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Abstract: A detailed and extensive mark-recapture-recovery study of red deer on the island of Rum forms the basis of the modeling of this article. We analyze male and female deer separately, and report results for both in this article, but use the female data to demonstrate our modeling approach. We provide a model-selection procedure that allows us to describe the survival by a combination of age-classes, with common survival within each class, and senility, which is modeled continuously as a parametric function of age. Dispersal out of the study area is modeled separately. Survival and dispersal probabilities are examined for the possible influence of both environmental and individual covariates, including a range of alternative measures of population density. The resulting model is succinct and biologically realistic. We compare and contrast survival rates of male and female deer of different ages and compare the factors that affect their survival. We demonstrate large differences in the rate of senescence between males and females even though their senescence begins at the same age. The differences between the sexes suggest that, in population modeling of sexually size-dimorphic species, it is important to identify sex-specific survival functions.

Species may become obligate cooperative breeders when parents are unable to raise their offspring unassisted. We measured the daily energy expenditure of mothers, helpers and offspring during peak lactation in cooperatively breeding meerkats Suricata suricattausing the doubly labelled water technique. Lactating mothers expended more energy per day than allo–lactating subordinate females, non–lactating females or suckling offspring. Metabolizable energy intakes of lactating mothers were calculated from isotope–based estimates of offspring milk energy intake, and were not significantly different from the previously suggested maximal limit for mammals. Allo–lactating females were the only category of animals that lost weight during the period of study, probably because they spent more time babysitting than non–lactating females. Daily energy expenditure (DEE) of lactating mothers increased with litter size but decreased with the number of helpers. Calculations show that for every 10 helpers, even in the absence of allo–lactators, mothers are able to reduce their DEE during peak lactation by an amount equivalent to the energy cost of one pup. These results indicate that helpers have beneficial energetic consequences for lactating mothers in an obligate cooperatively breeding mammal.

Attempts to relate species differences in population dynamics to variation in life histories rely on the assumption that the causes of contrasts in demography are sufficiently simple to be derived from first principles. Here, we investigate the causes of contrasts in dynamics between two ungulate populations on Hebridean islands (red deer and Soay sheep) and show that differences in stability, as well as in the effects of variation in density and climate, are related to differences in timing of reproduction relative to seasonal variation in resource abundance. In both populations, attempts to predict changes in population size sufficiently accurately for the results to be useful for management purposes require a knowledge of the responses of different age and sex categories to changes in density and climate, as well as of population structure.

A previous review of inbreeding in natural populations suggested that close inbreeding (inbreeding coefficient f= 0.25) is generally rare in wild birds and mammals. However, the review did not assess rates of moderate inbreeding (f= 0.125), which may make a rather larger contribution to overall inbreeding in a population. Furthermore, previous studies may have underestimated the prevalence of inbreeding in wild populations with incomplete pedigrees. By categorizing inbreeding events by the relationship of the parental pair, we suggest a simple method for estimating rates of close and moderate inbreeding from incomplete pedigree data. We applied this method to three wild populations of ruminants: red deer on Rum, Scotland, Soay sheep on Hirta, Scotland and reintroduced Arabian oryx on the Jiddat–al–Harasis, Oman. Although paternal half–sib pairs were the most common category of inbreeding in all three populations, there was considerable variation among populations in the frequencies of the various categories of inbreeding. This variation may be largely explained by differences in population size and dynamics, in maternal and paternal sibship size and in the overlap of reproductive lifespan of consecutive generations. Close and moderate inbreeding appear to be a routine part of breeding behaviour in these ruminant populations.

