Immature Males Research Articles

Seasonal and genetic effects on lipid profiles of juvenile Atlantic salmon

Seasonality can influence many physiological traits requiring optimal energetic capacity for life-history stage transitions. In Atlantic salmon, high-energy status is essential for the initiation of maturation. Earlier studies have linked a genomic region encoding vgll3 to maturation age, potentially mediated via body condition. Vgll3 has also been shown to act as an inhibitor of adipogenesis in mice. Here we investigate the influence of season and vgll3 genotypes associating with early (EE) and late (LL) maturation on lipid profiles in the muscle and liver of juvenile Atlantic salmon. We reared Atlantic salmon for two years from fertilization and sampled muscle and liver during the spring and autumn of the second year (at which time some males were sexually mature). We found no seasonal or genotype effect in the muscle lipid profiles of immature males or females. However, in the liver we detected a triacylglycerol enrichment and a genotype specific direction of change in membrane lipids, phosphatidylcholine and phosphatidylethanolamine, from spring to autumn. Specifically, from spring to autumn membrane lipid concentrations increased in vgll3*EE individuals but decreased in vgll3*LL individuals. This could be explained by 1) a seasonally more stable capacity of endoplasmic reticulum (ER) functions in vgll3*EE individuals compared to vgll3*LL individuals or 2) vgll3*LL individuals storing larger lipid droplets from spring to autumn in the liver compared to vgll3*EE individuals at the expense of ER capacity. This genotype specific seasonal direction of change in membrane lipid concentrations provides more indirect evidence of a potential mechanism linking vgll3 with lipid metabolism and storage.

Assessing boar taint in Portuguese pork: A small-scale study of prevalence and classification via established detection thresholds

Aim of study: To assess the boar taint prevalence in the Portuguese pork industry through an observational study model by measuring skatole and androstenone levels in fat and to compare it with the estimated thresholds for these compounds among Portuguese consumers. Area of study: Portugal. Material and methods: Adipose tissue samples from 140 animals (102 entire males and 38 females) were collected in three Portuguese abattoirs for boar taint quantification. Cut-off limits were determined using best-estimate thresholds (BET) for skatole and androstenone. Main results: Boar taint quantification for the 140 animals revealed levels of 36.0±4.7 ng/g of skatole and 64.5±21.3 ng/g of androstenone, and values were significantly higher in males. Group BET values were 35.4 ng/g and 566.3 ng/g for skatole and androstenone, respectively. BET values were exceeded in 28.8% of the samples for skatole and 0.7% for androstenone. Research highlights: The investigation revealed a generally low level of boar taint in the samples of this small-scale study on skatole and androstenone prevalence in Portugal's pork supply chain. However, occasionally a significantly elevated boar taint levels suggest that relying solely on slaughtering sexually immature males might not fully resolve this issue.

Squid male alternative reproductive tactics are determined by birth date.

Alternative reproductive tactics (ARTs) are discontinuous phenotypes associated with reproduction, observed in males of many species. Typically, large males adopt a tactic of competing with rivals for mating, while small males adopt a tactic of stealing fertilization opportunities from the large males. The 'birth date hypothesis', proposing that the date of birth influences the determination of each male's reproductive tactic, has been tested only in teleost fish to date. Here, the birth date hypothesis was tested in ARTs of Japanese spear squid Heterololigo bleekeri (consort/sneaker) by analysing statolith growth increments. The birth date significantly differed between consorts (early-hatched) and sneakers (late-hatched). However, no differences were detected in growth history up to 100 days from hatching. Most immature males caught during the reproductive season were larger than sneakers, and their hatch date was similar to that of consorts, suggesting that these immature males had already been following a life-history pathway as a consort. These results indicate that ARTs of H. bleekeri are determined based on their hatch date in early life. This study firstly suggests that the birth date hypothesis applies to aquatic invertebrates, suggesting that the mechanism by which birth date determines the individual phenotype is a phenomenon more common than previously believed.

