Non-breeding Males Research Articles

288 Chemical Characterization of the Marking Fluid of Breeding and non-Breeding Male Cheetahs

Abstract Volatile semiochemicals released, amongst other methods, through marking fluid (MF), and characterized by scent/odor, are involved in communication and identification of an individual. Scent has an important role in reproduction of cheetahs and other felids; in fact, the presence/odor of a male cheetah has been noted to trigger the estrous cycle of females. The objectives of the study were to analyze the MF of male cheetahs from different breeding groups to determine the composition of volatile organic chemicals (VOCs) present. Five males per group (e.g., breeding vs non-breeding) were selected from two facilities. The first facility only had breeding males (B; e.g., animals regularly exposed to females on estrus and actively involved in breeding programs); the second facility, only had non-breeding males (NB). The average age of the B and NB males was of 8.1±2.3 and 6.7±2.8 years respectively. Eighteen MF samples were collected from both groups. VOCs were extracted from the headspace, using solid-phase microextraction techniques and analyzed with gas-chromatography mass-spectrometry. Possible relationships between the frequency of presence/absence of each VOC and the respective groups were evaluated through a contingency test with Fisher’s exact test. Differences in relative concentration (RC) of the identified compounds between groups were analyzed using analysis of variance for repeated measures. Fifty-eight VOCs were identified from the MF, and twelve were commonly identified in the samples collected. The RC of dodecanoic acid and nonanoic acid was significantly greater in the B compared with the NB males; whereas indole tended to be greater in the NB compared with the B group. Although the observed differences could indicate the possible involvement of specific VOCs in reproductive behavior, the different diets and age could have also affected the VOCs RC. Further studies are needed to better understand possible differences in RC of VOCs between breeding groups to confirm their role in reproduction.

Chemical Characterization of the Marking Fluid of Breeding and Non-Breeding Male Cheetahs.

Simple SummaryThe study aimed at chemically characterizing the marking fluid of both breeding and non-breeding male cheetahs (Acinonyx jubatus). Specifically, it focused on identifying potential differences in pheromones related to sexual behavior/attraction in this species. Furthermore, it aimed at providing more information as a basis for future studies, such as the investigation of specific semiochemicals in the reproductive behavior of cheetahs. The results of this study support the hypothesis of differences in the relative concentration of volatile organic chemicals between male cheetahs; however, they highlight the importance of diet and age on the presence of volatile organic chemicals in the marking fluid.Scent is known to play an important role in the reproduction of cheetahs and other felids. In fact, the presence/odor of a male cheetah has been noted to trigger the estrous cycle in females. The objective of this study was to analyze the marking fluid (MF) of male cheetahs from different breeding groups to determine the composition of volatile organic compounds (VOCs) present, with the aim of identifying potential pheromones relating to sexual behavior/attraction in this species. Four breeding (B; age: 8.9 ± 1.3 years old) and four non-breeding (NB; age: 5.5 ± 0.8 years old) males were selected for this study. Samples were collected into a glass beaker, transferred immediately into a 20 mL glass screw-cap vial with a polytetrafluoroethylene (PTFE) coated silicone septum, and stored until analyzed by headspace solid-phase microextraction (HS-SPME) using gas chromatography–mass spectrometry. A contingency test with Fisher’s exact test, using the frequency (FREQ) procedure of SAS 9.4, was conducted to determine the difference between the number of VOCs identified per breeding group; furthermore, differences in relative concentration (RC) of the identified VOCs between breeding groups were analyzed using ANOVA for repeated measures with the GLIMMIX procedure. From the 13 MF samples analyzed, 53 VOCs were identified, and 12 were identified in all the samples. Five of these (dimethyl disulfide, benzaldehyde, acetophenone, phenol, and indole) are known to be involved in attraction/sexual behavior in mammals. Between the two groups, the RC of indole was significantly higher in the NB group, whereas the RC of dodecanoic acid was significantly higher in the B group. Although not significant, the RC of benzaldehyde was higher in the B versus the NB group. The results of this study do support the hypothesis of differences in VOCs’ between B and NB male cheetahs. However, the overlapping of age and breeding status and the diet differences could not be controlled. Still, the evidence of changes in MF composition in male cheetahs necessitates further studies on possible strategies to improve reproduction in captivity.

