Dominant Bulls Research Articles

Male blue wildebeest increase activity during the rut, but not at the expense of rest

Rest is a state of adaptive inactivity that increases the efficiency of activity by regulating its timing and reducing energy use when activity is not beneficial. Thus, animals can go without rest when specific demands, such as mating, favour being awake. Sexually active male blue wildebeest (bulls) are typically territorial, and it has been reported that when a bull is protecting a harem during the mating season (rut), he neither eats nor rests. We examined the daily activity and inactivity patterns of dominant bulls by means of actigraphy for 3 months, which included the rut. We also measured faecal androgen metabolite (fAM) levels and subcutaneous temperature, both of which have variances known to delineate the rut. During the rut, wildebeest bulls experienced higher levels of activity, fAM, and a greater daily range of subcutaneous temperature. Despite previous reports, the male blue wildebeest rested daily during the rut, and while the amount of rest was low, it was not substantially lower than prior to the rut. The amount of time spent inactive increased substantially after the rut. The timing of daily activity and inactivity patterns did not vary substantially across the recording period. Across the recording period, the average daily ambient temperatures decreased (seasonality), and the subcutaneous temperature followed this pattern, although it was not as marked. It appears that in the post-rut period a substantive increase in time spent at rest occurs, potentially allowing the wildebeest bulls time to recover following a period of intense activity.

Intervention by an older, dominant bull elephant (Elephas maximus) during an agonistic interaction between adolescents at Denver Zoo

Bull Asian elephant (Elephas maximus) sociality is complex and understudied. Increasingly, researchers recognize the role of mature bull elephants in teaching adolescent bulls appropriate social and reproductive behaviours that enable them to have normal intra-species relationships after the adolescents leave their natal herds. We describe a specific intervention event by a mature, dominant bull in a novel social group with adolescent bull elephants at Denver Zoo, Colorado, USA. The mature bull intervened on behalf of an adolescent elephant, allowing this adolescent to escape from two other adolescents who were repeatedly chasing him, marking boundaries of appropriate behaviour for the adolescent bulls. This example provides evidence for adolescent bull elephants learning appropriate social behaviours from mature conspecifics and suggests that mature bulls play an active role in this relationship. Overall, this intervention behaviour supports the inclusion of mature bulls in social groupings of bull elephants in managed care.

Latrine ecology of nilgai antelope

Abstract The use of scent for communication is widespread in mammals, yet the role of scent-marking in the social system of many species is poorly understood. Nilgai antelope (Boselaphus tragocamelus) are native to India, Nepal, and Pakistan. They were introduced to Texas rangelands in the United States during the 1920s to 1940s, and have since expanded into much of coastal South Texas and northern Mexico. The nilgai social system includes the use of latrines or repeated defecation at a localized site. We quantified and described physical and behavioral characteristics of nilgai latrine ecology to investigate drivers of latrine use at three sites in South Texas, during April 2018 to March 2019. Latrines were abundant (2.6–8.7 latrines/ha on unpaved roads, 0.4–0.9 latrines/ha off-roads), with no evidence for selection as to vegetation communities; latrines were dynamic in persistence and visitation rates. We found higher densities of latrines in Spring surveys, just after the peak of nilgai breeding activity, compared to Autumn surveys. Density of nilgai latrines was 3–10 times greater than estimated population densities, indicating individual nilgai must use multiple latrines. Camera traps and fecal DNA analysis revealed latrines were mainly (70%) visited by bulls and defecated on by bulls (92% in photos, 89% for DNA samples). The greatest frequency of visits occurred during the peak in the nilgai breeding season, from December–February; latrines were visited every 2–3 days on average. Body characteristics of photographed individuals and genetic analysis of feces indicated repeated visits from the same individuals. Nilgai cows occasionally used latrines; their use was sometimes followed by bulls showing flehmen responses after a female defecated or urinated on the latrine. We propose that dominant bulls use latrines for territory demarcation to display social dominance to both cows in estrus and subordinate bulls. Cows likely use latrines to communicate reproductive status. This study is the first intensive assessment focused on latrine ecology in nilgai. Our results directly contradict anecdotal descriptions of latrine use and behavior in nilgai but are consistent with predictions of antelope social systems based on body size, feeding type, and group dynamics.