Tanner crab at southwestern Kamchatka: fishing, stock condition and specifics of the assessment

Results of the current stage of research on tanner crab at the southwestern coast of Kamchatka, harvested in the Kamchatka-Kuril fishing subzone are presented. The stock dynamics since 2001 is analyzed, with special attention to its assessing and forecasting. Features of the crab biology associated with terminal molting are described. The algorithm for separation of the tanner crab recruits into morphometrically mature and immature males is developed that allows to calculate probability for a particular size group of morphometrically immature males to undergo the terminal molt and join to the commercial stock. This algorithm is applied for the data collected at southwestern Kamchatka since 2010. Two peaks in total male abundance of tanner crab were observed in 2005–2006 and 2020–2022. Landing of this species was banned in the Kamchatka-Kuril fishing subzone in 2019–2020, as the result of the local population abundance drop in the previous two years, but was resumed in 2021 after its full restoration. Possible reasons for underestimation of the crab recruitment are discussed, related both with features of the species biology and methodological problems. The population in the Kamchatka-Kuril fishing subzone is currently the most abundant for tanner crab, and this stock in 2020–2022 has reached the historical peak. The fishing of tanner crab in the last three years is distinguished by high catches and high rate of the total allowable catch (TAC) utilization.

Gonadal transcriptome analysis of genes related to sex differentiation and sex development in the Pomacea canaliculata

As an invasive alien animal, Pomacea canaliculata poses a great danger to the ecology and human beings. Recently, there has been a gradual shift towards bio-friendly control. Based on the development of RNA interference and CRISPR technology as molecular regulatory techniques for pest control, it was determined if the knockout of genes related to sex differentiation in P. canaliculata could induce sterility, thereby helping in population control. However, the knowledge of sex differentiation- and development-related genes in P. canaliculata is currently lacking. Here, transcriptomic approaches were used to study the genes expressed in the two genders of P. canaliculata at various developmental stages. Gonad transcriptomes of immature or mature males and females were compared, revealing 12,063 genes with sex-specific expression, of which 6066 were male- and 5997 were female-specific. Among the latter, 581 and 235 genes were up-regulated in immature and mature females, respectively. The sex-specific expressed genes identified included GnRHR2 and TSSK3 in males and ZAR1 and WNT4 in females. Of the genes, six were involved in reproduction: CCNBLIP1, MND1, DMC1, DLC1, MRE11, and E(sev)2B. Compared to immature snail gonads, the expression of HSP90 and CDK1 was markedly reduced in gonadal. It was hypothesized that the two were associated with the development of females. These findings provided new insights into crucial genetic information on sex differentiation and development in P. canaliculata. Additionally, some candidate genes were explored, which can contribute to future studies on controlling P. canaliculata using molecular regulatory techniques.

Social Play In African Savannah Elephants May Inform Selection Against Aggression

Abstract In social groups, competition for individual advantage is balanced with cooperation, for the collective benefit. Selection against aggression has favoured cooperation and non-aggressive competitive strategies. Because social play is a behavioural system that fluctuates between cooperation and competition, selection against aggression might have especially influenced this behaviour. African savannah elephants (Loxodonta africana) are a low aggressive species, therefore suitable to investigate this aspect. We collected all occurrences observational audio-video data on social play, aggression/threats, and affiliation on an African elephant colony housed in a 25-ha open space at Parque de la Naturaleza de Cabarceno (Cantabria, Spain) and composed of four family groups (3 immature males, 3 immature females, and 7 adult females) and two adult males. Anticipating the influence of reduced aggression, we found that social play decreased with age, persisting in adults, and that it was highest in males. Social play was associated with affiliation (informing cooperation). Indeed, individuals that were central in the social play network were also central in the affiliation network. For immature subjects, we found a correlation between social play and affiliation sociomatrices. However, such correlation was absent in adults and social play mostly occurred between families. Despite the limitations related to dealing with a small captive group, this study largely supports the idea that the features of social play in African savannah elephants may be related to low aggression. This investigation hints toward a non purely cooperative use of play, possibly as a non-aggressive interaction that accommodates different levels of cooperation and competition.

Gene co-expression patterns in Atlantic salmon adipose tissue provide a molecular link among seasonal changes, energy balance and age at maturity.

