Reproductive cycle length and pregnancy in the southern white rhinoceros (Ceratotherium simum simum) as determined by fecal pregnane analysis and observations of mating behavior

Pregnancy and the reproductive cycle were monitored in 13 captive southern white rhinoceros (Ceratotherium simum simum) by measuring progesterone metabolites in fecal extracts and by observing behavior patterns. Fecal hormones were measured using a monoclonal antibody produced against 4‐pregnen‐11‐o1‐3,20‐dione hemisuccinate:BSA. Several subjects exhibited flat or erratic endocrine profiles, but we found evidence for 17 reproductive cycles in five females. Mating behavior coincided with nadirs in pregnane concentrations. These cycles appeared to fall into two general categories: those of approximately 1 month in duration (Type I: X¯ ± SEM = 35.4± 2.2 days; n = 10) and those lasting approximately 2 months (Type II: 65.9± 2.4 days; n = 7). Interluteal phase lengths were similar for the two cycle types, but Type II cycles were characterized by extended luteal phases lasting more than twice as long as Type I luteal phases. Because Type I cycles predominated in our data and because evidence suggests that some Type II cycles may be aberrant, we argue that these approximately monthly cycles represent the typical reproductive cycle for this species. Three females became pregnant during the course of the study. We were able to detect pregnancy by approximately 3 months post‐breeding, as indicated by sustained pregnane concentrations markedly higher than nonpregnant luteal phase concentrations. These data help to characterize important reproductive events of this species and should be useful for captive breeding efforts for this threatened species. Zoo Biol 18:111–127, 1999. © 1999 Wiley‐Liss, Inc.     

Seasonal variation in male testosterone levels in a tropical bird with year‐round territoriality

Testosterone is important in mediating investment in competing activities such as territoriality, parental care, and maintenance behavior. Most studies of testosterone function have focused on temperate species and less is known about the role of testosterone in territoriality or variation in mating systems of tropical species. Results of studies of tropical species with year‐round territoriality indicate that territorial aggression during the non‐breeding season is maintained with low levels of testosterone, and increased levels of testosterone in males during the breeding season may increase mating opportunities or aid in competition for mates. We studied seasonal variation in testosterone levels of male Red‐throated Ant‐tanagers (Habia fuscicauda), a socially monogamous species with year‐round territoriality and with high levels of extra‐pair matings (41% of young), to determine if testosterone levels increased during the breeding season. We captured males during the non‐breeding and breeding seasons and collected blood samples for hormone analysis. We found that mean testosterone concentrations were low during the non‐breeding season (0.18 ± 0.05 [SD] ng/ml, range = 0.11–0.31 ng/ml), and significantly higher during the breeding season (2.37 ± 2.47 ng/ml, range = 0.14–6.28 ng/ml). Testosterone levels of breeding males were not related to aggression levels as measured by attack rates toward a stuffed decoy or singing rates during simulated territorial intrusions. These results suggest that the higher testosterone levels of breeding male Red‐throated Ant‐tanagers may be important in an extra‐pair mating context, possibly in display behavior or mate attraction, but additional study is needed to clarify the role of testosterone during the breeding season.     

Reproductive biology and management of captive black-footed ferrets (Mustela nigripes)

A captive breeding program is being conducted with black-footed ferrets (Mustela nigripes), an endangered species. Results of 5 years of study are reported. Simple, but specialized, nontraumatic handling techniques allowed assessment of reproductive status with minimal stress, which was important in breeding management. Black-footed ferrets are sexually mature and may successfully reproduce in their 1st year. Proestrus lasts approximately 2-3 weeks. Duration of estrus in unbred females was 32–42 days; females usually bred within 20 days. Most breeding activity occurred during April. Mean gestation length was 42.7 days (±0.7, range 42–45 days), litter size averaged 3.0 kits (±1.4, range 1–6 kits), and weaned kits/litter averaged 2.4 (±1.7, range 1–6 kits). Weaning rate of kits was 80%. Sex ratio of kits was essentially 1:1. Productivity was greatest among females ?3 years of age. Rapid expansion of the captive population is possible and will be important for genetic management of the species and for achieving the primary goal of the recovery program, which is to return black-footed ferrets to the wild.     