Sparring dynamics and individual laterality in male South African giraffes

AbstractSparring by male giraffes has been commonly reported since its first description in 1958 and is believed to play a role in establishing male dominance hierarchies. However, despite being often documented, quantitative investigations of sparring behaviour are currently lacking. Here, we investigate the factors affecting the frequency, duration and intensity of sparring bouts in a population of giraffes Giraffa camelopardalis giraffa living on a private fenced reserve in Limpopo, South Africa. We show that sparring bouts were most frequently observed in young adults, and between males that were more evenly matched in size. Sparring bouts between males of similar body size were also characterised by being of high intensity and of short duration. Taken together, these results support the suggestion that sparring functions principally to provide maturing males a means of testing their competitive ability without escalating to full‐scale fights. Additionally, mature bulls intervened on young adults possibly to disable any winner effect achieved by the latter, with the most dominant bull being responsible for the majority of interventions. For the first time, we also show that individuals displayed strong laterality when engaged in sparring: individuals consistently preferred delivering blows from either their left or right side, and these preferences dictated the orientation of sparring bouts (whether head‐to‐head or head‐to‐tail). Lastly, we show that sparring displayed a seasonal peak which coincided with the onset of the wet season and possibly reflected the increased aggregation of males at this time. A more nuanced understanding of how social and environmental factors shape interactions among individuals, such as sparring, will improve our understanding and management of this charismatic animal.

The effects of short-term medroxyprogesterone acetate on rut related behaviors, semen characteristics and fertility in farmed reindeer bulls

The effects of medroxyprogesterone acetate (MPA) on velvet antler cleaning, hypophagia, aggressive behavior and fertility were evaluated in farmed reindeer bulls during a 2-year study. Eight reindeer bulls aged 1–4 years were divided into 2 groups balanced for age. During each year, one group (MPA, n = 4) was treated with MPA 2 wk prior to the expected onset of rut while the other group (CTL, n = 4) served as untreated controls. Feed consumption, behavior and antler cleaning were recorded daily or 3 x weekly for 3 mo. Each year a dominant CTL and MPA bull were put into separate harems of estrous synchronized females for 1 wk in mid-September. Following harem breakup, semen was collected from all bulls via electroejaculation and evaluated. In Year 2 the bulls were switched such that year 1 MPA bulls received the CTL treatment and year 1 CTL bulls received MPA treatment. In Year 2 all eight bulls received MPA treatment/booster following semen collection. In both years, MPA treatment reduced rut associated body weight loss (p ≤ 0.05), rut associated hypophagia (p ≤ 0.001), interfered with velvet antler cleaning, and abolished aggressive rut related behavior. All of these changes suggest suppression of testosterone mediated effects. Alternatively, semen parameters differed little between treatment groups with the exception of reduced sperm concentration and total sperm production in MPA bulls (p ≤ 0.05). All CTL bulls in Year 2 exhibited full rut behavior with the dominant bull successfully breeding 100% of females available for breeding, suggesting no carryover effect of MPA treatment from the previous year. The MPA bull successfully bred 4 of 6 females (Year 1) but the MPA bull in Year 2 failed to sire any offspring. A single 400 mg treatment of MPA just prior to rut was sufficient to suppress rut associated aggression and hypophagia on a short-term (3 mo) basis. It did not however, completely suppress fertility.

Combining molecular and incomplete observational data to inform management of southern white rhinoceros (Ceratotherium simum simum)

Conservation efforts have preserved the southern white rhinoceros (SWR) in protected areas and have resulted in substantial overall growth in population size, but in small, fragmented populations in which inbreeding is an important risk. However, field observation of breeding often lacks sufficient accuracy to inform translocation strategies that are intended to increase genetic variation. The purpose of this study was to integrate microsatellite genotypes with an incomplete, field-observed pedigree to make inferences about mean kinship and basic demographic data that could be used to inform translocation programmes for SWR in a confined population in Botswana. Using this approach, we identified parents for 29 out of 45 offspring born in the reserve between 1993 and 2013 and detected eight non-breeding bulls with high mean kinship as candidates for translocation. The method also allowed inferences about demographic parameters that could influence the effectiveness of intervention strategies, such as age and timing of reproduction, and natal sex ratios. Importantly, the reproductive dominance of the bulls was not as skewed as expected after the original dominant bull was removed from the population, suggesting that closed populations can maintain multiple, simultaneously breeding males. The genetic data also confirmed that the accuracy of field-based parentage assignment was increased after implementation of an ear-notching programme. This study demonstrates the value of combining genetic information with ongoing surveillance to inform management of threatened populations, and of using mean kinship to inform metapopulation management by identifying candidates for translocation.