Sexual maturation in many fishes requires a major physiological change that involves a rapid transition between energy storage and usage. In Atlantic salmon, this transition for the initiation of maturation is tightly controlled by seasonality and requires a high-energy status. Lipid metabolism is at the heart of this transition since lipids are the main energy storing molecules. The balance between lipogenesis (lipid accumulation) and lipolysis (lipid use) determines energy status transitions. A genomic region containing a transcription co-factor of the Hippo pathway, vgll3, is the main determinant of maturation timing in Atlantic salmon. Interestingly, vgll3 acts as an inhibitor of adipogenesis in mice and its genotypes are potentially associated with seasonal heterochrony in lipid storage and usage in juvenile Atlantic salmon. Here, we explored changes in expression of more than 300 genes directly involved in the processes of adipogenesis, lipogenesis and lipolysis, as well as the Hippo pathway in the adipose tissue of immature and mature Atlantic salmon with distinct vgll3 genotypes. We found molecular evidence consistent with a scenario in which immature males with different vgll3 genotypes exhibit contrasting seasonal dynamics in their lipid profiles. We also identified components of the Hippo signalling pathway as potential major drivers of vgll3 genotype-specific differences in adipose tissue gene expression. This study demonstrates the importance of adipose gene expression patterns for directly linking environmental changes with energy balance and age at maturity through genetic factors bridging lipid metabolism, seasonality and sexual maturation.

Growth and reproduction of the shrimp population in a lagoon system in southern Benin (West Africa)

Abstract The aim of this work was to characterize the growth and reproduction dynamics of shrimp in the Lac Nokoué-Chenal de Cotonou complex. The results of one year’s sampling from five stations (North, South, East, Central and West) of the lagoon complex revealed that linear growth in size in Lake Nokoué is decreasing over time in Macrobrachium macrobrachion (the most representative species of the genus Macrobrachium), but positive in Penaeus notialis (the most representative species of the genus Penaeus). Size-weight relationships indicate that the lowest growth coefficient () is obtained in immature males of Macrobrachium felicinum, while the highest growth coefficient () is obtained in mature females of Macrobrachium vollenhovenii, with an average of 2.84 for all shrimp species over both sexes considered. The test indicated that only the species Macrobrachium vollenhovenii has a significant sexual imbalance in favour of females in Lake Nokoué. Fisher’s Least Significant Difference test indicated that the estimated first sexual maturity sizes in Macrobrachium vollenhovenii and M. macrobrachion are significantly different from those estimated in M. felicinum at the threshold. However, the same test indicates that there is not enough evidence to differentiate the sizes of first sexual maturation in M. vollenhovenii and M. macrobrachion. This work revealed that Penaeus monodon was the only species to show better positive growth within all its groups in Lake Nokoué while exposed to anthropogenic effects. A gradual average increase in the size of Penaeus notialis in Lake Nokoué is found between the beginning and end of the saline intrusion (which confirms the life cycle of the species presented). Species of the genus Macrobrachium showed good reproductive capacity, with the absence of sexually mature Penaeus in this lagoon.

Video evidence of mountings by female‐plumaged birds of paradise (Aves: Paradisaeidae) in the wild: Is there evidence of alternative mating tactics?

AbstractThe bewildering courtship phenotypes of male birds of paradise (Paradisaedae) represent a classic example of sexual selection through mate choice. While the majority of sexual selection studies have focused on either mate choice or intrasexual competition, males across a variety of taxa adopt alternative mating tactics as additional means of obtaining fertilization when they are otherwise unable to. For example, across various polygynous birds, subordinate males engage in sneak copulations, which may offset the fitness costs of prolonged subordinate periods. Despite exhibiting strong mating skews and male delayed plumage maturation, reports of sneak copulation in the birds of paradise are exceedingly rare. After reviewing an extensive video collection of courtship interactions, we found examples of mountings by female‐plumaged birds in three birds of paradise species: the Western parotia Parotia sefilata, Carola's parotia Parotia carolae, and the magnificent bird of paradise Cicinnurus magnificus. While homosexual mountings by females have been documented previously in Lawes' parotia P. lawesii, adult males in the magnificent bird of paradise violently attacked intruding female‐plumaged birds attempting to mount receivers, suggesting that they may be immature males engaging in alternative mating tactics. Overall, the rare video footage described here is suggestive of two fascinating, yet unexplored phenomena in polygynous birds: alternative mating tactics and female homosexual behaviour.