Objectives:Although retrograde cerebral perfusion has become a popular adjunctive technique and may improve cerebral ischemic tolerance during hypothermic circulatory arrest, direct cerebral metabolic benefit has yet to be demonstrated in human subjects. We investigated the post-arrest metabolic phenomena with and without retrograde cerebral perfusion in patients. Methods:In a prospective randomized trial, 42 patients undergoing aortic surgery requiring hypothermic circulatory arrest were allocated to receive hypothermic circulatory arrest alone (n = 21) or hypothermic circulatory arrest with additional retrograde cerebral perfusion (n = 21). Circulatory arrest was commenced at 15°C, and retrograde perfusion was instituted through the superior vena cava at a maximum jugular bulb pressure of 25 mm Hg. Transcranial, paired, repeated samples of the arterial and jugular bulb blood were analyzed for oxygen and glucose. Velocity in the right middle cerebral artery was also measured simultaneously. Results:There were 3 (7.1%) deaths and 3 (7.1%) episodes of neurologic deficit. Mean bypass and circulatory arrest duration (in minutes) were similar between groups (P= .4 and .14). The mean retrograde perfusion duration was 23 minutes. Post-arrest nasopharyngeal temperature was similar (15.3°C vs 15.3°C). Retrograde perfusion did not affect post-arrest oxygen extraction, glucose extraction, or jugular bulb Po2. There was no immediate lactate release immediately after hypothermic circulatory arrest. Conclusions:Retrograde cerebral perfusion did not influence immediate post-arrest nasopharyngeal temperature or cerebral metabolic recovery. The low jugular bulb Po2suggests equivalent ischemia. These findings cast doubt on the effectiveness of retrograde cerebral perfusion as a metabolic adjunct to hypothermic circulatory arrest.

1Studies of the effect of vagus nerve stimulation on ventricular myocardial function in mammals are limited, particularly in the human.2The present study was designed to determine the effect of direct electrical stimulation of the left vagus nerve on left ventricular contractile state in hearts paced at 10 % above the natural rate, in anaesthetised pigs and anaesthetised human subjects undergoing open chest surgery for coronary artery bypass grafting.3Contractility of the left ventricle was determined from a series of pressure‐volume loops obtained from a combined pressure and conductance (volume) catheter placed in the left ventricle. From the measurements a regression slope of the end‐systolic pressure‐volume relationship was determined to give end‐systolic elastance (Ees), a load‐independent measure of contractility.4In six anaesthetised open chest pigs, stimulation of the peripheral cut end of the left cervical vagus nerve induced a significant decrease in Ees of 26 ± 14 %.5In nine patients electrical stimulation of the left thoracic vagus nerve close to its cardiac branch resulted in a significant drop in Ees of 38 ± 16 %.6The effects of vagal stimulation were blocked by the muscarinic antagonist glycopyrronium (5 mg kg−1).7Administration of the β‐adrenoreceptor antagonist esmolol (1 mg kg−1) also attenuated the effect of vagal stimulation, indicating a degree of interaction of vagal and sympathetic influences on contractility.8These studies show that in the human and pig heart the left vagus nerve can profoundly decrease the inotropic state of the left ventricular myocardium independent of its bradycardic effect.

Inter-sexual segregation between habitats or between sites within a habitat is very widespread in sexually dimorphic ungulates. As an explanation, it has been suggested that males, because of their larger forage requirements, are driven from preferred, high quality forage habitats into marginal habitats of lower forage quality but higher forage biomass by female competition (‘indirect competition hypothesis’). However, this hypothesis has hardly been tested. In the present study, we tested the indirect competition hypothesis for site segregation of red deer on the Isle of Rum, Scotland, within two vegetation communities: short Agrostis/Festuca grassland and Calluna heath. We predicted that: (1) males should choose sites within each vegetation community that are of higher forage biomass but lower forage quality, than sites selected by females; (2) the degree of inter-sexual site segregation should be highest within the vegetation community in which indirect competition was most intense. We found that the sexes were significantly segregated between sites within both vegetation communities, but males did not use sites of lower forage quality or of higher forage biomass than did females. Moreover, degree of site segregation was not significantly higher in the vegetation community in which competition was more intense (i.e. short Agrostis/Festuca grassland). We conclude that the indirect competition hypothesis cannot explain site segregation in red deer on the Isle of Rum.

Evolutionary and conservation biologists have a long-standing interest in the consequences of inbreeding. It is generally recognized that inbred individuals may experience reduced fitness or inbreeding depression. By the same token, relatively outbred individuals can have greater than average fitness, i.e. heterosis. However, nearly all of the empirical evidence for inbreeding depression comes from laboratory or domestic species. Inbreeding depression and heterosis are difficult to detect in natural populations due to the difficulties in establishing pedigrees. An alternative method is to correlate heterozygosity, which is measured using genetic markers, with a trait related to fitness. The typically studied traits, such as juvenile survival and growth rates, either cover only early life or are weakly correlated with lifetime breeding success (LBS). In this paper we show that heterozygosity is positively associated with male and female adult LBS in a wild population of red deer (Cervus elaphus) on the Isle of Rum, Scotland. To the authors' knowledge, this is the first time that inbreeding depression and/or heterosis have been detected for a trait highly correlated with overall fitness in both sexes in a wild population.