Profiling patterns of fecal 20-oxopregnane concentrations during ovarian cycles in free-ranging southern white rhinoceros (Ceratotherium simum simum)

Unlike their wild counterparts, many white rhinoceros females in captivity fail to reproduce successfully such that current captive populations are not self-sustaining. The causes of the problem are poorly understood. Variation in cycle length and long periods of acyclicity are characteristics of the majority of these non-reproducing females in captivity but it is unknown whether these characteristics are a feature of reproductively successful free-ranging females. This study therefore aimed to monitor cyclic activity in a wild population of southern white rhinoceros at Lapalala Wilderness, South Africa, by measuring the concentrations of immunoreactive fecal progestagen metabolites (fPM). Five adult females were tracked twice per week for 20 months and if located a fresh fecal sample was collected. Reproductive events and group structural dynamics were also recorded and subsequently correlated with the fPM data. The baseline concentration of fPM was 0.69±0.20μg/g DW while concentrations during pregnancy were 30–400-fold higher. The females exhibited estrous cycle lengths of 30.6±7.7 days and, based on fPM data, gestation length in one female was 502±3 days. Year-round monitoring showed no clear evidence of seasonality in ovarian activity. During cyclic luteal activity females were often seen in the presence of a dominant bull. One female stopped cycling after removal of the local dominant bull and luteal activity only returned after a new bull was introduced. This suggests that white rhinoceros females in the wild might need external stimuli from a male to ovulate. These findings indicate that the irregular cyclicity reported for white rhinoceros housed in zoos and animal parks may result from conditions in captivity and account for reduced fertility.

Reproductive effort of bison bulls (Bison bison) in semi-natural conditions

Reproductive effort (RE) is defined as the investment in any current reproductive act. In male ungulates, variation in RE can be explained by differences in age, dominance, phase in the breeding season and number of oestrus females simultaneously present. We investigated the relation between these factors and RE in American bison males in semi-natural conditions. We looked for differences between males in RE, measured by tending behaviour, and maintenance activities (feeding/resting) during the rut. We found no effect of age on RE. During early rut there was no difference in RE between males of different rank. Dominant males had a higher RE during peak rut, and in late rut both the first and second ranking males showed more RE than lower ranking bulls. For all males, there was a clear increase in RE towards peak rut and when more females were attractive. Maintenance behaviours decreased when more females were synchronously in oestrus. The most dominant bulls spent less time grazing than lower ranking males, and all males decreased feeding during peak rut. Resting decreased with age. We conclude that dominance, phase of rut and the number of females synchronously in oestrus are the factors that best explain variation in RE.

ThePROM1Mutation p.R373C Causes an Autosomal Dominant Bull's Eye Maculopathy Associated with Rod, Rod–Cone, and Macular Dystrophy

To characterize in detail the phenotype of five unrelated families with autosomal dominant bull's eye maculopathy (BEM) due to the R373C mutation in the PROM1 gene. Forty-one individuals of five families of Caribbean (family A), British (families B, D, E), and Italian (family C) origin, segregating the R373C mutation in PROM1, were ascertained. Electrophysiological assessment, fundus autofluorescence (FAF) imaging, fundus fluorescein angiography (FFA), and optical coherence tomography (OCT) were performed in available subjects. Mutation screening of PROM1 was performed. The R373C mutant was present heterozygously in all affected patients. The age at onset was variable and ranged between 9 and 58 years, with most of the individuals presenting with reading difficulties. Subjects commonly had a mild to moderate reduction in visual acuity except for members of family C who experienced markedly reduced central vision. The retinal phenotype was characterized by macular dystrophy, with retinal pigment epithelial mottling in younger subjects, progressing to typical BEM over time, with the development of macular atrophy in older patients. In addition, all members of family C had typical features of RP. The electrophysiological findings were variable both within and between families. Mutations in PROM1 have been described to cause a severe form of autosomal recessive RP in two families of Indian and Pakistani descent. The results of this study have demonstrated that a distinct redundant PROM1 mutation (R373C) can also produce an autosomal dominant, fully penetrant retinopathy, characterized by BEM with little inter- and intrafamilial variability, and retinal dystrophy with variable rod or rod-cone dysfunction and marked intra- and interfamilial variability, ranging from isolated maculopathy without generalized photoreceptor dysfunction to maculopathy associated with very severe rod-cone dysfunction.

