Species-specific patterns in fecal glucocorticoid and androgen levels in zoo-living orangutans (Pongo spp.)

In contrast to most primate species, including the other great apes, orangutans maintain a fission-fusion social system in the wild without being part of a stable community. In zoos, however, they are kept in permanent groups, usually consisting of one adult male and several females. In zoo orangutans, we predict higher levels of glucocorticoids and androgens in the Bornean species compared to its congener from Sumatra, due to the much more solitary lifestyle of Bornean orangutans and the apparent higher frequency of male aggression directed towards females in this species in the wild. To compare hormone levels of the two orangutan species, we validated a fecal glucocorticoid and a fecal androgen assay. Subsequently, fecal samples from a total of 73 female and 38 male orangutans housed in 29 European zoos were analyzed to investigate the effect of species, social group size, age and (for female glucocorticoid levels) reproductive state and the presence of adult males on fecal hormone metabolite concentrations. The results of linear mixed effect models indicate that both male and female Bornean orangutans show a steeper increase in glucocorticoid levels with increasing group size than Sumatran orangutans. We therefore conclude that Sumatran zoo orangutans are better able to adjust to social housing conditions than their Bornean congeners. In addition, our analyses reveal higher glucocorticoid levels in lactating females of both species compared to non-lactating and juvenile females. Concerning androgen levels in males, our analyses revealed significantly higher concentrations in Bornean than Sumatran orangutans. These differences in both glucocorticoid and androgen output between the two species of orangutan are presumably linked to ecological and behavioral differences and could possibly be attributed to phenotypic plasticity. However, given that we found interspecific differences in hormone excretion in captivity, where both species live under very similar conditions, we conclude that this variation has a genetic basis.     

Patterns of testicular activity in captive and wild Canada lynx (Lynx canadensis)

Canada lynx are listed as a threatened species in the contiguous US. Understanding the reproductive characteristics (i.e., mating system, behavior, physiology) of a species is useful for ensuring effective in situ and ex situ management plans. The goal of this study was to describe patterns of androgen expression in both captive and wild male Canada lynx using fecal hormone metabolite analysis. Among captive lynx, juvenile and castrated males had lower concentrations of fecal androgens (fA) than intact males, thereby demonstrating that the assay detects biologically meaningful differences in testicular activity. We found that captive males in general had much higher fA levels than wild males. All males showed strong seasonal variation in fA concentrations, with significantly higher levels being expressed during the breeding season (February and March) than during the non-breeding season. Among captive males, variation in seasonal fA levels did not correlate with latitude. Finally, males housed with intact cage-mates (either male or female) had significantly higher fA levels than males housed alone or with a neutered cage-mate.     

Non-invasive monitoring of fecal androgens in spotted hyenas (Crocuta crocuta)

Spotted hyenas (Crocuta crocuta) exhibit an array of behavioral and morphological characteristics that set them apart from other mammals: females are heavier and more aggressive than males, and females have external genitalia that closely resemble those of the male. Because androgenic hormones might mediate the expression of these traits, androgens are of great interest in this species. Past work on circulating androgens in wild hyenas has been limited, in part because of small sample sizes. In this study we validated a non-invasive method of monitoring variation in androgens by measuring total androgen metabolites in the feces of wild and captive spotted hyenas with an enzyme immunoassay. HPLC analysis revealed multiple immunoreactive androgen metabolites in fecal extracts from both males and females. LHRH challenge in three male and two female hyenas in captivity caused an increase in fecal androgens one to three days after LHRH injection. Furthermore, presence of bone in the diet did not affect fecal androgen concentrations in captive female hyenas. In wild spotted hyenas, time of day of fecal deposition, time elapsed between deposition and freezing of the sample, and time elapsed between freezing and extraction did not systematically affect fecal androgen concentrations. Finally, in wild hyenas, fecal androgen patterns mirrored plasma testosterone patterns in that adult immigrant males had higher concentrations than adult natal males, and pregnant females had higher concentrations than lactating females. These methods can therefore be used in future studies addressing relationships among fecal androgens, social status, reproductive state, and behavior in spotted hyenas.     