Click-click, who’s there? Acoustically derived estimates of sperm whale size distribution off western Ireland

Understanding the structure of populations is a critical element to the establishment of management and conservation measures. Sperm whales Physeter macrocephalus are characterised by a demographic spatial segregation, associated with a conspicuous sexual dimorphism reflected in their vocalisations. These characteristics make acoustic techniques very relevant to the study of sperm whale population structure, especially in remote, challenging environments. The reliability of using inter-pulse intervals of sperm whale clicks to infer body size has long been verified and extensively used. We provide the first size structure estimates of the sperm whale population in an area where assumptions on population structure mainly relied on sparse observations at sea, whaling records and stranding data. Over 10,000 hours of acoustic data collected using both static acoustic recorders and towed hydrophone arrays in Irish offshore waters were processed using a machine learning-based tool aimed at automatically extracting inter-pulse intervals from sperm whale recordings. Our analyses suggested that, unlike previously thought, large males would not account for the majority of the animals recorded in the area. We showed that adult females/juvenile males (length 9-12 m) were predominant, accounting for 49% (n = 788) of the number of individuals recorded (n = 1,595), while the proportions of immature individuals (length<9 m) and adult males (length >12 m) were well balanced, accounting for 25% (n = 394) and 26% (n = 413) of the recorded whales, respectively. Our data also suggested some size segregation may be occurring within the area, with smaller individuals to the south. The implications of such findings are crucial to the management of the population and provide an important baseline to monitor changes in population structure, particularly relevant under changing habitat conditions.

Sources of persistent organic pollutants and their physiological effects on opportunistic urban gulls

Urbanization is associated with drastic shifts in biodiversity. While some species thrive in urban areas, the impact of inhabiting these human-altered environments on organism physiology remains understudied. We investigated how exposure to polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) affects the physiology of yellow-legged gulls (Larus michahellis) inhabiting a densely populated, industrialized city. We analyzed blood samples from 50 gulls (20 immatures and 30 adults) and assessed 27 physiological parameters and biomarkers related to xenobiotic protection, health, and feeding habits in these same individuals. We also tracked the movements of 25 gulls (15 immatures and 10 adults) to identify potential sources of persistent organic pollutants (POPs). Both adult and immature gulls primarily inhabited urban areas, followed by marine habitats. Immature gulls spent more time in freshwater, landfills, and agricultural areas. Bioaccumulated ΣPCB (median = 92.7 ng g-1 ww, 1.86–592) and ΣPBDE (median = 1.44 ng g-1 ww, 0.022–9.58) showed no significant differences between age and sex groups. Notably, immature males exhibited the highest correlations with POP concentrations, particularly with the activity of carboxylesterases (CEs), suggesting a higher sensitivity than adults. These findings highlight the potential of plasmatic CEs in immature yellow-legged gulls as effective tracers of POPs exposure and effects, offering insights into the anthropogenic impacts on urban biodiversity.

Methyl eugenol aromatherapy: a delivery system facilitating the simultaneous application of male annihilation and sterile insect technique against the peach fruit fly.

The peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae) is an economically important polyphagous, quarantine pest endemic to South and South-East Asia. The male annihilation technique (MAT) and the sterile insect technique (SIT) are environmentally benign techniques used to suppress fruit fly populations on an area-wide basis. The MAT and SIT are typically used sequentially to avoid killing released sterile males; however, MAT and SIT potentially could be used simultaneously and thereby increase the overall efficiency of control programmes. Mating competitiveness of sterile males against wild counterparts is critical for the success of the SIT. Feeding on a semiochemical, methyl eugenol (ME) has been reported to enhance the male mating performance of many Bactrocera spp., including B. zonata, but its use in SIT operational programmes is limited owing to the absence of a viable delivery system. In the present study, we demonstrated that ME aromatherapy, a practical method for large-scale delivery of ME olfactorily, enhances the mating success of treated B. zonata males. ME aromatherapy application to 5-day-old immature males for a duration of 5 h resulted in increased mating success of males tested when sexually mature, compared to untreated males. The ME-aromatized males also exhibited reduced attraction to ME-lure. A practical delivery system for applying ME by aromatherapy to mass-reared males was developed. ME-aromatherapy enhanced male mating success and suppressed their subsequent attraction to ME, thus enabling the application of MAT and SIT at the same time. © 2023 Society of Chemical Industry.