Hormonal changes during the mating and conception seasons of wild northern muriquis (Brachyteles arachnoides hypoxanthus)

We investigated hormonal and behavioral changes in wild male and female northern muriquis (Brachyteles arachnoides hypoxanthus) at the Estação Biológica de Caratinga, Minas Gerais, Brazil, during a 6‐mo period that encompassed the onset of the 1998–1999 mating and conception seasons. Individual females resumed mating with the resumption of ovarian cycling, which was not synchronized among them or related to their cortisol levels. Females experienced two to seven cycles prior to conceiving, and the first conception occurred 2 mo after the onset of the group's mating season. There were no differences in female cortisol levels across their premating, mating, and conception conditions. Cortisol levels were significantly higher in females than in males prior to the conception season, consistent with the prediction that energy reserves may be associated with breeding readiness in females, but not males, in this species. The sustained elevation in male cortisol occurred after the peak in their sexual activity, which resulted in the first conception of the year. Male cortisol levels were positively correlated between years that were similar in rainfall, but differed in the timing of sexual and reproductive events. The timing of cortisol elevations in males appears to be generally regulated by environmental cues, but is responsive to fine‐tuning by social and behavioral cues related to the unpredictable timing of reproductive opportunities within their extended mating season. Am. J. Primatol. 61:85–99, 2003. © 2003 Wiley‐Liss, Inc.     

Reproductive behavior of the captive Sunda pangolin (Manis javanica Desmarest, 1822)

Understanding reproductive behavior is important for the conservation of endangered species, but research on the reproductive behavior of Sunda pangolins (Manis javanica Desmarest, 1822) is still very scarce. In this study, we used focal animal sampling and all-occurrence recording by an infrared monitor to observe the behaviors of two Sunda pangolins during a 5-day breeding period at the Pangolin Research Base for Artificial Rescue and Conservation Breeding of South China Normal University (PRB-SCNU). The behavioral characteristics and breeding strategies were analyzed, and the results were discussed together with information on other captive Sunda pangolin pairs at PRB-SCNU. The results found that there was no obvious estrus behavior in the captive female, while the male could exhibit sexual excitement and courtship behavior after a brief introduction period. Repeated copulation continued over many days after the female accepted the courtship. The average duration of copulatory behavior was 248.9 ± 148.7 s (n = 25), and all copulation occurred between 20:00 and 08:00 hr in the natural day–night photoperiod. The mating position of Sunda pangolins was lateral–ventral and was classified as the ninth or eleventh pattern under both Dewsbury's and Dixson's classification systems. This study can provide scientific guidance for the captive breeding and management of Sunda pangolins and other pangolin species, which is of great significance for ex situ conservation tactics.     

Prolonged and flexible primary moult overlaps extensively with breeding in beach‐nesting Hooded Plovers Thinornis rubricollis

We present the first report of complete overlap of breeding and moult in a shorebird. In southeastern Australia, Hooded Plovers Thinornis rubricollis spend their entire lives on oceanic beaches, where they exhibit biparental care. Population moult encompassed the 6‐month breeding season. Moult timing was estimated using the Underhill–Zucchini method for Type 2 data with a power transformation to accommodate sexual differences in rates of moult progression in the early and late stages of moult. Average moult durations were long in females (170.3 ± 14.2 days), and even longer in males (210.3 ± 13.5 days). Breeding status was known for most birds in our samples, and many active breeders (especially males) were also growing primaries. Females delayed the onset of primary moult but were able to increase the speed of moult and continue breeding, completing moult at about the same time as males. The mechanism by which this was achieved appeared to be flexibility in moult sequence. All moult formulae fell on one of two linked moult sequences, one faster than the other. The slower sequence had fewer feathers growing concurrently and also had formulae indicating suspended moults. Switching between sequences via common formulae is possible at many points during the moult cycle, and three of 12 recaptures were confirmed to have switched sequences in the same moult season. Hooded Plovers thus have a prolonged primary moult with the flexibility to change their rate of moult; this may facilitate high levels of replacement clutches that are associated with passive nest defence and low reproductive success.     

Delayed egg‐laying and shortened incubation duration of Arctic‐breeding shorebirds coincide with climate cooling

Biological impacts of climate change are exemplified by shifts in phenology. As the timing of breeding advances, the within‐season relationships between timing of breeding and reproductive traits may change and cause long‐term changes in the population mean value of reproductive traits. We investigated long‐term changes in the timing of breeding and within‐season patterns of clutch size, egg volume, incubation duration, and daily nest survival of three shorebird species between two decades. Based on previously known within‐season patterns and assuming a warming trend, we hypothesized that the timing of clutch initiation would advance between decades and would be coupled with increases in mean clutch size, egg volume, and daily nest survival rate. We monitored 1,378 nests of western sandpipers, semipalmated sandpipers, and red‐necked phalaropes at a subarctic site during 1993–1996 and 2010–2014. Sandpipers have biparental incubation, whereas phalaropes have uniparental incubation. We found an unexpected long‐term cooling trend during the early part of the breeding season. Three species delayed clutch initiation by 5 days in the 2010s relative to the 1990s. Clutch size and daily nest survival showed strong within‐season declines in sandpipers, but not in phalaropes. Egg volume showed strong within‐season declines in one species of sandpiper, but increased in phalaropes. Despite the within‐season patterns in traits and shifts in phenology, clutch size, egg volume, and daily nest survival were similar between decades. In contrast, incubation duration did not show within‐season variation, but decreased by 2 days in sandpipers and increased by 2 days in phalaropes. Shorebirds demonstrated variable breeding phenology and incubation duration in relation to climate cooling, but little change in nonphenological components of traits. Our results indicate that the breeding phenology of shorebirds is closely associated with the temperature conditions on breeding ground, the effects of which can vary among reproductive traits and among sympatric species.     

The social organization and breeding behaviour of the Yellow-faced Honeyeater Lichenostomus chrysops– a migratory passerine from the Southern Hemisphere

Southern Hemisphere passerines are generally thought to have long breeding seasons and high annual survivorship, but this may reflect a bias resulting from a disproportionate concentration on sedentary species. This study presents a detailed examination of the breeding biology and social organization of a migratory population of a passerine from the Southern Hemisphere – the Yellow‐faced Honeyeater Lichenostomus chrysops. It took place between 1997 and 2000 in the Coranderrk Reserve, Healesville, Australia. Following the birds’ return from migration, breeding commenced in mid‐November, roughly 2 months after arrival. The breeding season was short (3.5–4 months) compared with sedentary honeyeaters occupying the same habitat. Territories (0.19 ± 0.11 ha) were established by males but defended by both sexes against conspecific and heterospecific intruders. Within a breeding season, pairs were multibrooded (mean no. of clutches per season 2.14 ± 0.76, range 1–3) and always re‐nested within the same territory with the same partner. However, only 12.5% of pairs bred together in a subsequent breeding season despite, on many occasions, their partner from the previous season being alive (divorce rate of 75% for males and 66% for females). Females alone built the nest, incubated the eggs and brooded the nestlings. However, males contributed 44.5% of feeding visits to nestlings. The breeding cycle of Yellow‐faced Honeyeaters (clutch size 1–3 eggs, mean 2.4 ± 0.6, n = 84, incubation period 14.4 ± 0.7 days, n = 11, nestling period 13.0 ± 1.7 days, n = 6) was similar to that of sedentary honeyeaters (and Southern Hemisphere Corvidae in general), except that fledglings only remained on the parental territory for 2–3 weeks post‐fledging. At least one young fledged from 32.1% of nests (n = 156). Predation was the major cause of nest failure (74.5% of 106 failed nests). Only 4.4% of nestlings (n = 136) were observed on the study site in subsequent seasons (five males and one female). None of those males was observed on the study site until their second year of life. Adult annual survivorship (ignoring losses due to dispersal) was 43% for females and 51% for males. Our study suggests that if more data were available for the numerous migratory species from the Southern Hemisphere, some apparent differences from northern hemisphere passerines might disappear.     

Annual reproductive activity of Caiman crocodilus fuscus in captivity

We describe the gonadal and abdominal fat storage cycles for a population of Caiman crocodilus fuscus kept in captivity at a breeding farm. The reproductive cycles of males and females are clearly seasonal. Vitellogenic follicles were observed in females year‐round; however, the follicular growth that produces the preovulatory follicles for the breeding season occurs in November–May (most of the dry season to the beginning of the rainy season). These months correspond with the presence of physiologically reproductive males. Oviposition takes place during the wet season (April–August) and the births occur at the end of this season (September–November). Fat storage was not related to reproductive activity, and did not vary by month or between sexes. Although environmental and hormonal conditions have been improved for these captive animals, they maintain a strongly seasonal reproductive cycle, historically fixed to oviposit in the most favorable period for nest construction and hatching during the rainy season. Zoo Biol 22:121–133, 2003. © 2003 Wiley‐Liss, Inc.     

