Better off alone! Reproductive competition and ecological constraints determine sociality in the African striped mouse (Rhabdomys pumilio)

1.?While the reasons for group-living have been studied for decades, little is known about why individuals become solitary. 2.?Several previous experimental studies could demonstrate that group-living can arises as a consequence of ecological constraints. 3.?It has been argued that reproductive competition between group members leads to significant costs of group-living, being a main reason of solitary-living. However, so far, no studies tested experimentally whether reproductive competition can explain solitary-living. 4.?Using a socially flexible species, the African striped mouse (Rhabdomys pumilio), we tested experimentally in the field whether dispersal and solitary-living are more likely to occur when reproductive competition is present. 5.?We investigated ecological constraints, here expressed as a function of population density, by removing groups of striped mice and creating vacant territories. To control for the effect of reproductive competition, which occurs only during the breeding season, we performed experiments during both the breeding and the non-breeding season. This is the first removal experiment performed in a species with communal breeding during the non-breeding season. 6.?During the breeding season, when population density was low, more striped mice from experimental groups moved into the vacant territories and became solitary than striped mice from control groups. This is in support of the ecological constraints hypothesis. 7.?During the non-breeding season, striped mice remained group-living despite the availability of free territories. Significantly, more striped mice became solitary-living during the breeding than during the non-breeding season. This is the first experimental support for the reproductive competition hypothesis explaining solitary-living. 8.?Analysis of the sexual maturity of males showed that males which became solitary had a higher reproductive potential than males that remained group-living. Analysis of the body mass data of females showed that more solitary females reproduced than group-living females. These results indicate that by becoming solitary individuals of both sexes avoided costs of reproductive competition within groups. 9.?Our study provides experimental evidence that reproductive competition within groups can lead to dispersal and solitary-living.     

Female reproductive competition in Eulemur rufifrons: eviction and reproductive restraint in a plurally breeding Malagasy primate

In mammals with female philopatry, co-resident females inevitably compete with each other for resources or reproductive opportunities, thereby reducing the kin-selected benefits of altruism towards relatives. These counteracting forces of cooperation and competition among kin should be particularly pronounced in plurally breeding species with limited alternative breeding opportunities outside the natal group. However, little is still known about the costs of reproductive competition on females' fitness and the victims' potential counter-strategies. Here we summarize long-term behavioural, demographic and genetic data collected on a plurally breeding primate from Madagascar to illuminate mechanisms and effects of female reproductive competition, focusing on forcible eviction and potential reproductive restraint. The main results of our study indicate that females in groups of redfronted lemurs (Eulemur rufifrons) above a critical size suffer from competition from their close relatives: females in larger groups face an increased probability of not giving birth as well as a higher probability of being evicted, especially during the annual mating and birth seasons. Eviction is not predicted by the number of adult females, the number of close female relatives, female age or inter-annual variation in rainfall but only by total group size. Thus, eviction in this species is clearly linked with reproductive competition, it cannot be forestalled by reproductive restraint or having many relatives in the group, and it occurs in the absence of a clear dominance hierarchy. Our study therefore also underscores the notion that potential inclusive fitness benefits from living with relatives may have been generally over-rated and should not be taken for granted.     

The cost of dominance: suppressing subordinate reproduction affects the reproductive success of dominant female banded mongooses

Social species show considerable variation in the extent to which dominant females suppress subordinate reproduction. Much of this variation may be influenced by the cost of active suppression to dominants, who may be selected to balance the need to maximize the resources available for their own offspring against the costs of interfering with subordinate reproduction. To date, the cost of reproductive suppression has received little attention, despite its potential to influence the outcome of conflict over the distribution of reproduction in social species. Here, we investigate possible costs of reproductive suppression in banded mongooses, where dominant females evict subordinates from their groups, thereby inducing subordinate abortion. We show that evicting subordinate females is associated with substantial costs to dominant females: pups born to females who evicted subordinates while pregnant were lighter than those born after undisturbed gestations; pups whose dependent period was disrupted by an eviction attained a lower weight at independence; and the proportion of a litter that survived to independence was reduced if there was an eviction during the dependent period. To our knowledge, this is the first empirical study indicating a possible cost to dominants in attempting to suppress subordinate breeding, and we argue that much of the variation in reproductive skew both within and between social species may be influenced by adaptive variation in the effort invested in suppression by dominants.     

