Differences In Reproductive Biology Research Articles

Time budget of daily activity of silvery lutung (Trachypithecus cristatus) in coastal forest habitat at Gunung Padang, West Sumatra

Primate’s time budgets are the important aspect to investigate their ecological influences in their habitat. This study collected data on daily activities in a group of silvery lutung (Trachypithecus cristatus) in coastal forest habitat at Gunung Padang, West Sumatra, Indonesia from August 2018 – July 2019, using instantaneous scan sampling method with 10-min intervals. This study analyzed the activity of wild silvery lutungs in study site, with emphasis on the age-sex differences and montly changes in their activity budget. This group spent most of time resting in their daily activity (average 47.50% of the total daytime resting), then followed by moving, feeding, grooming and other activities (conflict, nursing, urinating-defecating, playing, etc.). Resting peaked simultaneously in the morning and peaked back in the afternoon while moving and feeding decreased in this period. Their time budgets showed significant monthly variation: they spent a higher value of time feeding from September - Oktober 2018. They also differed among different sex-age classes: nursing females spent more time for actively moving, whereas adult male and single females devoted more time to resting, feeding, and grooming. These differences in their time budgets may reflect fundamental differences in reproductive biology, parental investment and development among the different age-sex classes.

Reproductive cycle and fecundity of the bonnethead Sphyrna tiburo L. from the northwest Atlantic Ocean.

The present study examined temporal changes in plasma sex hormone concentrations and the morphology and histology of reproductive organs in mature northwest Atlantic (NWA) bonnetheads Sphyrna tiburo L. to characterize reproductive cycle, breeding periodicity and fertility in this still poorly studied population. Progressive increases in testis width, epididymis head width, plasma testosterone (T) concentrations, and occurrence of mature spermatozoa were observed in male S. tiburo from June to September, demonstrating that spermatogenesis occurs during the summer. Nonetheless, increases in maximum follicle diameter, oviducal gland width, plasma 17β-estradiol and T concentrations, and occurrence of vitellogenic follicles were not observed in mature females until between October and April, demonstrating non-synchronous patterns of gametogenesis in males and females. Fresh copulatory wounds were observed in females collected during late September along with histological evidence for sperm presence in the oviducal gland between September and April, confirming a 6- to 7 month period of female sperm storage. Ovulation occurred between mid-April and early May in concert with increases in female plasma progesterone concentrations. Gestation occurred during a 4.5- to 5 month period between May and early September, and 97% of mature females collected during this period were gravid, indicating a highly synchronized, annual reproductive periodicity. Brood size was significantly correlated with maternal size and ranged from 1 to 13 pups with a mean ± S.D. of 8.1 ± 2.2, which was significantly lower than reported in Gulf of Mexico (GOM) populations. The occurrence of non-fertile offspring was observed in 17% of broods with a range of 1-7 non-fertile eggs present in individual females. Thus, as previously reported in GOM S. tiburo, this unusual form of infertility also appears to be prevalent in the NWA population and requires further study. This study has demonstrated meaningful differences in reproductive biology of these populations, emphasizing the need for region-specific approaches for population management.

Effects of thermal and oxygen conditions during development on cell size in the common rough woodlice Porcellio scaber.

During development, cells may adjust their size to balance between the tissue metabolic demand and the oxygen and resource supply: Small cells may effectively absorb oxygen and nutrients, but the relatively large area of the plasma membrane requires costly maintenance. Consequently, warm and hypoxic environments should favor ectotherms with small cells to meet increased metabolic demand by oxygen supply. To test these predictions, we compared cell size (hindgut epithelium, hepatopancreas B cells, ommatidia) in common rough woodlice (Porcellio scaber) that were developed under four developmental conditions designated by two temperatures (15 or 22°C) and two air O2 concentrations (10% or 22%). To test whether small‐cell woodlice cope better under increased metabolic demand, the CO2 production of each woodlouse was measured under cold, normoxic conditions and under warm, hypoxic conditions, and the magnitude of metabolic increase (MMI) was calculated. Cell sizes were highly intercorrelated, indicative of organism‐wide mechanisms of cell cycle control. Cell size differences among woodlice were largely linked with body size changes (larger cells in larger woodlice) and to a lesser degree with oxygen conditions (development of smaller cells under hypoxia), but not with temperature. Developmental conditions did not affect MMI, and contrary to predictions, large woodlice with large cells showed higher MMI than small woodlice with small cells. We also observed complex patterns of sexual difference in the size of hepatopancreatic cells and the size and number of ommatidia, which are indicative of sex differences in reproductive biology. We conclude that existing theories about the adaptiveness of cell size do not satisfactorily explain the patterns in cell size and metabolic performance observed here in P. scaber. Thus, future studies addressing physiological effects of cell size variance should simultaneously consider different organismal elements that can be involved in sustaining the metabolic demands of tissue, such as the characteristics of gas‐exchange organs and O2‐binding proteins.