Vasectomy of older bulls to manage elephant overpopulation in Africa: a proposal

This article is a proposal based on literature, it provides a concept that still requires on the ground investigation and implementation. When it was initially presented at the EMOA symposium in 2004 vascetomy had not yet performed on a bull elephant, but since tht time the opertion has been carried out several times in South Africa. The article reviews the advantages of male sterilization over that of females and looks at the 'general, technical, sex-related and financial aspects of the vascetomy of elephant bulls'. It appears that after dominant bulls are selected, treatment of less that 2% of the elephants would stabilize a population in parks with a natural population growth rate. Analysis suggests that for parks with 100 to 300 elephants, occasional vasectomy of a dominant bull would provide an effective elepahnt family planning tool.

Glucocorticoids of bison bulls in relation to social status

A primary response to stress is an increase in circulating adrenal glucocorticoids (GC) such as cortisol. Two hypotheses propose differential stress responses to agonistic and aggressive interactions in social groups. If subordinate animals are subjected to social and psychological stressors leading to chronic GC elevation, the ‘stress of subordination’ hypothesis predicts that GCs will be higher in subordinates than dominants. Alternatively, if dominant animals are subject to physiological stressors (e.g., fight at higher rates than subordinates) or hierarchies are unstable, the ‘stress of domination’ hypothesis predicts higher GCs in dominant individuals. Both models predict that GC levels will peak during the breeding season. We tested these predictions in bison bulls ( Bison bison) using fecal steroid analysis to characterize GC concentration and behavioral observations to determine dominance rank, copulatory success, and tending status of bulls. Fecal samples were collected during 2003 from adult bison bulls during pre-rut (June), rut (July–August), and post-rut (September). Matched sample data indicated that mean GC levels (ng/g feces) of bulls strongly peaked during the 4-week rut, doubling from pre-rut to rut and then declining again during post-rut. High ranked dominant bulls maintained higher GC levels than lower ranked subordinate bulls. Dominance rank was positively correlated with copulatory success and age, and dominant bulls were more likely to tend (guard) cows as they approached estrus. There was a positive correlation between GC level and copulatory success, with prime-aged bulls (≥7 years) obtaining the most copulations. GC levels were positively correlated with bull androgen levels determined in a previous study. These results support the ‘stress of domination’ hypothesis, indicating that dominant bison bulls pay a significant physiological price for high social status and the opportunity to mate.

Fecal androgens of bison bulls during the rut

The influence of sex hormones is a key proximate factor underlying male reproductive behavior in mammals. Effective conservation policies for the remaining purebred plains bison ( Bison bison bison) herds require knowledge of the physiology underlying bison reproductive biology. We used fecal steroid analysis to characterize androgen levels in adult bison bulls before, during, and after the rut, and to examine androgen levels of bulls differing in reproductive status, age, and mating success. Fieldwork was carried out at the Fort Niobrara National Wildlife Refuge in north-central Nebraska. All adult bison in the herd were individually known by unique brands. Fecal samples were collected during 2003 from bulls during pre-rut (June), rut (July–August), and post-rut (September), and behavioral observations focused on reproductive status and mating success during the rut. Matched sample data indicated that androgen levels (ng/g feces) of bulls peaked during the rut, doubling from pre-rut to rut and then declining by 75% during post-rut. Dominant bulls that tended (guarded) cows maintained higher androgen levels than bulls that were not tending. There was a positive correlation between bull age (associated with mating success) and androgens, with higher androgen levels in prime-aged bulls compared with younger bulls. Nonetheless, there was no correlation between mating success (measured by number of copulations observed) and androgen level. This suggests that while androgens may provide the proximate motivation to compete for matings, other factors determine the mating success of bison bulls.

Mammalian exocrine secretions. XVIII: Chemical characterization of interdigital secretion of red hartebeest, Alcelaphus buselaphus caama.

Gas chromatography, coupled gas chromatography-mass spectrometry (electron impact mode and chemical ionization with methane as reactant gas), gas chromatography-infrared spectroscopy, and derivatization techniques were used to identity 53 compounds in the interdigital secretion of the red hartebeest, Alcelaphus buselaphus caama. These compounds included alkanes, isoalkanes, alcohols, ketones, carboxylic acids, oxiranes, furanoid linalool oxides, and a large number of branched and unbranched saturated and unsaturated aldehydes. The secretion probably plays a role in demarcation of territories by dominant bulls.