Unrelated helpers will not fully compensate for costs imposed on breeders when they pay to stay

Unrelated subordinates may invest in costly help to avoid being evicted from groups (the 'pay-to-stay' hypothesis). However, the effectiveness of eviction to enforce help should depend on its being applied accurately and on the costs it imposes on both dominants and subordinates. The relative cost of being evicted is a function of the population frequency of eviction when population growth is limited by density-dependent factors. We describe a stage-structured pay-to-stay model incorporating density-dependent population growth, costly eviction and occasional errors. Breeders demand some amount of help and evict subordinates that do not provide it. Helpers decide on the amount of help they will provide. The threat of eviction alone is sufficient to enforce helping. However, helping will not be favoured if helpers do not impose costs on breeders. The amount of help provided is less than the cost that subordinates impose upon breeders, when any help is provided. Thus, the net fitness effect of a helper under pay-to-stay alone is negative, even if it is investing in cooperative behaviour. Constraints on dispersal have no effect on the amount of help, although they may influence the tolerance threshold of breeders and group stability, depending on the mechanism of density dependence.     

Seasonal variation of reproductive success under female philopatry and male-biased dispersal in a common vole population

Variation of reproductive success, an important determinant of the opportunity for sexual selection, is an outcome of competition within one sex for mating with members of the other sex. In promiscuous species, males typically compete for access to females, and their reproductive strategies are strongly related to the spatial distribution of females. I used 10 microsatellite loci and the mtDNA control region to determine seasonal differences in the reproductive success of males and females of the common vole (Microtus arvalis), one of the most numerous mammals in Europe. The sex-related spatial structure and bias in dispersal between genders were also assessed. Standardized variance of the reproductive success of females did not vary seasonally due to the continuity of female philopatry throughout the breeding season and to the constancy of the number of females reproducing successfully in each season. The males are the dispersing sex, undergoing both natal and breeding dispersal. Their standardized variance of reproductive success was significantly higher than that for females in July, when only two males monopolized 80% of the females in the population and when variance of male reproductive success was highest (I_m = 7.70). The seasonally varying and high standardized variance of male reproductive success may be explained by male-male competition for matings, coupled with seasonal changes in the age structure of the population.     

Territorial cooperation and social monogamy: factors affecting intersexual behaviours in pair-living snapping shrimp

Among the factors that may contribute to the evolution of social monogamy are selection for extended mate guarding of females and selection for territorial ‘cooperation’. Many socially monogamous taxa are also territorial, with ‘partners’ sharing a single territory, suggesting that one or both partners may benefit by sharing territorial maintenance. Snapping shrimp (genus Alpheus) are socially monogamous and territorial, living in excavated burrows or with host organisms, with females performing all parental care. The territorial cooperation hypothesis predicts that male and female partners share (1) territorial defence, resulting in a reduction in the risk of eviction from the burrow, (2) burrow construction duties, such that individuals in pairs spend less time in burrow construction relative to solitary individuals, and/or (3) foraging duties, by returning food to the burrow, where it is consumed by both partners. UsingA. angulatus as a model species, a territorial defence experiment revealed that females in pairs were significantly less likely than solitary females to be evicted by female intruders, but males in pairs were not significantly less likely than solitary males to be evicted by male intruders. A subsequent experiment revealed that paired males were significantly less likely to be evicted by an intruding male if paired with sexually receptive females than if paired with nonreceptive females. Another experiment revealed that (1) paired females spent significantly more time in burrow construction than paired males, and (2) both males and females consistently returned food items to the burrow, perhaps incidentally provisioning their mates. These data suggest that social monogamy may have been selected for in part because of the advantages of territorial cooperation, as both males and females are likely to benefit by dividing the labour of territorial defence and maintenance. These tests of the territorial cooperation hypothesis are synthesized with data from tests of the extended mate-guarding hypothesis to place snapping shrimp pairing behaviour into a larger construct incorporating both the influence of ecological pressures (territoriality) and mating interactions between the sexes. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Reproductive control via eviction (but not the threat of eviction) in banded mongooses

