The reproductive endocrinology and behavior of Vancouver Island marmot (Marmota vancouverensis)

The Vancouver Island marmot (Marmota vancouverensis; VIM) is one of North America's most endangered species with fewer than 150 individuals remaining in the wild. A captive breeding program was established across four facilities in Canada as an insurance population and source of animals for reintroduction to the wild. The purpose of this study was to gather information about the basic reproductive biology and behavior of this species, which is essential to improve captive breeding programs. Regular fecal samples were obtained from adult female (n = 14) and male (n = 10) marmots, 2 years of age and older, over 1-3 breeding seasons (2-3 months duration posthibernation) for steroid hormone analysis. Enzyme immunoassays were validated for quantifying fecal testosterone metabolite concentrations for males, and fecal estrogen and progesterone metabolite concentrations for females. Results indicated that fecal progesterone metabolite concentrations can be used to monitor ovulation and pregnancy. Behavioral monitoring through infrared video surveillance was conducted in four breeding pairs over a 2-year period (n = 7 behavioral profiles). Breeding behaviors correlated strongly with changes in reproductive endocrine profiles. A high frequency of play behavior or "wrestling" was observed in conjunction with breeding activity before an elevation in progesterone metabolite concentrations. Impending parturition was associated with increased aggression and exclusion of the male from the maternal nestbox as well as an increase in nesting activity. Observational data combined with hormonal analysis suggest that female VIMs are induced ovulators and that multiple breeding attempts may be required for ovulation and conception. Gestation appears to be approximately 34 days from peak breeding activity (32 days from estimated ovulation). Fecal testosterone concentrations suggest that testicular activity is seasonal with the reproductive activity occurring immediately posthibernation. Monitoring breeding behavior is a useful means of indicating estrus, conception and pregnancy, which can also be supported by the hormonal analysis of daily fecal samples of individual animals.     

Comparative patterns of adrenal activity in captive and wild Canada lynx (<Emphasis Type="Italic">Lynx canadensis</Emphasis>)

Stress and animal well-being are often assessed using concentrations of glucocorticoids (GCs), a product of the hypothalamic–pituitary–adrenal axis. However, GC concentrations can also be modulated by predictable events, such as changes in season or life history stage. Understanding normative patterns of adrenal activity is critical for making valid conclusions about changes in GC concentrations. In this study, we validated an assay for monitoring fecal glucocorticoid metabolites (FGM) in Canada lynx. We then used this technique to assess patterns of adrenal activity in Canada lynx across several contexts. Our results show that captive lynx have higher FGM concentrations than wild lynx, which may be related to differences in stress levels, metabolic rate, diet, or body condition. We also found that FGM concentrations are correlated with reproductive status in females, but not in males. For males, seasonal increases in FGM expression coincide with the onset of the breeding season, whereas in females, FGM increase toward the end of the breeding season. This information provides a valuable foundation for making inferences about normative versus stress-induced changes in adrenal activity in Canada lynx.     

Long-term monitoring of fecal steroid hormones in female snow leopards (Panthera uncia) during pregnancy or pseudopregnancy

Knowledge of the basic reproductive physiology of snow leopards is required urgently in order to develop a suitable management conditions under captivity. In this study, the long-term monitoring of concentrations of three steroid hormones in fecal matter of three female snow leopards was performed using enzyme immunoassays: (1) estradiol-17β, (2) progesterone and (3) cortisol metabolite. Two of the female animals were housed with a male during the winter breeding season, and copulated around the day the estradiol-17β metabolite peaked subsequently becoming pregnant. The other female was treated in two different ways: (1) first housed with a male in all year round and then (2) in the winter season only. She did not mate with him on the first occasion, but did so latter around when estradiol-17β metabolite peaked, and became pseudopregnant. During pregnancy, progesterone metabolite concentrations increased for 92 or 94 days, with this period being approximately twice as long as in the pseudopregnant case (31, 42, 49 and 53 days). The levels of cortisol metabolite in the pseudopregnant female (1.35 μg/g) were significantly higher than in the pregnant females (0.33 and 0.24 μg/g) (P<0.05). Similarly, during the breeding season, the levels of estradiol-17β metabolite in the pseudopregnant female (2.18 μg/g) were significantly higher than those in the pregnant females (0.81 and 0.85 μg/g) (P<0.05). Unlike cortisol the average levels of estradiol-17β during the breeding season were independent of reproductive success.The hormone levels may also be related to housing conditions and the resulting reproductive success in female leopards. The female housed with a male during the non-breeding season had high levels of cortisol metabolites and low levels of estradiol-17β in the breeding season, and failed to become pregnant. This indicates that housing conditions in snow leopards may be an important factor for normal endocrine secretion and resulting breeding success.     