Whole genome analysis reveals aneuploidies in early pregnancy loss in the horse

The first 8 weeks of pregnancy is a critical time, with the majority of pregnancy losses occurring during this period. Abnormal chromosome number (aneuploidy) is a common finding in human miscarriage, yet is rarely reported in domestic animals. Equine early pregnancy loss (EPL) has no diagnosis in over 80% of cases. The aim of this study was to characterise aneuploidies associated with equine EPL. Genomic DNA from clinical cases of spontaneous miscarriage (EPLs; 14–65 days of gestation) and healthy control placentae (various gestational ages) were assessed using a high density genotyping array. Aneuploidy was detected in 12/55 EPLs (21.8%), and 0/15 healthy control placentae. Whole genome sequencing (30X) and digital droplet PCR (ddPCR) validated results. The majority of these aneuploidies have never been reported in live born equines, supporting their embryonic/fetal lethality. Aneuploidies were detected in both placental and fetal compartments. Rodents are currently used to study how maternal ageing impacts aneuploidy risk, however the differences in reproductive biology is a limitation of this model. We present the first evidence of aneuploidy in naturally occurring equine EPLs at a similar rate to human miscarriage. We therefore suggest the horse as an alternative to rodent models to study mechanisms resulting in aneuploid pregnancies.

Reproductive biology of black seabream Acanthopagrus schlegelii, threadfin porgy Evynnis cardinalis and red pargo Pagrus major in the northern South China Sea with consideration of fishery status and management needs.

The reproductive biology of three commercially significant seabream species (family: Sparidae) Acanthopagrus schlegelii, Evynnis cardinalis and Pagrus major, taken from Hong Kong and adjacent northern South China Sea (SCS) waters, were investigated for their sexual patterns, spawning seasons, length at maturity and exploitation in relation to their conservation and management status. Histological analysis showed E. cardinalis and P. major to be functionally gonochoristic, the latter having a bisexual juvenile stage and being a rudimentary hermaphrodite. Acanthopagrus schlegelii is a protandric hermaphrodite. Standard length (LS ) at 50% sex change for A. schlegelii is 291 mm. LS at 50% female maturity for E. cardinalis and P. major are 117 and 332 mm, respectively. For all three species, the spawning period falls between November and March. The study highlights geographical differences in reproductive biology among the species and a paucity of fishery or other population-related data. While heavy fishing pressure, life-history characteristics and absence of effective management throughout the geographic ranges of these species make them susceptible to overfishing, they nonetheless appear to be generally more resilient than many other taxa that comprise the multi-species fisheries of the region, possibly due to their relatively rapid sexual maturation and spatial movement patterns. Overall, however, little is known of the biology, fishing history and current fishery status of sparids in general in the northern SCS and the current study is one of the first to examine such aspects of this family in the region and to consider appropriate management options.

Ameliorating the loss of genetic diversity in captive wildlife populations

Ameliorating the loss of genetic diversity in captive wildlife populations

Elucidation of population connectivity in synanthropic mesopredators: Using genes to define relevant spatial scales for management of raccoons and Virginia opossums

Raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana) are highly abundant, synanthropic mesocarnivores that can transmit epizootic diseases of critical importance to human and livestock health such as rabies and tuberculosis. Individuals of both species can exhibit large dispersal distances and our understanding of population connectivity for both of these species is limited. Data on population connectivity and potential for disease transmission are needed for each of these species for the development of data-informed management, control, and vaccination programs. Genetic connectivity among populations can be estimated by evaluation of metrics such as of isolation by distance (IBD) signatures and population structure. Such metrics are influenced not only by geographic distance and barriers to dispersal but also by the life-history characteristics of the species in question. We investigated the scale at which these species exhibited evidence of connectivity via gene flow, using samples collected from 9 sites spanning 254 km across north-central, west-central, south-central, and southern Indiana, USA. We evaluated genetic connectivity and signatures of IBD using Bayesian clustering analyses and matrix correlation methods. In the Bayesian model, raccoons were assigned to 3 genetic clusters, whereas Virginia opossums exhibited apparent panmixia. Spatial autocorrelation results indicated a significant positive correlation between genetic and geographic distance for raccoons at distances up to 25 km and for Virginia opossums up to 4 km. Interspecific differences in reproductive biology, social behavior, and dispersal are likely the causes for differences between these 2 species in the spatial partitioning of populations across broad ranges. In addition, geographic features and past glaciation events may be affecting the genetic characteristics of present-day raccoon populations. Improved information regarding interpopulation distance for these 2 synanthropic species may contribute to more effective management and disease-control programs. © 2014 The Wildlife Society.