Effects of environmental low-dose irradiation on functional-metabolic organ responses in a natural mouse population (Apodemus agrarius Pallas, 1771) within the East Urals Radioactive Trace (EURT) area, Russia

Hypothesis The level of radiation-induced functional metabolic reactivity can differ among organs (spleen, liver and myocardium) and reproductive-sexual groups (breeding and non-breeding under-yearlings: females and males). Materials and methods We analyzed Apodemus agrarius individuals captured in the zone of the East Urals Radioactive Trace (EURT, Russia). In this area, concentrations are 90Sr and 137Cs at 10,000 and 1000 Bq/kg, respectively, in a layer of soil not deeper than 10 cm. Comparative analysis was based on six biochemical parameters including the glycolysis level, peroxidation of lipids, H2O2-oxidoreductase status and concentrations of protein, DNA and RNA in tissues. Results External and internal doses of 137Cs and 90Sr for A. agrarius varied by an order of magnitude, from 0.013 to 0.177 mGy/d. The level of radiation exposure was found to not differ among females but it differed between the two male reproductive groups (breeding < non-breeding under-yearlings). Sexually mature males received a significantly lower dose than females. An increase in the dose rate correlated with an increase in all biochemical indicators, thus indicating high level of tissue metabolic functions. The reproductive status of females did not affect their radiation-induced organ response rate, whereas the response to radiation of breeding males was more than 1.5-fold higher than that of non-breeding males and 2-fold higher than that of females. Conclusions We believe that the variation of the dose load is due to migration processes: breeding males are more likely to migrate than females and therefore have less contact with radionuclides. The higher the response to radiation of breeding males can be explained by a hormonal factor: testosterone causes radiosensitivity. The reactivity of the tissues examined (myocardium < liver < spleen) develops apparently in accordance with the degree of their ‘staticity’ in accordance with the law of radiosensitivity of Bergonié and Tribondeau.

Filling in the holes: The reproductive biology of the understudied Mahali mole-rat (Cryptomys hottentotus mahali)

African mole-rats have provided great insight into mammalian evolution of sociality and reproductive strategy. However, some species have not received attention, and these may provide further insights into these evolutionary questions. The cooperatively breeding Mahali mole-rat (Cryptomys hottentotus mahali (Roberts, 1913)) is one such species. Body mass, reproductive-tract morphometrics, gonad histology, and plasma reproductive hormone concentrations were studied for breeding and non-breeding males and females over 1 year. This study aimed to discern if this species exhibits a seasonal or aseasonal breeding pattern and whether there is a relaxation of reproductive suppression at any point in the year in non-breeding animals. The pattern of reproductive relaxation during the wetter months is similar to other African mole-rat species. Interestingly, births and pregnant breeding females were recorded throughout the year, thus indicating an aseasonal breeding strategy, despite inhabiting a region that experiences seasonal rainfall. However, there were periods of the year favouring increased reproduction to enable an increased likelihood of offspring survival. This suggests that the Mahali mole-rat may be an opportunistic breeder possibly brought about by the benefits of living in a cooperatively breeding group and potentially moving into more arid environments that were previously unexploited by the genus Cryptomys Gray, 1864.

Sex-specific costs of reproduction on survival in a long-lived seabird.