Abstract: In non-territorial species, individuals can move freely and should be distributed in an ideal free manner between habitats and areas with respect to resources that influence lifetime reproductive success (LRS). Consequently, no relationship between diet quality and LRS should be expected. However, there have been no attempts to test this prediction. The present paper investigates the relationship between forage habitat use and LRS in red deer (Cervus elaphus) hinds within three neighbouring areas on the Isle of Rum which differed in their amounts of high-quality-forage habitat. Within areas, hinds move widely and have access to the same resources. We found no correlation between LRS of individual hinds and their use of high-quality-forage habitat (i.e. short Agrostis/Festuca grassland). Our analysis suggests that high hind densities on short Agrostis/Festuca grassland offset any advantages of increased access to preferred forage. These results support the hypothesis that red deer hinds are distributed in an ideal free manner with respect to the use of high-quality-forage habitat. However, hinds rarely leave areas where they are born, and the analysis suggests that constraints in changing areas hindered an ideal free distribution on a larger spatial scale. Consequently, mean LRS was not the same within the three investigated areas: one area, with a low amount of short Agrostis/Festuca grassland and a low hind density, contributed more male offspring (and more total offspring) per hind to the population than the other two areas.

Abstract: Sex differences in habitat use (termed `habitat segregation') are widespread in sexually dimorphic ungulate species. They are a puzzling phenomenon, particularly when females use better foraging habitats than males. It has been suggested that males, owing to their larger body size and higher forage requirements, are inferior in indirect competition to females and are forced by female grazing pressure into marginal habitats (`indirect-competition hypothesis'). This hypothesis has been widely cited and has important theoretical and practical implications. However, evidence for it is inconclusive. The present paper presents the results of the first experimental test of the indirect-competition hypothesis. We manipulated female and male numbers of red deer (Cervus elaphus L.) on a large scale on the Isle of Rum, Scotland, and tested the influence of this manipulation on deer habitat use. We predicted that where female numbers were reduced, male use of preferred habitat should increase and sex differences in habitat use should decrease, while a reduction in male numbers should not have such effects. In contrast, we found that the manipulation of female and male numbers did not affect habitat use, and conclude that the indirect-competition hypothesis does not explain habitat segregation on Rum.

In polygynous, sexually dimorphic species, sexual selection should be stronger in males than in females. Although this prediction extends to the effects of early development on fitness, few studies have documented early determinants of lifetime reproductive success in a natural mammal population. In this paper, we describe factors affecting the reproductive success of male and female red deer (Cervus elaphus) on the island of Rum, Scotland. Birthweight was a significant determinant of total lifetime reproductive success in males, with heavier–born males being more successful than lighter ones. In contrast, birthweight did not affect female reproductive success. High population density and cold spring temperatures in the year of birth decreased several components of fitness in females, but did not affect the breeding success of males. The results confirm the prediction that selection on a sexually dimorphic trait should be greater in males than in females, and explain the differential maternal expenditure between sons and daughters observed in red deer. Differences between the sexes in the effects of environmental and phenotypic variation on fitness may generate differences in the amount of heritable genetic variation underlying traits such as birthweight.

Obligate cooperative breeding species demonstrate a high rate of group extinction, which may be due to the existence of a critical number of helpers below which the group cannot subsist. Through a simple model, we study the population dynamics of obligate cooperative breeding species, taking into account the existence of a lower threshold below which the instantaneous growth rate becomes negative. The model successively incorporates (i) a distinction between species that need helpers for reproduction, survival or both, (ii) the existence of a migration rate accounting for dispersal, and (iii) stochastic mortality to simulate the effects of random catastrophic events. Our results suggest that the need for a minimum number of helpers increases the risk of extinction for obligate cooperative breeding species. The constraint imposed by this threshold is higher when helpers are needed for reproduction only or for both reproduction and survival. By driving them below this lower threshold, stochastic mortality of lower amplitude and/or lower frequency than for non–cooperative breeders may be sufficient to cause the extinction of obligate cooperative breeding groups. Migration may have a buffering effect only for groups where immigration is higher than emigration; otherwise (when immigrants from nearby groups are not available) it lowers the difference between actual group size and critical threshold, thereby constituting a higher constraint.

