Cover Caption

Cover: Wild vicuñas grazing on lands of the community of Tambo Cañahuas in the Salinas Aguada Blanca National Reserve, Arequipa, Peru (top), and a female vicuña being held by villagers prior to being shorn (bottom). Fiber obtained from this vicuña will be sold and exported, with proceeds going to the community on whose land it grazes.The vicuña will be released after shearing. Photos by Catherine Teresa Sahley. See pages 98–105.     

Short-term temporal variation in population structure of two harpacticoid copepods,Zausodes arenicolus and Paradactylopodia brevicornis

Aspects of the population biology of two harpacticoid copepod species [Zausodes arenicolus Wilson and Paradactylopodia brevicornis (Claus)] living in Tampa Bay, Florida, USA, were studied on time scales of hours to days during November 1983. Fluctuations in population agestructure, adult sex-ratio, and proportion of ovigerous females were determined for these two species in a control plot and in an experimental plot defaunated by raking. For both species, immigrants into the defaunated plot differed significantly from conspecifics in the control plot in all characteristics examined. The disturbed plot contained a larger proportion of young juveniles of both species compared to the unmanipulated site after 4 h but not after 8 h. In Z. arenicolus, adult males returned to the experimental plot more quickly than adult females. For both species, rapid and significant changes in population age-structure, adult sex-ratio, and the proportion of adult females with eggs occurred within the control plot. It is suggested that this variation was too large and occurred too rapidly to be accounted for solely by in situ processes in the absence of large-scale immigration and/or emigration of individuals. Potential implications of these results for population studies of harpacticoid copepods and other benthic invertebrates are discussed.     

Applying the Declining Population Paradigm: Diagnosing Causes of Poor Reproduction in the Marbled Murrelet

Abstract:  We identified six approaches to diagnosing causes of population declines and illustrate the use of the most general one ("multiple competing hypotheses") to determine which of three candidate limiting factors—food availability, nesting site availability, and nest predation—were responsible for the exceptionally poor reproduction of Marbled Murrelets (  Brachyramphus marmoratus ) in central California. We predicted how six attributes of murrelet demography, behavior, and physiology should be affected by the candidate limiting factors and tested predictions with field data collected over 2 years. The average proportion of breeders, as estimated with radiotelemetry, was low (0.31) and varied significantly between years: 0.11 in 2000 and 0.50 in 2001. Murrelets spent significantly more time foraging in 2000 than in 2001, suggesting that low food availability limited breeding in 2000. In 2001, 50% of radio-marked murrelets nested and 67% of females were in breeding condition, suggesting that enough nest sites existed for much of the population to breed. However, rates of nest failure and nest predation were high (0.84 and 0.67–0.81, respectively) and few young were produced, even when a relatively high proportion of murrelets bred. Thus, we suggest that reproduction of Marbled Murrelets in central California is limited by food availability in some years and by nest predation in others, but apparently is not limited by availability of nesting sites. The multiple-competing-hypotheses approach provides a rigorous framework for identifying causes of population declines because it integrates multiple types of data sets and can incorporate elements of other commonly used approaches.     

Sexual dimorphism, reproductive strategy, and human activities determine resource use by brown bears

Despite significant sexual dimorphism and differing reproductive strategies in carnivores, sexual segregation is rarely studied and is often overlooked in the management of wild populations. Potential nutritional constraints imposed by sexual dimorphism and differing reproductive strategies between the sexes have important implications, particularly when combined with differential effects of human activities on sex and age classes. We examined the effects of sexual dimorphism, reproductive strategies, and human activities (bear-viewing and hunting) on resource use by different sex and age classes of brown bears (Ursus arctos). Sexual segregation of habitat use and effects of experimental bear-viewing were quantified at a single site in south-central Alaska, U.S.A., by capturing, collaring, and observing brown bears at a salt marsh and salmon stream. Effects of salmon capture rate, availability of alternative salmon runs, harvest pressure, and numbers of annual visitors on sex and age class use were examined from data collected or previously published from 13 other sites. Bear-viewing sites on salmon streams where salmon capture rates were low (<4 salmon/hour) resulted in low use by adult males (<10% of all bears), except for sites with falls. However, maximum male use of viewing areas also depended on the availability of alternative salmon streams and harvest pressure. Use of habitats by females with dependent young was significantly related to the prevalence of adult males at the site. Thus, both sexual dimorphism and differing reproductive strategies led to sexual segregation in habitat use by bears. As a result of infanticide, females with young appear to prioritize avoidance of male bears over avoidance of humans when choosing habitats, in contrast to responses documented in herbivores. Because carnivores often exhibit both sexual dimorphism and infanticide, selection for sexual segregation is likely to be high. In these cases, the nutritional demands of large adult males, balanced with responses to human activity, drive dynamic temporal and spatial distributions of individuals in the population.     