Analysis of fecal glucocorticoids in the North Atlantic right whale (Eubalaena glacialis)

Very little is known about the endocrinology of the baleen whales. The highly endangered North Atlantic right whale (NARW; Eubalaena glacialis) is a good model species, because most NARW individuals are photo-identified with known histories. We used an 125I corticosterone assay, shown to reliably measure cortisol metabolites, to determine glucocorticoid metabolite concentrations in 177 NARW fecal samples collected between 1999-2004 in the Bay of Fundy, Canada. Fecal glucocorticoid metabolite concentrations varied significantly with sex and reproductive category, being highest in pregnant females (mean +/-SE: 238.14+/-74.37 ng/g) and mature males (71.6+/-11.36), intermediate in lactating females (39.33+/-5.82), and lower in non-reproducing females (23.11+/-4.25) and immature males (34.33+/-5.01) and females (14.0+/-0.41). One case also suggests that glucocorticoids rise markedly in response to severe entanglement in fishing lines. Whales with fecal glucocorticoid content over 100 ng/g (termed "high-cort" samples) were rare, and included most pregnant females, some mature males, a fatally entangled whale, and several very young animals. Glucocorticoid concentrations were highly correlated with androgen concentrations in males and pregnant females. We analyzed the elution profiles of glucocorticoid and androgen metabolites in 13 samples with high-performance liquid chromatography (HPLC) to determine the extent to which androgen metabolites cross-react with our glucocorticoid assay. Males, pregnant females, non-pregnant females, and "high-cort" whales each had distinctly different immunoreactive HPLC profiles of glucocorticoid and androgen metabolites. A major glucocorticoid metabolite was prominent in all "high-cort" whales including the fatally entangled whale. The major fecal androgen was not testosterone but was instead a more nonpolar steroid (possibly dihydrotestosterone), which may be diagnostic of males. Androgen metabolites showed only minor cross-reactivity to our glucocorticoid assay, having a slight influence on glucocorticoid results in particular individuals. We conclude that fecal glucocorticoid analysis appears to be a useful measure of adrenal activity and reproductive condition for NARW.     

Annual cycles of urinary reproductive steroid concentrations in wild and captive endangered Fijian ground frogs (Platymantis vitiana)

Annual cycles of reproductive steroid metabolites were measured in urine collected from free-living and captive tropical endangered Fijian ground frogs (Platymantis vitiana) a terrestrial breeding. Free-living frogs were sampled on Viwa Island, Fiji and captive frogs were maintained in an outdoor enclosure in Suva, Fiji. Urinary estrone, progesterone and testosterone metabolite concentrations increased in male and female frogs after hCG challenges, with clear peaks in steroid concentrations 2 or 3 days after the challenges. There were annual cycles of testosterone metabolites in wild and captive males, and of estrone and progesterone metabolites in wild and captive females. Peaks of steroid concentrations in the wet season corresponded with periods of mating and egg laying in females in December and January. Steroid concentrations declined in January and February when maximum egg sizes in females were also declining. Body weights of wild male and vitellogenic female frogs showed annual cycles. Body weights of non-vitellogenic female frogs varied significantly between months, although there was no clear pattern of annual changes. Body weights of the 3 captive male frogs and 4 captive female frogs were similar to those of the wild frogs. Estrone metabolites were 80% successful in identifying non-vitellogenic females from males. The results suggest that the Fijian ground frog is a seasonal breeder with an annual gonadal cycle, and this species is likely to be photoperiodic. Urinary steroid measurements can provide useful information on reproductive cycles in endangered amphibians.     

Longitudinal gonadal steroid excretion in free-living male and female meerkats (Suricata suricatta)

Slender-tailed meerkats (Suricata suricatta) are small, diurnal, cooperatively breeding mongooses of the family Herpestidae. A prerequisite to fully understanding the mating system of meerkats is the development of a normative reproductive-endocrine database. This study examined longitudinal gonadal steroid excretion in all adult and juvenile individuals of both sexes within a social group of free-living meerkats sampled across an entire breeding season. The specific objectives of this study were to (1) validate noninvasive (fecal and urinary) gonadal steroid hormone monitoring techniques in male (testosterone) and female (estrogens, progestagens) meerkats; (2) test the feasibility of using these noninvasive methods under field conditions; (3) characterize the endocrine correlates associated with the female reproductive cycle, including estrus, gestation, and postpartum estrus; (4) examine longitudinal androgen excretion in males; and (5) determine whether social status (i.e., dominant versus subordinate) affected gonadal steroid excretion. In females, the results demonstrated the physiological validity of noninvasive monitoring in meerkats by corresponding excretory hormone concentrations to major reproductive events (i.e., estrous, pregnancy, parturition). Hormone excretory patterns during estrous intervals suggested possible mechanisms whereby reproductive suppression may operate in female meerkats. In males, androgen excretion did not correspond to changes in reproductive and aggressive behaviors, suggesting that dominance, and hence breeding access to females, was not regulated strictly by gonadal steroid production. The consistency in androgen excretion among male meerkats indicated that reproductive suppression may be mediated by behavioral (i.e., intermale aggression) rather than physiological (i.e., depressed spermatogenesis) mechanisms.     

Glucocorticoid stress hormones and the effect of predation risk on elk reproduction

Predators affect prey demography through direct predation and through the costs of antipredator behavioral responses, or risk effects. Experiments have shown that risk effects can comprise a substantial proportion of a predator''s total effect on prey dynamics, but we know little about their strength in wild populations, or the physiological mechanisms that mediate them. When wolves are present, elk alter their grouping patterns, vigilance, foraging behavior, habitat selection, and diet. These responses are associated with decreased progesterone levels, decreased calf production, and reduced population size [Creel S, Christianson D, Liley S, Winnie JA (2007) Science 315:960]. Two general mechanisms for the effect of predation risk on reproduction have been proposed: the predation stress hypothesis and the predator-sensitive-food hypothesis. Here, we used enzyme immunoassay to measure fecal glucocorticoid metabolite concentrations for 1,205 samples collected from 4 elk populations over 4 winters to test the hypothesis that the effect of predation risk on elk reproduction is mediated by chronic stress. Across populations and years, fecal glucocorticoid concentrations were not related to predator-prey ratios, progesterone concentrations or calf-cow ratios. Overall, the effect of wolf presence on elk reproduction is better explained by changes in foraging patterns that carry nutritional costs than by changes in glucocorticoid concentrations.     

Seasonal and population variation in male testosterone levels in breeding orange-crowned warblers (Vermivora celata)

Comparative hormone studies can reveal how physiology underlies life history variation. Here, we examined seasonal variation in plasma testosterone concentration between populations of male orange-crowned warblers (Vermivora celata) breeding in Fairbanks, Alaska (V. c. celata) and on Santa Catalina Island, California (V. c. sordida). These populations face different ecological constraints and exhibit different life histories. Alaska birds have a short breeding season, low annual adult survival, and high reproductive rates. In contrast, Catalina Island birds exhibit high adult survival and low reproductive rates despite having a long breeding season. We examined seasonal variation in male testosterone concentrations as a potential mechanism underlying differences in male reproductive strategies between populations. From 2006 to 2008, we sampled males during the pre-incubation, incubation, and nestling stages. Alaska males exhibited a seasonal testosterone pattern typical of northern passerines: testosterone levels were high during pre-incubation and declined during incubation to low levels during nestling provisioning. Testosterone concentrations in Catalina Island males, however, did not vary consistently with breeding stage, remained elevated throughout the breeding season, and were higher than in Alaska males during the nestling stage. We hypothesize that in Alaska, where short seasons and high adult mortality limit breeding opportunities, the seasonal testosterone pattern facilitates high mating effort prior to incubation, but high parental investment during the nestling stage. On Catalina Island, elevated testosterone levels may reflect the extended mating opportunities and high population density facing males in this population. Our results suggest that population variation in seasonal testosterone patterns in orange-crowned warblers may be a function of differences in life history strategy and the social environment.     

Seasonal variation of plasma testosterone in a wild population of male Eastern quoll, Dasyurus viverrinus (Marsupialia: Dasyuridae), from Tasmania

In the wild, male Eastern quoll, Dasyurus viverrinus, exhibit a synchronized sequence of increase and decrease in plasma testosterone concentration, body weight, and scrotal size in response to the breeding season. Basal concentrations of peripheral testosterone between 0.5 and 0.7 ng/ml circulate during the nonbreeding period. By April, 2 months prior to breeding, testosterone concentrations increased to around 1.6 ng/ml. This increase may reflect a resurgence in testicular activity, as scrotal size is maximal at this time. A synchronized testosterone peak of 5.0 ng/ml was observed during the mating period in early June. With the cessation of breeding, testosterone concentrations in resident males returned to basal levels by July; however, transient males maintained elevated levels for slightly longer. The timing of breeding and the short duration of the testosterone breeding peak enable the quoll to intensify its reproductive effort.     

Are hotshots always hot? A longitudinal study of hormones, behavior, and reproductive success in male marine iguanas

Polygynous lek-mating systems are characterized by high reproductive skew, with a small number of males gaining a disproportionate share of copulations. In lekking species, where female choice drives male mating success and patterns of reproductive skew, female preferences for ‘good genes’ should lead to preferred males having high reproductive success in all years. Here we investigate whether these ‘hotshot’ males have steroid hormone patterns that are consistent over time (between two mating seasons), and whether hormone levels consistently predict display behavior. We test these questions in the Galápagos marine iguana (Amblyrhynchus cristatus), a lekking vertebrate with high male reproductive skew. We found that male mating success and testosterone levels were not consistent across years. The most successful males showed an inverse relationship in copulation success between years. Similarly, territorial males that had high testosterone in one year had low levels in the next. Across years, testosterone was strongly associated with head-bob display, suggesting that this steroid plays a key role in mate attraction. These results suggest that female marine iguanas are not choosing the same ‘hotshot’ males in every year, but instead base their reproductive decisions on male behavioral traits that are hormonally mediated and variable across years. By using testosterone to regulate their costly display behaviors male marine iguanas appear to have a mechanism that allows them to adjust their reproductive effort depending on extrinsic and/or intrinsic factors.     

Seasonal changes in cortisol and progesterone secretion in Common hamsters

In this study, we investigated endocrine factors and behaviour in free-living Common hamsters (Cricetus cricetus) during reproductive and non-reproductive periods of the annual cycle. We applied a non-invasive method to gain information on seasonal changes in adrenocortical activity in male and female hamsters by analysing faecal glucocorticoid metabolite concentrations (FCM). In addition, plasma progesterone concentrations were monitored in females throughout the non-hibernation season. The animals were live-trapped from spring emergence until the onset of hibernation in autumn. Reproductive status was determined at capture and blood and faecal samples were collected. During behavioural observations, agonistic and sexual interactions were recorded. FCM concentrations were significantly higher in males than in females during the reproductive period. In males, a pronounced increase in FCM during the reproductive period coincided with high frequencies of intrasexual aggression. In females, FCM levels remained relatively constant. Aggressive behaviour in females increased during the reproductive period, but was much less frequent than in males. Females, which successfully raised a second litter after a postpartum oestrus and concurrent lactation and gestation had lower FCM levels than individuals, which lost their second litter after parturition. As expected, plasma progesterone concentrations were low before and after the reproductive period. During gestation, levels peaked and remained elevated during lactation. The results of this field study provide insight in critical periods associated with reproduction in male and female Common hamsters.     

The effects of combined aromatase inhibitor and anti-androgen on male territorial aggression in a tropical population of rufous-collared sparrows, Zonotrichia capensis

Territorial aggression, exhibited by male vertebrates in a reproductive context, is generally thought to be mediated by elevated levels of the gonadal steroid hormone testosterone. Rufous-collared sparrows from Papallacta, Ecuador are only aggressive during the breeding season when plasma testosterone concentrations are elevated. However, previous experiments have determined that during the breeding season testosterone does not increase in response to territorial challenges and testosterone implants do not make males more aggressive. This relationship between testosterone and aggression is different from closely related northern latitude species. We conducted another experiment investigating the role of testosterone in mediating territorial aggression, during the breeding season, in male rufous-collared sparrows. We predicted that blocking the actions of the testosterone would suppress aggression in response to territorial challenges. During the early breeding season males were captured using a simulated territorial intrusion and there was no relationship between time to capture and plasma testosterone, dihydrotestosterone, and corticosterone concentrations. Individual males were then implanted with both the aromatase inhibitor ATD and the anti-androgen Flutamide or empty implants as a control. After one week, birds were challenged with a simulated territorial intrusion and the aggressive responses measured. There were no differences in individual behavioral responses (number of songs, flights, closest approach, or time within 5 m) or overall aggression between the two groups. Androgen levels were elevated, post-implant, in the experimental group suggesting that the treatment was successful by blocking the negative feedback system. We conclude that pharmacologically inhibiting testosterone during the breeding season does not affect territorial aggression in these birds.     

Monitoring testicular activity of male Eurasian (Lynx lynx) and Iberian (Lynx pardinus) lynx by fecal testosterone metabolite measurement

The aim of the present study was to identify relevant fecal testosterone metabolites in the Eurasian lynx (Lynx lynx) using HPLC analysis and to evaluate the specificity of two testosterone immunoassays against these fecal metabolites. Finally, fecal hormone analysis was used to characterize seasonal reproductive activity of captive male Eurasian and Iberian (Lynx pardinus) lynx. Fecal samples from a male Eurasian lynx who received an i.v. injection of [3H]testosterone were subjected to HPLC analysis. All HPLC fractions were analyzed for radioactivity and androgen content by two testosterone immune assays (EIA and Testosterone-Immulite kits, DPC Biermann, Germany). Furthermore, fecal samples from four Eurasian lynx males (n=174) and three Iberian lynx (n=52) were collected throughout the year and fecal testosterone metabolites were determined with Testosterone-Immulite assay. HPLC separation of radiolabeled Eurasian lynx fecal extract indicated that the majority of testosterone metabolites are substances with a higher polarity than testosterone. Only minor proportion of radioactivity co-eluted with authentic testosterone and dihydrotestosterone. Enzymatic hydrolysis and solvolysis of the fecal extract were insufficient to liberate testosterone. After solvolysis relatively more activity was eluated the position of DHT, but the majority of metabolites remained unaffected. The EIA measured substantial amount of immunoreactivity, which corresponded with two radioactive peaks. Additionally, both immunoassays recognized two metabolites, which were only minor components according to their radioactivity. The Immulite assay was able to recognize a metabolite at the position of dihydrotestosterone. HPLC separation of Iberian lynx feces extracts revealed a similar metabolite pattern determined by EIA that were typical for Eurasian lynx fecal extracts. Simultaneous analyses of fecal samples with both testosterone assays provided comparative results for both lynx species (Eurasian lynx, r2=0.488; p<0.001; Iberian lynx, r2=0.85, p<0.0001). Thus, seasonal reproductive activity of male Eurasian lynx was demonstrated also by Immulite -assay, confirming high testosterone levels during breeding season in March/April as previously documented with EIA. Preliminary results on testosterone measurements in Iberian lynx feces confirmed the suitability of the applied Immulite test in this highly endangered species.     

Urinary hormone metabolites identify sex and imply unexpected winter breeding in an endangered, subterranean-nesting frog

Urinary hormone analysis has proved accurate for identifying sex and breeding periods in dimorphic amphibians with known reproductive cycles. We examined whether these techniques could provide this much needed information for a monomorphic anuran with an unconfirmed mating season in the wild. We analysed urinary estrone conjugate, testosterone, and progesterone metabolites to infer the time of breeding and to identify sex in the endangered Maud Island frog, Leiopelma pakeka. Testosterone metabolites in males and estrone and progesterone metabolites in females were at their peak during winter for both wild and captive frogs. These urinary metabolite patterns were consistent with the high proportion of females exhibiting enlarged ovarian follicles in winter months. Sex identification based on urinary estrone metabolite levels was 94% correct in this monomorphic species, in which the sexes overlap in snout-to-vent length (SVL) for over half of their adult size range and in which no other sexually dimorphic trait is known. The seasonal profiles imply unexpected winter or early spring breeding in L. pakeka. Overall, these results demonstrate use of urinary hormone metabolites for reproductive monitoring and sex identification in one of the world's most threatened and evolutionarily distinct amphibians.     

Annual cycles of steroid hormone production, gonad development, and reproductive behavior in the Atlantic stingray

The mating season of the Atlantic stingray (Dasyatis sabina), which begins in August and continues through April, is the longest documented for any elasmobranch fish. Despite this protracted mating period, female stingrays ovulate synchronously at the end of the mating season and there is no evidence for sperm storage by females. Thus, the proximate causal factors and ultimate function of this extended preovulatory mating are unknown. Annual cycles of the gonadal steroids testosterone (T), dihydrotestosterone (DHT), 17beta-estradiol (E2), and progesterone (P4) were measured for 26 months in a wild estuarine population of Atlantic stingrays to test for associations with their reproductive biology, gametogenesis, and sexual behavior. Serum androgen levels in males showed four phases within an annual cycle: (1) androgen suppression between reproductive seasons (April-July), (2) primary androgen increase during the onset of spermatocyte development (August-October), (3) androgen decrease following maximum testis growth and spermatocyte development (November-December), and (4) secondary androgen increase during the peak of sperm maturation (January-March). Increases in male E2 and P4 were correlated with spermatocyte/spermatocyst formation, maximum testis weight, and the primary (but not secondary) androgen surge. We propose that the production of male androgens across the full seven-month preovulatory mating period promotes their aggressive reproductive behavior and drives the protracted mating season of this species. In females, serum T and DHT showed relatively brief increases near ovulation, whereas E2 and P4 showed brief increases near both ovulation and parturition. The increase in female androgens near ovulation may increase female aggression when they are impregnable by courting males and enhance their choice of mates. This estuary sample population shows higher absolute steroid levels and distinct differences in temporal cycles compared to another Florida fresh water lake population, but the cause and significance of these differences are unknown. Experiments are needed to confirm that the aggressive and protracted mating behavior is the result of prolonged male androgen production and to determine whether the sustained preovulatory mating serves some function related to female reproduction.     

Endocrine changes in dasyurid marsupials with differing mortality patterns

A comparison was made between the breeding-related endocrine changes in two species of dasyurid marsupial (Antechinus swainsonii and A. flavipes), which exhibit a catastrophic male mortality after a brief mating period; and those of another dasyurid species (Sminthopsis crassicaudata), the males of which survive an extended breeding period. In the males of both Antechinus species, the mating period was preceded by a rapid rinse in plasma androgen concentration and accompanied by a marked fall in plasma corticosteroid-binding globulin (CBG) concentration, to less than the total glucocorticoid concentration, which itself rose. As a consequence plasma free glucocorticoid concentration rose approximately 10-fold just before the males disappeared from the populations. Severe hemorrhagic ulceration of the upper digestive tract was consistently found soon after capture near the time of mating. In females, CBG concentration was always well in excess of total glucocorticoid concentration and free glucocorticoid concentration remained low. There was a significant negative correlation between plasma androgen and CBG concentrations in male Antechinus species from the natural populations. In laboratory-held castrate male A. swainsonii, injection of either testosterone or dihydrotestosterone caused a dose-related fall in CBG. In contrast to the above, the CBG concentration was always well in excess of total glucocorticoid concentration in the plasma of male S. crassicaudata and there was no evidence of interaction between plasma androgen and CBG concentration. These findings support the hypothesis that, in those species with a breeding-related mortality of males, an androgen-dependent fall in plasma CBG concentration and a stressful mating period result in death from adrenocortical suppression of the immune and inflammatory responses.     

Seasonal changes in steroid hormone profiles, body weight, semen quality, and the reproductive tract in captive African wild dogs (Lycaon pictus) in South Africa

Characterization of reproductive seasonality in the African wild dog (Lycaon pictus) could assist reintroduction programs. Male wild dogs (n=14) were assessed quarterly (January, mid-summer; April, late summer; August, late winter; November, early summer) for serum testosterone, body weight, testicular and prostatic volume, preputial gland measurement, and ejaculate characteristics. Bi-monthly fecal samples were collected from male (n=11) and female (n=4) wild dogs for analysis of fecal androgens and progestagens. Fecal androgens were higher in early summer (246.4±14.5ng/g) than in early winter (218.6±13.4ng/g). Serum testosterone was higher in mid-summer (1.4±0.3ng/ml) than in late winter (0.7±0.1ng/ml). Number of spermatozoa per ejaculate was greatest in late summer (301.4±39.3×10(6)). Other semen parameters peaked in mid-summer (pH: 7.4; progressive motility: 85.0±0.1%; live spermatozoa: 81.0±16%; normal morphology: 71.5±8.2%). Total testicular and prostatic volume were greater during summer (testicular: 36.7±4.2cm(3); prostatic: 12.0±1.9cm(3)) than winter (testicular: 25.2±1.9cm(3); prostatic: 5.8±0.8cm(3)). Preputial pendulance also was greater in summer (7.1±0.5cm; n=9) than winter (5.9±0.2cm). Baseline fecal progestagen metabolites were 6.2±2.5μg/g and peak fecal progestagen metabolites were 14.7±2.8μg/g. Copulations resulting in pregnancies (n=2) occurred in late summer and gestation was 71days. Female wild dogs were seasonally monoestrous with mating in summer and winter. In conclusion, wild dogs are reproductively seasonal with improvement in male reproductive variables during summer and a bi-phasic seasonal pattern to female receptivity.     

High levels of LH and testosterone in a tropical seabird with an elaborate courtship display

For birds breeding in temperate areas, territoriality and courtship co-occur during spring and are mirrored by elevated plasma levels of luteinizing hormone (LH) and testosterone. By contrast, several tropical species show no major changes in LH and testosterone throughout the year and plasma levels are often low. This study describes changes in body condition, LH and testosterone levels throughout breeding in a tropical seabird, the magnificent frigatebird (Fregata magnificens). Although bi-parental care is the rule in frigatebirds, these seabirds are unique among seabirds in having a lek-like mating system where males perform an elaborate courtship display during which an extravagant sexual ornament (gular pouch) is inflated. Body condition peaked during the displaying stage in males and declined gradually in both sexes, being the lowest during chick-rearing. LH and testosterone titers were the highest in displaying males with a fully inflated gular pouch (means: 23.6 ng/ml for LH and 6.2 ng/ml for testosterone) and remained low (means: 3.8 ng/ml for LH and 0.3 ng/ml for testosterone) during incubation and chick-rearing in both sexes. Body condition was positively related to testosterone levels in displaying males. In male frigatebirds, high levels of testosterone are not associated with aggression but are probably required to display the inflated gular pouch and to perform an elaborate courtship display. Because males invest in incubation and chick-rearing, testosterone has to return to low levels, to permit parental care. This hormonal pattern differs greatly with that of the few tropical seabirds studied so far and is probably related to the unique reproductive strategy of frigatebirds.     

Patterns of ovarian and luteal activity in captive and wild Canada lynx (Lynx canadensis)

Canada lynx face some unique breeding restrictions, which may have implications for population viability and captive management. The goal of this study was to improve our understanding of basic reproductive physiology in Canada lynx. Using fecal hormone metabolite analysis, we established normative patterns of fecal estrogen (fE) and progestagen (fP) expression in captive and wild female Canada lynx. Our results indicate that Canada lynx have persistent corpora lutea, which underlie their uncharacteristic fP profiles compared to other felids. Thus, fP are not useful for diagnosing pregnancy in Canada lynx. We also found that Canada lynx are capable of ovulating spontaneously. Captive females had higher concentrations of fE and fP than wild females. Both populations exhibit a seasonal increase in ovarian activity (as measured by fE) between February and April. Finally, there was evidence of ovarian suppression when females were housed together.     

Failure of glucocorticoid feedback in males of a population of small marsupials (Antechinus swainsonii) during the period of mating

In an investigation of the factors leading to the increase in the concentration of plasma free glucocorticoid, which results in immunosuppression and death after mating of all males in natural populations of a small shrew-like marsupial, the dusky antechinus (Antechinus swainsonii), the integrity of the glucocorticoid feedback control of the concentration of plasma cortisol was examined by use of dexamethasone-suppression tests. Injection of 0.2 mg dexamethasone/kg i.m. caused a marked fall in the concentration of plasma cortisol 17 h later, approximately 2 months and 2 weeks before the annual mating period in mid-July. However, the same dose had no significant effect on the increased concentration of plasma cortisol characteristic of the mid- to late July mating period. Injection of 100 i.u. ACTH/kg i.m. caused a significant increase in the concentration of plasma cortisol 6-7 h later on all occasions, indicating that the responsiveness of the adrenal cortex to ACTH did not change. Pretreatment with dexamethasone had no effect on the ACTH-stimulated cortisol concentration, ruling out a possible direct effect of dexamethasone on adrenocortical secretion in this species. Dexamethasone also reduced the concentration of plasma testosterone when the level was low, before the mating period, but not when the level was high, at the beginning of the mating period. It is concluded that, in association with a rapid increase in the concentration of plasma testosterone, an increase in aggression and intense mating activity, glucocorticoid feedback control of ACTH secretion is impaired.(ABSTRACT TRUNCATED AT 250 WORDS)