Migration and diving activity in three non‐breeding flesh‐footed shearwaters Puffinus carneipes

The flesh‐footed shearwater Puffinus carneipes is a medium‐sized shearwater and transequatorial migrant within the Pacific Ocean. We used archival data loggers to study the non‐breeding migration and diving behaviour of three flesh‐footed shearwaters following breeding in New Zealand. In early April, the birds migrated to the western North Pacific Ocean in 23±2 days, occupying core distributions within the Kuroshio/Oyashio transition system for 91±17 days. Subsequent movements were made into the Sea of Okhotsk prior to return migrations to New Zealand in mid September (19±1 days). Diving depths during migration (2.5±2.4 m), and in the western North Pacific (2.4±2.6 m) were shallower than during the onset of breeding (4.8±8.7 m). Non‐breeding flesh‐footed shearwaters occupy a region of high fisheries activity and the impact of these fisheries on adult survival in this declining species warrant further study.     

Breeding biology of the endangered Dupont’s Lark Chersophilus duponti in two separate Spanish shrub-steppes

Capsule: The Dupont’s Lark Chersophilus duponti in Iberia has relatively high breeding success in both core and fragmented habitats, so population declines are more likely to be the result of low juvenile or adult survival.

Aims: To measure important aspects of the reproductive biology of one of the most endangered and least known larks: the Dupont’s Lark C. duponti.

Methods: We monitored 36 nests in 2 Spanish shrub-steppes, one holding one of the largest European populations (250 pairs) and one composed by fragmented habitat patches holding a smaller population (50 pairs).

Results: The breeding season went from late-March to early July. Overall mean (±sd) clutch size was 3.47?±?0.56, and the number of fledglings per successful nest was 3.0?±?1.15. Mean nestling period was short (8.2 days). Nests showed similar daily survival rate during the incubation period (0.9750?±?0.0110) as during the nestling period (0.9545?±?0.0168), with a mean breeding success of 50%. Predation was the main cause of complete nest failure (83.3% of failed nests in both localities).

Conclusion: Breeding parameters did show no significant variation between populations. Breeding success in both sites was generally higher than recorded in previous studies of this and most other lark species, which suggests that breeding success does not compromise long-term viability of these populations. The decline of the studied populations should be explained by other causes, such as a general decrease in habitat quality, habitat loss or habitat fragmentation.     

Aspects of reproduction in the eastern rufous mouse lemur (Microcebus rufus) and their implications for captive management

The eastern rufous mouse lemur is one of the smallest primate species. It inhabits the eastern rain forest of Madagascar. Its reproductive biology has not been examined because of its rarity in laboratories. We present the first data on reproduction and variation in reproductive success from a breeding colony of wild‐caught Microcebus rufus. The eastern rufous mouse lemur shows a seasonal change in testicular size and in the occurrence of estrus. Females had 2.5 cycles (range, one to four) per season. The estrous cycle length was 59 days (range, 51–66), the duration of vaginal opening during estrus was 7.5 days (range, 5–8), receptivity occurred on the third day of estrus, gestation length was 56.5 days (range, 56–57), litter size was two neonates (range, one to three). The frequency and duration of mating behavior varied widely among the pairs. Copulation seemed to occur on a single day per estrus within the first to fourth hour after light change to red light. In four cases (three pairs), copulation lasted between 15 and 240 seconds. Breeding success can be increased by choosing mates carefully. Microcebus rufus seems to be a seasonal breeder like its sibling species Microcebus murinus. In wild‐caught animals, males seemed to adapt quickly (first season) to the conditions of captivity, whereas in the females, individual variation (first to third season) in reproductive activity was observed. Air humidity of >60% seems to facilitate the breeding success in wild‐caught pairs. First pregnancy and successful rearing of offspring occurred in the second and fourth year of captivity in two of three females. Wild‐caught eastern rufous mouse lemurs seemed to demonstrate variation in adapting to the conditions of captivity with regard to sex and individuality. Zoo Biol 20:157–167, 2001. © 2001 Wiley‐Liss, Inc.     

Changes in breeding phenology of eastern Ontario frogs over four decades

Global climate change has been implicated in phenological shifts for a variety of taxa. Amphibian species in particular are sensitive to changes in their environment due to their biphasic life history and restricted reproductive requirements. Previous research has shown that not all temperate amphibian species respond similarly to the same suite of climatic or environmental cues, nor are individual species necessarily uniform in their responses across their range. We examined both the timing of spring emergence and calling phenology of eight anuran species in southeastern Ontario, Canada, using an approximately 40‐year dataset of historical records of amphibian activity. Rana pipiens was the only species out of eight considered to emerge significantly earlier, by an estimated 22 days over four decades. Both R. pipiens and Bufo americanus have advanced initiation of calling over a four‐decade span significantly earlier by an estimated 37.2 and 19.2 days, respectively. Rana sylvatica showed a trend toward earlier emergence by 19 days, whereas we did not detect changes in emergence phenology for the remaining five species. This significant shift in breeding behavior for two species correlates to significant regional increases in spring temperatures of an estimated 2.7–2.8°C overall over four decades. Our study suggests that local temperature increases have affected the timing of emergence and the onset of calling activity in some Ontario anuran species. Global decline or range shifts ultimately may be related to changes in reproductive behavior and timing mediated by shifting climate.     

