Sex differences in the drivers of reproductive skew in a cooperative breeder

Many cooperatively breeding societies are characterized by high reproductive skew, such that some socially dominant individuals breed, while socially subordinate individuals provide help. Inbreeding avoidance serves as a source of reproductive skew in many high‐skew societies, but few empirical studies have examined sources of skew operating alongside inbreeding avoidance or compared individual attempts to reproduce (reproductive competition) with individual reproductive success. Here, we use long‐term genetic and observational data to examine factors affecting reproductive skew in the high‐skew cooperatively breeding southern pied babbler (Turdoides bicolor). When subordinates can breed, skew remains high, suggesting factors additional to inbreeding avoidance drive skew. Subordinate females are more likely to compete to breed when older or when ecological constraints on dispersal are high, but heavy subordinate females are more likely to successfully breed. Subordinate males are more likely to compete when they are older, during high ecological constraints, or when they are related to the dominant male, but only the presence of within‐group unrelated subordinate females predicts subordinate male breeding success. Reproductive skew is not driven by reproductive effort, but by forces such as intrinsic physical limitations and intrasexual conflict (for females) or female mate choice, male mate‐guarding and potentially reproductive restraint (for males). Ecological conditions or “outside options” affect the occurrence of reproductive conflict, supporting predictions of recent synthetic skew models. Inbreeding avoidance together with competition for access to reproduction may generate high skew in animal societies, and disparate processes may be operating to maintain male vs. female reproductive skew in the same species.     

Drivers of age-specific survival in a long-lived seabird: contributions of observed and hidden sources of heterogeneity

1.?We assessed the relative influence of variability in recruitment age, dynamic reproductive investment (time-specific reproductive states) and frailty (unobserved differences in survival abilities across individuals) on survival in the black-legged kittiwake. Furthermore, we examined whether observed variability in survival trajectories was best explained by immediate reproductive investment, cumulative investment, or both. 2.?Individuals that delayed recruitment (≥ age 7) suffered a higher mortality risk than early recruits (age 3), especially later in life, suggesting that recruitment age may be an indicator of individual quality. Although recruitment age helped explain variation in survival, time-varying reproductive investment had a more substantial influence. 3.?The dichotomy of attempting to breed or not explained variability in survival across life better than other parameterizations of reproductive states such as clutch size, brood size or breeding success. In the kittiwake, the sinequanon condition to initiate reproduction is to hold a nest site, which is considered a very competitive activity. This might explain why attempting to breed is the key level of investment that affects survival, independent of the outcome (failure or success). 4.?Interestingly, the more individuals cumulate reproductive attempts over life, the lower their mortality risk, indicating that breeding experience may be a good indicator of parental quality as well. In contrast, attempting to breed at time t increased the risk of mortality between t and t + 1. We thus detected an immediate trade-off between attempting to breed and survival in this population; however, the earlier individuals recruited, and the more breeding experience they accumulated, the smaller the cost. 5.?Lastly, unobserved heterogeneity across individuals improved model fit more (1·3 times) than fixed and dynamic sources of observed heterogeneity in reproductive investment, demonstrating that it is critical to account for both sources of individual heterogeneity when studying survival trajectories. Only after simultaneously accounting for both sources of heterogeneity were we able to detect the 'cost' of immediate reproductive investment on survival and the 'benefit' of cumulative breeding attempts (experience), a proxy to individual quality.     

Management of pre-pubertal small ruminants: physiological basis and clinical approach

Puberty is a gradual process, during which animal reproductive competence is attained with respect to physiology, morphology and behaviour. Onset of puberty in small ruminants differs between sexes, due to early sexual differentiation in the control of steroid feedback systems and, thus, GnRH secretion. A number of puberty determinants have been identified, which include genetic factors, as well as endogenous signals, such as energy balance and environmental cues, whose dynamic interplay is responsible for the timing of puberty onset. Puberty timing affects reproduction through age at first lambing, which impacts on subsequent reproductive life and productivity of small ruminants. Thus, a greater knowledge of the mechanisms underlying puberty process would lead to optimisation of commonly applied strategies for selection of replacement animals. In addition, understanding reproductive responses of animals to exteroceptive factors, such as photoperiod, nutrition and socio-sexual signals, will enable development and improvement of those management tools that that will fulfil the requirements of a 'clean, green and ethical' production.     