Fecal progesterone and estrogen metabolite monitoring for cyclicity and pregnancy in southern tamandua (Tamandua tetradactyla)

Reproductive management of the southern tamandua (Tamandua tetradactyla) should include timed introductions for breeding to minimize aggression and pregnancy monitoring. Since serial blood sampling could cause unnecessary stress, and urinary progesterone metabolites are found in very low concentrations, this study sought to validate progesterone and estradiol enzyme immunoassays for measuring fecal progesterone metabolite (FPM) and fecal estrogen metabolite (FEM) concentrations in two females. Peaks in FEM concentrations coincided with breeding and conception, were 5–6 times higher than baseline concentrations, and were followed by clear luteal phases distinguished by FPM concentrations 5–6 times higher than baseline concentrations. FPM concentrations during the first 30–53 days of gestation overlapped with luteal phase concentrations, thereafter increasing to 8–25 times higher than baseline concentrations. FEM concentrations during the first 41–44 days of gestation remained near basal values for one female, whereas concentrations were 1.8 times higher than baseline for the second. FEM concentrations became elevated for the former by 44 days of gestation and increased further for the latter after 53 days, ultimately averaging four times higher than baseline for both females. The biphasic increase in FPM and FEM concentrations, follicular and luteal phase durations (follicular: 7 ± 1 days, luteal: 25 ± 1 days), total cycle length (41 ± 1 days), and gestation (161–165 days) documented in this study were consistent with previous reports from serum and urine analyses. Monitoring FPM and FEM is a reliable noninvasive method for tracking reproductive cycles and pregnancy in southern tamandua that overcomes the challenges associated with serum or urinary hormone analysis.     

Urinary hormone analysis assists reproductive monitoring and sex identification of bell frogs (Litoria raniformis)

With the world currently facing a global amphibian extinction crisis, the development of techniques to help meet the needs of conservation managers and researchers studying the reproductive biology of amphibians is needed. Here, we developed enzyme immunoassays to measure estrone, testosterone, and progesterone hormone metabolites in the urine of Litoria raniformis, the southern bell frog. Concentrations of urinary estrone, testosterone, and progesterone increased during the breeding season for females (P < 0.05). Concentrations of urinary testosterone and progesterone increased for males during the breeding season compared with that for months where no reproductive behaviors were observed (P < 0.05). Furthermore, urinary estrone concentrations proved to be a reliable sexing tool for adult frogs, with no overlap between the sexes in 98% of cases, regardless of season. There was no difference in estrone (P = 0.204) or testosterone (P = 0.485) metabolite concentrations between samples taken immediately upon capture and those taken 12 to 24 h later from the same individual. Progesterone metabolite concentrations were lower on Day 2 than upon collection (P = 0.004). This is the first study to show that urinary hormone analysis can be a useful technique for reproductive monitoring in an amphibian. Additionally, hormone metabolite measures offer promise as sex identification tools for monomorphic species and for those whose secondary sex characteristics are visible only during the breeding season.     

Estrous cyclicity and reproductive success are unaffected by translocation for the formation of new reproductive pairs in captive red wolves (Canis rufus)