Marion Island elephant seals: the paucity-of-males hypothesis tested

The southern elephant seal, Mirounga leonina, population at Marion Island has declined since the start of research activities there in 1973, as have populations at other Indian Ocean breeding sites. One suggested mechanism for the decline at Marion Island is a shortage of males, resulting in low insemination rates. We tested this "paucity-of-males" hypothesis by looking at (i) adult sex ratios, (ii) male sexual activity, and (iii) the relationship between levels of sexual activity and the probability of a cow pupping in the following season. Sex ratios were similar to those at other sites where populations are either stable (South Georgia) or increasing (Peninsula Valdes). Dominant bulls monopolised mating opportunities, achieving 98.1% of 629 observed copulations over three seasons. Of the 138 cows coming ashore, only 4 (2.9%) were not seen mating and 89% copulated with only one bull; dominant bulls copulated with all but 1 of the 134 (99.3%) cows that did mate. Cows were mated more frequently than at sites with stable and increasing populations. There was no difference in the observed level of sexual activity between cows seen pupping in the following season and those who failed to pup. This indicates that bulls monopolising harems are capable of inseminating all the cows. Such findings refute the paucity-of-males hypothesis.

Effect of the presence of a dominant bull on performance of two age group bulls in libido tests

It is not clear if the presence of a dominant bull affects in different ways the sexual behavior of two age groups of young bulls, and if its effect is different when this mature bull is maintained in an adjacent pen, rather than when he has physical contact. Twelve 15 month old and ten 27 month old sexually naive Simmental bulls were libido tested under the presence or absence of a dominant bull under two trials: (1) individual sexual performance tests were conducted. On alternate tests days, a mature bull was present in an adjacent pen where the stimulus female stanchion was attached. In trial (2), same age animals, as a group, were exposed to a female, and on alternate test days, a mature bull was present, allowing physical contact with the tested bulls. In trial (1), no difference was found in sexual behavior activities or libido scores within age groups between treatments ( P>0.05). Nevertheless, in the older age group, the time spent close to the stimulus female was reduced during mature male presence ( P=0.02). In trial (2), both age groups of bulls were affected by the physical presence of the mature bull, reducing the number of times that the animals were seen in sexual proximity with the stimulus female ( P<0.01). It was concluded that the sexual behavior of both age groups was affected in different ways when a dominant bull was present.

Marion Island elephant seals: the paucity-of-males hypothesis tested

The southern elephant seal, Mirounga leonina, population at Marion Island has declined since the start of research activities there in 1973, as have populations at other Indian Ocean breeding sites. One suggested mechanism for the decline at Marion Island is a shortage of males, resulting in low insemination rates. We tested this "paucity-of-males" hypothesis by looking at (i) adult sex ratios, (ii) male sexual activity, and (iii) the relationship between levels of sexual activity and the probability of a cow pupping in the following season. Sex ratios were similar to those at other sites where populations are either stable (South Georgia) or increasing (Peninsula Valdes). Dominant bulls monopolised mating opportunities, achieving 98.1% of 629 observed copulations over three seasons. Of the 138 cows coming ashore, only 4 (2.9%) were not seen mating and 89% copulated with only one bull; dominant bulls copulated with all but 1 of the 134 (99.3%) cows that did mate. Cows were mated more frequently than at sites with stable and increasing populations. There was no difference in the observed level of sexual activity between cows seen pupping in the following season and those who failed to pup. This indicates that bulls monopolising harems are capable of inseminating all the cows. Such findings refute the paucity-of-males hypothesis.

Breeding Strategies, Mate Choice, and Reproductive Success in American Bison

The objectives of this study were to assess the adaptive significance of various reproductive strategies in American bison bulls and cows. The study was conducted with a herd of 260 to 360 animals at the Fort Niobrara National Wildlife Refuge near Valentine, Nebraska, USA. Dominance (or fighting ability) was not correlated with age for 7to 13-yr-old bulls or with body mass for animals > 750 kg. Reproductive success among 6 + yr-old bulls ranged from 0 to 16 young sired per bull in 3 yr and was positively correlated with dominance rank. Dominant bulls bred during the first 2-3 weeks of rut and lower ranking bulls conserved energy and achieved a significant number of matings during the late rut. Challenging bulls engaged tending bulls in bellowing contests, probably to assess their stamina and elicit the attention of cows. Tending bulls bellowed defensively and bellowed at the same time and attempted to "outbellow" challengers. Cows apparently assessed variance in male "quality" and approached high-ranking bulls and ran away from low-ranking bulls. Bulls did not discriminate between cows based on their age or prior breeding performance, but tended and mated with any cows that were in estrus. Cows exhibited flehmen behavior toward each other, probably to stimulate the onset of estrus and synchronize time of copulation. All cows were equally likely to have a son or a daughter and did not exhibit a facultative adjustment in sex ratio based on prior breeding performance. The results are discussed relative to other studies on bison and other ungulates.