Obstetrics in elephants

Obstetrics, one of the oldest fields in veterinary medicine, is well described and practiced in domestic and exotic animals. However, when providing care during elephant birth or dystocia, veterinary intervention options differ greatly from any domestic species, and are far more limited due to the dimensions and specific anatomy of the elephant reproductive tract. In addition, aging of captive elephant populations and advanced age of primiparous females make active birth management increasingly important. Intrauterine infection, uterine inertia and urogenital tract pathologies are emerging as major causes for dystocia, often leading to foetal and dam death. This paper reviews the current knowledge on elephant birth and the factors associated with dystocia. It then summarises recommendations for birth and dystocia management. As Caesarean section, the most common ultima ratio in domestic animal obstetrics, is lethal and therefore not an option in the elephant, non-invasive medical treatment, induction of the Fergusson reflex or the conscious decision to leave a retained foetus until it is expelled voluntarily, are key elements in elephant obstetrics. Surgical strategies such as episiotomy and foetotomy are sometimes inevitable in order to try to save the life of the dam, however, these interventions result in chronic post-surgical complications or even fatal outcome. Limited reliable data on serum calcium concentrations, and pharmacokinetics and effect of exogenous oestrogen, oxytocin, and prostaglandins during birth provide the scope of future research, necessary to advance scientific knowledge on obstetrics in elephants.     

Is hissing behaviour of incubating great tits related to reproductive investment in the wild?

Anti-predator behaviour of breeding animals is a complex trait that depends on current reproductive investment as well as individual differences in risk-taking propensities. In response to nest predation, many bird species produce specific sounds, such as the hissing calls in incubating great tits (Parus major), that may provoke an acoustic startle response in the predator. However, it is still unclear whether the propensity of incubating females to produce hissing calls towards nest predators depends on the reproductive investment. With our 3-year study, we show that response type (females that do not hiss versus females giving hissing calls) to a potential nest predator, the woodpecker, is a repeatable trait. We found no differences in the studied reproductive traits between hissing and non-hissing birds. Interestingly, among hissing birds, fast-responding females started egg-laying earlier than slow-responding ones. Among non-hissing birds, heavier birds initiated clutches earlier. We also revealed that hissing birds breed in areas with decreased nest-box occupancy, suggesting either that they potentially select different areas to breed or that territory size is larger as a result of hissing birds being more aggressive. These findings demonstrate that response type is not related to the early reproductive value of the brood across distinct behavioural groups. However, our results do suggest that non-hissing and hissing females differ in terms of individual quality or dominance or personality related aspects.     

Individual breeding decisions and long-term reproductive strategy in the King Penguin Aptenodytes patagonicus

Although studied for 35 years, knowledge of the reproductive biology of the King Penguin Aptenodytes patagonicus remains incomplete. The chick requires more than 12 months of care, which extends the breeding cycle, including moult, to more than one year, i.e. the King Penguin is neither annual nor biennial. In an attempt to resolve ambiguities in the literature and to elucidate the long-term breeding strategy of the species, we studied breeciing frequency at the individual level, considering the decision to breed in relation to breeding history over the previous few years. Although adult birds attempted to breed annually (0.83 breeding attempts per year), successful rearing occurred, at best, every two years only (maximum of 0.41 fledged chick per pair). Comparing successive years, the number of breeding birds in the colony was stable but the number of fledged chicks varied from 29 to 278 over eight years. These results suggest that King Penguins adopt (as individuals) an opportunistic reproductive strategy, in that they usually lay an egg every year, even when failure is certain. Nevertheless, the decision to breed was not entirely blind, and we identified groups of birds that invested differentially in breeding attempts. The decision to breed was related to the previous breeding frequency, i.e. 81% of the birds that had bred continuously in the past started a new breeding attempt, but only 67% of birds that had missed a year did so. In intermittent breeders, birds that had bred frequently, more often started a new breeding attempt than birds that had largely missed years (71% versus 57%, respectively). Classes of breeders could correspond to age classes, to birds of different breeding quality or to alternative breeding strategies coexisting in the species. Testing the hypothesis that reproductive effort increases with age should be possible in future.     

Age-related fertility and productivity in Red foxes, Vulpes vulpes, in suburban London

In some areas of the Red fox's range, such as northern Sweden, the number of yearling vixens which breed each year is dependent on food availability, and in years of poor food supply a high incidence of barren yearling vixens may occur. But most previous studies on Red fox reproduction record an overall low incidence of barren vixens, and it has therefore been assumed that most vixens breed in their first year. The present study shows that in suburban London, an area of high fox population density in which food availability is not limited, 52% of yearling vixens fail to breed. Possible reasons for this are discussed. It is also shown that senescence reduces the reproductive capability of vixens in their fifth and sixth breeding seasons.     

