Institute of Forestry Development granted me permission to work in Emas Park and the Director, Heber Silva de Oliveira and Assistant Director, Antonio Malheiros da Cruz, provided me with help while in the Park. Ms Sonia Pereira provided invaluable service in helping me follow anteaters. The members of the Order of Saint Benedict in Mineiros, and especially Father Eric Deitchman, helped me greatly. The Brasilia Zoo, and particularly Raimundo David Monteiro Lima, kindly gave me access to their animals and greatly aided my work. The Laboratories of Zoology and Ecology at the University of Brasilia provided working space and support; I would particularly like to thank Drs Cleber J. R. Alho, Tony Raw, Helen Coles de Negret and Tom E. F. Lacher. Dr Alan Mill kindly shared his knowledge of Brazilian termites and identified the termites from Emas Park, while Dr E. O. Wilson helped me with the ants.Dr Lee‐Ann Hayek and Jim Craig helped me with statistical analyses; Ms V. Garber and Ms B. L. Stanton typed the manuscript. This manuscript was greatly improved by J. Shaw, K. Sebens, A. W. Crompton, B. Holldobler, N. T. Wheelwright, S. D. Thompson, J. F. Eisenberg and, particularly, P. L. Shaw and J. G. Robinson. I would also like to thank my parents, R. H. Redford and L. C. Redford, and Peter Eisner for helping me to recov

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03544.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The Great white pelicanPelecanus onocrotalusis a major predator of some freshwater fish stocks in much of Africa. Detailed population time‐activity budgets allowed us to estimate that the south‐western Cape Province population consumed 184 tonnes offish annually. Of this, 69% was required for adult existence, 17% for chicks and 14% for flight.Per capitaconsumption averaged 840 g per day, or 8–8% of body weight; very much less than the figure of 17–6% used in some energy budget calculations. Our integrative bioenergetics approach lends some support for the use of 10% of body weight as the amount of food consumed per day by large piscivorous birds for initial estimates of their impact on stocks.Predation by Great white pelicans may account for some 10–25% offish production, a shortage of reliable data on fish production in African freshwater ecosystems makes a more precise estimate impossible. Food supplies and shoreline length may both be important factors for pelican po

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03545.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Early in molluscan evolution, the development of a conical shell with shell or pedal retractor muscles led to the need of a mechanism for the extension of the foot or the raising of the shell. The forces generated during pedal retraction and extension have been studied inHaliotis midae, an easily obtainable and conveniently large archaeogastropod. In the mantle cavity, cephalopedal venous sinus and ventricle pressure pulses were observed during pedal retraction elicited by the shadow withdrawal reflex, but were never present during extension. However, pressure pulses were recorded in the proximal region of the columellar (or shell) muscle, both during retraction and pedal extension. Sections of this region of the muscle show a three dimensional network of muscle fibres, consisting of retractor fibres passing down to the foot and circumferential and radial fibres. Contraction of the two latter sets of fibres would bring about extension of the retractors, without the use of a discrete hydrostatic skeleton, and appears to be the principal mechanism of pedal extension. Similar muscular structures, here termed the muscular antagonistic system, have been observed in the columellar muscle of other gastropods and in the cephalopod mantle. In contrast, this system has not been observed in the proximal region of the pedal retractors of bivalves or scaphopods, for the pedal haemocoel, which allows muscular antagonism in the manner of a classical hydrostatic skeleton, has developed in association with the burrowing habit. The significance of the muscular antagonistic system in molluscan evolution is discussed.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03546.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

A three‐year study on reproduction in wild populations ofTestudo hermannihas shown that:(a) sexual activity occurs between March and October, except the nesting season (May and June), and is most frequent in August and September,(b) tortoises are promiscuous in their mating habits, there is no evidence of mate selection in relation to size,(c) nest site selection is correlated to ground temperature and nesting itself mainly occurs in the early evening before dark, when the ground temperature characteristics are most indicative of a specific site's relative temperature,(d) incubation takes about three months and is probably temperature dependent,(e) most nests are preyed upon by mammalian predators within a few days after laying (>90% being destroyed), the main cue being the smell of the eggs,(f) average clutch size in Greece is higher than in France, while mean egg weight in France is higher than in Greece, and there is no strong relationship between body size or weight and egg or clutch weight in either country,(g) in contrast to other studies, there is no apparent correlation between rainfall and reproduction parameters,(h) some females nest in successive years, and more than once in a year, with a laying interval of 10–20 days,(i) mean size of sexually active individuals is not significantly different from the mean size of adults, although nesting females are significantly bigger; the minimum size for sexually active males is about 120 mm and for females 130 mm.The discussion examines these observations in an evolutionary cont

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1985.tb03547.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY