Estrous Females Research Articles

Chemical characterization and response of house rats towards faecal odour of conspecifics

Repeated use of rodenticides for rodent pest management leads to the development of bait shyness and resistance in rodents. Therefore, using pheromones for rodent management could be a significant step forward. The present study was conducted to determine the response of house rats towards odour of faecal extracts of conspecifics of different age groups and sexes. Rats of different maturity groups and sexes were exposed to 20% faecal extract of mature and immature male and female rats. Results indicated that faecal extract of estrous stage mature females has a significant attractant/repellent effect on mature rats of opposite/same sex, respectively. Gas chromatography-linked mass spectrometry of the faecal extract of estrous female rats identified 62 compounds, of which 16 were already reported in other animals as pheromonal compounds and might be used in communication by house rats. In the future, these identified compounds can be used in a fixed proportion after testing their efficacy to develop a stable lureto increase the trappability and acceptability of antifertility agents and rodenticide-based baits for the management of house rats.

Cycle-dependent sex differences in expression of membrane proteins involved in cerebrospinal fluid secretion at rat choroid plexus

BackgroundFemale sex is a known risk factor of brain disorders with raised intracranial pressure (ICP) and sex hormones have been suggested to alter cerebrospinal fluid (CSF) dynamics, thus impairing ICP regulation in CSF disorders such as idiopathic intracranial hypertension (IIH). The choroid plexus (CP) is the tissue producing CSF and it has been hypothesized that altered hormonal composition could affect the activity of transporters involved in CSF secretion, thus affecting ICP. Therefore, we aimed to investigate if expression of various transporters involved in CSF secretion at CP were different between males and females and between females in different estrous cycle states. Steroid levels in serum was also investigated.MethodsFemale and male rats were used to determine sex-differences in the genes encoding for the transporters Aqp1 and 4, NKCC1, NBCe2, NCBE; carbonic anhydrase enzymes II and III (CA), subunits of the Na+/K+-ATPase including Atp1a1, Atp1b1 and Fxyd1 at CP. The estrous cycle stage metestrus (MET) and estrous (ES) were determined before euthanasia. Serum and CP were collected and subjected to RT-qPCR analysis and western blots. Serum was used to measure steroid levels using liquid chromatography tandem mass spectrometry (LC–MS/MS).ResultsSignificant differences in gene expression and steroid levels between males and ES females were found, while no differences were found between male and MET females. During ES, expression of Aqp1 was lower (p < 0.01) and NKCC1 was higher in females compared to males. CAII was lower while CAIII was higher in ES females (p < 0.0001). Gene expression of Atp1a1 was lower in ES compared to male (p = 0.0008). Several of these choroidal genes were also significantly different in MET compared to females in ES. Differences in gene expression during the estrus cycle were correlated to serum level of steroid hormones. Protein expression of AQP1 (p = 0.008) and CAII (p = 0.035) was reduced in ES females compared to males.ConclusionsThis study demonstrates for the first time that expression at CP is sex-dependent and markedly affected by the estrous cycle in female rats. Further, expression was related to hormone levels in serum. This opens a completely new avenue for steroid regulation of the expression of CSF transporters and the close link to the understanding of CSF disorders such as IIH.

Evaluation of later timepoints for fixed-time artificial insemination of beef heifers and cows when using sex-sorted semen