The application of reproductive technology to endangered species breeding programmes

Captive breeding plays an increasingly important role in species conservation, but special problems are encountered in achieving the ideal of a demographically stable but genetically diverse population. Breeding programmes involving co-operation among a number of centres are now being developed which will overcome some of these difficulties by identifying individual animals, genetic lineages or age cohorts from which to breed. Application of techniques such as artificial insemination, embryo transfer and semen collection and storage, as well as the monitoring of reproductive status will contribute to the success of such programmes. The usefulness of these procedures for various population problems is discussed and criteria for their appropriate implementation within breeding programmes is outlined.     

Effects of tamoxifen dose and nutrition scheme during growth on stimulation of the reproductive system in cornish breed cocks

The effects of tamoxifen (TAM) antiestrogen dose as well as protein and energy content in feed on stimulation of the reproductive system development in meat type cocks were studied. The experiment was conducted on males of the Dominant White Cornish chicken breed. The optimum TAM dose for stimulation of reproductive system development was at the level of 5 mg per kg body weight. The effects of TAM administration on the following traits were investigated: body weight, breast muscle thickness, age at sexual maturity, egg fertilization and hatchability. No effect of TAM on breast muscle thickness was found. It was also noted that semen obtained from 11 to 12 week old males of the Dominant White Cornish breed could be used successfully in the insemination of females.     

Initial insights on the performances and management of dairy cattle herds combining two breeds with contrasting features

Finding ways of increasing animal production with low external inputs and without compromising reproductive performances is a key issue of livestock systems sustainability. One way is to take advantage of the diversity and interactions among components within livestock systems. Among studies that investigate the influence of differences in animals’ individual abilities in a herd, few focus on combinations of cow breeds with contrasting features in dairy cattle herds. This study aimed to analyse the performances and management of such multi-breed dairy cattle herds. These herds were composed of two types of dairy breeds: ‘specialist’ (Holstein) and ‘generalist’ (e.g. Montbeliarde, Simmental, etc.). Based on recorded milk data in southern French region, we performed ANOVA: (i) to compare the performances of dairy herds according to breed-type composition: multi-breed, single specialist breed or single generalist breed and (ii) to test the difference of milk performances of specialist and generalist breed cows (n = 10 682) per multi-breed dairy herd within a sample of 22 farms. The sampled farmers were also interviewed to characterise herd management through multivariate analysis. Multi-breed dairy herds had a better trade-off among milk yield, milk fat and protein contents, herd reproduction and concentrate-conversion efficiency than single-breed herds. Conversely, they did not offer advantages in terms of milk prices and udder health. Compared to specialist dairy herds, they produce less milk with the same concentrate-conversion efficiency but have better reproductive performances. Compared to generalist dairy herds, they produce more milk with better concentrate-conversion efficiency but have worse reproductive performances. Within herds, specialist and generalist breed cows significantly differed in milk performances, showing their complementarity. The former produced more milk for a longer lactation length while the latter produced milk with higher protein and fat contents and had a slightly longer lactation rank. Our results also focus on the farmers’ management of multi-breed dairy herds underlying herd performances. Three strategies of management were identified and structured along two main axes. The first differentiates farmers according to their animal-selection practices in relation with their objectives of production: adapting animal to produce milk with low-feeding inputs v. focussing on milk yield trait to intensify milk production. The second refers to the purpose farmers give to multi-breed dairy herds: milk v. milk/meat production. These initial insights on the performances and management of multi-breed dairy herds contribute to better understanding the functioning of ruminant livestock systems based on individual variability.     

Variation in the timing of the reproductive season among breeds of sheep in relation to differences in photoperiodic synchronization of an endogenous rhythm.