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.     

Reproductive behavior in captive California condors (Gymnogyps californianus)

From the fall of 1987 to the spring of 1994, data on reproductive behavior were collected on seven different pairs of California condors (Gymnogyps californianus) housed at the San Diego Wild Animal Park. Behavioral data were collected from videotaped activities in their flight pens. Behaviors for this report include male and female displays and incomplete and complete copulations. Data on the time it took for females to recycle and lay another egg after egg removal were acquired from the California Condor Studbook. Male display rates were significantly higher than female rates throughout the breeding season. Males began displaying 52–132 days before the start of copulations. Copulations slowly increased from Day -51 and peaked ∼ Day -8, prior to egg laying. Female display rates were significantly more frequent at the end of the season after the last egg was laid. An average of 26.8 (±3.1 SEM) copulations occurred prior to egg laying. Copulations occurred throughout the day, with the higher mean percentages occurring between 0700 and 0900 hours. After egg removal, the interval between laying of the first and second eggs and between the second and third eggs had a mean of 34.1 (±10.1 SD) days. © 1996 Wiley-Liss, Inc.     

Photoperiodic requirements for timing onset and duration of the breeding season of the ewe: Synchronization of an endogenous rhythm of reproduction

Summary A study was conducted to test the hypothesis that different portions of the annual photoperiodic cycle play different roles in timing the breeding season of the ewe, Ovis aries, an animal in which an endogenous rhythm generates the seasonal reproductive transitions. Adult female sheep were pinealectomized to disrupt transduction of photoperiodic cues at 4 times of the year (summer and winter solstices, vernal and autumnal equinoxes), and the effects on seasonal reproductive neuroendocrine activity were evaluated. Time of pinealectomy greatly influenced the subsequent seasonal reproductive cycle such that the following inferences are possible. Lengthening days between the winter and summer solstices synchronize reproductive onset to the appropriate time of year. The relatively long days around the summer solstice act to suppress reproductive activity and forestall the start of the breeding season until late summer/early autumn. The shortening days between the summer solstice and autumnal equinox maintain a normal intensity and duration of reproductive neuroendocrine induction during the impending breeding season. However, the shortening days between the autumnal equinox and winter solstice (i.e., after breeding season onset) do not appear to play a critical role in maintaining the breeding season of that year, but may provide important cues for timing the breeding season of the following year.Abbreviations LH luteinizing hormone Presented in preliminary form at the 21st Annual Meeting of the Society for the Study of Reproduction, 1988, Biol Reprod 38 (Suppl. 1): 184 (Abstract 408). This work was performed in partial fulfillment of the requirements for the degree of Ph.D. at The University of Michigan (to N.L.W.), and was funded by NIH-HD-18337 and NIH-HD-18258, T-32-HD-07048, the Institut National de la Recherche Agronomique (France) and the Office of the Vice President for Research of The University of Michigan.     

Comparison of Reproductive Characteristics and Changes in Body Weight Between Captive Populations of Rufous and Gray Mouse Lemurs

The nocturnal Malagasy mouse lemurs are among the smallest primates worldwide. Several sibling species are known. Of these, the rufous and the gray mouse lemur differ with respect to morphology, genetics, and communication. They might also differ in seasonal reproduction and body weight changes. We investigated and compared reproductive activities and changes in monthly body weight in males and females of successfully breeding colonies of both species under the same photoperiodic conditions. Females of both species showed estrous cycles only during the long-day period. Rufous mouse lemur females seemed to have a shorter gestation than their sibling species (57 vs. 62 days). The number of estrous cycles (2.25 vs. 2.5/season) and their lengths (59 vs. 52 days) were similar. Litter size (2) seemed to be similar. Latency of estrous occurrence after photoperiodic stimulation was longer in Microcebus rufus than in its sibling species (71.6 and 42.3 days). The same was true for the onset of the growth of the testes. The rate of growth and size of the testes were similar, and precede the estrous onset in both species. The reproductive activity was shorter in both sexes of the rufous than of the gray mouse lemurs. In both species, body weight showed similar seasonal changes. Males lost more weight during the breeding season than females did. In rufous mouse lemurs, body weight was similar in both sexes during the nonbreeding season. In gray mouse lemurs, sexes differed throughout the year.     

