Teams in animal societies

We review the existence of teams in animal societies. Teamshave previously been dismissed in all but a tiny minority ofinsect societies. "Team" is a term not generally used in studiesof vertebrates. We propose a new rigorous definition of a teamthat may be applied to both vertebrate and invertebrate societies.We reconsider what it means to work as a team or group andsuggest that there are many more teams in insect societies than previously thought. A team task requires different subtasksto be performed concurrently for successful completion. Thereis a division of labor within a team. Contrary to previousreviews of teams in social insects, we do not constrain teamsto consist of members of different castes and argue that teammembers may be interchangeable. Consequently, we suggest thata team is simply the set of individuals that performs a teamtask. We contrast teams with groups and suggest that a grouptask requires the simultaneous performance and cooperationof two or more individuals for successful completion. In agroup, there is no division of labor—each individual performs the same task. We also contrast vertebrate and invertebrateteams and find that vertebrate teams tend to be associatedwith hunting and are based on individual recognition. Invertebrateteams occur in societies characterized by a great deal of redundancy,and we predict that teams in insect societies are more likelyto be found in large polymorphic ("complex") societies thanin small monomorphic ("simple") societies.     

Longevity suppresses conflict in animal societies

Models of social conflict in animal societies generally assume that within-group conflict reduces the value of a communal resource. For many animals, however, the primary cost of conflict is increased mortality. We develop a simple inclusive fitness model of social conflict that takes this cost into account. We show that longevity substantially reduces the level of within-group conflict, which can lead to the evolution of peaceful animal societies if relatedness among group members is high. By contrast, peaceful outcomes are never possible in models where the primary cost of social conflict is resource depletion. Incorporating mortality costs into models of social conflict can explain why many animal societies are so remarkably peaceful despite great potential for conflict.     

Dominance, aggression and reproduction in primate societies

Dominance relationships in primate societies are generally inferred by analyses of agonistic interactions. This aspect of social organization is so striking in macaque and baboon societies that many theoreticians have postulated selective mechanisms operating on the genetic attributes which contribute to high dominance rank. Alpha males were hypothesized to increase their genetic fitness by successfully competing with other males for access to ovulating females.Evidence relevant to these speculations has been mixed. Whereas some investigators found alpha males had near exclusive sexual access to females, others failed to confirm preferential access to ovulating females. Indeed, considerable variability in competition for females existed not only among species, but also among troops of the same species living in different habitats. Further, partner selection was not an exclusive male prerogative; females proved to express active preferences for particular males as sexual partners, and these preferences were not related to high male aggressivity.Alpha males, however, were noted to maintain their positions through social skills as members of a central core or alliance, and high rank was related primarily to seniority. Moreover, alpha males responded actively to challenges to the troop and were judged to contribute significantly to the survival of infants. It was therefore hypothesized that increased genetic fitness related to the increased survival of immature animals in the troop, most of which would already be the offspring of senior (and hence alpha) males. Selection would then be for the social skills leading to successful alliances in troop defense. Such skills might also relate to female partner preferences thus increasing the reproductive effectiveness of alpha males at any point in their careers, including years prior to and following their assumption of alpha rank.     

Social complexity and kinship in animal societies

Studies of eusocial invertebrates regard complex societies as those where there is a clear division of labour and extensive cooperation between breeders and helpers. In contrast, studies of social mammals identify complex societies as those where differentiated social relationships influence access to resources and reproductive opportunities. We show here that, while traits associated with social complexity of the first kind occur in social mammals that live in groups composed of close relatives, traits associated with the complexity of social relationships occur where average kinship between female group members is low. These differences in the form of social complexity appear to be associated with variation in brain size and probably reflect contrasts in the extent of conflicts of interest between group members. Our results emphasise the limitations of any unitary concept of social complexity and show that variation in average kinship between group members has far‐reaching consequences for animal societies.     