Tissue hypoxia may be defined as abnormal oxygen utilization such that cells are experiencing anaerobic metabolism. Tissue hypoxia can be defined biochemically by low levels of ATP, high levels of NADH, or decreased oxidized cytochrome aa3. It is possible to measure these biochemical markers in the laboratory setting with, for example, nuclear magnetic resonance spectroscopy. However, this is not as yet a clinical option. There is no 'gold standard' for the diagnosis of clinical hypoxia. We can detect the gross consequences of tissue hypoxia, such as organ dysfunction and metabolic markers of anaerobic metabolism (e.g. lactic acidosis). We have also become familiar with the measurement of both global and regional oxygen dispatch and consumption. However, organ dysfunction and metabolic acidosis consistent with established tissue hypoxia commonly exists in the presence of normal and even supra normal global measures of oxygen dispatch and consumption. Therefore, we should ideally make measurements at the end of the oxygen trail, i.e. cellular oxygen delivery and effective utilization.

In cooperative groups of suricates (Suricata suricatta), helpers of both sexes assist breeding adults in defending and feeding pups, and survival rises in larger groups. Despite this, dominant breeding females expel subordinate females from the group in the latter half of their (own) pregnancy, apparently because adult females sometimes kill their pups. Some of the females that have been expelled are allowed to rejoin the group soon after the dominant female's pups are born and subsequently assist in rearing the pups. Female helpers initially resist expulsion and repeatedly attempt to return to their natal group, indicating that it is unlikely that dominant females need to grant them reproductive concessions to retain them in the group.

In sexually dimorphic mammals, high population density is commonly associated with increased mortality of males relative to females and with female–biased adult sex ratios. This paper investigates the consequences of these changes on the distribution of male breeding success, the intensity of competition for females and the opportunity for sexual selection. After the red deer (Cervus elaphusL.) population of the North Block of Rum (Inner Hebrides) was released from culling, female numbers rose and male numbers declined, leading to an adult sex ratio of around one male to two females. This change was the result of increased mortality of males relative to females during the first two years of life; of increased emigration rates by young males; and of reduced immigration by males from outside the study area. The increasing bias in the adult sex ratio affected the timing of breeding as well as the distribution of mating success in males. As the adult sex ratio became increasingly biased towards females, the degree of skew in mating success (calculated across all harem–holders) increased, but mature males defended harems for shorter periods and a higher proportion of males held harems. In addition, a higher proportion of calves were fathered by immigrant males and the proportion fathered by males born in the study area declined. These results support the convention that, where high population density is associated with a female–biased adult sex ratio, competition for mates is likely to decline.

Extensive variation in life‐history patterns is documented across primate species. Variables included are gestation length, neonatal weight, litter size, age at weaning, age at sexual maturity, age at first breeding, longevity, and length of the estrous cycle. Species within genera and genera within subfamilies tend to be very similar on most measures, and about 85% of the variation remains when the subfamily is used as the level for statistical analysis. Variation in most life‐history measures is highly correlated with variation in body size, and differences in body size are associated with differences in behavior and ecology. Allometric relationships between life‐history variables and adult body weight are described; subfamily deviations from best‐fit lines do not reveal strong correlations with behavior or ecology. However, for their body size, some subfamilies show consistently fast development across life‐history stages while others are characteristically slow. One exception to the tendency for relative values to be positively correlated is brain growth: those primates with relatively large brains at birth have relatively less postnatal brain growth. Humans are a notable exception, with large brains at birth and high postnatal brain growth.

The breeding systems of mammalian species are strongly influenced by the density and dispersion of their populations. These in turn are affected by variations in the distribution of resources. Through quantitative comparisons, it is possible to trace evolutionary relationships between feeding behaviour, population dispersion, breeding systems and morphology.

The fitness consequences of inbreeding and outbreeding are poorly understood in natural populations. We explore two microsatellite–based variables, individual heterozygosity (likely to correlate with recent inbreeding) and a new individual–specific internal distance measure, meand2(focusing on events deeper in the pedigree), in relation to two measures of fitness expressed early in life, birth weight and neonatal survival, in 670 red deer calves (Cervus elaphus) born on the Isle of Rum between 1982 and 1996. For comparison, we also analyse inbreeding coefficients derived from pedigrees in which paternity was inferred by molecular methods.Only 14 out of 231 calves (6.1) had non–zero inbreeding coefficients, and neither inbreeding coefficient nor individual heterozygosity was consistently related to birth weight or neonatal survival. However, meand2was consistently related to both fitness measures. Low meand2was associated with low birth weight, especially following cold Aprils, in which foetal growth is reduced. Low meand2was also associated with low neonatal survival, but this effect was probably mediated by birth weight because fitting birth weight to the neonatal survival model displaced meand2as an explanatory variable. We conclude that in the deer population fitness measures expressed early in life do not show evidence of inbreeding depression, but they do show evidence of heterosis, possibly as a result of population mixing. We also demonstrate the practical problems of estimating inbreeding via pedigrees compared with a direct marker–based estimate of individual heterozygosity. We suggest that, together, individual heterozygosity and meand2, estimated using microsatellites, are useful tools for exploring inbreeding and outbreeding in natural populations.