Two experiments were designed to evaluate later timepoints for fixed-time artificial insemination (FTAI) of beef heifers and cows, with the hypothesis that use of a later timepoint would allow a greater proportion of animals to express estrus prior to FTAI and result in greater conception rates among estrous females inseminated with sex-sorted semen. In Experiment 1, estrus was synchronized for 1640 heifers using the 14 d CIDR-PG protocol: insertion of an intravaginal progesterone-releasing insert (CIDR; 1.38 g progesterone) on Day −33 and removal on Day −19, and administration of prostaglandin F2α (PG; 500 μg cloprostenol sodium) on Day −3. Heifers were inseminated at one of three FTAI timepoints: 66 h, 70 h, or 74 h after PG administration. In Experiment 2, estrus was synchronized for 414 beef cows using the 7 & 7 Synch protocol: administration of PG coincident with CIDR insertion on Day −17, gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin) on Day −10, and PG coincident with CIDR removal on Day −3. Cows were inseminated at one of two FTAI timepoints: 66 h or 72 h after PG administration. In both experiments, only animals that expressed estrus prior to FTAI were inseminated with sex-sorted semen. In Experiment 1, the proportion of heifers that expressed estrus prior to FTAI (66 h: 62 %; 70 h: 67 %; 74 h: 71 %) was greater when FTAI was performed at 74 h versus 66 h (P = 0.0097); however, conception rate of heifers that expressed estrus and were serviced with sex-sorted semen did not differ among treatments (P = 0.67; 66 h: 56 %; 70 h: 53 %; 74 h: 53 %). In Experiment 2, the proportion of cows expressing estrus prior to FTAI did not differ between treatments (P = 0.30; 66 h: 71 %; 72 h: 76 %). Additionally, conception rate of estrous cows inseminated with sex-sorted semen did not differ between treatments (P = 0.24; 66 h: 45 %; 72 h: 40 %). These results indicate that performing FTAI later following the 14 d CIDR-PG protocol increases the proportion of heifers that express estrus and are serviced with sex-sorted semen but does not improve conception rates. Later timing of FTAI following the 7 & 7 Synch protocol was not observed to increase the proportion of cows expressing estrus prior to FTAI or improve conception rates among estrous cows inseminated with sex-sorted semen. Together, these results provide further insight into optimal timing of FTAI when using sex-sorted semen.

292 Tandem Administration of Prostaglandin F2α and Gonadotropin-Releasing Hormone in Beef Heifers and Cows as a Convergent Presynchronization Method in the 7 &amp; 7 Synch Protocol

Abstract An experiment was designed to evaluate modifications to the 7 &amp; 7 synch protocol with the hypothesis that tandem administration of prostaglandin F2α (PG) and gonadotropin-releasing hormone (GnRH) during the presynchronization portion of the protocol would generate a convergent ovarian response among anestrous and estrous cycling females. Nulliparous (n = 153), primiparous (n = 92), and multiparous (n = 413) Angus-cross females across four locations were blocked based on parity and pre-treatment cyclicity status (presence or absence of a corpus luteum) as assessed via transrectal ovarian ultrasonography. Within block, females were randomly assigned to one of three treatments. Females assigned to the 7 &amp; 7 Synch treatment received an intravaginal progesterone-releasing insert (CIDR) and administration of PG on day 0, administration of GnRH on day 7, and administration of PG coincident with CIDR removal on day 14. Females assigned to 7 &amp; 7 Synch + G received the same treatment schedule with the modification that GnRH was administered in tandem with the PG on day 0. Females assigned to 7 &amp; 7 Synch + G + P received GnRH in tandem with PG on both day 0 and day 7 of the treatment schedule. Fixed-time artificial insemination (FTAI) was performed at 54 h after CIDR removal for nulliparous females and at 66 h for primiparous and multiparous females. Transrectal ovarian ultrasonography was performed on day 7 and day 14 to characterize the largest follicle diameter (LFD) as well as the presence/absence and number of corpora lutea (CL). Expression of estrus before FTAI was characterized in three locations using estrus detection patches (Estrotect. Approximately 75 to 90 days after FTAI, pregnancy status was determined via transrectal ultrasonography. Day 7 CL status was affected by treatment (P = 0.002), with a greater proportion of females presenting with CL on Day 7 when treated with the modified treatments (64%) as compared with the 7 &amp; 7 Synch treatment (31%). Day 14 LFD was affected by treatment (P = 0.002), with a larger average LFD among females treated with 7 &amp; 7 Synch + G + P (12.0 mm) as compared with 7 &amp; 7 Synch (11.4 mm) or 7 &amp; 7 + G (10.7 mm). Pregnancy rate to FTAI was affected by pre-treatment cyclicity status (P &amp;lt; 0.0001) and semen type (P = 0.0003) and tended to be affected by treatment (P = 0.09) with 7 &amp; 7 Synch + G + P tending to result in a greater proportion pregnant (58.86%) as compared with 7 &amp; 7 Synch (49.17%) and 7 &amp; 7 Synch + G (48.79%). Tandem administration of GnRH and PG on days 0 and 7 of the 7 &amp; 7 Synch protocol effectively generated a convergent ovarian response among anestrous and estrous cycling beef females and tended to result in increased pregnancy rates to FTAI.