Natal origin and dispersal of problem saltwater crocodiles in the Darwin Harbor, Australia

AbstractManagement programs that successfully recovered wild saltwater crocodile (Crocodylus porosus) populations in the Northern Territory of Australia did so with an expanding commitment to maintaining public safety. One aspect of the program is the ongoing removal of resident and immigrant crocodiles within Darwin Harbor (since 1979), the main urban center. We determined the likely sources of crocodiles caught as problem animals between 2015–2017 by comparing recently developed methods for population assignment. Depending on the assignment model used, we estimated that between 30% and 50% of crocodiles in Darwin Harbor originated from the Adelaide and Mary rivers, and the Kakadu region east of Darwin, and between 20% and 30% of crocodiles originated from the Finniss, Reynolds, and Daly rivers southwest of Darwin. Saltwater crocodiles occur at particularly high densities in these catchments. The remainder came from a mixture of different sources across the Northern Territory. The most common animals captured were immature (150–180 cm) males that have traveled 100–200 km. We did not identify any relationships between the distance from the inferred origin to Darwin Harbor and the size and sex of the crocodiles, or the year of capture. The targeted removal of crocodiles from specific sites such as Darwin Harbor, near where most people live, improves public safety in the highest risk areas, without compromising abundant source populations in most areas.

Sequential mountings of a possible immature male by an adult male in Victoria’s Riflebird (Ptiloris victoriae)

Sexual behaviour in the Birds-of-paradise (family Paradisaeidae) is poorly understood and few studies have offered detailed descriptions of copulatory behaviours. We recorded courtship behaviours of Victoria’s Riflebird Ptiloris victoriae in the Atherton Tablelands in Queensland, Australia using motion triggered cameras and report a rare case of three sequential mountings by an adult male. While the recipient of these mountings performed female-typical sexual behaviours, it also briefly performed a male courtship display behaviour, suggesting that it may be an immature male. This observation raises several questions about the courtship behaviour of this species. Females may, for instance, occasionally solicit multiple copulations from preferred males to maximize the amount of transferred sperm. Another intriguing possibility is that immature males tolerate being mounted and potentially even mimic female sexual behaviours when learning from adult male displays. We also describe a novel adult male courtship behaviour, namely ‘nape-pecking’.

Thermal Stress and Adult Fitness in a Drosophila suzukii Neotropical Propagule.

Drosophila suzukii (Matsumura 1931) is a cosmopolitan horticultural pest originally from temperate East Asia; yet, its recent introduction in southeast and central Brazil raises the possibility it might expand into warmer climatic zones. In theoretical terms, the adaptive potential of invasive species can be impaired by the lack of genetic variation, but, on the other hand, phenotypic plasticity might play an important role in the adaptation to the new environment. In this context, we investigated the effects of temperature variation (18°C, 22°C, and 28°C) on fitness traits and size of male reproductive organs (accessory glands and testis) in a natural D. suzukii population recently introduced in the neotropical region. Development time decreased significantly with increasing temperature, but egg-to-adult survival was not affected, attaining rates around 50% for the three temperatures. Development at 28°C affected differentially adult male and female biological performance: males displayed higher mortality and severe and permanent reduction in offspring production, whereas females showed the same mortality as controls and a temporary decrease in offspring production, followed of a clear recovery. Finally, reproductive organs size in immature and mature males was affected by developmental temperature variation in the following ways. Testis length decreased with body size (i.e., at higher temperatures) and increased with maturation time after adult hatching, whereas for accessory glands there was no significant difference between different temperatures, resulting in proportionally larger glands for smaller body sizes. These results show differences in developmental dynamics of reproductive tract structures due to temperature variation.

Catalase enzymatic activity in adult mosquitoes (Diptera: Culicidae): taxonomic distribution of the continuous trait suggests its relevance for phylogeny research.