Costs of reproduction on survival have captured the attention of researchers since life history theory was formulated. Adults of long-lived species may increase survival by reducing their breeding effort or even skipping reproduction. In this study, we aimed to evaluate the costs of current reproduction on survival and whether skipping reproduction increases adult survival in a long-lived seabird. We used capture-mark-recapture data (1450 encounters) from two populations of Bulwer's petrel (Bulweria bulwerii), breeding in the Azores and Canary Islands, North Atlantic Ocean. Using a multi-event model with two different breeding statuses (breeders versus non-breeders), we calculated probabilities of survival and of transitions between breeding statuses, evaluating potential differences between sexes. Females had lower survival probabilities than males, independent of their breeding status. When considering breeding status, breeding females had lower survival probabilities than non-breeding females, suggesting costs of reproduction on survival. Breeding males had higher survival probabilities than non-breeding males, suggesting that males do not incur costs of reproduction on survival and that only the highest quality males have access to breeding. The highest and the lowest probabilities of skipping reproduction were found in breeding males from the Azores and in breeding males from the Canary Islands, respectively. Intermediate values were observed in the females from both populations. This result is probably due to differences in the external factors affecting both populations, essentially predation pressure and competition. The existence of sex-specific costs of reproduction on survival in several populations of this long-lived species may have important implications for species population dynamics.

Immune profiles of male giant panda (Ailuropoda melanoleuca) during the breeding season

BackgroundThe giant panda (Ailuropoda melanoleuca) is a threatened endemic Chinese species and a flagship species of national and global conservation concern. Life history theory proposes that reproduction and immunity can be mutually constraining and interrelated. Knowledge of immunity changes of male giant pandas during the breeding season is limited.ResultsHere, we researched peripheral blood gene expression profiles associated with immunity. Thirteen captive giant pandas, ranging from 9 to 11 years old, were divided into two groups based on their reproductive status. We identified 318 up-regulated DEGs and 43 down-regulated DEGs, which were enriched in 87 GO terms and 6 KEGG pathways. Additionally, we obtained 45 immune-related genes with altered expression, mostly up-regulated, and identified four hub genes HSPA4, SUGT1, SOD1, and IL1B in PPI analysis. These 45 genes were related to pattern recognition receptors, autophagy, peroxisome, proteasome, natural killer cell, antigen processing and presentation. SUGT1 and IL1B were related to pattern recognition receptors. HSP90AA1 was the most up-regulated gene and is a member of heat shock protein 90 family. HSP90 contributes to the translocation of extracellular antigen. KLRD1 encodes CD94, whose complex is an inhibitor of the cytotoxic activity of NK cells, was down-regulated. IGIP, which has the capability of inducing IgA production by B cells, was down-regulated, suggesting low concentration of IgA in male giant pandas. Our results suggest that most immune-related genes were up-regulated and more related to innate immune than adaptive immune.ConclusionsOur results indicated that breeding male giant pandas presented an immunoenhancement in innate immunity, enhanced antigen presentation and processing in cellular immunity compared to non-breeding males. The humoral immunity of male giant pandas may show a tendency to decrease during the breeding season. This study will provide a foundation for further studies of immunity and reproduction in male giant pandas.

Illuminating the Nocturnal Habits of Owls with Emerging Tagging Technologies

ABSTRACTOwls play important cultural, ecological, and indicator roles throughout the world. Yet owls’ cryptic behavior has led to uncertainties about their basic ecology, including foraging, communication, and functional roles within the community, and potentially hindered the implementation of effective conservation measures. Here we demonstrate the potential for next‐generation GPS tags capable of recording high‐precision, minute‐by‐minute locations paired with other technologies to resolve some of these uncertainties. We combined high‐precision GPS tagging data with infrared (IR) video recorded by arboreally‐mounted cameras at 5 spotted owl (Strix occidentalis) nest sites in the Sierra Nevada, USA to provide a uniquely detailed examination of owl foraging patterns. Our approach allowed us to identify the precise time and location of 54 predation events and prey identity. We also used high‐precision GPS tags with on‐board audio recorders to map the vocal activity of 8 individuals by matching the time of vocalizations in the audio data to GPS locations recorded at one‐minute intervals. The combined spatial and acoustic data revealed that nonbreeding males had the most widespread territorial vocal activity (i.e., producing 4‐note territorial calls), while females provisioning fledglings displayed extensive nonterritorial vocal activity (i.e., producing many contact calls). Thus, the GPS‐tag technologies we employed can provide opportunities to better understand owl foraging, communication, territoriality, and population dynamics. The methods we describe are time‐ and resource‐intensive but can be paired with techniques that are more applicable at landscape scales, such as stable isotope analyses, LiDAR‐based habitat analyses, and passive acoustic monitoring to link local processes to broad‐scale ecological patterns. Therefore, our approach could be applied to many species whose behavior inhibits direct observation. © 2021 The Wildlife Society.