Mathematical model of self-organizing hierarchies in animal societies

We propose a mathematical approach to the modelling of self-organizing hierarchies in animal societies. This approach relies on a basic positive feedback mechanism that reinforces the ability of a given individual to win or to lose in a hierarchical interaction, depending on how many times it won or lost in previous interactions. Motivated by experiments carried out on primitively eusocial waspsPolistes, the model, is based on coupled differential equations supplemented with a small stochastic term. Numerical integrations allow many different hierarchical profiles to be obtained depending on the model parameters: (1) the particular form of the probability for an individual to win or lose a fight given its history, (2) the probability of interaction between two individuals, (3) the forgetting strength, which determines the rate at which events in the past are forgotten and no longer influence the force of an individual and (4) two individual recognition parameters, which set the contribution of individual recognition in the process of hierarchical genesis. We compare the results, expressed in terms of a hierarchical index or of the Landau number that describes the degree of linearity of the hierarchy, with various experimental results.     

Costly young and reproductive skew in animal societies

Many recent models of reproductive skew explain subordinatereproduction as a staying incentive offered by dominants, whocan produce more young with a helper present than without. Here,we present a new, alternative explanation for subordinate reproduction,which applies whenever the fitness cost to a parent of producingyoung is an accelerating function of the number produced (ascommonly assumed in optimal clutch size theory). Under these circumstances,a dominant individual may be selected to offer a share of reproductionto a related subordinate, not as an incentive to stay, but becauseadditional offspring that would be expensive for the dominantto produce are cheap for the subordinate. "Beneficial sharing"of this kind is more likely the more closely related the subordinateis to the dominant, so that the model predicts a negative relationshipbetween skew and relatedness. This result runs directly counterto the positive relationship predicted by previous incentive-basedmodels. We explore the interaction of these contrasting effectsby developing an integrated model that allows for both beneficialsharing and staying incentives. When offspring are cheap to produce,this integrated model predicts that the incentive effect will dominate,and skew will increase with relatedness. When young are costly,in contrast, beneficial sharing will be of greater importance,and skew will decrease with relatedness.     

Social stability and helping in small animal societies

In primitively eusocial societies, all individuals can potentially reproduce independently. The key fact that we focus on in this paper is that individuals in such societies instead often queue to inherit breeding positions. Queuing leads to systematic differences in expected future fitness. We first discuss the implications this has for variation in behaviour. For example, because helpers nearer to the front of the queue have more to lose, they should work less hard to rear the dominant''s offspring. However, higher rankers may be more aggressive than low rankers, even if they risk injury in the process, if aggression functions to maintain or enhance queue position. Second, we discuss how queuing rules may be enforced through hidden threats that rarely have to be carried out. In fishes, rule breakers face the threat of eviction from the group. In contrast, subordinate paper wasps are not injured or evicted during escalated challenges against the dominant, perhaps because they are more valuable to the dominant. We discuss evidence that paper-wasp dominants avoid escalated conflicts by ceding reproduction to subordinates. Queuing rules appear usually to be enforced by individuals adjacent in the queue rather than by dominants. Further manipulative studies are required to reveal mechanisms underlying queue stability and to elucidate what determines queue position in the first place.     

Organismic sets. Sex in animal and human societies

The question is discussed as to the reason why some animal societies, such as bees or ants, are sexually differentiated, that is, onlysome of its members are exhibiting reproducing activities. It is indicated that human society may be on its way to such a sexual differentiation which may eventually come.     

Helping effort and future fitness in cooperation animal societies

Little attention has been paid to a conspicuous and universal feature of animal societies: the variation between individuals in helping effort. Here, we develop a multiplayer kin-selection model that assumes that subordinates face a trade-off because current investment in help reduces their own future reproductive success. The model makes two predictions: (i) subordinates will work less hard the closer they are to inheriting breeding status; and (ii) for a given dominance rank, subordinates will work less hard in larger groups. The second prediction reflects the larger pay-off from inheriting a larger group. Both predictions were tested through a field experiment on the paper wasp Polistes dominulus. First, we measured an index of helping effort among subordinates, then we removed successive dominants to reveal the inheritance ranks of the subordinates: their positions in the queue to inherit dominance. We found that both inheritance rank and group size had significant effects on helping effort, in the manner predicted by our model. The close match between our theoretical and empirical results suggests that individuals adjust their helping effort according to their expected future reproductive success. This relationship has probably remained hidden in previous studies that have focused on variation in genetic relatedness.     