Considerable research has focused on understanding variation in reproductive skew in cooperative animal societies, but the pace of theoretical development has far outstripped empirical testing of the models. One major class of model suggests that dominant individuals can use the threat of eviction to deter subordinate reproduction (the ‘restraint’ model), but this idea remains untested. Here, we use long-term behavioural and genetic data to test the assumptions of the restraint model in banded mongooses (Mungos mungo), a species in which subordinates breed regularly and evictions are common. We found that dominant females suffer reproductive costs when subordinates breed, and respond to these costs by evicting breeding subordinates from the group en masse, in agreement with the assumptions of the model. We found no evidence, however, that subordinate females exercise reproductive restraint to avoid being evicted in the first place. This means that the pattern of reproduction is not the result of a reproductive ‘transaction’ to avert the threat of eviction. We present a simple game theoretical analysis that suggests that eviction threats may often be ineffective to induce pre-emptive restraint among multiple subordinates and predicts that threats of eviction (or departure) will be much more effective in dyadic relationships and linear hierarchies. Transactional models may be more applicable to these systems. Greater focus on testing the assumptions rather than predictions of skew models can lead to a better understanding of how animals control each other''s reproduction, and the extent to which behaviour is shaped by overt acts versus hidden threats.     

Sex-biased dispersal in a salmonid fish

We tested the hypothesis that dispersal is sex biased in an unexploited population of brook trout, Salvelinus fontinalis, on Cape Race, Newfoundland, Canada. Based on the assumptions that trout are promiscuous and that reproductive success is limited primarily by either number of mates (males) or fecundity (females), we predicted that males would disperse greater distances than females. We also tested the hypothesis that trout populations comprise stationary and mobile individuals, predicting that males have greater mobility than females. Based on a mark-recapture study of 943 individually tagged fishes, 191 of which were recaptured over 5 years, we find strong support for our hypothesis of male-biased dispersal in brook trout. Averaged among all 11 resampling periods, males dispersed 2.5 times as far as females; during the spawning period only, male dispersal exceeded that by females almost fourfold. Both sexes were heterogeneous with respect to movement, with a lower incidence of mobility among females (29.6%) than males (41.1%); mobile males dispersed six times further than mobile females. We conclude that this sex bias reduces mate competition among male kin and decreases the probability that males will reproduce with related females.     

Competition for mates and predominant juvenile male dispersal in mammals

Competition among males for mates may partially explain the predominant dispersal of juvenile male California ground squirrels (Spermophilus beecheyi). I tested the generality of this hypothesis by comparing dispersal patterns in many species of mammals. In most polygynous and promiscuous species of mammals, juvenile males are the predominant dispersers. In most monogamous species of mammals, juvenile males and juvenile females are predominant dispersers with little distinction as to sex. While many factors may influence dispersal, achieving outcrossing and advantages in competition for mates are most likely to explain predominant dispersal by juvenile males in many mammal species.     