Why do female Belding's ground squirrels disperse away from food resources?

We examined the effects of food provisioning on the natal dispersal behavior of Belding's ground squirrels (Spermophilus beldingi). We provided extra food to adult and yearling females in their maternal territories during pregnancy and lactation, and to offspring of these females in their natal areas for 6 weeks after weaning. We used unprovisioned young of unprovisioned mothers as controls. Provisioning influenced the probability of dispersal from the natal area by female but not male S. beldingi. All surviving male S.␣beldingi dispersed by 55 weeks of age, regardless of whether they and their mothers received extra food. By contrast, we observed a significant trend, beginning 3 weeks after weaning and continuing through the yearling year, for a greater proportion of provisioned than control female S. beldingi to emigrate from the natal area. Competition for food did not appear to influence natal dispersal of females. However, overall population density, density of females weaning litters, and rates of aggression and vigilance among these females, were higher in provisioned than control areas, suggesting that competition for non-food resources was unusually intense in provisioned areas. We propose that juvenile female, but not juvenile male, S. beldingi may emigrate from the natal site to increase access to areas with low densities of conspecifics. Together with findings of earlier workers, our results suggest that spatial and temporal distributions of environmental resources are important influences on the dispersal behavior of female ground squirrels. Received: 28 February 1996 / Accepted after revision: 16 October 1996     

Correlates of extra-pair fertilization success in hooded warblers

We examined correlates of extra-pair fertilization (EPF) success in the hooded warbler (Wilsonia citrina), a species where females pursue extra-pair matings. The good genes hypothesis predicts that females choose extra-pair mates with morphological or behavioral traits that reflect differences in male genetic quality. EPFs were common, as 35.3% (42/119) of broods contained extra-pair young (EPY) and 26.7% (95/356) of nestlings were the result of EPFs. There was a strong skew in male EPF success which increased the variance in annual male mating success 2–3 fold. However, male morphology did not predict EPF success, as extra-pair males were not older or larger than the males they cuckolded. Likewise, there were no significant correlations between the proportion of extra-pair young in a brood and male size or age. The good genes hypothesis predicts that high-quality males will be consistently preferred as genetic mates, but the number of young sired by a male with his social mate was not consistent from one year to the next. There was a significant negative correlation between female age and proportion of EPY produced, which could result if older females obtain higher-quality social mates. We found no strong evidence that females choose extra-pair mates for good genes, but females may use behavioral rather than morphological cues to assess relative male quality. Received: 31 May 1996 / Accepted after revision: 17 October 1996     

Polygyny and male parental care in Savannah sparrows: effects on female fitness

Summary To determine the effects of male mating status on female fitness, we compared the reproductive success, survival, and future fecundity of female Savannah sparrows (Passerculus sandwichensis) mated to monogamous vs. polygynous males in a 5-year study on Kent Island, New Brunswick, Canada. The proportion of males with more than one mate varied from 15 to 43% between years and sites. Polygynous and monogamous males fledged young of equal size in every year of the study. Females who shared paternal care with other females laid as many eggs per clutch and clutches per season as monogamously mated females. In most years polygynously mated females showed no delay in laying a second clutch, and they suffered no reduction in fecundity the following year. Recruitment of a female's offspring into the breeding population was generally independent of her mating status. Fitness costs of being mated to a polygynous male were only apparent in one year of the study, during which females mated to polygynous males had higher over-winter mortality than those mated to monogamous males. That same year, young raised by polygynous males were only one-third as likely to survive to reproductive maturity (as inferred by returns) as those raised by monogamous males. A male's mating status had no effect on his own survivorship. A male's mating status did not necessarily reflect his contributions to raising nestlings, which may partially explain why monogamously and polygynously mated females had equal fitness. At 35 nests the proportion of food deliveries brought by individual males varied from 0 to 75%; on average, males brought fewer than 30% of all food deliveries. Yet parental care by polygynous males was no less than that of monogamous males, at least at the nests of their primary females. Secondary females tended to receive less male assistance during the nestling stage, but their reproductive success was indistinguishable from that of primary females. Females feeding young without male assistance made as many food deliveries/h as did pairs in which males brought at least 30% of all food deliveries. Unassisted females did not suffer diminished fledging success or produce smaller fledglings. The benefits of polygyny for male Savannah sparrows are clear: polygynous males recruit more surviving offspring into the breeding population than monogamous males. The fitness of females, on the other hand, appears to be unaffected by whether their mate was monogamous or polygynous except in occasional years. Polygyny may be maintained in this population by the constraints of a female-biased sex ratio, the inability of females to predict a male's paternal care based on his morphology or behavior, the poor correlation between a male's mating status and his assistance at the nest, and inconsistent natural selection against mating with a polygynous male. Correspondence to: N.T. Wheelwright     