Worker reproduction and policing in insect societies: an ESS analysis

Insect societies are vulnerable to exploitation by workers who reproduce selfishly rather than help to rear the queen's offspring. In most species, however, only a small proportion of the workers reproduce. Here, we develop an evolutionarily stable strategy (ESS) model to investigate factors that could explain these observed low levels of reproductive exploitation. Two key factors are identified: relatedness and policing. Relatedness affects the ESS proportion of reproductive workers because laying workers generally work less, leading to greater inclusive fitness costs when within-colony relatedness is higher. The second key factor is policing. In many species, worker-laid eggs are selectively removed or 'policed' by other workers or the queen. We show that policing not only prevents the rearing of worker-laid eggs but can also make it unprofitable for workers to lay eggs in the first place. This can explain why almost no workers reproduce in species with efficient policing, such as honeybees, Apis, and the common wasp, Vespula vulgaris, despite relatively low relatedness caused by multiple mating of the mother queen. Although our analyses focus on social insects, the conclusion that both relatedness and policing can reduce the incentive for cheating applies to other biological systems as well.     

Magnesium in animal and human reproduction]

The literature concerned with the amount of magnesium in genital organs and products of sexual activity is analysed in the first chapter; these data are compared with those concerning other organs and replaced in a comprehensive view of the body, related or not with the medium. It is likely that magnesium plays a role in ovule maturation, sperm viability and fecundation in Invertebrates and Fishes. In Birds and Mammals, it appears to be necessary for fecundation. In the Discoglossus (Anurian Amphibian), the deficiency and the excess in Mg2+ reduce development and influence the growth of the body and the ovary. In the Rat, the pregnancy cannot be normal, unless the food contains an adequate supply of magnesium. Severe or mild deficiencies affect the site of fetal implantation and, if they are prolonged, lead to abortion in the first instance and pathological disorders in the latter. An ionic determination of sex has been established in various animal species and in Man. In some marine Invertebrates, and in the Discoglossus, changes in ionic concentration of the breeding medium carried out immediately after fecundation induce, at will, a majority of one sex or the other; in various Mammals and in Man, variations in the composition of mineral food administered to the female before fecundation may also induce changes in the sex ratio of the progeny.     

Dominance orders in animal societies: The self-organization hypothesis revisited

In previous papers (Theraulaz et al., 1995; Bonabeau et al., 1996) we suggested, following Hogeweg and Hesper (1983, 1985), that the formation of dominance orders in animal societies could result from a self-organizing process involving a double reinforcement mechanism: winners reinforce their probability of winning and losers reinforce their probability of losing. This assumption, and subsequent models relying on it, were based on empirical data on primitively eusocial wasps (Polistes dominulus). By reanalysing some of the experimental data that was previously thought to be irrelevant, we show that it is impossible to distinguish this assumption from a competing assumption based on preexisting differences among individuals. We propose experiments to help discriminate between the two assumptions and their corresponding models—the self-organization model and the correlational model. We urge other researchers to be cautious when interpreting their dominance data with the ’self-organization mindset’; in particular, ‘winner and loser effects’, which are often considered to give support to the self-organization assumption, are equally consistent with the correlational assumption.     

Relations between animal transgenesis and reproduction

Transgenesis has become an essential tool for the study of gene expression mechanisms and functions. Transgenesis is also more and more used for biotechnological applications such as the study of human diseases, the adaptation of pig organs to humans, the production of pharmaceutical proteins in milk and likely in the future for the improvement of animal production. The use of transgenesis relies on the efficiency of gene transfer. New tools have been recently designed to improve gene transfer. The methods of gene transfer are highly dependent on the techniques of animal reproduction. Conversely, the need to improve transgenesis urges researchers to study some of the key steps in reproduction and to find new techniques for gene transfer. This paper summarises the recent data and the perspectives offered by animal transgenesis.     