Social modulation of testosterone levels in male black howlers (Alouatta pigra)

The influence of social factors on the modulation of male testosterone levels has been demonstrated among several vertebrate species. In addition to sexual activity, parental care and reproductive competition affect testosterone secretion. We examined variations in testosterone levels among male black howlers (Alouatta pigra) in various social contexts. Fecal samples were collected from nine males living in five different groups in the Mexican state of Campeche. The potential for intragroup and extragroup competition varied among the groups. The number of resident males living in the groups was the only variable that significantly explained variations in testosterone levels. Males living in unimale groups had higher testosterone levels; the highest testosterone levels were recorded for males that had experienced a shift from multimale to unimale group compositions. In this species, the probability of being challenged by extragroup males and evicted from the group during immigration events increases when males live in unimale groups. Therefore, our results suggest that male black howlers respond to competition for group membership by increasing their testosterone levels. In this context, testosterone secretion represents an anticipatory response to reproductive conflicts. Therefore, although males living in unimale groups have exclusive access to females, they face higher physiological costs associated with sustaining high testosterone levels for extended time periods.     

Dispersal mechanisms in a captive wild house mouse population (Mus domesticus Rutty)

The ecological implications of dispersal have been discussed in many studies of wild animals in the field but little is known about the social mechanisms leading to the emigration of certain members of a group. To study the social background of dispersal in wild house mice ( Mus domesticus Rutty) a population cage system was evaluated that allowed permanent observation of individually marked animals. It consisted of ten cages connected to a central cage by transparent plastic tubes. Two of these cages were defined as 'dispersal cages' and could be reached only by swimming through a water basin. Dispersal was defined as a permanent stay in one of these cages for at least 4 days. At the beginning of the experiment one pair of house mice with their litter was placed into the cage system. Each of six experiments lasted for 6 months during which data on spacing, social interactions, body condition, reproduction, mortality and dispersal were collected by daily observations. Results regarding this study could be summarized as follows: (1) dispersal in house mice is male-biased; (2) there are interfamiliar differences in dispersal age, dispersal rate, and in the development of the population structure; (3) after reaching sexual maturity subdominant males are evicted by the dominant one; (4) reproductive rate among females drops with increasing birth order, thus only the oldest females within a group reproduce; (5) females born under high population density conditions can only reproduce after dispersal.     

Social Behavior,Reproductive Strategies,and Population Genetic Structure of <Emphasis Type="Italic">Lagothrix poeppigii</Emphasis>

For species of primates in which females emigrate, we would expect males within groups to be related to one another. Kin selection theory suggests that these males should associate preferentially with one another, be more affiliative and cooperative with one another than females are, and compete less overtly with one another over reproductive opportunities than males in female philopatric taxa do. Precisely these patterns of social behavior characterize well-studied populations of 2 of the 3 atelin primate genera: spider monkeys (Ateles) and muriquis (Brachyteles). For the third atelin genus, Lagothrix, patterns of intragroup social behavior have been less well-documented. We studied the social and reproductive behavior of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in Ecuador during a one-year observational study and subsequently used molecular techniques to investigate population genetic structure and dispersal patterns for this taxon. Among adult male woolly monkeys, both affiliative and agonistic interactions were rare, and males were seldom in close proximity to one another. Relationships among male woolly monkeys are best characterized as tolerant, especially in the context of mating wherein direct competition among males was minimal despite the fact that females mated with multiple males. Relationships among females were likewise generally tolerant but nonaffiliative, though females often directed harassment towards copulating pairs. Affiliative interactions that did occur among woolly monkeys tended to be directed either between the sexes—primarily from female to male—or from younger towards older males, and the proximity partners of females tended to be members of the opposite sex. These results suggest that bonds between the sexes may be more important than same-sex social relationships and that direct female-female competition is an important feature of woolly monkey reproductive biology. Our genetic results indicate that, as in other atelins, dispersal by females is common, but some male dispersal likely occurs as well. In some but not all groups we studied, nonjuvenile males within social groups were more closely related to one another on average than females were, which is consistent with greater male than female philopatry. However, differences in these patterns among our study groups may reflect local variation in dispersal behavior.     