Harem choice and breeding experience of female southern elephant seals influence offspring survival

Female mammals can increase their lifetime fitness through modification of investment potential and by providing better rearing environments with improved breeding experience. We examined the relationships between reproductive fitness and the behavioural decisions that female southern elephant seals (Mirounga leonina) made during the breeding season. We examined whether mother age and breeding experience influenced reproductive success (measured as 1st-year survival probability), and whether there was a change in the choice of harem size with increasing age. Pups produced by young mothers had lower 1st-year survival probability than pups produced by older mothers. A significant increase in mean female mass with age required an analysis of both these effects on offspring survival. There was a significant positive effect of both female age and mass, and the interaction between the two, on 1st-year pup survival. The proportion of young mothers (<5 years old) decreased and the proportion of older mothers (>6 years old) increased with increasing harem size (harems surveyed from 1997 to 2001). Females chose larger harems in which to breed as they aged. Females demonstrated fidelity to breeding areas among successive breeding seasons, with older females displaying greater breeding-site fidelity than younger females. The mean number of previous breeding attempts per female within a harem (breeding experience) increased significantly with increasing harem size. Breeding females returned to breed later in the breeding season as they aged—we hypothesize that young, subordinate females gain a priority advantage by returning earlier. These results lend support to the hypothesis that there are fitness advantages, in terms of offspring survival, that are conferred to females that breed in successively larger harems with age. Potential mechanisms that select for females to improve their breeding conditions include improved mate selection and the avoidance of conspecific harassment in harems.Communicated by F. Trillmich     

Brood sex ratio and male UV ornamentation in blue tits (<Emphasis Type="Italic">Cyanistes caeruleus</Emphasis>): correlational evidence and an experimental test

Sex-allocation theory predicts that females paired to attractive males should bias the brood sex ratio towards male offspring, as these would inherit the attractiveness of their father. We studied sex allocation based on male ornamentation in blue tits. Brood sex ratios varied with male UV coloration in an age-dependent manner. For juvenile males, the proportion of sons increased with increasing UV ornamentation, which is in agreement with previous findings from a Swedish population. However, the relationship between UV ornamentation and brood sex ratio was reversed for adult males, with females paired to less UV-ornamented adult males producing more sons. This pattern fits with the observation that, in our population, less UV-ornamented adult males sire the majority of extra-pair young. To test the causality of the association between brood sex ratio and male coloration, we experimentally manipulated crown colour largely within the natural range. We created two groups of males: one with higher and one with lower UV reflectance, UV(+) and UV(−), respectively. Contrary to our expectations, there was no significant treatment effect. However, in UV(−), but not UV(+) males, the proportion of sons was negatively correlated with male coloration before manipulation. This suggests that the UV(−) treatment caused males that were more UV ornamented to decline more in attractiveness, as shown in a similar experiment in Sweden. However, given that correlational patterns differ between these populations, similarities in experimental results should not be taken as evidence for consistent patterns of adaptive sex allocation in this species.     