Seasonal Changes in the Sexual Size Dimorphisms of the Chelipeds and Pleons of the Porcellanid Crab Petrolisthes japonicus.

Decapod crustaceans develop secondary sexual structures, such as large chelipeds for weaponry and/or display in males and a wider pleon for incubating eggs in females. These structures should be costly to produce and maintain; hence, the crustacean reproductive strategy might have adapted to conserve energy for developing secondary sexual characteristics during the reproductive season. However, little is known about seasonal changes in the sexual size dimorphisms of the chelipeds and pleons of decapod crustaceans. Anomuran crabs from the family Porcellanidae exhibit a true crab-like body shape, with relatively large chelipeds for their body size and a well-developed pleon. They also show sexual size dimorphism (i.e., males with larger chelipeds and females with wider pleons); therefore, it was expected that seasonal changes in the sexual size dimorphisms of these organs would occur in porcellanid crabs. We tested this expectation using Petrolisthes japonicus, which is common on the intertidal cobble and boulder shores of the temperate and tropical regions of Japan. We employed allometric growth analyses of the cheliped and pleon dimensions of P. japonicus females and males collected over a year. Our analyses supported our expectation regarding the seasonal changes in the sexual size dimorphisms of the chelipeds and pleons in P. japonicus. Intersexual size dimorphism of the chelipeds and pleons was evident during the breeding season: females allocated more energy to pleon growth, while reducing cheliped growth, and investment in the pleon increased with increasing female body size, whereas males invested their energy in cheliped growth, and the investment in chelipeds increased with increasing male body size. During the nonbreeding season, females and males conserved energy by reducing the size of pleons and chelipeds relative to their respective body sizes. Our results highlighted the sex-specific and season-dependent resource allocation and reproductive strategies of porcellanid crabs.

Behavioural differences between breeding and nonbreeding pairs of protandry monogamous false clown anemonefish Amphiprion ocellaris

Anemonefishes are some of the most popular marine ornamental fishes. Due to the adverse impacts of commercial fishing on the wild populations of anemonefishes, a more suitable and efficient captive breeding programme must be promoted. In the wild, anemonefishes are protandrous sex-changing fish, but when two immature individuals with ambisexual gonads are raised together in captivity, the two differentiate directly into a male and a female, to form a breeding pair. However, not all the formed pairs spawn, explaining the great care required in captive breeding. This behaviour appears to be counter-adaptative, as anemonefish social groups form randomly in the wild, and such phenomenon would disturb their breeding success. This study evaluated the behavioural and physiological differences between breeding and nonbreeding pairs of false clown anemonefish Amphiprion ocellaris under captive conditions. Behavioural observations revealed that nonbreeding females monopolized the shelter provided, whereas breeding females allowed breeding males to use the shelter and the pair frequently stayed together in the shelter. Both nonbreeding and breeding females possessed mature ovarian tissue and similar level of plasma estradiol concentrations, but nonbreeding males had a smaller amount of testicular tissue and lower plasma 11-ketotestosterone levels compared to breeding males.

Long-Term Effects of Fatherhood on Morphology, Energetics, and Exercise Performance in California Mice (Peromyscus californicus).