Female philopatry and male-biased dispersal in a direct-developing salamander, Plethodon cinereus

The local resource competition hypothesis and the local mate competition hypothesis were developed based on avian and mammalian systems to explain sex-biased dispersal. Most avian species show a female bias in dispersal, ostensibly due to resource defence, and most mammals show a male bias, ostensibly due to male-male competition. These findings confound phylogeny with mating strategy; little is known about sex-biased dispersal in other taxa. Resource defence and male-male competition are both intense in Plethodon cinereus, a direct-developing salamander, so we tested whether sex-biased dispersal in this amphibian is consistent with the local resource competition hypothesis (female-biased) or the local mate competition hypothesis (male-biased). Using fine-scale genetic spatial autocorrelation analyses, we found that females were philopatric, showing significant positive genetic structure in the shortest distance classes, with stronger patterns apparent when only territorial females were tested. Males showed no spatial genetic structure over the shortest distances. Mark-recapture observations of P. cinereus over 5 years were consistent with the genetic data: males dispersed farther than females during natal dispersal and 44% of females were recaptured within 1 m of their juvenile locations. We conclude that, in this population of a direct-developing amphibian, females are philopatric and dispersal is male-biased, consistent with the local mate competition hypothesis.     

Male dispersal patterns in white-faced capuchins, Cebus capucinus: Part 2: patterns and causes of secondary dispersal

Male dispersal from the birth group is common in the majority of social mammals, and in many species, males also engage in secondary or breeding dispersal following natal emigration. However, the patterns and causes of secondary dispersal are poorly understood due to the difficulty in following emigrants. Here, we detail the patterns and causation of male secondary dispersal in several groups of white-faced capuchins observed between 1985 and 2000 in Santa Rosa National Park, Costa Rica. Subsequent to natal emigration, which occurs between 2 and 8 years of age (median 4.5 years), male white-faced capuchins embark on a life of continual movement. Although males of all age classes engage in voluntary secondary dispersal, the ways by which males enter groups varies according to their age class. Adult males (≥10 years old) are more likely to enter groups aggressively, and they display longer tenure than either subadult males (7-10 years of age) or juvenile males (1-7 years of age). Given our finding that adult males face the highest risks in terms of aggressive interactions with conspecifics, we examined several explanations as to why they continue to disperse throughout their lives. Our data best support the intragroup mating competition hypothesis for secondary dispersal, whereby males move frequently between groups as a means of increasing their reproductive opportunities. Males may also engage in frequent secondary dispersal to avoid mating with their maturing daughters, although this hypothesis was not strongly supported by the current data. Males of all age classes displayed very high levels of parallel dispersal, which probably serves to offset the high costs of dispersal (predation, starvation and/or aggression from conspecifics) and it may also serve as a means of retaining kinship among group males.     

The Function of Male Agonistic Displays in Ursine Colobus Monkeys (Colobus vellerosus): Male Competition,Female Mate Choice or Sexual Coercion?

Male agonistic displays may allow males to assess competitors, females to assess mates, or could be directed at cycling females to sexually coerce them. We analysed the display output of 26 male ursine colobus monkeys (Colobus vellerosus) in four groups over 13‐mo at the Boabeng‐Fiema Monkey Sanctuary, Ghana. Display indices (including three behaviours, loud calls, stiff‐legs, and jump‐displays) were calculated for males in each group. Males vary in their expression of these behaviours suggesting they are sexually selected signals. We investigated the target of displays and whether display indices varied in relation to male dominance rank, eviction of other males, copulation rate, and proceptive behaviours received from females, to assess the primary function of these behaviours. Male displays decreased in vigour over time and were targeted to other groups and males. High‐ranking males displayed more than low‐ranking males. Alpha male display indices correlated with the number of other males evicted from the group. Display rates were generally higher when cycling females were present in the group. However, neither male display index nor rank correlated with copulation rates. Alpha and non‐alpha males gave cycling females equal rates of sexual solicitations; likewise cycling females showed no difference in the rates of proceptive behaviours directed towards alpha and non‐alpha males. Females mated promiscuously and did not seem to base mating decisions on male display output, although data on female hormones is needed to determine if they mate with strongly displaying males more in the periovulatory period. The male–male competition hypothesis received the greatest support, with some support for the female mate choice hypothesis. Although behaviours that appeared sexually coercive were observed, the function of male displays did not seem to be sexual coercion. Displays were rarely directed at females and males that displayed more did not have greater mating success.     