Reproductive strategy of the European perch, Perca fluviatilis Linnaeus, 1758 (Osteichthyes: Percidae) in the Anzali wetland, southwest Caspian Sea

Summary Temporal variation in reproductive traits of geographically distributed fish is supposed to take place in response to the spatial and environmental variations. With regard to the wide distribution of the European perch in the northern hemisphere, important reproductive traits such as the initiation and duration of the spawning activity are likely to vary in different latitudinal gradients. In this study, reproductive biology of the European perch, Perca fluviatilis, is described, based on 324 specimens caught in the Anzali wetland (southwest Caspian Sea) between June 2008 and May 2009. The gonadosomatic index, oocyte frequency distribution and histological examination suggested a long vitellogenic process (October to February) and a short spawning season (January and February). The size-frequency distribution of the oocytes showed that this perch is a species with group-synchronous ovarian development. Ovarian development occurred only in one clutch of oocytes (700–900 μm oocyte diameter) with no indication of maturation of any subsequent clutch in the spawning season. The average of (realized) fecundity (±SD) was estimated to be 16177 ± 5846 eggs in late vitellogenic stage, which was lower than the potential fecundity (17188 ± 6917 eggs). Histological examination of the gonads revealed the existence of atretic oocytes in early vitellogenic stages (October and November). This investigation highlights the temporal variation in the initiation and duration of the reproductive activity of the European perch in this region compared to other geographical regions. The results emphasize the necessity of specific temporal management in fishing of European perch based on spatial differences in reproductive biology.

Sexual dimorphism in size and shell shape, and dichromatism of spotted turtles (Clemmys guttata) in Southwestern Michigan

Differences in pigmentation, morphometry, and body size between sexes within populations can imply inter-sexual differences in reproductive biology. We assessed variation in body size, morphometrics, and pigmentation in Spotted Turtles (Clemmys guttata) in a southwestern Michigan population.Clemmys guttatawas not sexually dimorphic in body size but when compared to males, positive allometric increases in shell height resulted in relatively domed shells in females. Integumental reflectance was mostly limited to the visual spectrum 400-700 nm with little to no reflectance in the UV spectrum (340-700 nm). We found no intersexual differences in the intensity (brightness) of yellow spots or black ground color of the head and carapace, perhaps suggesting that such markings are involved in cryptic coloration. The orange-red stripes of the head and forelimbs, that were similar in intensity between the sexes, would look conspicuous in the full spectrum light of the shallow aquatic habitats ofC. guttataand thus could be involved in mate recognition. Chins of males were darker than those of females suggesting that chin color is a sexually selected trait.

Oogenesis and spawn formation in the invasive lionfish, <i>Pterois miles</i> and <i>Pterois volitans</i>

The Indo-Pacific lionfish, Pterois miles and P. volitans, have recently invaded the U.S. east coast and the Caribbean and pose a significant threat to native reef fish communities. Few studies have documented reproduction in pteroines from the Indo-Pacific. This study provides a description of oogenesis and spawn formation in P. miles and P. volitans collected from offshore waters of North Carolina, U.S.A and the Bahamas. Using histological and laboratory observations, we found no differences in reproductive biology between P. miles and P. volitans. These lionfish spawn buoyant eggs that are encased in a hollow mass of mucus produced by specialized secretory cells of the ovarian wall complex. Oocytes develop on highly vascularized peduncles with all oocyte stages present in the ovary of spawning females and the most mature oocytes placed terminally, near the ovarian lumen. Given these ovarian characteristics, these lionfish are asynchronous, indeterminate batch spawners and are thus capable of sustained reproduction throughout the year when conditions are suitable. This mode of reproduction could have contributed to the recent and rapid establishment of these lionfish in the northwestern Atlantic and Caribbean.