This study investigated possible female-related causes for inconsistent success among reproductive pairs in the zoo-based red wolf (Canis rufus) population. Females (n = 13) at seven institutions were assessed for evidence of ovulation and normal reproductive cycles through the measurement of estradiol and progesterone metabolite excretion in feces. Fecal cortisol metabolites (FCM) were also measured. Factors potentially affecting FCM and/or estrous cyclicity were recorded, including exhibit status (on vs. off), reproductive history (proven vs. unproven), copulatory behaviors (ties observed: yes or no), pregnancy/parturition (pups or no pups produced), and translocation before the observed breeding season (yes or no). No differences were observed in baseline FCM between females housed on versus off-exhibit (p = .46) or between females producing pups and those who did not (p = .19). Baseline FCM were significantly lower among females observed in copulatory ties compared to females never observed in a tie (p = .04), and tended to be higher in females translocated before the breeding season compared to females in existing reproductive pairs (p = .11), and among historically unproven females compared to proven females (p = .11). All females evaluated had an endocrine profile indicative of ovulation and among the four females translocated to be paired with a new male before the breeding season, two had successful pregnancies, producing litters. Therefore, despite observed differences in baseline FCM among factors, estrous cyclicity and reproductive success are unaffected by translocation for the formation of new reproductive pairs in the zoo-based red wolf population.     

Noninvasive monitoring of female reproductive hormone metabolites in the endangered European mink (Mustela lutreola)

This study examined the reproductive physiology of female European mink (Mustela lutreola) to augment the available information on estrus, ovulation, and pregnancy with the long-term goal of supporting ex situ breeding management of this highly endangered species. Fecal reproductive hormone metabolites were measured using EIAs for estrogen and 20-oxo-pregnane metabolites. Seasonal hormone profiles were established. A comparison of hormone fluctuations in pregnant and nonpregnant females showed that both estrogen and 20-oxo-pregnane metabolites were significantly elevated during gestation, which is 42 days in length. Delayed implantation or embryonic diapause does not occur in this species. Litter size was correlated with 20-oxo-pregnane levels but not with estrogen concentrations. During lactation, 20-oxo-pregnane metabolite levels remained higher than in nonpregnant females. The breeding season was characterized by peaks in vaginal cornified cells and fecal estrogen metabolite levels. Up to four peaks in estrogen levels were identified and confirmed that European mink are seasonally polyestrous. The results of 20-oxo-pregnane measurements indicated that hCG can be applied to induce ovulation. With the establishment of this noninvasive method, we present a new tool to support population management of this species.     

Trade-off between current reproductive effort and delay to next reproduction in the leatherback sea turtle

The trade-off between current and future reproduction plays an important role in demographic analyses. This can be revealed by the relationship between the number of years without reproduction and reproductive investment within a reproductive year. However, estimating both the duration between two successive breeding season and reproductive effort is often limited by variable recapture or resighting effort. Moreover, a supplementary difficulty is raised when nonbreeder individuals are not present sampling breeding grounds, and are therefore unobservable. We used capture–recapture (CR) models to investigate intermittent breeding and reproductive effort to test a putative physiological trade-off in a long-lived species with intermittent breeding, the leatherback sea turtle. We used CR data collected on breeding females on Awa:la-Ya:lima:po beach (French Guiana, South America) from 1995 to 2002. By adding specific constraints in multistate (MS) CR models incorporating several nonobservable states, we modelled the breeding cycle in leatherbacks and then estimated the reproductive effort according to the number of years elapsed since the last nesting season. Using this MS CR framework, the mean survival rate was estimated to 0.91 and the average resighting probability to 0.58 (ranged from 0.30 to 0.99). The breeding cycle was found to be limited to 3 years. These results therefore suggested that animals whose observed breeding intervals are greater than 3 years were most likely animals that escaped detection during their previous nesting season(s). CR data collected in 2001 and 2002 allowed us to compare the individual reproductive effort between females that skipped one breeding season and females that skipped two breeding seasons. These inferences led us to conclude that a trade-off between current and future reproduction exists in leatherbacks nesting in French Guiana, likely linked to the resource provisioning required to invest in reproduction.     

Reproductive endocrine patterns in captive female and male red wolves (Canis rufus) assessed by fecal and serum hormone analysis