In male mammals that provide care for their offspring, fatherhood can lead to changes in behavioral, morphological, and physiological traits, some of which might constitute trade-offs. However, relatively little is known about these changes, especially across multiple reproductive bouts, which are expected to magnify differences between fathers and nonreproductive males. We evaluated consequences of fatherhood in the monogamous, biparental California mouse (Peromsycus californicus) across seven consecutive reproductive bouts. We compared breeding adult males (housed with sham-ovariectomized females) with two control groups: nonbreeding males (housed with ovariectomized females treated with estrogen and progesterone to induce estrous behavior) and virgin males (housed with untreated ovariectomized females). At five time points (before pairing, early postpartum of the first litter, late postpartum of the second litter, early postpartum of the sixth litter, and late postpartum of the seventh litter or comparable time points for nonbreeding and virgin males), we measured males' body composition, hematocrit, predatory aggression, resting metabolic rate, maximal oxygen consumption (), grip strength, and sprint speed. We also weighed organs at the final time point. We predicted that fathers would have lower relative body fat and lower performance abilities compared with control groups and that these effects would become more pronounced with increasing parity. Contrary to predictions, breeding and control males differed in surprisingly few measures, and the number and magnitude of differences did not increase with parity. Thus, our expectations regarding trade-offs were not met. As reported in studies of single reproductive events, these results suggest that fatherhood has few costs in this species when housed under standard laboratory conditions, even across multiple reproductive bouts.

Relationships between personality traits and the physiological stress response in a wild mammal.

Glucocorticoids (GCs) are involved in the regulation of an animal’s energetic state. Under stressful situations, they are part of the neuroendocrine response to cope with environmental challenges. Animals react to aversive stimuli also through behavioral responses, defined as coping styles. Both in captive and wild populations, individuals differ in their behavior along a proactive–reactive continuum. Proactive animals exhibit a bold, active-explorative and social personality, whereas reactive ones are shy, less active-explorative and less social. Here, we test the hypothesis that personality traits and physiological responses to stressors covary, with more proactive individuals having a less pronounced GC stress response. In wild populations of invasive gray squirrels Sciurus carolinensis, we measured fecal glucocorticoid metabolites (FGMs), an integrated measure of circulating GCs, and 3 personality traits (activity, sociability, and exploration) derived from open field test (OFT) and mirror image stimulation (MIS) test. Gray squirrels had higher FGMs in Autumn than in Winter and males with scrotal testes had higher FGMs than nonbreeding males. Personality varied with body mass and population density. Squirrels expressed more activity-exploration at higher than at lower density and heavier squirrels had higher scores for activity-exploration than animals that weighed less. Variation in FGM concentrations was not correlated with the expression of the 3 personality traits. Hence, our results do not support a strong association between the behavioral and physiological stress responses but show that in wild populations, where animals experience varying environmental conditions, the GC endocrine response and the expression of personality are uncorrelated traits among individuals.

Effects of short- and long-term cold acclimation on morphology, physiology, and exercise performance of California mice (Peromyscus californicus): potential modulation by fatherhood.

California mice (Peromyscus californicus) differ from most other mammals in that they are biparental, genetically monogamous, and (compared with other Peromyscus) relatively large. We evaluated effects of cold acclimation on metabolic rate, exercise performance, and morphology of pair-housed male California mice, as well as modulation of these effects by fatherhood. In Experiment 1, virgin males housed at 5° or 10°C for approximately 25days were compared with virgins housed at standard vivarium temperature of 22°C. Measures included resting metabolic rate (RMR), maximal oxygen consumption ([Formula: see text]max), grip strength, and sprint speed. In Experiment 2, virgin males housed at 22°C were compared with three groups of males housed at 10°C: virgins, breeding males (housed with a female and their pups), and non-breeding males (housed with an ovariectomized, estrogen- and progesterone-treated female) after long-term acclimation (mean 243days). Measures in this experiment included basal metabolic rate (BMR), [Formula: see text]max, maximal thermogenic capacity ([Formula: see text]sum), and morphological traits. In Experiment 1, virgin males housed at 5° and 10°C had higher RMR and [Formula: see text]max than those at 22°C. In Experiment 2, 10°C-acclimated groups had shorter bodies; increased body, fat, and lean masses; higher BMR and [Formula: see text]sum, and generally greater morphometric measures and organ masses than virgin males at 22°C. Among the groups housed at 10°C, breeding males had higher BMR and lower [Formula: see text]max than non-breeding and/or virgin males. Overall, we found that effects of fatherhood during cold acclimation were inconsistent, and that several aspects of cold acclimation differ substantially between California mice and other small mammals.