Activity budgets in a group of Sichuan snub-nosed monkeys in Shennongjia Nature Reserve, China

Abstract We examined time allocation by Sichuan snub-nosed monkeys Rhinopithecus roxellana in the montane, temperate and highly seasonal forests of the Shennongjia Nature Reserve in China, in order to improve our understanding of the ecological and social influences on monkey behavior. We collected data on activity budgets in relation to food availability in a group of monkeys from July 2003 to September 2004 (except February 2004), using instantaneous scan samples. The monkeys spent 36.21% of daytime moving (n = 2l, 269 records), 24.39% foraging, 9.33% inactive, 11.7% performing social behaviors, and 18.38% performing other behaviors. There were seasonal and annual variations in the proportions of time devoted to some activities. These variations were largely attributed to seasonal or annual fluctuations in the distribution and quality of food resources. Adult males spent more time moving, searching, and displaying other behaviors' but less time feeding and performing social behaviors than adult females. Adults performed other behaviors more often and moving less often than juveniles. These differences in activity budgets may reflect fundamental differences in reproductive biology, parental investment, and development among the different age/sex classes.

Sex-related spatial segregation and growth in a dioecious conifer along environmental gradients in northwestern Patagonia

The separation of sexes in plants (dioecy) implies differences in reproductive biology that in many cases favour sexual dimorphism and spatial segregation. Females of the dioecious conifer Austrocedrus chilensis have higher reproductive effort than males. We examined the spatial distribution of male and female Austrocedrus trees along a range of environmental conditions and sex-related growth patterns in northwestern Patagonia. Males were more abundant on high-radiation slopes (M:F ≈ 1.7), while low-radiation slopes had higher abundances of females (M:F ≈ 0.6). This pattern was consistent and equally strong in mesic and xeric sites along a strong rainfall gradient, suggesting that moisture is not the only triggering factor for tree distribution. Austrocedrus females tended to occupy the moister aspects, but genders were not isolated at large geographical scales, avoiding detrimental effects on species fitness. As evidenced by ring widths, males grew ~100% more per year than females on high-radiation exposures, while on low-radiation aspects, males and females did not differ significantly, suggesting that in moister, low-radiation exposures female trees are able to compensate for the reproductive expenses they have. Alternatively, reproductive effort may differ between male and females on different slopes.

Reproduction of the gorgonian Plexaura flexuosa in Bermuda

This study examined geographically based differences in reproductive biology of Plexaura flexuosa, a gonochoric broadcasting gorgonian that is abundant across the tropical and subtropical Western Atlantic. Gametogenesis, spawning, and per polyp fecundity-colony height ratios were assessed in Bermuda and then compared with existing studies of populations in the Bahamas, Florida, and the Caribbean and in conjunction with analyses of mean sea surface temperature (MSST) at these locales. Differences documented in the Bermudian population include: lag in onset of spermary development and completion of oogenesis as compared to southern populations; later spawning that occurred over fewer days; and lack of correlation between fecundity polyp − 1 and colony height. These findings suggest that important differences occur in major reproductive events between the distantly separated northern-most populations of P. flexuosa found in Bermuda compared with more tropical populations of this species. Such population-level variability in life history characteristics needs to be incorporated into approaches for conservation planning efforts.

Novel variation in the floral development of two species ofParthenocissus

This study compares the development of the inflorescences and flowers of Parthenocissus quinquefolia (Virginia creeper) and Parthenocissus tricuspidata (Boston ivy). The development of the reproductive shoots is described from inception to maturity using epi-illumination and scanning electron microscopy. In both species, the shoot apex initiates inflorescence primordia low on the apical flank. An inflorescence primordium produces several bract-opposed branches, which in early development resembles the main shoot. As inflorescence development continues, branch primordia initiate as increasingly larger portions than the inflorescence apical meristem. By late development, branch primordia initiate as larger portions than the apex, which is a process that has been observed in other vitaceous inflorescences. With respect to initiation and early development, the Parthenocissus inflorescence is very similar to the tendril, which has been previously studied; these two organs have never been described to be so similar, and their likeness to the shoot, in early development, provides an idea as to how they may have arisen. An inflorescence branch terminates as a dichasium, which is formed by two nearly simultaneous branching events. Parthenocissus tricuspidata flowers develop a more robust gynoecial disc and stigma than in the P. quinquefolia flower; but the calyx is ring-like in the former and cup-like in the latter. Contrary to the previous assumption that there are no differences in reproductive biology within genera of the Vitaceae, this study has clearly demonstrated variation between two species of Parthenocissus.Key words: floral, development, monopodial, Parthenocissus, inflorescence, Vitaceae.