Reproductive steroid profiles in female (n=13) and male (n=5) red wolves (Canis rufus) were characterized in fecal samples collected during the breeding season (December—May) and over a 1 year period, respectively. Blood samples from females (n=12) also were collected during the periovulatory period for luteinizing hormone (LH) and steroid analysis. High performance liquid chromatography (HPLC) of fecal extracts determined that estradiol and estrone constituted the major and minor forms, respectively, of fecal estrogen metabolites. Although native progesterone was present, pregnane metabolites predominated as the major forms of fecal progestins. HPLC analysis of fecal extracts from males revealed no native testosterone, but rather the predominance of more polar androgen metabolites. Based on hormone profiles and/or pup production, females were classified as pregnant (n=3), ovulatory‐nonpregnant (n=9), or acyclic (n=3). Longitudinal monitoring of females indicated no pregnancy‐specific differences in concentrations of either fecal progestagen or estrogen metabolites compared to ovulatory‐nonpregnant individuals; however, baseline progestagen concentrations were consistently elevated in acyclic females. There was good correspondence between serum and fecal steroid concentration during the periovulatory period. A rise in serum estrogens preceded the ovulatory LH surge which was then followed by a significant progesterone rise during the luteal phase. In males, changes in fecal androgen metabolite concentrations coincided with photoperiod fluctuations, increasing in late autumn and reaching peak concentrations during mid‐ to late winter just before the start of the breeding season. Collectively, these results serve as a database of ovarian and testicular endocrine events in this species, which can be utilized in population management and application of assisted reproductive technologies. Zoo Biol 21:321–335, 2002. © 2002 Wiley‐Liss, Inc.     

Brief communication: Female fecal androgens prior to the mating season reflect readiness to conceive in reproductively quiescent wild macaques

An extensive body of research exists on androgen secretion in males. Although androgens are also known to drive patterns of female reproductive physiology and behavior, little attention has been paid to these “male” hormones in females. Here, we examined female fecal androgen excretion in strictly seasonally breeding wild Assamese macaques (Macaca assamensis) and tested the hypothesis that changes in premating season fecal androgens vary with female readiness to resume ovarian cycling and thus to conceive. Across 2 years, 155 fecal samples were collected from seven reproductively quiescent (i.e., acyclic) females during the premating season months, August and September. Samples were analyzed for immunoreactive epiandrosterone (iEA), a major fecal metabolite of testosterone in macaques. Changes in iEA concentrations during the premating season were significantly negatively associated with (1) the presence of dependent offspring, i.e., lactating females showed a smaller change, and (2) with the timing of conceptions in the mating seasons, i.e., females that conceived early exhibited the greatest changes. These results provide strong evidence for a relationship between changes in androgens during the premating season and female readiness to conceive. Am J Phys Anthropol 151:311–315, 2013. © 2013 Wiley Periodicals, Inc.     

Hormonal and Behavioral Variation in Pied Tamarins Housed in Different Management Conditions

Pied tamarins are an endangered Amazonian primate that has limited breeding success in zoos. Unfortunately, little is known about their reproductive biology and adrenocortical activity. Objectives were: (1) determine if fecal hormones could be utilized to monitor gonadal and adrenocortical activity; (2) characterize male and female gonadal and adrenocortical hormones; and (3) determine if there were differences between adrenocortical activity and behavior in a nonbreeding, on‐exhibit (NB‐ON) pair compared to a breeding, off‐exhibit (B‐OFF) pair. Fecal samples were collected from four (two males; two females) individuals. Hormones were analyzed for fecal progesterone (FPM), androgen (FAM), and glucocorticoid (FGM) metabolites by enzyme immunoassay. Behavioral observations were conducted for 6 months. Data were collected on instantaneous behavior, location, and all occurrences of intraspecific behaviors. Fecal progesterone metabolites were validated by pregnancy (mean ± SE, pregnant: 28.47 ± 1.60 μg/g; nonpregnant: 8.63 ± 0.89 μg/g). Fecal androgen metabolites were higher (T = 31,971, P < 0.05) in the B‐OFF male (863.66 ± 46.30 μg/g) than the NB‐ON male (838.63 ± 60.70 μg/g). Fecal glucocorticoid metabolites were validated by response to veterinary procedure with elevated values (7.31 ± 1.48 μg/g) seven times the baseline (0.37 ± 0.04 μg/g) at 24‐hr postphysical. Females had higher baseline FGM than the males (P < 0.05). Baseline FGM were higher (P < 0.05) in the NB‐ON female (0.93 ± 0.03 μg/g) compared to the B‐OFF female (0.38 ± 0.02 μg/g). Similarly, the NB‐ON male's FGM baseline (0.71 ± 0.03 μg/g) were higher (P < 0.05) than the B‐OFF male (0.21 ± 0.01 μg/g). Behavioral data revealed stereotypical behaviors in the NB‐ON pair but no stereotypical behaviors in the B‐OFF pair. Fecal hormone monitoring and behavioral analysis may provide insight on the limited breeding success of pied tamarins in zoos. Zoo Biol. 32:299–306, 2013. © 2012 Wiley Periodicals, Inc.     