Photoperiod may regulate seasonal reproduction either by providing the primary driving force for the reproductive transitions or by synchronizing an endogenous reproductive rhythm. This study evaluated whether breed differences in timing of the reproductive seasons of Finnish Landrace (Finn) and Galway ewes are due to differences in photoperiodic drive of the reproductive transitions or to differences in photoperiodic synchronization of the endogenous rhythm of reproductive activity. The importance of decreasing photoperiod after the summer solstice in determining the onset and duration of the breeding season was tested by housing ewes from the summer solstice in either a simulated natural photoperiod or a fixed summer-solstice photoperiod (18 h light:6 h dark; summer-solstice hold). Onset of the breeding season within each breed did not differ between these photoperiodic treatments, but Galway ewes began and ended their breeding season earlier than Finn ewes. The duration of the breeding season was shorter in Galway ewes on summer-solstice hold than on simulated natural photoperiod; duration did not differ between photoperiodic treatments in Finn ewes. The requirement for increasing photoperiod after the winter solstice for initiation of anoestrus was tested by exposing ewes from the winter solstice to either a simulated natural photoperiod or a winter-solstice hold photoperiod (8.5 h light:15.5 h dark). Onset of anoestrus within each breed did not differ between these photoperiodic treatments, but the time of this transition differed between breeds. These observations suggest that genetic differences in timing of the breeding season in Galway and Finn ewes do not reflect differences in the extent to which photoperiod drives the reproductive transitions, because neither breed requires shortening days to enter the breeding season or lengthening days to end it at appropriate times. These findings are consistent with the hypothesis that photoperiod synchronizes an endogenous rhythm of reproductive activity in both breeds and that genetic differences in timing of the breeding season reflect differences in photoperiodic synchronization of this rhythm.     

Reproductive biology of female titi monkeys (Callicebus moloch) in captivity

Titi monkeys (Callicebus spp., Cebidae) are monogamous neotropical primates that live in family-like groups typically consisting of an adult monogamous pair and one or two young. Knowledge about the reproductive biology of this genus is scanty. This study investigated the reproductive biology of female dusky titi monkeys (Callicebus moloch). An initial analysis characterized reproductive parameters of 32 females from a captive colony maintained for 23 years at the California Regional Primate Research Center (CRPRC). The colony records provided data on reproductive parameters such as interbirth intervals, seasonality, age at first pregnancy, and reproductive rate in captivity. Changes in urinary levels of estrone conjugates (E1C) and pregnanediol-3alpha-glucuronide (PdG) were used to characterize major reproductive events. Urine samples from eleven females were collected during 17 months. The endocrine data were used to examine changes associated with cycling, conception, and the post-partum period as well as to determine the duration of the ovarian cycle and gestation length. The analysis of colony records indicated that females whose infant survived through weaning gave birth at intervals remarkably close to one year, while those who lost their offspring showed a significantly shorter interval. As long as they lived within the family group, mature female offspring did not breed. The analysis of the endocrine profiles indicated that after giving birth to a viable offspring, females undergo a relatively prolonged period of anovulation (approx. 6.5 months), followed by 1-3 non-conceptive cycles (approx. 1 month), after which they conceive and gestate (4.3 months).     

Artificial reproduction of the Yangtze field vole: in vitro embryo development and fertilization with fresh and freeze-thawed sperm

Several research groups are using the Yangtze field vole as a model for studying schistosome infection, but relatively little is known about the species's reproductive physiology. The authors examined the vole's in vivo and in vitro embryonic development as well as the efficacy of in vitro fertilization using either fresh or cryopreserved sperm to breed these rodents.     

16 Years of breed management brings substantial improvement in population genetics of the endangered Cleveland Bay Horse

The consequences of poor breed management and inbreeding can range from gradual declines in individual productivity to more serious fertility and mortality concerns. However, many small and closed groups, as well as larger unmanaged populations, are plagued by genetic regression, often due to a dearth in breeding support tools which are accessible and easy to use in supporting decision‐making. To address this, we have developed a population management tool (BCAS, Breed Conservation and Management System) based on individual relatedness assessed using pedigree‐based kinship, which offers breeding recommendations for such populations. Moreover, we demonstrate the success of this tool in 16 years of employment in a closed equine population native to the UK, most notably, the rate of inbreeding reducing from more than 3% per generation, to less than 0.5%, or that attributed to genetic drift, as assessed over the last 16 years of implementation. Furthermore, with adherence to this program, the long‐term impact of poor management has been reversed and the genetic resource within the breed has grown from an effective population size of 20 in 1994 to more than 140 in 2020. The development and availability of our BCAS for breed management and selection establish a new paradigm for the successful maintenance of genetic resources in animal populations.     

Inbreeding avoidance and reproductive skew in a cooperative mammal

In animal social groups, socially subordinate individuals frequently show low reproductive success or completely fail to breed. This suppression of subordinate reproduction is currently typically attributed to control by dominant individuals. However, subordinates in cooperative groups often lack access to unrelated mates, and an alternative possibility is that their reproduction is limited by inbreeding avoidance. Using the eusocial Damaraland mole-rat Cryptomys damarensis, this paper provides the first experimental evidence, to our knowledge, for this explanation. Subordinate, non-breeding female mole-rats were given access to unrelated mates while remaining in the presence of dominant females, and many became reproductively active soon after unrelated males were introduced. Inbreeding avoidance and the availability of unrelated mates provides a plausible and untested explanation for variation in reproductive skew across animal societies.     