Attempts to relate interspecific differences in social organisation among primates to gross differences in habitat or diet type have been largely unsuccessful. This is probably partly because distantly related species have adapted to similar ecological situations in different ways and partly because much finer ecological differences are important.

Functional interpretations of helping behaviour suggest that it has evolved because helpers increase their direct or indirect fitness by helping. However, recent critiques have suggested that helping may be an unselected extension of normal parental behaviour, pointing to evidence that all mature individuals commonly respond to begging young (whether they are parents, relatives or non–relatives) as well as to the lack of evidence that cooperative activities have appreciable costs to helpers. Here we provide an example of one form of cooperative behaviour that is seldom performed by parents and has substantial energetic costs to helpers. In the cooperative mongoose, Suricata suricatta, non–breeding adults commonly babysit young pups at the natal burrow for a day at a time, foregoing feeding for 24 hours. Parents rarely contribute to babysitting, and babysitting has substantial energetic costs to helpers. Members of small groups compensate for the reduced number of participants by babysitting more frequently, and neither the proportion of time that babysitters are present nor the survival of litters vary with group size.

The survival of red deer (Cervus elaphusL.) calves to two years of age was examined in relation to electrophoretic variation in a population on the Scottish island of Rhum. Survival was analyzed using logistic analysis in which the “phenotypic” factors birth weight, birth date, subdivision of the study area, cohort, and sex, which affect the probability of a calf's survival, were taken into account. All three polymorphic loci examined, Mpi, Idh‐2,and Trf(each with two detected alleles) are significantly associated with juvenile survival. At Mpi,there is selection against one allele, f(or an allele at a linked locus), and there are indications that this effect is stronger in females than males. For Idh‐2,overall, the heterozygote class survives better than the two homozygotes, which survive equally well. However, again there is a difference between the sexes; female heterozygotes survive much better than homozygotes, whereas male homozygotes survive better than heterozygotes, and the difference in survival is smaller. Furthermore, there is an interaction involving Mpi, Idh‐2,and survival in which Mpifcarriers that are also Idh‐2homozygotes survive very badly compared with other Mpi‐Idh‐2combinations, which all survive equally well. For Trf,the heterozygote class survives best, and there is also a difference in survival between the two homozygote classes. Genotype frequencies in the adult population are consistent with the results for calf survival, in that the Mpiffrequency is lower in succeeding cohorts of surviving adults, whereas no significant gene frequency change is apparent for Idh‐2or Trf.

In the naturally regulated population of Soay sheep Ovis ariesL.) on Hirta (St Kilda), 12 of males and 24 of females have scurred horns. This trait reduces the competitive ability of males in the mating season but is associated with higher overwinter survival rates in both sexes (Moorcroft et al. 1996). In this paper, we show that scurred females also show higher conception rates and weaning rates than non–scurred ones, and that these differences are associated with heavier maternal body weight as well as higher birth weights of offspring. Selection pressures favouring scurredness in females vary with population density and are generally more pronounced among younger animals than adults. We discuss these results with reference to recent suggestions that temporal fluctuation in selection pressures may help to maintain genetic diversity within populations. We suggest that selection against scurredness operating through male mating success is opposed by selection favouring this trait, operating through the breeding success of females and the survival of both sexes.