The high frequency of extra-pair paternity in tree swallows is not an artifact of nestboxes

A common criticism of nestbox studies is one of creating artificial nesting conditions and breeding behavior different from what would be seen under natural conditions. We assessed the frequency of extra-pair paternity (percentage of broods with at least one extra-pair young) in 25 families of tree swallows (Tachycineta bicolor) nesting in natural cavities and compared it to that in a nestbox population. We found that 84% of females nesting in natural cavities obtained fertilizations from extra-pair males. These extra-pair males fathered 69% of all nestlings. Studies of tree swallows breeding in nestboxes have shown that 50–87% of broods contained extra-pair young, with extra-pair males fathering 38–53% of all the young. In broods with extra-pair paternity, natural cavities contained a significantly greater proportion of extra-pair young than did nestboxes. Despite differences in nesting habitat and female age structure, the frequency of extra-pair paternity did not differ significantly between the natural-cavity and nestbox populations. Therefore, the presence of extra-pair paternity in tree swallows is not an artifact of nestboxes or of artificial nesting conditions. Received: 2 May 1995/Accepted after revision: 14 January 1996     

Linking Wild and Captive Populations to Maximize Species Persistence: Optimal Translocation Strategies

Abstract:  Captive breeding of animals is widely used to manage endangered species, frequently with the ambition of future reintroduction into the wild. Because this conservation measure is very expensive, we need to optimize decisions, such as when to capture wild animals or release captive-bred individuals into the wild. It is unlikely that one particular strategy will always work best; instead, we expect the best decision to depend on the number of individuals in the wild and in captivity. We constructed a first-order Markov-chain population model for two populations, one captive and one wild, and we used stochastic dynamic programming to identify optimal state-dependent strategies. The model recommends unique sequences of optimal management actions over several years. A robust rule of thumb for species that can increase faster in captivity than in the wild is to capture the entire wild population whenever the wild population is below a threshold size of 20 females. This rule applies even if the wild population is growing and under a broad range of different parameter values. Once a captive population is established, it should be maintained as a safety net and animals should be released only if the captive population is close to its carrying capacity. We illustrate the utility of this model by applying it to the Arabian oryx ( Oryx leucoryx ). The threshold for capturing the entire Arabian oryx population in the wild is 36 females, and captive-bred individuals should not be released before the captive facilities are at least 85% full.     

Effects of forest fragmentation on avian breeding activity

Biodiversity declines and ecosystem decay follow forest fragmentation; initially, abundant species may become rare or be extirpated. Underlying mechanisms behind delayed extirpation of certain species following forest fragmentation are unknown. Species declines may be attributed to an inadequate number of breeding adults required to replace the population or decreased juvenile survival rate due to reduced recruitment or increased nest predation pressures. We used 10 years of avian banding data, 5 years before and 4 years after fragment isolation, from the Biological Dynamics of Forest Fragments Project, carried out near Manaus, Brazil, to investigate the breeding activity hypothesis that there is less breeding activity and fewer young after relative to before fragment isolation. We compared the capture rates of active breeding and young birds in 3 forest types (primary forest, fragment before isolation, and fragment after isolation) and the proportion of active breeding and young birds with all birds in each unique fragment type before and after isolation. We grouped all bird species by diet (insectivore or frugivore) and nesting strategy (open cup, cavity, or enclosed) to allow further comparisons among forest types. We found support for the breeding activity hypothesis in insectivorous and frugivorous birds (effect sizes 0.45 and 0.53, respectively) and in birds with open-cup and enclosed nesting strategies (effect sizes 0.56 and 0.44, respectively) such that on average there were more breeding birds in fragments before isolation relative to after isolation. A larger proportion of birds in the community were actively breeding before fragment isolation (72%) than after fragment isolation (11%). Unexpectedly, there was no significant decrease in the number of young birds after fragment isolation, although sample sizes for young were small (n = 43). This may have been due to sustained immigration of young birds to fragments after isolation. Together, our results provide some of the strongest evidence to date that avian breeding activity decreases in response to fragment isolation, which could be a fundamental mechanism contributing to ecosystem decay.     