Attraction of female house mice to male ultrasonic courtship vocalizations depends on their social experience and estrous stage.

Male house mice (Mus musculus) produce complex ultrasonic vocalizations (USVs), especially during courtship and mating. Playback experiments suggest that female attraction towards recordings of male USVs depends on their social experience, paternal exposure, and estrous stage. We conducted a playback experiment with wild-derived female house mice (M. musculus musculus) and compared their attraction to male USVs versus the same recording without USVs (background noise). We tested whether female attraction to USVs is influenced by the following factors: (1) social housing (two versus one female per cage); (2) neonatal paternal exposure (rearing females with versus without father); and (3) estrous stage. We found that females showed a significant attraction to male USVs but only when they were housed socially with another female. Individually housed females showed the opposite response. We found no evidence that pre-weaning exposure to a father influenced females' preferences, whereas estrous stage influenced females' attraction to male USVs: females not in estrus showed preferences towards male USVs, whereas estrous females did not. Finally, we found that individually housed females were more likely to be in sexually receptive estrous stages than those housed socially, and that attraction to male USVs was most pronounced amongst non-receptive females that were socially housed. Our findings indicate that the attraction of female mice to male USVs depends upon their social experience and estrous stage, though not paternal exposure. They contribute to the growing number of studies showing that social housing and estrous stage can influence the behavior of house mice and we show how such unreported variables can contribute to the replication crisis.

Effects of Loligo Squid Ink on Sexual Arousal Parameters in D-Galactose-Induced Aging Male Mice

Squid ink is known to contain many bioactive properties such as antioxidant, anticancer activity, antimicrobial activity, and anti-inflammatory activity. Through its antioxidant properties squid was suggested to have therapeutic potential for sexual function disorders. This study is an attempt to evaluate whether squid ink has therapeutic benefits against age-related decreases in sexual arousal in D-galactose-induced aging male mice. Four groups of male mice were treated as follows. Group-1 received only standar food but no D-galactose induction nor squid ink given. Group-2 received D-galactose induction but not squid ink. Group-3 and group-4 received D-galactose induction and squid ink at the dose of 40 and 100 ml/kg body weight respectively. After 35 days of treatment, the test mice were mated with estrous virgin females to determine their levels of sexual arousal. The results, Loligo squid ink extract at a dose of 100 ml/kg body weight significantly enhances sexual arousal parameter values in the D-galactose-induced aging mouse model. However, the recovery rate did not achieve nor surpassed the parameter values of sexual arousal in normal mice. It suggests that Loligo squid ink has the potential to prevent damage to sexual function in males but is less effective in restoring it.

Protective Effect of Vitis gracilis Wall (Vitaceae) Leaf Decoction on Sexual Vitality and Testis of Alloxan-Induced Diabetic Mice