In individually monitored red deer (Cervus elaphus) living in the North Block of the Isle of Rhum, Scotland, juvenile survival is related to the genotype at the enzyme loci Mpiand Idh‐2(each with two alleles, fand s). To establish whether other fitness components also are related to genetic differences, we examined whether age at first breeding, fecundity, and adult survival of females were related to genotype at the same loci. Fertility in females shot outside the study area was also analyzed in relation to Mpiand Idh‐2genotype. The analyses controlled for phenotypic and environmental factors affecting female reproductive performance. At Mpi, f‐carrying females in the study area bred earlier than ssindividuals and tended to be more fecund. However, no association was found between Mpigenotype and adult survival. In culled females, Mpi f‐carriers were more likely to be pregnant than ssfemales. At Idh‐2, homozygous females in the study area started breeding earlier than heterozygous females. Idh‐2 fsand ssfemales were more fecund than fffemales though this relationship was complicated by an interaction with spring temperature in the year of birth. When the population was at high density, adult survival of Idh‐2 ssfemales was better than survival of fffemales, which was, in turn, better than survival of fsfemales. No association was found between Idh‐2genotype and fertility in culled females. Overall, the associations found in female reproductive measures favor those genotypes that survive particularly badly over the first two years of life. This result supports the idea that countervailing selection in different fitness components (antagonistic pleiotropy) is a common and powerful force maintaining polymorphism in natural populations. It may also explain how fitness components can have large heritabilities while overall fitness may have a low heritability.

Parents will increase their fitness by varying the sex ratio of their progeny in response to differences in the costs and benefits of producing sons and daughters. Sex differences in energy requirements or viability during early growth, differences in the relative fitness of male and female offspring, and competition or cooperation between siblings or between siblings and parents might all be expected to affect the sex ratio. Although few trends have yet been shown to be consistent, growing numbers of studies have demonstrated significant variation in birth sex ratios in non-human mammals. These are commonly cited as evidence of adaptive manipulation of the sex ratio. However, several different mechanisms may affect the birth sex ratio, and not all of them are likely to be adaptive. Valid evidence that sex ratio trends are adaptive must be based either on the overall distribution of those trends or on cases in which the sex ratio can be shown to vary with the relative fitness of producing sons and daughters. The distribution of observed sex ratio trends does not conform closely to the predictions of any single adaptive theory. Some recent studies, however, indicate that, within species, the sex ratio varies with the costs or benefits of producing male or female offspring.

We have compared arterial pressures measured by an indwelling radial cannula with those obtained non-invasively by the Finapres 2000 (Ohmeda) during spinal anaesthesia for lower segment Caesarean section. The digital outputs of both pressures were recorded using a computerized system. We studied 20 patients, yielding a total of 18,772 data points after elimination of data recorded during arterial flushing and erroneous results from each source. The data analysis demonstrated a normal distribution for differences between the two methods of measurement, and the correlations between invasive and Finapres readings for systolic, diastolic and mean pressures were 0.78, 0.72 and 0.79, respectively, indicating an overall poor reflection of intra-arterial pressure by the Finapres under these circumstances. Some patients and some periods of readings reflected a high degree of precision and little bias. However, unexplained large differences in pressure and trends of change that were out of phase over time occurred frequently. We conclude that the Finapres cannot be recommended as a monitor of arterial pressure in this group of patients in whom sudden hypotension may be a threat to maternal or fetal outcome.

Abstract: The performance of three electrodes used for transcutaneous carbon dioxide (tcPCO2) monitoring is compared in 15 healthy volunteers and 26 critically ill adults. All three electrodes showed good correlation between tcPCO2 and arterial blood PCO2 (PaCO2) with a correlation coefficient (r) greater than 0.86. There was little difference in the performance characteristics of the three monitors. They may be usefully employed to estimate PaCO2 values when used with a modified calibration recommended by the manufacturers.

Summary.In a population of free-ranging red deer hinds on the Isle of Rhum (Inner Hebrides) we investigated relationships between four aspects of reproductive performance (fertility, calf birth weight, birth sex ratio and calving date) and four variables likely to affect the mother's condition: age, reproductive status, home range area and year of calving. Fertility was significantly related to mother's age, reproductive status and home range area as well as to year of calf's birth. Stag calves were heavier than hind calves and birth weight was significantly related to mother's age, home range area and year of (calf's) birth but not to mother's reproductive status. Birth sex ratio did not differ from parity, and was not significantly associated with any of the four variables examined. Birth date was significantly related to the mother's reproductive status, home range area and year of (calf's) birth but not to mother's age or the sex of the calf.