Characterization of Ovarian Steroid Patterns in Female African Lions (Panthera leo), and the Effects of Contraception on Reproductive Function

Because of poor reproduction after the lifting of an 8-year breeding moratorium, a biomedical survey of female lions in U.S. zoos was initiated in 2007. Fecal estrogen (FEM), progestagen (FPM) and glucocorticoid (FGM) metabolites were analyzed in samples collected 3–4 times per wk from 28 lions at 17 facilities (0.9–13.8 yr of age) for 4 mo—3.5 yr and body weights were obtained ~monthly from 17 animals at eight facilities (0.0–3.0 yr of age). Based on FEM, estrous cycle length averaged 17.5 ± 0.4 d in duration, with estrus lasting 4.4 ± 0.2 d. All but one female exhibited waves of estrogenic activity indicative of follicular activity; however, not all females expressed estrous behaviors (73%), suggesting silent estrus was common. Female lions experienced puberty earlier than expected; waves of estrogenic activity were observed as young as 1.1 yr of age, which may be related to a faster growth rate of captive vs. wild lions. Mean gestation length was 109.5 ± 1.0 d, whereas the non-pregnant luteal phase was less than half (46.0 ± 1.2 d). Non-mating induced increases in FPM were observed in 33% of females housed without a male, consistent with spontaneous ovulation. A number of study animals had been contracepted, and the return to cyclicity after treatment withdrawal, while variable, was ~4.0 yr and longer than the 1-yr expected efficacy, especially for those implanted with Suprelorin. For FGM, there were no differences in overall, baseline or peak mean concentrations among the age groups or across seasons, nor were there any relationships between reproductive parameters and FGM concentrations. Overall, results suggest that poor reproduction in lions after the breeding moratorium was not related to altered adrenal or ovarian steroid activity, but for some females may have been a consequence of individual institutions’ management decisions.     

The interaction of testosterone and breeding phase on the reproductive behavior and use of space of male zebra finches

It is well known that androgens play a critical role in mediating the reproductive behavior of males. However, many laboratory experiments that examined the effects of testosterone in male songbirds typically limited their investigations to the early phase of breeding. We sought to determine the influence of testosterone on social behavior, pair bonding, nesting, and use of space in captive zebra finch (Taeniopygia guttata) males as a function of breeding stage (pre-laying, incubation, and nestling phases). Fourteen males were released into an aviary with 14 females and allowed to breed for 7 weeks. Half of the males were given testosterone implants and half were given control implants. During the pre-laying phase, testosterone-implanted males spent significantly more time in nesting activities than control birds and more time elapsed from starting to build a nest to when their mates initiated egg-laying. During the incubation phase, testosterone-implanted subjects spent significantly more time in female-directed and undirected singing. Use of space varied between hormone conditions depending upon breeding phase: there was no difference during pre-laying, but during the incubation and nestling phases, testosterone-implanted subjects used significantly more space. This significant increase in "home range" during the latter phase of the breeding cycle coincides with results from field studies on other species. These results underscore the importance of considering breeding phase in assessing the behavioral sensitivity to hormones.     

Seminal and endocrine characteristics of male Pallas' Cats (Otocolobus manul) maintained under artificial lighting with simulated natural photoperiods