Diabetes mellitus is profoundly associated with various detrimental outcomes including sexual dysfunction and infertility in males. On the other hand, a medicinal plant namely Vitis gracilis Wall (Vitaceae) has been used as a traditional medicine to enhance vitality. This present study aimed to investigate the protective effect of V. gracilis leaf decoction against diabetes-induced sexual dysfunction and testicle histopathology in adult male mice. The experiment was composed of five different groups namely the control (non-diabetic) group, the diabetes group (without any treatments), and the diabetes treated with V. gracilis decoction at the doses of 25, 50, and 100 g/L, respectively. In addition, the phytochemical constituents of leaf decoction were determined by using Ultra performance-liquid chromatography-mass spectroscopy (UPLC-MS). Our data demonstrated that, despite failing to improve blood glucose profile and body weight, V. gracilis leaf decoction sustained intense sexual behaviors including face and genital kissing, genital licking, and mount toward estrous females. Moreover, lower doses of decoction (25 and 50 g/L) attenuated the diabetes-induced reduction of testis weight and precluded malondialdehyde accumulation in the testicle tissue. The decoction at the lower doses also ameliorated histopathological alterations in the testis, particularly the wall thickness of tubulus seminiferous and the number of necrotic cells. V. gracilis decoction also improved hematological values including hemoglobin, red blood cell count and hematocrit level. In addition, UPLC-MS analysis revealed a total of 26 phytochemical compounds with seven predominant substances. In conclusion, leaf decoction of V. gracilis, particularly at lower doses but not at a higher dose, exerted a protective effect on sexual vitality, testicle tissue, and hematological value under diabetic condition. The beneficial effects of V. gracilis decoction might be associated with its various bioactive compounds. Therefore, V. gracilis leaves may be a future candidate as a potent natural drug for male sexual vitality and testicle protection against diabetes. &#x0D;

Estradiol receptors inhibit long-term potentiation in the dorsomedial striatum.

Estradiol, a female sex hormone and the predominant form of estrogen, has diverse effects throughout the brain including in learning and memory. Estradiol modulates several types of learning that depend on the dorsomedial striatum (DMS), a subregion of the basal ganglia involved in goal-directed learning, cued action-selection, and motor skills. A cellular basis of learning is synaptic plasticity, and the presence of extranuclear estradiol receptors ERα, ERβ, and G protein-coupled estrogen receptor (GPER) throughout the DMS suggests that estradiol may influence rapid cellular actions including those involved in plasticity. To test whether estradiol affects synaptic plasticity in the DMS, corticostriatal long-term potentiation (LTP) was induced using theta-burst stimulation in ex vivo brain slices from intact male and female C57BL/6 mice. Extracellular field recordings showed that female mice in the diestrus stage of the estrous cycle exhibited LTP similar to male mice, while female mice in estrus did not exhibit LTP. Furthermore, antagonists of ERα or GPER rescued LTP in estrus females and agonists of ERα or GPER reduced LTP in diestrus females. In males, activating ERα but not GPER reduced LTP. These results uncover an inhibitory action of estradiol receptors on cellular learning in the DMS and suggest a cellular mechanism underlying the impairment in certain types of DMS-based learning observed in the presence of high estradiol. Due to the dorsal striatum's role in drug addiction, these findings may provide a mechanism underlying an estradiol-mediated progression from goal-directed to habitual drug use.Significance StatementThis study examined the role of the female reproductive cycle and female sex hormones in synaptic plasticity, a cellular process that underlies learning behavior, in a brain region involved in goal-directed learning. Synaptic plasticity was similar between male mice and female mice in the low estradiol phase of the cycle. In contrast, female mice in a high estradiol phase of the cycle did not exhibit synaptic plasticity. The effect of estradiol was mediated by two of the three estradiol receptors found in the brain. The results have implications for the role of the female reproductive cycle in the development of drug addiction, which involves a progression from goal-directed learning to habit-based learning as drug use switches from recreational to compulsive.

Sexual stimulation of captive Iberian ibex bucks (Capra pyrenaica): Effect of male social rank on the response to estrous females

The aims were to determine if the contact with estrous females stimulates testosterone and cortisol secretion in Iberian ibex bucks during or out of the breeding season and if their social rank affects this response. Nine Iberian ibex bucks (Capra pyrenaica), were challenged with estrous does during two periods: winter-spring and autumn (three tests at each season, separated 10 days). Individual success index (SI) was calculated in both season. Bucks were exposed to an estrous doe, their sexual and agonistic behavior was recorded, testosterone and cortisol concentrations were measured. There were no sexual interactions toward the estrous doe in any test. Testosterone concentration was unrelated to the SI in any season and was not modified with the tests. Cortisol concentration was greater in the first than in the second and third tests in both seasons (winter-spring: 99.7 ± 15.7 ng/mL, 65.9 ± 9.4 ng/mL and 62.3 ± 10.1 ng/mL P < 0.0001; autumn: 110.1 ± 15.8 ng/mL, 79.2 ± 13.4 ng/mL, and 87.6 ± 13.5 ng/mL; P < 0.01). Iberian ibex bucks allocated in captivity did not display sexual behaviors nor modify the testosterone secretion, which was not modified by social hierarchy, after estrous doe exposition, during or out of the pre-rutting period.

Neopterin Levels in Bonobos Vary Seasonally and Reflect Symptomatic Respiratory Infections

As environmental changes exacerbate the threat coming from infectious diseases in wild mammal species, monitoring their health and gaining a better understanding of the immune functioning at the species level have become critically important. Neopterin is a biomarker of cell-mediated immune responses to intracellular infections. We investigated the variation of urinary neopterin (uNeo) levels of wild, habituated bonobos (Pan paniscus) in relation to individual and environmental factors. We used 309 urine samples collected between 2010 and 2018 at the LuiKotale field site, DRC. Based on current knowledge on zoo-housed conspecifics and closely related species, we predicted uNeo levels to increase (1) during infections, (2) with increasing age, (3) over the gestation period and in estrous females; and (4) to vary seasonally. Our results showed uNeo levels varied over a one-year period and increased in individuals showing respiratory symptoms. Contrary to chimpanzees, uNeo levels did not vary with age or female reproductive status, possibly due to our small sample size. Our study provides a baseline for a better understanding of bonobo’s immunocompetence in the context of socio-ecological pressures and for monitoring the health of wild populations.

Love is in the air: additional evidence for a volatile sex-attractant pheromone in snakes

Abstract Many taxa utilise chemosensation as their primary sensory modality and communicate with one another using pheromones. Sex-attractant pheromones facilitate mate location and provide information regarding the reproductive status of the potential mate. Snakes have adaptively radiated to many different habitats, some of which preclude the possibility of depositing a continuous terrestrial pheromone trail (e.g., arboreal, semi-aquatic). We suggest that volatile signals are present in species inhabiting such environments. The majority of investigations into snake sex-attractant pheromones have examined terrestrial species, largely ignoring non-terrestrial species and their signal modality. We examined the potential existence of terrestrial and volatile signals in the northern watersnake (Nerodia sipedon) with a modified Y-maze. During the mating period, males of this semi-aquatic species successfully trailed both the terrestrial and volatile signals from estrous females but did not successfully trail the terrestrial or volatile signals from non-estrous females and other males. Whether a single multimodal sex-attractant pheromone (or multiple sex-attractant pheromones) produced this result remains unknown. However, we feel future investigations into the volatile nature of sex-attractant pheromones in the Ophidia would prove fruitful; particularly for arboreal, aquatic, and semi-aquatic taxa providing a greater understanding of communication and mating system dynamics.

Sex-dependent effects of multiple acute concurrent stresses on memory: a role for hippocampal estrogens.

Memory disruption commonly follows chronic stress, whereas acute stressors are generally benign. However, acute traumas such as mass shootings or natural disasters—lasting minutes to hours and consisting of simultaneous physical, social, and emotional stresses—are increasingly recognized as significant risk factors for memory problems and PTSD. Our prior work has revealed that these complex stresses (concurrent multiple acute stresses: MAS) disrupt hippocampus-dependent memory in male rodents. In females, the impacts of MAS are estrous cycle-dependent: MAS impairs memory during early proestrus (high estrogens phase), whereas the memory of female mice stressed during estrus (low estrogens phase) is protected. Female memory impairments limited to high estrogens phases suggest that higher levels of estrogens are necessary for MAS to disrupt memory, supported by evidence that males have higher hippocampal estradiol than estrous females. To test the role of estrogens in stress-induced memory deficits, we blocked estrogen production using aromatase inhibitors. A week of blockade protected male and female mice from MAS-induced memory disturbances, suggesting that high levels of estrogens are required for stress-provoked memory impairments in both males and females. To directly quantify 17β-estradiol in murine hippocampus we employed both ELISA and mass spectrometry and identified significant confounders in both procedures. Taken together, the cross-cycle and aromatase studies in males and females support the role for high hippocampal estrogens in mediating the effect of complex acute stress on memory. Future studies focus on the receptors involved, the longevity of these effects, and their relation to PTSD-like behaviors in experimental models.