Changes in Fecal Estrogen Levels and Sexual Behavior in Captive Sichuan Snub‐Nosed Monkeys (Rhinopithecus roxellana) Following a Male Replacement

Rhinopithecus roxellana are generally seasonal breeders, although copulation can occur throughout the year. Previous studies suggest that estradiol modulates female sexual behavior during the mating season. However, the effects of social context on estrogen levels and behavior have not been fully explored. We studied the relationship between sexual behaviors and fecal estrogens in a group of captive R. roxellana during a period of social instability. We collected behavioral data for six months and collected fecal samples at 2–3‐day intervals for four months spanning the mating and nonmating seasons, and analyzed fecal estrogen levels via RIA. Females showed clear cyclic solicitation and copulation peaks in the mating season, which corresponded with sharp peaks in fecal estrogens. During the nonmating season, solicitation rates, copulation rates, and fecal estrogens were generally low. However, one nonpregnant female displayed a sharp peak in solicitations, copulations, and estrogens during the nonmating season 10–14 days after a male replacement. Our results provide preliminary evidence that social and behavioral changes affect estrogen levels in R. roxellana. Zoo Biol. 32:342–346, 2013. © 2012 Wiley Periodicals, Inc.     

Temporal patterns of circulating LH and steroid hormones in a brood parasite, the Brown-headed cowbird, Molothrus afer.

The breeding behaviour of female Brown-headed cowbirds, Molothrus ater , is remarkably distinct from that of females of most other passerine species. Cowbirds are brood parasites that do not build nests, incubate eggs or feed young. Instead, they have an extended egg-laying stage, and deposit eggs in the nests of hosts within large breeding territories that are defended from other female cowbirds. In this communication, we report the changes in plasma levels of circulating hormones and in morphological characteristics that occur in free-living female Brown-headed cowbirds over a breeding season.
Plasma LH in female cowbirds increases at the onset of breeding and remains elevated for approximately eight weeks, at which time levels decline to basal values. This pattern is similar to that of follicle development, and is consistent with the prolific reproductive output by individuals of this species. Circulating E, levels are quite variable and do not demonstrate any discernible pattern, while plasma B is elevated during the egg-laying period and declines subsequently.
Testosterone titre (T) is highest early in the breeding season, when territorial interactions are generally most frequent. T levels decline slowly thereafter, reaching their lowest values at the season's end. Plasma DHT levels are slightly higher than those for T; DHT exhibits little change until late in the breeding season, when it declines. Fat scores are highest prior to egg laying, and fat reserves diminish as the breeding season progresses. In contrast, body weight increases during the reproductive season, probably as a result of developing eggs in the ovary. These results are consistent with the hypothesis that temporal patterns of hormone secretion are correlated with the expression of social systems.     

Seasonal dynamics of agonistic behavior and hormones in an ex situ all‐male colony of large flying foxes

Large flying foxes (Pteropus vampyrus) are a socially complex species. In situ colonies typically comprise thousands of individuals in small harems of one male to many females. In ex situ environments, all‐male colonies are becoming more common due to a surplus of males in the population. There is limited information describing the hormonal and behavioral patterns of all‐male colonies during the breeding season. We assessed seasonal changes in hormones and behavior in an all‐male colony of 12 large flying foxes at Disney's Animal Kingdom^®. We validated hormone assays using morning urine and fecal samples to assess seasonal changes in excreted immunoreactive testosterone and glucocorticoid metabolites. We collected behavior data using an all‐occurrence method, recording agonistic behaviors related to territorial defense (hooking, biting, wing flexing, vocalizing, and wrestling), and sexual behavior (mounting and frontal grabbing). Results indicated that (i) we could reliably measure testosterone and glucocorticoid metabolites concentrations from fecal and urine samples collected from individual bats; (ii) there were distinct relationships between changes in levels of agonism and hormone concentrations throughout the year; and (iii) three agonistic behaviors (chasing, wrestling, and open‐mouth threat) peaked prior to the increase in testosterone and glucocorticoid hormones measured during the breeding season. These three behaviors could potentially be used as early indicators to signal the onset of the breeding season and allow time to implement ex situ management changes to reduce the incidence of agonism between individuals.