Objective.Our objective was to investigate the accuracy of a new intravascular blood gas sensor, the Paratrend 7 (P7) (Biomedical Sensors Ltd, Pfizer Hospital Products Group, High Wycombe, England) in a porcine model.Methods.A total of 12 sensors were inserted into 10 animals under total intravenous anesthesia. Changes in blood gas chemistry were produced over a wide range by manipulating the inspired oxygen and carbon dioxide concentrations and by adjustments in minute ventilation. Blood gas samples (BGA) were taken and analyzed during periods of stability; the results obtained were compared with the readings from the intravascular sensor.Results.A total of 292 blood gas samples were taken and analyzed for pHa, Paco2, andPo2; the results were compared with the readings from the intravascular sensor. Correlation coefficients ofr=0.98 forPco2andr=0.99 for Po2were obtained. Analysis of bias and precision as mean±SD of the difference (P7 — BGA) gave the following results: pH bias=−0.03, precision=±0.04;Pco2bias = 0.65 mm Hg, precision=±3.1 mm Hg; andPo2bias=−6.50 mm Hg, precision=±0.6 mm Hg. No problems with clot formation on the sensor were seen, and the sensors did not appear to show the “wall effect” seen with other systems.Conclusions.The results obtained were well within the requirements for a clinically useful blood gas monitoring system.

Elevated pulmonary vascular resistance and transpulmonary gradient are predictors of increased perioperative mortality in patients undergoing orthotopic heart transplantation. Sodium nitroprusside and prostacyclin PGI2 are routinely used to assess the reversibility of pulmonary vascular resistance and transpulmonary gradient in heart transplant candidates, but their use is limited by their systemic vasodilatory effect. The aim of this study was to evaluate the systemic and pulmonary haemodynamic effects of low concentration (10 and 20 parts per million) inhaled nitric oxide in patients with severe heart failure with elevated transpulmonary gradient and pulmonary vascular resistance undergoing assessment for cardiac transplantation, and to compare the haemodynamic effects of inhaled nitric oxide with those of sodium nitroprusside and prostacyclin PGI2.

The paper examines systematic relationships among primates between brain size (relative to body size) and differences in ecology and social system. Marked differences in relative brain size exist between families. These are correlated with inter‐family differences in body size and home range size. Variation in comparative brain size within families is related to diet (folivores have comparatively smaller brains than frugivores), home range size and possibly also to breeding system. The adaptive significance of these relationships is discussed.

BECAUSE the primates are a particularly well studied group they provide a rare opportunity to investigate the adaptive significance of species differences in sexual dimorphism in body size. We describe here an investigation of the relationship between the degree of sexual dimorphism and three variables which are predicted might affect it.

The tendency for large deer species to have relatively big antlers for their body size has been explained as the result of an inevitable evolutionary trend leading to increased antler size1–4, of linkage between genetic factors influencing body size and relative antler size5, of the increased need for larger deer to lose heat6and of an increased reliance of larger deer species on displays to avoid fighting7. Here we test an alternative hypothesis: that large deer species tend to be more polygynous than smaller ones and that intense inter-male competition in large species has led to the development of relatively large antlers. Analysis of comparative data8–42confirms two predictions based on this hypothesis: (1) that large deer species form bigger breeding groups than small ones; and (2) that deer which form large breeding groups have relatively larger antlers for their body size than those that form smaller ones. However, antler size is not proportional to body size among species that form breeding groups of similar size, indicating that other factors must also be involved.

Like a number of plants1,2, some mammals commonly produce more progeny than they can afford to rear, terminating investment in some or even all of their offspring once the resources available for breeding are known3–5. Adaptive interpretations of juvenile wastage rely on the argument that the costs of gestation are small compared to those of feeding offspring. Though energetic evidence supports this conclusion6, it is unsafe to assume that the relative costs of gestation and lactation to the mother's survival and future reproductive success follow the same pattern because lactation commonly coincides with the period of maximum food availability. Controlling for individual variation, we show that in wild red deer (Cervus elaphus L) any costs of gestation to the mother's subsequent survival and reproductive success are slight compared to those of lactation.

The common finding that juvenile male mammals show higher mortality than females1,2is usually attributed either to the expression of deleterious recessive alleles on the X chromosome3or to adaptive manipulation of the postnatal sex ratio by mothers who are unable to rear successful sons4,5. As a general explanation of differential juvenile mortality, the first of these two theories is unsatisfactory because increased male mortality is known to occur in several bird species where females are the heterogametic sex6,7. The second hypothesis was first proposed by Trivers and Willard4and suggests that differential mortality should occur early in the period of parental investment8. We now show that, although several predictions of the latter explanation are fulfilled, the distribution of differential mortality in red deer and other mammals suggests that higher mortality rates among male juveniles are a consequence of a greater susceptibility of males to food shortage associated with their faster growth rates and increased nutritional requirements.