SMALL-MAMMAL FORAGING BEHAVIOR: MECHANISMS FOR COEXISTENCE AND IMPLICATION FOR POPULATION DYNAMICS

We investigated predation risk and competition as they affected small-mammal foraging behavior in semiarid north-central Chile. Giving-up densities (GUD) of seeds were used to measure the foraging activity of the three most common small mammals at the site: degu (Octodon degus), Darwin's leaf-eared mouse (Phyllotis darwini), and the olivaceous field mouse (Akodon olivaceus), under shrubs (cover) and in the open on predator-excluded and competitor-excluded (Octodon) plots. Experiments were conducted during both new and full moons. Monthly small-mammal censuses using standard mark–recapture techniques provided data on movement, reproduction, and long-term fluctuations in density between 1989 and 1994. Diurnal Octodon foraged more (had lower GUD) in the absence of predators (although this was confounded by a numerical increase resulting from predator exclusion), and foraged more under shrubs than in the open. However, the lack of a significant cover × predator exclusion interaction and thermoregulation studies suggest that physiological constraints play a greater role than predation risk in determining microhabitat selection by Octodon. Predation risk, as influenced by lunar light levels and predator exclusion, had only weak effects on microhabitat selection by Phyllotis. The strong tendency of Octodon to forage under cover could depress food availability, forcing Phyllotis to feed more in the open. Concomitantly, Phyllotis exhibits several morphological characters that would favor detection and avoidance of predators. There is extensive evidence that interspecific competition is the primary constraint on Akodon foraging; predation risk appears to be relatively unimportant. Akodon is also a less efficient forager than the two other species, having significantly higher GUD, on average. This is partially offset by differences in reproductive biology; Akodon exhibits extremely rapid demographic responses to favorable changes in the environment. A fourth species, Abrothrix longipilis, may coexist in the system because of its opportunistic nature, but no data are available on its foraging efficiency. These behavioral and biotic interactions occur within a background of periodic El Niño–Southern Oscillations (ENSO), which may ultimately contribute to species coexistence.

Extra-pair paternity and egg dumping in birds: life history, parental care and the risk of retaliation.

Molecular techniques have revealed striking variation among bird species in the rates of extra-pair paternity (EPP) and intraspecific brood parasitism (IBP). In terms of the proportion of broods affected, rates of EPP and IBP vary across species from 0-95% and 0-50%, respectively. Despite a plethora of hypotheses and several careful comparative analyses, few robust correlates of this interspecific variation have been identified. One explanation for this shortfall is that most comparative studies have tended to focus on contemporary ecological factors and ignored fundamental differences in reproductive biology that evolved millions of years ago. We show that, for both EPP and IBP, over 50% of interspecific variation is due to differences among taxonomic families and orders. Therefore, we test hypotheses that predict interspecific variation in the rate of alternative reproductive strategies should be associated with differences in life history and the form of parental care. Our analyses largely support these predictions, with high rates of reproductive cheating being associated with 'fast' life histories. High EPP rates are associated with high rates of adult mortality and reduced paternal care. High IBP rates are associated with high-fecundity rates. These patterns remain intact whether we use species as independent data points or evolutionary contrasts based on either molecular or morphological phylogenies. These results are interpreted as supporting the idea that alternative reproductive strategies are most common in taxa in which the risks of retaliation are low. We suggest a hierarchical explanation for interspecific variation in the incidence of alternative reproductive strategies. Variation between major avian lineages in the EPP and IBP rates are determined by fundamental differences in life history and parental care that evolved many millions of years ago. Variation between populations or individuals of the same species, however, are more likely to be determined by differences in contemporary ecological and genetic factors.

Spatial synchrony of population changes in rocky shore communities in Shetland

Rocky shore monitoring around the Sullom Voe Oil Terminal in Shetland has produced a 20 yr dataset of population fluctuations for 40-plus species at 15 to 20 sites separated by distances up to 30 km. Synchrony in population changes was quantified by correlation among series of abundance categorised on quantitative scales. Two periods were analysed separately, pre- and post-1992, following changes in methods and extent of monitoring. Positive average correlations among sites were found for 10 out of 16 species pre-1992 and for 23 out of 26 post-1992, statistically significant for 4 and 8 species for the 2 periods, respectively. The intertidal barnacle Semibalanus balanoides showed most synchrony among sites for both periods, while dogwhelks Nucella lapillus and macroalgae (Fucus vesiculosus, F. serratus, Mastocarpus stellatus) had very low average correlations among sites. Littorina saxatilis was the only other species with significant positive correlation among sites in both periods. Corallinaceae, Verrucaria maura and V. mucosa, and Littorina neglecta were less synchronised pre-1992 than post-1992, while L. obtusata showed less synchrony post-1992. Differences in reproductive biology and ecology failed to explain patterns of synchrony among species. Species with planktonic larvae were no more likely to be synchronised than those without. There was a tendency for species living higher on the shore to be more synchronised post-1992, but species predominant on wave-exposed shores were no more synchronous than sheltered-shore species. The more synchronised species in this study need to be monitored at relatively few sites to detect change, whereas more sites may be needed for species in which change occurs on a local scale. Population synchrony also suggested usefulness of species as indicators of large-scale change: the barnacle S. balanoides is the best indicator among species in the study area.