Assessing space use in meadow voles: the relationship to reproduction and the stress axis

Abstract Voles are key mammals in understanding how social interactions can affect large-scale population processes. Previous studies have shown that at high population densities, meadow voles (Microtus pennsylvanicus) have a lower proportion of breeding animals, higher average corticosterone levels, and can be limited by female territorial spacing. Based on this, we compared corticosterone levels and spatial use between breeding and nonbreeding free-ranging adult meadow voles within populations. We measured intrasexual spatial overlap to examine if breeding females minimize occupying the same areas as other females, and noninvasively assessed corticosterone levels using fecal corticosterone metabolites (FCMs). We found that female meadow voles have much lower intrasexual spatial overlap than males, even though both sexes have similar range sizes, and that females have generally higher FCM levels than males. However, breeding and nonbreeding females did not differ from one another in spatial use or in FCM levels. Conversely, reproductive classes of males differed greatly in all measures: nonbreeding males had FCM levels that were two times higher than those of breeding males, occupied a smaller range, and had lower spatial overlap, indicating they were moving less widely than breeding males. We additionally validated an enzyme immunoassay for noninvasively measuring FCMs in meadow voles. The assay was successful in detecting an increase in corticosterone stimulated by adrenocorticotropic hormone injection; however, dexamethasone did not induce negative feedback. FCMs reflect circulating corticosterone levels approximately 5 h prior. These results highlight differences in FCMs and spacing in meadow voles related to sex and reproductive status, and reflect the respective strategies males and females employ during the breeding season.

Non-invasive assessment of glucocorticoid and androgen metabolite levels in cooperatively breeding Damaraland mole-rats (Fukomys damarensis)

Dominant females of cooperative breeding species often use aggression to suppress reproduction of subordinate females, resulting in subordinates experiencing stress-related increases in glucocorticoid levels, which may cause reproductive down-regulation. This would suggest a general pattern with higher glucocorticoid levels in subordinate compared to dominant individuals; however, the opposite was found in a number of cooperatively breeding species. Furthermore, breeding females of the cooperatively breeding Damaraland mole-rats (Fukomys damarensis) exhibit very high androgen concentrations during the wet season, presumably to support their breeding monopoly. Hormone analysis in Damaraland mole-rats have typically been measured using plasma and urine, but faecal analysis offers additional advantages especially for field studies on this species. The present study examines the suitability of Damaraland mole-rat faecal samples for determining glucocorticoid metabolite (fGCM) and androgen metabolite (fAM) concentrations using enzyme immunoassays. Using these assays, we further evaluated the effects of breeding status on fGCM and fAM concentrations in wild-caught and captive Damaraland mole-rats. Wild-caught breeding and non-breeding males and females exhibited no differences in fAM concentrations. Immunoreactive fGCM concentrations were only high in male breeders and comparatively low in non-breeders and breeding females. Concentrations of fAMs and fGCMs were similar in captive males and females, but fAM concentrations were elevated in captive compared to wild-caught individuals, which may be related to a higher reproductive activity due to removal from the breeding female. The relatively uniform fAM and fGCM concentrations found in wild-caught mole-rats may be explained by a stable colony structure during the dry season during which this study was conducted. Limited dispersal opportunities result in lower aggression and stress levels within a colony and as a result lower fAM and fGCM concentrations.