The Association of Intergroup Encounters,Dominance Status,and Fecal Androgen and Glucocorticoid Profiles in Wild Male White‐Faced Capuchins (Cebus capucinus)

Androgens play a role in male reproductive competition, frequently via aggression, while glucocorticoids are associated with the stress response. However, the relationships of these hormones with different sources of competition (intra‐ vs. intergroup) and dominance status are highly variable. Here, we consider the fecal androgen (fA) and glucocorticoid (fGC) profiles of alpha and subordinate male Cebus capucinus in the context of intergroup competition during a rare period of low intragroup competition (i.e. all females were either pregnant or lactating). Intergroup encounters (IGEs) are a long‐term reproductive strategy in male white‐faced capuchins, enabling them to assess the composition of neighboring groups. IGEs pose a threat to resident males as these can result in injury or death, loss of dominance rank, group eviction, and group takeovers that are frequently associated with infanticide. From February to July 2007, fecal samples were collected from eight males in three groups of white‐faced capuchins in the Santa Rosa Sector of the Área de Conservación Guanacaste, Costa Rica. IGE rate was positively associated with both fA and fGC levels, indicating that IGEs are perceived as reproductive challenges by resident males, and may be associated with elevated metabolic costs. Alpha males sire the majority of group offspring and, accordingly, the threat of IGEs to both future (via rank loss or eviction) and current (via infanticide) reproductive success is greater than for subordinate males. Consistent with this observation, alpha males had higher fA and fGC levels than subordinate males. Given that all females were either pregnant or lactating and pronounced overt intragroup competition was absent, we interpret the difference in hormone profiles of alpha and subordinate males as being primarily associated with variation in the perceived threats of IGEs according to dominance status. Future studies should focus on the interaction of intra‐ and intergroup competition by examining hormone levels in the presence of periovulatory females. Am. J. Primatol. 75:107‐115, 2013. © 2012 Wiley Periodicals, Inc.     

Mechanisms and reproductive consequences of breeding dispersal in a specialist predator under temporally varying food conditions

Individual variation in breeding dispersal has extensive ecological and evolutionary consequences, but the factors driving individual dispersal behaviour and their fitness consequences remain poorly understood. Our data on dispersal events of a rodent‐specialist predator, the Eurasian kestrel Falco tinnunculus, over 20 years in western Finland offers a unique opportunity to explore the mechanisms underlying breeding dispersal behaviour and its reproductive consequences in a wild bird population. Sex, age, body condition and previous breeding success affected breeding dispersal. Dispersal distances were longer in females than in males as well as longer in yearlings than in older individuals. Body condition was positively correlated to breeding dispersal distances, particularly for females. The lowest dispersal distances were recorded for intermediate brood sizes in the year preceding dispersal. Our results highlight sex‐ and environment‐specific consequences of breeding dispersal on reproductive performance. During increase phases of the three‐year vole cycles, males dispersing further had lower reproductive performance after dispersal, whereas in females, long breeding dispersal distances were associated with increased breeding success under all environmental conditions. These results suggest benefits associated to breeding dispersal in females, potentially related to large spatio‐temporal variation in main food abundance and intensity of intra‐specific competition. Breeding dispersal of males was costly during increasing food abundance, indicating the potential fitness benefits of environmental familiarity in this migratory species. Overall, our results indicate that both individual traits and environmental factors interact to shape breeding dispersal strategies in wide‐ranging predator populations under fluctuating food conditions.     