Pallas' cats (Otocolobus manul) have a pronounced reproductive seasonality controlled by photoperiod. Previous studies of reproduction in captive Pallas' cats exposed to natural light showed a breeding season of December–April. This study evaluated the impact of artificial lighting timed to simulate natural photoperiods on male reproductive seasonality of four Pallas' cats housed indoors. Semen evaluation, blood collection, and body weight measurements were conducted every 1–2 months from November 2000–June 2001. Fecal samples were collected from each male twice weekly to assess testosterone and corticoid concentrations. Mean values for reproductive traits (sperm attributes, testicular volume) were highest from February–April, the defined breeding season. Fecal testosterone concentrations were highest from mid‐January to mid‐March. Male Pallas' cats managed indoors under simulated photoperiods experienced a delayed onset of the breeding season by 1–2 months and a decreased length of the breeding season. Over the course of the study, fecal corticoid concentrations did not seem to differ among seasons. Although mating attempts during this study were unsuccessful, subsequent pairings of male and female Pallas' cats in the same research colony during the 2002 and 2003 breeding seasons produced viable offspring. These results suggest that male Pallas' cats, housed indoors under simulated photoperiods, exhibit distinct reproductive cyclic patterns, characterized by a delayed and truncated breeding season. Adrenocortical activity varied among individuals, but did not adversely affect reproductive parameters. Housing Pallas' cats indoors under simulated photoperiods may represent a viable strategy for maintaining breeding success while limiting disease exposure. Zoo Biol 0:1–13, 2007. © 2007 Wiley‐Liss, Inc.     

Circulating LH levels and the response to exogenous GnRH in the common mole-rat: implications for reproductive regulation in this social, seasonal breeding species

The effects of breeding season and reproductive status on male and female reproduction were investigated in the common mole-rat, Cryptomys hottentotus hottentotus, a cooperatively breeding rodent which exhibits a unique combination of seasonal breeding and a reproductive division of labor. Pituitary function was examined by measuring the luteinizing hormone (LH) responses to single doses of 2 microg exogenous gonadotrophin-releasing hormone (GnRH) and physiological saline in 69 males and 58 females from 35 wild caught colonies. Neither males nor females exhibited any apparent manifestation of season on basal LH concentrations or on pituitary sensitivity to stimulation by exogenous GnRH. The continuance of reproductive function during the nonbreeding period is essential in common mole-rat males and females, as this period coincides with the period of maximal dispersal opportunity in the winter rainfall area they inhabit. Normal circulating levels of reproductive hormones in dispersing animals may aid intersexual recognition, assist pairbond formation, and thus prime animals for independent reproduction. Circulating basal concentrations of LH as well as LH levels measured in response to a single exogenous GnRH challenge were not significantly different between the reproductive and non-reproductive groups of either sex, suggest the absence of a physiologically well-defined suppression of reproduction in subordinate common mole-rats.     

Fecal sex steroids and reproductive behaviors in harpy eagles (Harpia harpyja)

Aiming to improve our reproductive knowledge of large birds of prey, behavioral data and fecal steroids were assessed in captive pairs of Harpy eagles, a keystone species that is monogamous and resides in the Neotropics year-round. Adult individuals exhibited different reproductive outcomes and a breeding season extending beyond summer solstice (5–9 months) suggests that harpy eagles may not be absolutely photorefractory. Comparisons among breeding stages in males revealed that mean androgen levels in courtship were higher than in copulation and incubation, but no differences were detected in fecal progestagens or estrogens. Females had higher mean estrogen concentrations in courtship and copulation, whereas mean progestagen levels peaked during egg laying. Mean androgen concentrations were not significantly different among breeding stages in females. Assessment of six egg-lay cycles from three females demonstrated that fecal estrogens peaked predominantly between 31 and 18 days before oviposition (–31 to –18 days), and then remained low until 45 days after laying the first egg (+45 days). In contrast, fecal progestagens raised mostly between –20 and +1 day, lowering to baseline concentrations by +3 days. To our knowledge, this is the first study to describe in detail endocrine and behavioral data regarding reproduction in tropical eagles, which may serve in the future as a reference to developing breeding programs.     

Do female green turtles (Chelonia mydas) exhibit reproductive seasonality in a year-round nesting rookery?