Reproductive and neonatal outcomes in captive bred baboons (Papio hamadryas)

Abstract: Baboons are widely used in biomedical research. Although it is widely held that Papio hamadryas breed well in captivity, each established colony has a different reproductive success often hypothesised to be due to husbandry practices. The National Baboon Colony in Australia is a unique colony that houses Papio hamadryas to mimic that structure seen in the wild. In this article; we have analysed their reproductive parameters and neonatal outcomes. The success of the colony husbandry practices was demonstrated by lack of maternal mortality, low foetal morbidity, and known maternal and paternal linage.     

Relationships between sexual behaviour, dominant follicle area, uterus ultrasonic image and pregnancy rate in mares of two breeds differing in reproductive efficiency

Weak or equivocal expression of oestrous behaviour, related to different level of mares' reactivity, may cause problems in oestrus detection and thus influence the reproductive efficiency. The aim of the study was to test whether a breed characterised by low pregnancy rate and high emotional reactivity (Thoroughbreds) differs in oestrous behaviour from a primitive breed with higher reproductive efficiency (Koniks). Additionally, the follicle size was examined to determine how it influences the intensity of oestrus and uterine ultrasonic image and whether the pregnancy rate differs in relation to the intensity of oestrous behaviour and the size of the dominant follicle(s) area on day preceding ovulation in both breeds. During four reproductive seasons the behaviour of 20 Konik polski (K) and 37 Thoroughbred (T) was observed during daily teasing. Simultaneously, the ultrasonic examinations of the reproductive system were carried out. The behaviour of mares was quantified by scoring on an 8-point scale (behavioural score, BS), according to increasing sexual receptivity. Cross-sectional follicular area (FA) was taken as a product of the two largest perpendicular follicular diameters and mean values for each breed were estimated on 1693 and 1982 mm2 for K and T mares, respectively (P < 0.05). Mares were classified according to the pooled area of dominant follicle (FA) during the preovulatory period: group A (FA < or = breed mean) and group B (FA > breed mean). Uterus image (UI) was scored (1-5) according to the increasing uterine echogenicity. The BS was higher (P < 0.01) in K mares (BS = 5.19) than in T mares (BS = 4.04). The BS was significantly related to increasing follicular area (FA). There was no breed difference in uterus image (UI) score. However, significant regression of UI on FA was found in K mares. The intensity of oestrus was positively related with UI (r = 0.29; P < 0.01) only in K mares, no such relationship was found in T mares. The pregnancy rate was significantly higher for K mares (88.5%) than for T mares (46.0%) and lower for T mares with less intense oestrous behaviour (29.4%) as compared to T mares with more intense oestrus (60.0%). No differences in pregnancy rate was found in mares belonging to A or B group of follicular area. The ascertained weaker oestrous behaviour in Thoroughbred was related to lower pregnancy rate. It is hypothesised that oestrus intensity may be the result of breed differences in the response of the neural system to follicular secretions, or may be an effect of higher incidence of multiple non-synchronic ovulation and/or higher sensitivity to stress in Thoroughbred mares.     

Seasonal changes in reproductive development in male spiny mice (Acomys spinosissimus) from South Africa

Seasonal reproduction is a common characteristic of many small mammals which inhabit seasonal environments in temperate regions, the sub-tropics as well as the tropics. It is important for an animal to reproduce during the most favourable time of the year to ensure the survival of the young and maximize reproductive success. In southern Africa, female spiny mice (Acomys spinosissimus) breed during the warm and wet spring and summer months, whereas the reproductive pattern of males is unknown although an opportunistic breeding pattern has been implicated. We investigated testes mass and volume, seminiferous tubule diameter, spermatogenesis and plasma testosterone concentrations in a South African population of male spiny mice on a 2-monthly basis over one year. Testes mass and volume started to increase in July/August and was high from September until December. Seminiferous tubule diameter and spermatogenesis increased during the same months. Plasma testosterone concentration was elevated from July/August to November/December. Development of the reproductive characteristics of male spiny mice was correlated with high rainfall and high ambient temperatures, but reproductive development had already started during the dry season and the coldest months. This shows that reproductive development in males may not be dependent on climatic conditions, and other factors, such as photoperiod, may trigger the onset of reproduction. The data, however, suggest that A. spinosissimus is a true seasonal breeder with reproduction confined to the spring and summer months in southern Africa.