Individual variations and effects of birth facilities on the fecal microbiome of laboratory-bred marmosets (Callithrix jacchus) assessed by a longitudinal study.

Laboratory animals are used for scientific research in various fields. In recent years, there has been a concern that the gut microbiota may differ among laboratory animals, which may yield different results in different laboratories where in-vivo experiments are performed. Our knowledge of the gut microbiota of laboratory-reared common marmosets (Callithrix jacchus) is limited; thus, in this study, we analyzed the daily changes in fecal microbiome composition, individual variations, and effects of the birth facility in healthy female laboratory-reared marmosets, supplied by three vendors. We showed that the marmoset fecal microbiome varied among animals from the same vendor and among animals from different vendors (birth facility), with daily changes of approximately 37%. The fecal microbiome per vendor is characterized by alpha diversity and specific bacteria, with Bifidobacterium for vendor A, Phascolarctobacterium for vendor B, and Megamonas for vendor C. Furthermore, we found that plasma progesterone concentrations and estrous cycles were not correlated with daily fecal microbiome changes. In contrast, animals with an anovulatory cycle lacked Megamonas and Desulfovibrio bacteria compared to normal estrous females. This study suggests that the source of the animal, such as breeding and housing facilities, is important for in-vivo experiments on the marmoset gut microbiota.

Male African Elephant (Loxodonta africana) Behavioral Responses to Estrous Call Playbacks May Inform Conservation Management Tools.

Simple SummaryDuring annual periods of heightened sexual activity (musth), male African elephants expend a significant amount of energy communicating their reproductive status, as well as searching and competing for potential mates. To locate females, musth males may risk venturing outside protected areas and into landscapes shared with humans where conflict between wildlife and people can occur. Adverse interactions between elephants and people can be detrimental to human livelihoods, resulting in negative attitudes towards elephants and, in some cases, retaliatory killings. Interactions with aggressive musth males can also be life-threatening to community members who attempt to confront them. Mitigation strategies that effectively target the reproductive motivations of musth males may offer solutions as the human–elephant interface continues to expand. In this study, we build on earlier research showing that playbacks of female elephant reproductive calls, (i.e., estrous rumbles) can change the movement trajectory and behavior of male elephants in Etosha National Park, Namibia. Individuals belonging to three male groups were opportunistically subjected to playback experiments and evaluated based on their reaction intensity. Our results demonstrate that mature musth adults are more likely to change directions and approach the source of a female’s estrous call than mature, sexually-inactive adult elephants. We also show that post-dispersal young males that were not in musth also respond strongly to the stimulus. These findings support further exploration of mitigation solutions that incorporate elephant behavior, reproductive status, and context-specific vocalizations.Driven by reproductive motives, male African elephants (Loxodonta africana) in musth often expand their home ranges to locate estrous females. This extended range, coupled with heightened aggression often observed in musth males, can be particularly problematic in regions where human-modified landscapes and elephant territories increasingly overlap. Several mitigation tools have been tested to resolve a wide range of human–elephant conflicts with varying degrees of success due to geographical disparities and habituation. We present findings on the potential application of estrous call playbacks in manipulating the behavior and movement of male elephants non-invasively, particularly mature musth adults and younger post-dispersal males, in Etosha National Park. Estrous vocalizations were presented across 26 experimental trials to mature musth adults (n = 5), mature non-musth adults (n = 6), and non-musth males belonging to younger, post-dispersal age classes (n = 8), with behavioral responses scored on a gradient scale from 0–1. Both mature musth adults and younger non-musth elephants were significantly more likely to respond with the highest intensity by approaching the acoustic source compared to mature non-musth adults that avoided the call. However, younger males tested in the presence of an older, higher-ranking male tended to react with a lower intensity than those tested alone. This result likely demonstrates the influence of social hierarchy and associations on male elephant behavior. We also observed a significant increase in physiological response, measured by defecation rate, across all male groups in response to the estrous call playbacks. Our findings suggest that using estrous calls as acoustic deterrents may effectively and non-invasively aid in reducing tension at the human–elephant interface, depending on the age, social context, and reproductive status of the male elephant.