No evidence for female kin association,indications for extragroup paternity,and sex‐biased dispersal patterns in wild western gorillas

Characterizing animal dispersal patterns and the rational behind individuals’ transfer choices is a long‐standing question of interest in evolutionary biology. In wild western gorillas (Gorilla gorilla), a one‐male polygynous species, previous genetic findings suggested that, when dispersing, females might favor groups with female kin to promote cooperation, resulting in higher‐than‐expected within‐group female relatedness. The extent of male dispersal remains unclear with studies showing conflicting results. To investigate male and female dispersal patterns and extragroup paternity, we analyzed long‐term field observations, including female spatial proximity data, together with genetic data (10 autosomal microsatellites) on individuals from a unique set of four habituated western gorilla groups, and four additional extragroup males (49 individuals in total). The majority of offspring (25 of 27) were sired by the group male. For two offspring, evidence for extragroup paternity was found. Contrarily to previous findings, adult females were not significantly more related within groups than across groups. Consistently, adult female relatedness within groups did not correlate with their spatial proximity inferred from behavioral data. Adult females were similarly related to adult males from their group than from other groups. Using R _ST statistics, we found significant genetic structure and a pattern of isolation by distance, indicating limited dispersal in this species. Comparing relatedness among females and among males revealed that males disperse farer than females, as expected in a polygamous species. Our study on habituated western gorillas shed light on the dispersal dynamics and reproductive behavior of this polygynous species and challenge some of the previous results based on unhabituated groups.     

Density-Dependent Natal Dispersal Patterns in a Leopard Population Recovering from Over-Harvest

Natal dispersal enables population connectivity, gene flow and metapopulation dynamics. In polygynous mammals, dispersal is typically male-biased. Classically, the ‘mate competition’, ‘resource competition’ and ‘resident fitness’ hypotheses predict density-dependent dispersal patterns, while the ‘inbreeding avoidance’ hypothesis posits density-independent dispersal. In a leopard (Panthera pardus) population recovering from over-harvest, we investigated the effect of sex, population density and prey biomass, on age of natal dispersal, distance dispersed, probability of emigration and dispersal success. Over an 11-year period, we tracked 35 subadult leopards using VHF and GPS telemetry. Subadult leopards initiated dispersal at 13.6 ± 0.4 months. Age at commencement of dispersal was positively density-dependent. Although males (11.0 ± 2.5 km) generally dispersed further than females (2.7 ± 0.4 km), some males exhibited opportunistic philopatry when the population was below capacity. All 13 females were philopatric, while 12 of 22 males emigrated. Male dispersal distance and emigration probability followed a quadratic relationship with population density, whereas female dispersal distance was inversely density-dependent. Eight of 12 known-fate females and 5 of 12 known-fate male leopards were successful in settling. Dispersal success did not vary with population density, prey biomass, and for males, neither between dispersal strategies (philopatry vs. emigration). Females formed matrilineal kin clusters, supporting the resident fitness hypothesis. Conversely, mate competition appeared the main driver for male leopard dispersal. We demonstrate that dispersal patterns changed over time, i.e. as the leopard population density increased. We conclude that conservation interventions that facilitated local demographic recovery in the study area also restored dispersal patterns disrupted by unsustainable harvesting, and that this indirectly improved connectivity among leopard populations over a larger landscape.     

Competition, breeding success and ageing rates in female meerkats

Competition between females is particularly intense in cooperatively breeding mammals, where one female monopolises reproduction in each group. Chronic competition often affects stress and may therefore have long-term consequences for fitness, but no studies have yet investigated whether intrasexual competition has effects of this kind and, in particular, whether it affects rates of reproductive senescence. Here, we use long-term data from a wild population of meerkats to test whether reproductive success and senescence in dominant females are affected by the degree of intrasexual competition experienced prior to dominance acquisition. Females that experienced greater competition had lower breeding success and higher rates of reproductive senescence. Furthermore, females that were evicted from the group more frequently as subordinates had lower breeding success when dominant. We conclude that the intense intrasexual competition between females in cooperatively breeding groups may carry fitness costs over a longer period than is usually recognised.