Infant care,infanticide, and female reproductive strategies in polygynous groups of common marmosets (Callithrix jacchus)

Reproduction in marmoset and tamarin groups is typically restricted to a single dominant female, but it is unclear why subordinate females tolerate delayed reproduction. The presence of two breeding females in free-ranging groups of common marmosets (Callithrix jacchus) presented a unique opportunity to examine differences in the reproductive strategies of dominant and subordinate females. Three groups were monitored for 12–18 months at a forest reserve in northeastern Brazil. Data on infant care were collected during two consecutive all-day follows every 10 days until the infants were 2 months old. Carrying patterns for infants born to dominant females were similar to those observed in groups containing a single breeding female. All group members over 5 months of age participated in infant care, and dominant females allowed some group members to carry their infants from the 1 st day of life. In contrast, subordinate females were protective of their offspring and were their sole caretakers for at least a week following birth. One infant born to a subordinate was killed in an attack involving the dominant female. Overall, dominant females gave birth to more infants and had higher infant survival than did subordinate breeding females. subordinate females were successful in rearing young only when the timing of births was such that they did not overlap with the dependency period of infants born to the dominant female. These patterns suggest that subordinate females may face resource competition, especially over access to helpers. In times of severe competition, subordinate females that delay reproduction may be avoiding a wasted reproductive effort.     

Age-dependent survival analyzed with Bayesian models of mark-recapture data

We describe a Bayesian random effects model of mark-recapture data that accounts for age-dependence in survival and individual heterogeneity in capture probabilities and survival. The model is applied to data on the Glanville fritillary butterfly (Melitaea cinxia) collected from a population enclosed in a large cage in the field. The cage population consisted of a mixture of butterflies originating from newly established and old populations in a large metapopulation in the Aland Islands in Finland. The explanatory variables in the model included the effects of temperature, sex, and population type (new vs. old) on capture probabilities, and the effects of age, sex, population type, and day vs. night on survival. We found that mortality rate increased with age, that mortality rate was much higher during the day than during the night, and that the life span of females originating from newly established populations was shorter than the life span of females from old populations. Capture probability decreased with increasing temperature and decreased with increasing mobility of individuals.     

Ecological correlates of duckling adoption among white-winged scoters Melanitta fusca: strategy, epiphenomenon, or combination?

Young waterfowl can frequently join foster females shortly after hatch, resulting in post-hatch brood amalgamation. Much uncertainty remains about physiological or ecological factors that motivate adoption including potential costs and benefits to fostered offspring as well as to females that either lose or accept young. Several hypotheses have been put forth to explain adoption. In this paper, we examine the salvage strategy (SSH) and accidental-mixing (AMH) hypotheses. According to the SSH, females abandon or lose their young due to substantial energetic constraints from incubation and brood rearing. The AMH posits that adoption results from local ecological conditions on breeding areas (i.e., adverse weather conditions, high brood densities) which act to separate offspring and mothers. We used multistate modeling to estimate relationships between probabilities of adoption by white-winged scoter (Melanitta fusca) ducklings from natal to foster females and a set of hypothesized ecological covariates. Results showed that most adoption occurred within 6 days of hatch; additionally, likelihood of adoption was positively related to inclement weather and negatively related to hatch date, size, and condition of natal females, and duckling condition. We conclude that adoption in this population is consistent with both the salvage strategy and accidental-mixing hypotheses. Ultimately, we suggest that adoption in our study population was foremost an outcome of intense gull predation but also of local environmental conditions.     

The length of growing season and adult sex ratio affect sexual size dimorphism in moose

While factors affecting body growth have been extensively studied, very little is known about the factors likely to affect the sexual size dimorphism (SSD) in polygynous mammals. Based on the carcass mass of 24420 male and female moose recorded in 14 Norwegian populations, we examine three hypotheses to explain geographical variation in SSD. First, SSD is expected to decrease when the relative density of animals (for a given habitat quality) increases, because resource limitation at high population densities is assumed to affect body growth of males more than females. Second, because males are selected to invest in growth more than females, environmental seasonality and related improvement of the forage quality during the short and intense growing season are expected to increase SSD. Third, by decreasing the proportion of adult males in the population, resulting in start of rutting earlier in life, hunting may decrease the SSD by increasing the reproductive cost of young males. We found that males grew faster and for a longer time of their life than did females and thus were heavier (-24%) when they reached adulthood. Sexual size dimorphism was independent of density but was higher in areas with short growing seasons. The low SSD in populations with largely adult female-biased sex ratios (males per female) shows that male body growth decreases with a decreasing proportion of adult males in the population. Our results indicate that geographical variation in moose SSD is influenced by divergent responses in the sexes to ecological factors affecting body growth.     