Neural and Hormonal Basis of Opposite-Sex Preference by Chemosensory Signals

In mammalian reproduction, sexually active males seek female conspecifics, while estrous females try to approach males. This sex-specific response tendency is called sexual preference. In small rodents, sexual preference cues are mainly chemosensory signals, including pheromones. In this article, we review the physiological mechanisms involved in sexual preference for opposite-sex chemosensory signals in well-studied laboratory rodents, mice, rats, and hamsters of both sexes, especially an overview of peripheral sensory receptors, and hormonal and central regulation. In the hormonal regulation section, we discuss potential rodent brain bisexuality, as it includes neural substrates controlling both masculine and feminine sexual preferences, i.e., masculine preference for female odors and the opposite. In the central regulation section, we show the substantial circuit regulating sexual preference and also the influence of sexual experience that innate attractants activate in the brain reward system to establish the learned attractant. Finally, we review the regulation of sexual preference by neuropeptides, oxytocin, vasopressin, and kisspeptin. Through this review, we clarified the contradictions and deficiencies in our current knowledge on the neuroendocrine regulation of sexual preference and sought to present problems requiring further study.

Natural reproductive performance is associated with captive management in adult male giant pandas

Through the implementation of giant panda ex situ conservation breeding programs, the giant panda has successfully been protected and has attained many conservation achievements. As of 2019, there were nearly 600 captive giant pandas worldwide, and the number of captive populations and the richness of genetic diversity have basically reached a self-sustainable state. However, to date, most captive adult male giant pandas do not mate naturally, and the reason is unclear, which has serious implications for implementation of the reintroduction training program of captive giant pandas. We used a combination of methods evaluating life history traits, behavioral observation, and bioinformatics statistical analysis and conducted comprehensive research on the factors that affected the natural mating success rates of captive adult giant pandas. The results showed that the management mode of singleton and parent rearing during cub development and mixed male and female group housing during the stage of subadult learning skills and experience could effectively improve the natural reproduction success rate of captive adult male giant pandas. Using odor stimulation during the mating period could change the courtship behavior of adult giant pandas in captivity, as males, when courting estrous females, behaved in a way that did not lead to successful mating. Applying these results to the breeding management and mating strategies of captive male giant pandas could not only help improve appropriate reproductive behavior and subsequently increase reproductive performance but also may provide more candidates for China's giant panda reintroduction programs.

The physiological reaction of Siberian hamsters (Phodopus sungorus, Cricetidae) to chemical signals of perspective mating partners before and during courtship.

ABSTRACTIn this investigation we assessed the physiological reaction of hamsters in response to chemical signals from potential sexual partners, and also after a private meeting with them, which allowed us to ascertain the type of mating system for this species. The reception of olfactory signals led to an increase in peroxidase activity in the blood for both sexes, indicative of activity of a non-specific line of immune defense in recipients. The increase in blood cortisol level in response to the chemical signals of a partner was only observed in females. Males spent more time near samples of estrous females, with elevated levels of cortisol in the urine. In olfactory tests, an hour after grouping all the individuals in pairs there was a significant increase in blood peroxidase activity, which indicates the reaction of a non-specific link in the immune system of partners. This increase was greater in the pairs with a mutual preference. Females from these pairs demonstrated a substantial decrease in stress hormone levels in the plasma after an hour of mating in comparison to females prior to mating, and in non-preferred coupling.