Rodent and predator population dynamics in an eruptive system

A computer model of the population dynamics of introduced house mice ( Mus musculus L.), ship rats ( Rattus rattus L.) and stoats ( Mustela erminea L.) in New Zealand forest was constructed, to test the relative importance of food availability and predation in shaping observed small-mammal population dynamics. Ship rats and mice are the two common rodent species present in most New Zealand forests, and exhibit eruptive population dynamics. Stoats are the only common mammalian predator, and undergo large density fluctuations following periodic rodent eruptions. A number of outputs and predictions from the model were developed. The model highlights the overall importance of variation in food availability in determining the timing and amplitude of rodent population eruptions. It indicates that predators can not prevent a prey–species eruption, primarily due to differences in reproductive biology. Predation however, can delay the start of the prey-population increase during the eruption. The role of predators in limiting the peak prey-population size will depend on the size of the energy input. In a full-scale eruption following maximal tree seeding, predators cannot significantly truncate peak prey-population size. Predators should be able to significantly hasten the rate of decline in the prey populations, although the strength of predator limitation will depend on the severity of food limitation and cold-induced mortality over the same period. Predators can limit prey populations during the post-crash low phase. As with the crash phase, the strength of predator limitation in the low phase will depend on the severity of food limitation and natural mortality. The model highlights gaps in current knowledge of predator and prey species biology and ecology. The model highlights key areas where further field study should provide a better understanding of the factors driving small-mammal communities in New Zealand.

Comparison of reproductive success in two orchids: the nectarless Dactylorhiza majalis s.s. and the nectar‐producing Gymnadenia conopsea s.l.

Differences in reproductive biology between two orchid species were examined: Eight Danish populations of the nectarless Dactylorhiza majalis ssp. majalis and six Swedish populations of the nectar‐producing Gymnadenia conopsea ssp. densiflora. Population size varied from 24 to 1700 flowering individuals in D. majalis and from 100 to 1200 in G. conopsea. Dactylorhiza majalis had only half as many flowers per spike as G. conopsea. Fruit‐set of D. majalis ranged from 16 to 39%, much lower than the fruit‐set of G. conopsea (78–91%). Thus in the species with a few flowers and no nectar a lower fruit‐set was observed than in the species with many flowers and presence of nectar. The low fruit‐set of D. majalis was pollen‐limited and fruit‐set was positively correlated with pollinia removal and the latter was negatively correlated with population size. In both species, fruit‐set and population size were uncorrelated.

Sex differences in the use of health care services.

Sex differences in the use of health care services can be substantial at several stages of life. However, the extent to which differences in reproductive biology and mortality affect the use of health care services is unclear. We studied age- and sex-specific per capita use of health care resources for a one-year period during 1994 and 1995 in the Canadian province of Manitoba, where there is universal insurance for a comprehensive range of health care services. Using information obtained from administrative records of physicians' services and acute hospital care, we tabulated the use of health care resources by male and female subjects in three categories: care for conditions specific to sex, care provided to persons who died during the study year, and care provided for all other conditions. The crude annual per capita use of health care resources (in Canadian dollars) was greater for female subjects ($1,164) than for male subjects ($918). Approximately 22 percent of health care expenditures for female subjects was associated with conditions specific to sex, including pregnancy and childbirth, as compared with 3 percent of expenditures for male subjects. An estimated 14 percent of health care expenditures for male subjects was consumed by persons who died during the study period, as compared with 10 percent of expenditures for female subjects. After adjustment for the use of health care associated with sex-specific conditions and differences in mortality, the female:male ratio in health care expenditures was reduced from 1.3 to 1.0. Expenditures for health care are similar for male and female subjects after differences in reproductive biology and higher age-specific mortality rates among men have been accounted for.