Toll-like receptors and their role in animal reproduction

Toll-like receptors (TLRs) are evolutionarily conserved innate immune receptors that recognize pathogen specific molecular pattern (PAMPs) in an efficient, non-self-reactive manner and initiate specific immune signaling that culminates in triggering antigen-specific adaptive responses. Different TLR genes in domestic animal species have been characterized and accumulating evidence from recent studies indicates an extended role for TLR signaling in reproductive physiology. In females, TLRs have been implicated in the regulation of ovulation, fertilization, gestation and parturition, as well as in pathological conditions such as endometritis and mastitis. In males, TLRs play a role in steroidogenesis and spermatogenesis. Use of TLR agonists has also been shown to be effective in the treatment of certain reproductive tract infections. Moreover, gene polymorphisms in TLRs have been associated with mastitis providing evidence that TLRs can potentially be exploited as markers in future breeding programs. The aim of this review is to provide a comprehensive treatise on role of TLRs in male and female reproductive physiology and associated pathology in domestic livestock.     

Partitioning variability in animal behavioral videos using semi-supervised variational autoencoders

Recent neuroscience studies demonstrate that a deeper understanding of brain function requires a deeper understanding of behavior. Detailed behavioral measurements are now often collected using video cameras, resulting in an increased need for computer vision algorithms that extract useful information from video data. Here we introduce a new video analysis tool that combines the output of supervised pose estimation algorithms (e.g. DeepLabCut) with unsupervised dimensionality reduction methods to produce interpretable, low-dimensional representations of behavioral videos that extract more information than pose estimates alone. We demonstrate this tool by extracting interpretable behavioral features from videos of three different head-fixed mouse preparations, as well as a freely moving mouse in an open field arena, and show how these interpretable features can facilitate downstream behavioral and neural analyses. We also show how the behavioral features produced by our model improve the precision and interpretation of these downstream analyses compared to using the outputs of either fully supervised or fully unsupervised methods alone.     

The role of pheromones and biostimulation in animal reproduction

It is now known that pheromonal communication plays an important role in mammalian behaviour and reproductive processes. Chemical communication with pheromones is one means of transmitting such information. In mammals, signalling and priming pheromones are thought to act either singly or in combination through olfaction, auditory, visual (sight) or tactile stimuli. Pheromones are air-borne chemical substances ("signals") released in the urine or feces of animals or secreted from cutaneous glands that are perceived by the olfactory system and that elicit both behavioural and endocrine responses in conspecifics.Extensive studies in insects, rodents, swine, sheep, goats and cattle have established the importance of pheromones in the strong influence exerted by the male on reproductive activity in the female. There is a pheromone produced by the queen honey bee, which has two functions: inhibition of queen rearing and suppression of oogenesis in workers and in addition attracts drones during nuptial flight. It has also been demonstrated that the urine of male mice, rats, feral species and other wild rodents contains a priming pheromone that is responsible for hastening puberty in the females. Pheromones in the wool, wax and urine of a ram are sufficient to stimulate ewes to ovulate, while the buck has a strong characteristic seasonal odor and a buck jar containing the odor of the buck can be used as an aid in the detection of oestrus in does. The mere presence of the boar at the time of insemination of the sow improves sperm transport and ovulation, while the presence of the vasectomised bull has been reported to hasten the onset of puberty in heifers and also early resumption of ovarian activity in cattle following parturition. The role of pheromones in bovine reproduction is not as clearly defined as in sheep, goats and swine.Pheromones and other allelomimetic cues can exert profound effects on reproductive activity via the hypothalamic system that generates pulses of gonadotropin-releasing hormone. Manipulations of these factors and other pathways linking environmental inputs to reproductive output can lead to developing the concept of "control systems technologies", aimed at controlling reproductive performance. The knowledge acquired on the effectiveness of biostimulation; the factor which conditions it and the biological mechanism which produces it in livestock species, allows its use as a breeding management tool. The understanding of the role of pheromones could be of potential economic importance in addressing some of the problems associated with livestock production in the tropics. The biostimulation technique offers a potentially useful and practical way to improve reproductive efficiency in livestock species in the tropics. The exact nature of the cues and the role of biostimulation in livestock species especially swine, sheep, goats and cattle in developing countries require more attention.