Foraging strategies and seasonal diet optimization of muskoxen in West Greenland

Various aspects of optimal foraging and seasonal diet composition of bulls (bachelor and dominant), cows, subadults, and yearlings of muskoxen Ovibos moschatus were investigated in West Greenland during the following seasons: calving, post-calving, summer, rut and mid-winter. The following hypotheses were tested: (1) muskoxen maximize daily energy intake during spring and summer, (2) dominant bulls monopolizing cows during the rutting season shift from an energy maximizing to a time minimizing foraging strategy in order to maximize the time available for reproductive activities, and (3) muskoxen employ a time minimizing foraging strategy during winter to conserve energy. As forage quality changed throughout the short Arctic growing season, muskoxen responded by changing the proportions of daily time spent feeding on graminoids (Cyperaceae, Poaceae) and dicots (Salix, Betula), respectively. This seasonal variation in the relative proportion of daily feeding time spent ingesting graminoids followed approximately the energy maximization prediction over the periods calving to rut. Neither time minimizing nor random foraging could explain the observed diets in this period, thus confirming hypothesis 1. Dominant bulls did not shift to the time minimizing strategy as predicted by hypothesis 2. However, during the pre-rutting and rutting seasons bulls deviated from the other sex/age classes by failing to obtain the daily maximum energy predicted by the model, as a result of a higher proportion of time allocated to agonistic and sexual behaviour. During winter, none of the sex/age classes employed a time minimizing strategy, so rejecting hypothesis 3. Instead, muskoxen were found to maximize Na intake, indicating that Na is of major importance for winter survival. The results emerging from a linear programming model with constraint settings varying over seasons confirm that the constraint parameters applied are indeed important limiting factors for muskoxen in natural populations.

Ranging behaviour of feral cattle (Bos taurus) in Doñana National Park, S.W. Spain

The cattle of Doñana (139 individuals in four social groups in 1989) have lived under free‐ranging conditions for centuries. Their ranging behaviour was analysed during a three‐year period. A total of 17,603 locations corresponding to 247 different animals allowed both for the estimation of global and seasonal home ranges of individuals and social groups and for the comparison of movement patterns. Cattle ranging behaviour was not affected by human interference, and was shown to be regulated by a complex interaction of environment, individual and social factors. Habitat structure and seasonal fluctuations in abundance and distribution of resources determined general patterns of ranging behaviour: the greater the concentration of resources, the smaller the home ranges of individuals and social groups. These patterns were modified at an individual level by the sex of the animal and its reproductive status if male. Social influences on ranging behaviour were important because these implied the segregation of home ranges among dominant bulls and among social groups. As a result, there was a great variability in space use and home‐range behaviour.

Differences in the sex and age composition of two muskox populations and implications for male breeding strategies

Muskox (Ovibos moschatus) breeding behaviour is centred on a harem of cows and sub-adults with a dominance hierarchy among adult bulls and a dominant herd bull breeding most cows during the August rut (Tener 1965, Smith 1976 and Gray 1987). Herd sizes even during the rut are not uniform but vary geographically. Herds tend to be larger at lower latitudes (Tener 1968, Gray 1987) in response to larger patches of forage plants and possibly greater threats of preda¬ tion. In turn, male breeding strategies wil l be influenced by herd size. In August 1988, I obtained large samples of muskox sex and age composition as part of ongoing management studies from southeast Victoria Island and on the nearby mainland (the Queen Maud Gulf area QMGulf) . The first hypothesis is that smaller herds are expected on Victoria Island because the distribution of muskoxen on the small dispersed sedge meadows would promote intra-group forage competition which, together with the lack of predators would favour the smaller herds. The second hypothesis is that fewer bulls would occur as singles or in bachelor herds during the rut on Victoria Island because distribution of the population among many small herds favours the opportunities for herd bulls. Muskoxen on Q M G u l f use large extensive sedge meadows and are exposed to predators although the level of interactions is unknown.