The individual courtship behaviour of male European mink (Mustela lutreola) is a good indicator for their breeding success

Conservation breeding of the critically endangered European mink (Mustela lutreola) is a challenge, because the genetically prioritised breeding pairs often fail to mate during the staged breeding attempts. For this study the courtship and mating behaviour of 33 males and the response behaviour of 28 females was observed and recorded throughout two breeding seasons at Tallinn Zoo using an ethogram. The behavioural patterns of the male European mink differed significantly depending upon their previous reproductive success and the outcome of the breeding attempt. “Clucking”, “flehmen”, “chase”, “anal drag”, “neck bite” and “mounting” were observed significantly more often among males that sired a litter during the study (“breeding males”) and during attempts that ended with copulation. More than half (61%) of the males were “non-breeding males”: they never sired a litter or copulated with a female. Females “chirped” significantly less often in attempts with “non-breeding males”. The male “clucking” sound was the best indicator to predict 1) a males ability to sire a litter and 2) whether a breeding attempt would end with copulation. The absence of species-specific courtship and mating behaviour in the “non-breeding males” threatens the conservation goal to maintain the genetic heterozygosity of the captive population. From a practical point of view, behavioural indicators could be used as a potential screening method for identifying successful future breeders. In an experimental setup, males were presented with scent cues from an oestrous female but without the opportunity for direct contact. In this experimental context 64% of “breeding males” responded with “clucking” and also presented “flehmen”, “rubbing” and “approach to the female/her nest box door” significantly more often than the “non-breeding males”.

Testis Size and Asymmetry in the Guinea Fowl (Numida Meleagris): A Test of the Compensation Hypothesis

Despite numerous studies on testicular asymmetry in birds, there are still inconsistent reports on the pattern of asymmetry in species belonging to various phylogenetic groups and exhibiting diverse lifestyles. In addition, there is a lack of clarity on whether functional differences exist between the left and right testes despite differences in size, as well as no evidence of naturally occurring compensation in testis size in terrestrial and galliform birds. A study involving 400 Guinea Fowl (Numida meleagris) cocks was conducted to determine asymmetry and compensatory growth in the testes as well as age-related changes in absolute and relative testicular asymmetry. The left testis had significantly higher weight, volume and relative weight than the right testis. Similarly, populations of round spermatids, type I spermatocytes, total germ cell, Sertoli efficiency, actual and apparent seminiferous tubular diameters and testicular sperm production were higher in the left than the right testis. Correlations between the left and right testicular gross anatomical and histological biometric traits were strong and positive. Left biased asymmetry was recorded in the Guinea Fowl. Absolute testicular asymmetry increased with age, but tended to stabilise from 20 weeks of age, while relative testicular asymmetry remained stable throughout. Both absolute and relative testicular asymmetries were higher in breeding than non-breeding males. Compensatory growth was recorded in both testes with no difference in the degree of compensation. The left biased asymmetry observed in the Guinea Fowl was reflected in functional differences between the two testes.

Use of space and homesite attendance by Iberian wolves during the breeding season

The persistence of large carnivores in human-dominated landscapes is conditional on the preservation of adequate ecological conditions during the reproduction period, when they may be particularly susceptible to human disturbance. However, little is known about the breeding behaviour of large carnivores in these landscapes, though this is important for conservation management. Here we describe the space use and homesite attendance patterns of wolves inhabiting humanised landscapes of north-western Portugal, based on GPS tracking of 11 individuals in 2008–2013. Parturitions (N = 3) occurred in late May, with pups remaining at natal dens for 24–85 days, after which they were moved to a first and then sometimes to a second rendezvous site. Two of these movements were associated with human disturbance events. Breeding females (N = 4) spent a large proportion of time with pups during pre-weaning (≈2 months after birth), leaving only at night during short periods; thereafter they progressively reduced time at homesites (i.e, natal dens and rendezvous sites), and increased both daily travel distances and daytime activity. Throughout the pup-rearing season, breeding females restricted their movements to within ≈2 km of homesites. Non-breeding females (N = 4) showed significantly lower attendance rates than breeding females, particularly during pre-weaning, and they had much less restricted movements throughout the breeding season, with activity occurring throughout the circadian cycle. Non-breeding males (N = 3) showed attendance and space-use patterns intermediate between breeding and non-breeding females, with movements largely concentrated within the same areas used by breeding females. Our findings suggest that breeding wolves may be particularly susceptible to human activities occurring within 2 km of homesites, although further research is needed to assess the ultimate effect of such disturbance on reproductive success and pup survival.