Sex ratio and maternal rank in wild spider monkeys: when daughters disperse

Summary Data from a long-term field study of the spider monkey, Ateles paniscus, in Peru indicate that a strongly female-biased sex ratio exists from birth in this population. Of 46 infants born between July 1981 and June 1986, 12 were male, 32 were female and 2 were of undetermined sex. This effect is consistent between years as well, with more females than males born in each year of the study (Table 1). This bias is driven by the fact that low-ranking females produce daughters almost exclusively, while high-ranking females bias their investment somewhat less strongly towards sons (Table 2). The unusual pattern of female-biased maternal investment observed in this population of Ateles probably occurs for a combination of the following reasons: (1) maternal investment in individual male offspring is somewhat greater than in individual female offspring; (2) males remain with their natal groups, and the sons of high-ranking females are likely to be competitively superior to the sons of low-ranking females; (3) males compete for mates, and only the one or two most dominant males within a community are likely to achieve significant reproductive success. Two possible mechanisms of sex-ratio adjustment and the evidence for each are discussed.     

Sexual selection favours small and symmetric males in the polygynous greater sac-winged bat Saccopteryx bilineata (Emballonuridae, Chiroptera)

We investigated how morphological traits of territorial males in the polygynous bat Saccopteryx bilineata were related to their reproductive success. Because of the frequency of aerial courtship displays and defence manoeuvres, and the high energetic costs of flight, we expected small and symmetric males to be better able to court females on the wing and to monopolize copulations with females in their harems. We predicted that small and symmetric males would sire more offspring within the colony and a larger portion of the young born within their harem than large or asymmetric males. We measured size and fluctuating asymmetry of 21 territorial males and analysed their reproductive success in 6 offspring cohorts (n=209 juveniles) using 11 microsatellite loci. As predicted, small and symmetric males had, on average, a higher reproductive success in the colony than large and asymmetric males. The percentage of young sired by males within their harem increased as males decreased in size, but was not influenced by fluctuating asymmetry. As fluctuating asymmetry of males correlated with their reproductive success within the colony but not within their harems, we infer that fluctuating asymmetry is probably related to female choice, whereas male size is probably important for harem defence on the wing.Communicated by G. Wilkinson     

Lifetime reproductive success in the spotted sandpiper (Actitis macularia) : sex differences and variance components

Summary Lifetime reproductive success (LRS) of male (N=103) and female (N= 66) spotted sandpipers (Actitis macularia) was studied for 13 years of a 17-year study at Little Pelican Island, Leech Lake, Minnesota. There was no sex difference in longevity, but females had significantly more mates, eggs, chicks, fledged young, and young returning in subsequent years than did males. Variance in LRS was partitioned into five life-history components: longevity (L), mates per year (M), eggs per mate (E), proportion eggs hatched (H), and proportion of chicks fledged (F). For both sexes, F accounted for the greatest proportion of variance in LRS (males, 43%; females, 47%), followed by L (males, 26%; females, 43%) and H (males, 21%; females, 28%). Positive covariance between H and F was consistent with predator-caused clutch and brood loss. Contrary to our expectations, males had a higher coefficient of variation in reproductive success than did females. This was because males were relatively more likely than females to produce no young.Offprint requests to: L.W. Oring at the current address     

Mating group composition influences somatic costs and activity in rutting dominant male reindeer (<Emphasis Type="Italic">Rangifer tarandus</Emphasis>)

In polygynous species, males devote considerable effort to reproduction during the rut. Both the number of females in the mating group and the ratio of sexually mature males to sexually mature females [adult sex ratio (ASR)] are expected to affect the amount of effort a male devotes to reproductive activities. We predicted the reproductive effort of dominant male reindeer, measured as relative mass loss, proportions of active reproductive behaviors, and frequencies of agonistic behaviors would (1) increase with an increasing number of females in the mating group and eventually level off, and (2) exhibit a dome shape with respect to ASR in the mating group. We tested these predictions using 12 years of data collected from semi-domesticated reindeer in northern Finland. We found a positive relationship between relative mass loss and the mean number of females in the mating group for mature, but not young males. The relationship between the proportion of active reproductive behaviors performed by mature males and the mean number of females in the group was quadratic while agonistic behaviors of mature males increased with the increasing female group size. We also found that active reproductive behaviors decreased with a rising mating group ASR for mature males; whereas, young males performed more agonistic behaviors as group ASR increased. Our results point to age-specific patterns of mass loss and activity during the mating season. They also indicate that both the number of females and ASR in the mating group are important factors in determining the level of reproductive effort of dominant male reindeer.