Molecular research based on gene sequence analysis and performed for decades, in general, supported morphology-based groupings of the species within the family Culicidae, but phylogenetic relationships between some genera and tribes remained uncertain for a long time. Interspecific differences in catalase, an antioxidant enzyme important for maintaining prolonged lifespan and reproduction, have not been studied extensively by estimating enzymatic activity levels. Here, catalase enzymatic activity was assayed in extracts of male mosquitoes belonging to 10 species of the subfamily Culicinae, including species from tribes of disputable phylogeny. Three species of Chaoboridae (nearest outgroup taxon) and mosquitoes from the subfamily Anophelinae (one species complex) were also added to the study. At least in Culicinae, immature adult males (less than one day after emergence) have distinctly elevated specific activity of catalase; therefore, only mature males of all species were used for the comparative study. As a result, significant differences in catalase activity were revealed between tribes, genera and particular species. Among culicids, the genera Coquillettidia and Culiseta were found to include the species with the highest and relatively high catalase activity, which is consistent with the affinity of the tribes Mansoniini and Culisetini to each other. Within Ochlerotatus, extremely low catalase activity in Oc. hexodontus suggests the more distant position of this species from Oc. cantans (Meigen) and Oc. communis (de Geer) than the positions of the latter two species from each other. Additional study of catalase activity in overwintering females of the genus Culex revealed significantly higher enzyme activity in Cx. torrentium in comparison with Cx. pipiens, which supports their quite distant positions from each other within the genus. Considering the distribution of catalase activity within the tree obtained, the preliminary outcome is that Culiseta retains the elevated level of catalase activity that was lost during the early separation of Anopheles and subsequent separation of Culex and Aedes/Ochlerotatus after Anopheles from their common branch with Culiseta/Coquillettidia. Overall, the use of taxonomic distribution of catalase activity levels appears to be effective for resolving disputed events of mosquito phylogeny.

Reproductive effects of pubertal exposure to neonicotinoid thiacloprid in immature male mice

Thiacloprid (THIA) is a kind of neonicotinoid, a widely used insecticide class. Animal studies of adult and prenatal exposure to THIA have revealed deleterious effects on mammalian sperm fertility and embryonic development. A recent cross-sectional study linked higher THIA concentrations to delayed genitalia development stages in adolescent boys, suggesting that pubertal exposure to THIA may adversely affect reproductive development in immature males. Hence, this study aimed to investigate the effects of daily oral administration of THIA during puberty on the reproductive system of developing male mice. Young male C57 BL/6 J mice aged 21 days were administrated with THIA at concentrations of 10 (THIA-10), 50 (THIA-50) and 100 mg/kg (THIA-100) for 4 weeks by oral gavage. It is found that exposure to 100 mg/kg THIA diminished sexual behavior in immature male mice, caused a decrease in the spermatogenic cell layers and irregular arrangement of the seminiferous epithelium, and down-regulated the mRNA levels of spermatogenesis-related genes Ddx4, Scp3, Atg5, Crem, and Ki67, leading to an increase of sperm abnormality rate. In addition, THIA exposure at 50 and 100 mg/kg reduced the serum levels of testosterone and FSH, and decreased the expression levels of Star and Cyp11a1 related to testosterone biosynthesis. THIA exposure at 10 mg/kg did not produce any of the above significant changes. In conclusion, the high dose of THIA exposure impaired reproductive function in immature mice. It seems that THIA has no detrimental effects on the reproductive system of mice at low dose of 10 mg/kg.

Ontogenesis of sociability of wild immature capuchin monkeys (Sapajus libidinosus): Sex more than personality explains interindividual variation.

Sociability is a fundamental trait that social animals need to survive and reproduce in societies. Sociability predicts how an individual can consistently interact with its conspecifics across time and situations. By studying capuchin monkeys (Sapajus libidinosus), a neotropical primate with complex social behavior and high cognitive capacity, our research aims to analyze the development of the social axis of personality of immature individuals, from birth to the third year of life. We studied wild monkeys belonging to a group with infants, juveniles, and adults of both sexes that inhabits northeastern Brazil. We analyzed the behavior of 12 immature capuchins (6 males and 6 females) in 94 h of videos recorded weekly from birth until 36 months, through daily focal sampling. We verified whether there was intraindividual consistency throughout development by fitting regression models for the effect of age on initiating affiliative social behaviors, controlling for monkey identity and sex. Our results indicate that the individuals of this study exhibit high variation in the initiation of behaviors at the beginning of infancy; there was low repeatability and high intra-individual variation during the first 3 years of life of these individuals, indicating that the social personality is not consolidated in this period. Immature females were more sociable than immature males. Therefore, differences in sociability in early life of bearded capuchin monkeys are best explained by sex rather than personality. We suggest that the high initial behavioral variation in the social axis of personality allows for plasticity influenced by the environment throughout development. The high sociability of females in infancy may be related to female philopatry and their high sociability in adulthood.

Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses.

Steroid-hormone concentrations from non-invasively obtained biomarkers, like hair, can provide a representation of circulating hormones diffused over relatively long time periods (e.g., weeks or months). The hormone cortisol is often associated with physiological or even psychological stress, while testosterone is strongly associated with male development and reproductive success. Increasingly, studies are using hormone levels derived from hair to make inferences among both domestic animals and wildlife. For horses, all previous hair hormone analysis has been done on companion or working animals. We evaluated the levels of hair cortisol (n = 153) and testosterone (n = 48) from 136 feral horses living on Sable Island, Canada that have been part of a long-term individual-based study since 2008. This population has been undisturbed and unmanaged for over 50 years, and exhibits the natural social organization for horses, harem defense polygyny. Hair samples were collected in mid to late summer and the segment analyzed corresponds with hair grown during, and following, the peak of the reproductive season. Social position was determined based on the male's role as either a dominant breeding Stallion (Stallion), a non-breeding subordinate male (tag), adult Bachelor (5 years old or older), or Immature male (2-4 years of age). While there was no difference in hair-cortisol concentration among any class of adult males (i.e., Stallion, tag, or Bachelor), Immature males had significantly lower hair cortisol concentrations than the other groups (p = 0.001). Hair testosterone levels among the four social positions were significantly higher among Stallions (p = 0.04). Hair testosterone concentration was also significantly related to the probability of a male being either a Bachelor or Stallion and was the only variable remaining in AICc model selection (p = 0.016, AICc = 32.3, Null AICc = 38.8). While not a significant relationship, Stallions had a negative correlation between hair cortisol concentrations and testosterone (R2 = -0.20, p = 0.383), and Bachelors, conversely, had a positive association (R2 = 0.43, p = 0.246). Our observations of hormone concentrations in relation to physiological, social, or reproductive parameters in this population suggest trends that are similar to what has been established using blood or other matrices.

Assessing the Movements, Habitat Use, and Site Fidelity of the Giant Freshwater Whipray (Urogymnus polylepis) with Acoustic Telemetry in the Maeklong River, Thailand

We used acoustic telemetry to assess site fidelity, movement patterns, and habitat use within the lower Maeklong River, Thailand, by 22 giant freshwater whipray Urogymnus polylepis. This study is the first of its kind for this rare, endangered species, and it begins to fill critical information gaps about its ecology and life history. Study animals were tagged subcutaneously in the dorsal area with acoustic transmitters and tracked for 12 months using a fixed array of eight receivers. Receivers were positioned within an 18 rkm section of the Maeklong, starting approximately 4 rkm upstream from the mouth. We calculated individual residency indices, tracked longitudinal movements, and assessed annual and seasonal patterns of site use. We also investigated spatial use patterns, diel activity patterns, and relationships of temperature and site fidelity. We detected 86% of our tagged whiprays, 53% of which were detected for the majority of the study period. Whiprays exhibited high site fidelity across seasons. Individuals made long longitudinal movements within the site for much of the study period but seemed to remain closer to the estuary during the second half of the rainy season and early winter. All receivers had large numbers of detections, but upstream receivers were visited for longer time durations than downstream receivers. A receiver in the middle of the study area had the highest detection rate, but low detection durations, suggesting that this receiver is in a migration corridor. A mix of immature and mature males and females was present in the site throughout the study period, suggesting that this area is not exclusively a breeding or nursery site. However, the high site fidelity suggests that this is an important aggregation site for the species. Effective conservation measures may include conservation zones and a shrimp reintroduction program upstream, ensuring fish passage through the middle of the site, and regulating traffic and pollution downstream. We found acoustic telemetry to be an effective study method and encourage its use to improve understanding of the giant freshwater whipray.