In circumglobal populations of sea turtles, little nesting activity occurs during cold seasons when the sand temperature on a nesting beach is inappropriate for successful egg incubation. However, it is not known whether reproductive seasonality also occurs in year-round nesting rookeries where the sand temperature may be suitable throughout the year. Therefore, we examined the hypothesis that female turtles exhibit reproductive seasonality even in a year-round nesting population. To determine whether the time of nesting of individuals fluctuates between successive nesting seasons, a year-round nesting rookery of green turtles Chelonia mydas at Huyong Island, Thailand, was patrolled on foot every night for 3190 consecutive days, and nesting females were identified using microchips and metal tags. The date of first nesting within a season for an individual (nesting date) was considered the nesting season of each individual. We identified 94 females and 463 nests (including 47 unidentified nests) during the survey. Nesting dates were distributed throughout the year. Nineteen turtles remigrated to the nesting beach, and the nesting dates of the remigrated females occurred in the same seasons. This indicates that females have a fixed individual nesting season even in a year-round nesting rookery. The year-round nesting of green turtles may be attributed to a wide variation in the nesting seasons of individuals. Satellite tracking revealed that the mean travelling duration of post-nesting migrations in this population was 13.5±6.1 days. The proximity of locations for reproduction and feeding may also play an important role in sustaining year-round nesting in this population.     

Age-related patterns of reproductive success in house sparrows Passer domesticus

A common life history pattern in many organisms is that reproductive success increases with age. We report a similar pattern in house sparrows Passer domesticus , older individuals performed better than yearlings for most measures of reproductive success. Older males and females began breeding earlier in a given season and fledged more young than their yearling counterparts. Individual males also fledged more young in their second breeding season than they did in their first, but individual females did not show consistent improvement in reproductive success from year one to two. A path analysis indicated that age in both sexes acted primarily through the timing of breeding; earlier nesters laid more eggs and hence fledged more young but did not have more nesting attempts. We tested whether the increased reproductive success with age arose from high quality individuals surviving to be older (selection hypothesis). In contrast to the main prediction of this hypothesis that reproductive success and survival should be positively related, we found that survival from one year of age to two years of age was negatively related to reproductive success in the first year for males and females combined. Additionally, individuals that survived to breed as two-year-olds did not differ in total young fledged in their first year from those that did not survive to their second season of breeding. Our results indicate that fledgling production increases with age due to improvements in timing of breeding, particularly in females, and not because of the loss of poor breeders or increased output. Mechanisms producing age-related differences in timing of breeding warrant further study.     

The effect of pregnant and oestrous females on male testosterone and behaviour in the tammar wallaby

Tammar wallaby females (Macropus eugenii) are seasonally breeding marsupials with a post-partum oestrus after a highly synchronised birth period when testosterone concentrations rise in males. Chemical communication appears to be important for mating, as males show checking behaviour, sniffing the urogenital opening (UGO) and the pouch of females. This study investigates whether the presence of pregnant and oestrous females directly influences testosterone in males and if oestrous odours or secretion from the pouch or UGO are attractive. Concentrations of plasma testosterone were measured in males housed with pregnant and oestrous females during two consecutive cycles in the breeding season, and an artificially induced cycle in the non-breeding season. Males were also tested for their interest in swabs taken from the urogenital opening (UGO) or pouch of oestrous females. Testosterone increased sharply in males in the presence of pregnant and oestrous females during all cycles in both seasons, but there was no change when males were exposed to non-cycling females in lactational or seasonal diapause. Males had no preference for either oestrous or non-oestrous samples taken from the pouch or from the UGO from oestrous females. This study confirms that the increase in plasma testosterone in tammar males can be induced through the presence of pregnant and oestrous females, regardless of season and that the increase began when the females were in late-pregnancy. This confirms that the male's reproductive state is dependent on a signal from females and is not blocked through seasonal effects.     

Plumage redness predicts breeding onset and reproductive success in the House Finch: a validation of Darwin's theory

Darwin (1871) and later Fisher (1958) suggested that sexual selection can drive the evolution of ornamental traits in monogamous species when female preferences for these traits allow well-ornamented males to begin breeding earlier in a season and, as a result, gain reproductive advantages over poorly ornamented males. However, few studies have been conducted to test this fundamental concept upon which much of the sexual selection theory for monogamous species has been based. In this study, we examined the relationship between breeding onset, reproductive success, and male ornamentation in the House Finch Carpodacus mexicanus , a species in which males display bright carotenoid-based plumage pigmentation. In previous work, it has been shown that bright male House Finches are preferred as social mates by females and, as a result, begin nesting earlier in the season than do drab orange and yellow males. Here we show that, by initiating breeding earlier in the season, brightly colored males fledge more offspring in a season than do drab males. Thus, differential timing of breeding generates considerable variance in reproductive success among male House Finches and contributes to sexual selection for male plumage ornamentation in this species.