Urine from domesticated male goats (Capra hircus) provides attractive olfactory cues to estrous females

During the breeding season, the male goat urinates onto his face, beard, and front legs in a behavior known as self-enurination (SE). Whereas it has been suggested that the behavior may be used by the buck to present chemical signals in the urine to attract estrous does for mating, this hypothesis lacks empirical evidence. Two experiments were conducted to determine if estrous female goats (does) are attracted to male goat (buck) urine and if there is a difference in attractivity of buck urine emitted during SE versus ordinarily emitted urine. In addition, the ability of androgens to activate the attractive chemical signals in buck urine was investigated in experiment 2. In the first experiment, a 5-minute preference test allowed estrous does (n = 16) to choose between ovariectomized (OVX) does that had either buck SE urine or wether (prepubertally castrated male goat) urine applied to their coats. The does preferred buck SE urine-treated OVX does over wether urine-treated OVX does (P < 0.05). In the second experiment, recycling fountains were used to present urine in a continuous stream. The urine choices were as follows: buck SE vs. wether; dihydrotestosterone propionate (DHTP)-treated wether vs. estradiol benzoate (EB)-treated wether; and buck SE vs. buck. Estrous does (n = 10) were subjected to a 5-minute preference test. The does chose buck SE urine over wether urine, DHTP-treated wether urine over EB-treated wether urine, and buck urine over buck SE urine (P < 0.05). In general, estrous females preferred urine from bucks over urine from wethers.

Ecological and reproductive drivers of fission-fusion dynamics in chimpanzees (Pan troglodytes schweinfurthii) inhabiting a montane forest

In species with flexible grouping dynamics (i.e., fission-fusion), party (or subgroup) size is often shaped by available resources. Food resources are thought to limit party size in a range of mammalian species, reflecting a strategy of reducing feeding competition. In montane habitats, where food is highly seasonal, we may expect to see strong effects of ecological constraints on party size. In the montane forest of Nyungwe National Park, Rwanda, we quantified changes in chimpanzee (Pan troglodytes schweinfurthii) party size. We used path analysis to analyze the direct and indirect effects of (i) ecological variables and (ii) a reproductive variable (estrous females) on party size. Our path analysis adds precision and directionality to the hypothesis that food availability and estrous females influence party size. We found that the presence of estrous females had the strongest effect on party size. Interestingly, the availability and distribution of important and preferred fruits did not directly influence party size but did influence the presence of estrous females. These findings indicate that fruit distribution may be the ecological precondition that attracts estrous females, which is the main driver of larger parties. Party size was, however, positively correlated with patch size, indicating that specific fruit species may be of particular importance to the ecology of these chimpanzees. In montane habitats with lower fruit tree density and diversity than lowland sites, it may be expected that ecological factors play a more important role in fission-fusion grouping patterns than reproductive factors. This is because the cost of competition for food among group members may be higher in a more resource-limited (montane) environment. We investigated the ecological and reproductive factors that influence grouping patterns of chimpanzees in a montane forest that encompasses the upper limit of this species’ altitudinal range. Our results showed that the presence of estrous females had the strongest influence on party size. These results have implications for evaluating ecological and reproductive drivers of chimpanzee party size across differing habitats.

Differential effects of progesterone on social recognition and the avoidance of pathogen threat by female mice

Although pathogen threat affects social and sexual responses across species, relatively little is known about the underlying neuroendocrine mechanisms. Progesterone has been speculated to be involved in the mediation of pathogen disgust in women, though with mixed experimental support. Here we considered the effects of acute progesterone on the disgust-like avoidance responses of female mice to pathogen threat. Estrous female mice discriminated and avoided the urinary and associated odors of males subclinically infected with the murine nematode parasite, Heligmosomoides polygyrus. These avoidance responses were not significantly affected by pre-treatment with progesterone. Likewise, brief (1 min) exposure to the odors of infected males attenuated the subsequent responses of females to the odors of the normally preferred unfamiliar males and enhanced their preferences for familiar males. Neither progesterone nor allopregnanolone, a central neurosteroid metabolite of progesterone, had any significant effects on the avoidance of unfamiliar males elicited by pre-exposure to a parasitized male. Progesterone and allopregnanolone, did, however, significantly attenuate the typical preferences of estrous females for unfamiliar uninfected males, suggestive of effects on social recognition. These findings with mice indicate that progesterone may have minimal effects on the responses to specific parasite threat and the expression of pathogen disgust but may influence more general social recognition and preferences.