Growth affects dispersal success in social mole-rats, but not the duration of philopatry.

In naked mole-rats (Heterocephalus glaber), some non-breeding males show faster growth and are more likely to disperse than others. These differences have been suggested to be the result of a specialized developmental strategy leading to shorter philopatry and independent breeding, as opposed to extended philopatry as non-reproductive helpers. However, it is unclear whether fast-growing males disperse sooner than slow-growing males. An alternative explanation is that variation in quality between individuals causes high-quality individuals to grow quickly and maximize dispersal success without reducing philopatry. Here we show that in Damaraland mole-rats (Fukomys damarensis), males that subsequently disperse successfully grow faster than other non-reproductive males. This pattern is predicted by both hypotheses and does not discriminate between them. However, contrary to the suggestion that faster growth represents a developmental specialization for early dispersal, fast-growing and slow-growing males remained equally long in their natal groups. Our study provides no evidence for adaptive divergence in male development leading either to early dispersal or extended philopatry. Instead of representing specialized dispersers, fast-growing males of this species may be high-quality individuals.

Levels of Leydig cell autophagy regulate the fertility of male naked mole-rats

Fertility is abolished in nonbreeding males in colonies of natal naked mole-rats (NMRs). Although spermatogenesis occurs in both breeding and nonbreeding male NMRs, the mechanisms underlying the differences in fertility between breeders and nonbreeders remain unexplored. In this study, a significant decrease in autophagy was observed in Leydig cells of the testis from nonbreeding male NMRs. This alteration was visualised as a significant decrease in the levels of autophagy-related gene 7 (Atg7), Atg5, microtubule-associated protein 1A/B light chain 3 (LC3-II/I) and the number of autophagosomes and an increase in P62 levels using Western blotting analyses. Furthermore, monodansylcadaverine (MDC) staining and Western blot analyses revealed that testosterone production decreased in nonbreeding male NMR Leydig cells, this decrease was associated with a reduction in autophagy. Primary Leydig cells from breeding and nonbreeding male NMRs were processed to investigate the effect of an autophagy inhibitor (3-MA, 3-methyladenine) or an autophagy activator (rapamycin) on testosterone production. Rapamycin induced an increase in testosterone production in NMR Leydig cells, whereas 3-MA had the opposite effect. Consequently, spermatogenesis, the weight of the testis, and androgen levels were dramatically reduced in nonbreeding male NMRs. While rapamycin treatment restored the fertility of nonbreeding male NMRs. Based on these results, inadequate autophagy correlates with a decrease in steroid production in nonbreeding male NMR Leydig cells, which may ultimately influence the spermatogenesis and fertilities of these animals.

Male cooperation for breeding opportunities contributes to the evolution of multilevel societies.

A small number of primate species including snub-nosed monkeys (colobines), geladas (papionins) and humans live in multilevel societies (MLSs), in which multiple one-male polygamous units (OMUs) coexist to form a band, and non-breeding males associate in bachelor groups. Phylogenetic reconstructions indicate that the papionin MLS appears to have evolved through internal fissioning of large mixed-sex groups, whereas the colobine MLS evolved through the aggregation of small, isolated OMUs. However, how agonistic males maintain tolerance under intensive competition over limited breeding opportunities remains unclear. Using a combination of behavioural analysis, satellite telemetry and genetic data, we quantified the social network of males in a bachelor group of golden snub-nosed monkeys. The results show a strong effect of kinship on social bonds among bachelors. Their interactions ranged from cooperation to agonism, and were regulated by access to mating partners. We suggest that an ‘arms race’ between breeding males' collective defence against usurpation attempts by bachelor males and bachelor males' aggregative offence to obtain reproductive opportunities has selected for larger group size on both sides. The results provide insight into the role that kin selection plays in shaping inter-male cohesion which facilities the evolution of multilevel societies. These findings have implications for understanding human social evolution, as male–male bonds are a hallmark of small- and large-scale human societies.