Comparisons of brain-body size relationships within small mammal and primate families reveal intergeneric differences related to diet and foraging strategy. These same associations between relative brain size and ecology are also evident among interfamily comparisons.

Two evolutionary theories predict how mammalian parents would be expected to allocate the resources at their disposal to their male and female progeny. Where reproductive success varies more widely among males than females and variation in success among adults is influenced by parental investment1, parents would maximize their reproductive success by allocating a greater proportion of their resources to individual sons than to individual daughters2–5. However, because the benefits of producing offspring of one sex are inversely related to the total investment allocated to them, parents should, on average, divide their total investment equally between their male and female progeny, rearing fewer of whichever sex is individually more expensive to produce6–10. Here we examine the extent to which parental investment in red deer (Cervus elaphus) and other polygynous mammals matches these predictions. We conclude that, in several mammals, mothers invest more heavily in individual sons than daughters but that, contrary to prediction, there is no indication that fewer male offspring are reared in these species.

In most social mammals, males leave their natal group to breed in other groups whereas females commonly remain in the same group throughout their lives1. In a few species however, females usually transfer between groups during adolescence1. The functional significance of sex differences in dispersal and their connection, if any, to the avoidance of inbreeding is disputed2–7. Here I show that in polygynous mammals where females commonly remain to breed in their natal group, thdr average age at first conception typically exceeds the average period of residence of adult males in breeding groups. In contrast, where females usually transfer to breed in other groups, the average residence of breeding males or of resident male kin groups typically exceeds the average age of females at first conception. These results support the suggestion that female mammals commonly transfer to avoid inbreeding with their father or other close relatives, although female dispersal may also occur for other reasons8,9.

That female vertebrates who are able to invest more than average in their offspring should produce male-biased sex ratios was first suggested by Trivers and Willard1who reasoned that the breeding success of males is more variable than that of females and so may be more strongly influenced by parental investment. Their evidence for a positive association between maternal condition and birth sex ratios was unconvincing2,3and no subsequent studies have produced conclusive evidence supporting their hypothesis4,8. We show here that, in polygynous red deer (Cervus elaphus), dominant mothers produce significantly more sons than subordinates and that maternal rank has a greater effect on the breeding success of males than females.

Evolutionary theory predicts that in sexual organisms the average parents should invest equally in their male and female progeny1except where related males compete with each other to mate, when selection may favour parents that produce a female-biased sex ratio2–4. It has recently been suggested that in species where daughters adopt home ranges overlapping those of their mothers while sons disperse, competition for resources between female siblings may select for mothers who produce male-biased sex ratios5. We show here that in a mammal living in matrilocal, non-territorial groups—the red deer (Cervus elaphus)—the presence of resident female relatives depresses the reproductive success of adult females, providing a possible explanation of the apparent bias in parental investment towards male offspring in this species6.

In group-living mammals, the eviction of subordinate females from breeding groups by dominants may serve to reduce feeding competition or to reduce breeding competition. Here, we combined both correlational and experimental approaches to investigate whether increases in food intake by dominant females reduces their tendency to evict subordinate females in wild meerkats (Suricata suricatta). We used 20 years of long-term data to examine the association between foraging success and eviction rate, and provisioned dominant females during the second half of their pregnancy, when they most commonly evict subordinates. We show that rather than reducing the tendency for dominants to evict subordinates, foraging success of dominant females is positively associated with the probability that pregnant dominant females will evict subordinate females and that experimental feeding increased their rates of eviction. Our results suggest that it is unlikely that the eviction of subordinate females serves to reduce feeding competition and that its principal function may be to reduce reproductive competition. The increase in eviction rates following experimental feeding also suggests that rather than feeding competition, energetic constraints may normally constrain eviction rates.

A 26-year-old woman developed the adult respiratory distress syndrome after a post-partum haemorrhage. After mechanical ventilation was started the signs of a tense and distended acute abdomen developed. The aspiration and subsequent analysis of copious intra-peritoneal gas confirmed the diagnosis of a tension pneumoperitoneum secondary to pulmonary barotrauma.

AMONG mammals, weapons such as canine teeth or antlers are often more pronounced in males than in females1–5. Two reasons are normally proposed for such sexual dimorphism. First, there is more competition among males than among females for access to mates and, in consequence, there is enhanced selection for fighting ability6–9. Second, such weapons are important organs of defence for the male, who often assumes the role of defending his mates and offspring from predators9,10. In this paper, we discuss a third factor that is involved: selection acting to influence the size of weapons in females.