A technique for sustained synchronization of hamster estrous cycles by hormonal means

Rapid synchronization of hamster estrous cycles was achieved by administration of two subcutaneous injections of 7.5 μg of estradiol, given 24 hr apart, followed by one injection of 1 mg of progesterone/135 g body weight, given 20 hr after the last estradiol injection. Behavioral estrus occurred 4 hr after the injection of progesterone. Synchronized animals were mated during the second natural estrus following hormone treatment. Abnormal vaginal discharges were noted in most animals during the first few days after treatment, and, occasionally, a dissociation between behavioral and vaginal estrus was observed. However, by the second natural estrus after treatment, 69% of the colony demonstrated synchronized estrous cycles, both vaginally and behaviorally, and all abnormal discharges disappeared. The fertility rate was comparable to that in the colony from which the treated animals were taken, and the gestation period was normal, with an 8-hr range in onset of parturition. Offspring were normal in litter size, body weight, time of eye and vagina opening, sex ratio, and regularity of estrus. It was concluded that the technique is suitable for use by investigators interested in litter size and neonate development, in addition to those requiring time-mated or behaviorally synchronized animals. With the information gained from the experiment, a treatment schedule was devised which would produce 94% synchronization in a colony.     

Chorionic gonadotropin administration in domestic cats causes an abnormal endocrine environment that disrupts oviductal embryo transport

Fecal steroid analysis was used to investigate relationships between endocrine parameters and embryo characteristics in domestic cats subjected to chorionic gonadotropin stimulation and artificial insemination (AI). In Study 1, normal endocrine patterns were assessed in 12 cycling domestic queens. Fecal estradiol (E) patterns established an anovulatory cycle length of 18.3 +/- 0.4 d with estrus lasting 6.3 +/- 0.3 d. Eight females (67%) exhibited at least one spontaneous ovulation based on sustained increases in fecal progestagens (P). In Study 2, queens were mated during natural estrus (NE, n = 5) or subjected to exogenous i.m. gonadotropin stimulation, 100 IU eCG followed by 75 IU hCG 80 h later, (GS, n = 5). Compared with NE queens, fecal E concentrations were higher (P < 0.05) and remained elevated longer after ovulation induction with hCG. In Study 3, gonadotropin-stimulated queens (n = 7) were artificially inseminated and ovariohysterectomized 160 h after hCG. Ancillary follicles and/or corpora lutea were observed in 5 of 6 (83%) ovulating queens. Both fecal E and number of unovulated follicles observed at ovariohysterectomy were negatively correlated with the percentage of embryos recovered from the uterus (r = -0.91 and r = -0.87, respectively; P < 0.05). In summary, exogenous gonadotropin administration causes an abnormal endocrine environment in domestic cats, likely due to ancillary follicle development. The sustained elevations in estradiol appear to impair oviductal transport of embryos, possibly leading to the reduced fertility typically observed in cats subjected to gonadotropin stimulation and AI.     

Actions of acetyl-L-carnitine on the hypothalamo-pituitary-gonadal system in female rats.

Acetyl-L-carnitine (ALC) is known to affect several aspects of neuronal activity. To evaluate the neuroendocrine actions of this compound, several endocrinological parameters were followed in ALC-treated and control animals during recovery from dark-induced anestrus. In treated animals, serum luteinizing hormone (LH) and prolactin levels were higher than those of controls during the proestrous and estrous phases of the cycle, and serum estradiol levels were higher during estrus. No significant changes were observed in serum levels of follicle-stimulating hormone and progesterone. Uterine weight was increased in ALC-treated rats during proestrus and estrus, but not in diestrus. The basal release of gonadotropin-releasing hormone (GnRH) from perifused hypothalamic slices of ALC-treated animals was elevated at proestrus and diestrus, and GnRH release elicited by high K+ was higher during all three phases of the cycle. The basal release of LH from perifused pituitaries of treated animals was elevated in diestrus, and the LH response to GnRH was higher in estrus and diestrus I. Depolarization with K+ caused increased LH secretion during proestrus and estrus in treated animals. In contrast to these effects of ALC treatment in vivo, no direct effects of ALC were observed during short- or long-term treatment of cultured pituitary cells. These results indicate that ALC treatment influences hypothalamo-pituitary function in a cycle stage-dependent manner, and increases the secretory activity of gonadotrophs and lactotrophs. Since no effects of ALC on basal and agonist-induced secretory responses of gonadotrophs were observed in vitro, it is probable that its effects on gonadotropin release are related to enhancement of GnRH neuronal function in the hypothalamus.     

Estrous behavior and the estrus-to-ovulation interval in Nelore cattle (Bos indicus) with natural estrus or estrus induced with prostaglandin F2 alpha or norgestomet and estradiol valerate

Estrous behavior and the estrus-to-ovulation interval are essential for estimating the best time to artificially inseminate cattle. Because these parameters are not well characterized in the Nelore breed (Bos indicus), the main purpose of the this study was to determine the estrus-to-ovulation interval in Nelore heifers and cows with natural estrus or with estrus induced by treatments with PGF2 alpha or norgestomet and estradiol valerate (NEV). The cows and heifers were observed continuously (24 h a day) to determine the onset of estrus and to study estrous behavior in the cows. Ten hours after the start of estrus the ovaries were scanned every 2 h by ultrasonography to monitor the dominant follicle until ovulation. Blood samples were collected periodically to determine progesterone levels by RIA. Administration of PGF2 alpha (2 injections, 11 days apart) did not induce estrus in most Nelore females in spite of the presence of functional CL, indicated by progesterone concentrations above 6.0 ng/ml in 25 of 28 animals. Treatment with NEV induced high sexual receptivity in cows (10/11), but only 66% ovulated. Cows with natural or induced estrus exhibited behavioral estrus of 10.9 +/- 1.4 h, and ovulation occurred 26.6 +/- 0.44 h (n = 26) after the onset of estrus. In most of the cows (53.8%) estrus began at night (between 1801 and 600 h), and 34.6% it started and finished during the night. It is concluded that in Nelore females ovulation occurs approximately 26 h after the onset of estrus. Additionally, estrous behavior is shorter than in European breeds, and there is a high incidence of estrus at night, which makes it difficult to detect and, consequently, impairs Al in Nelore cattle. The observation that a high percentage of Nelore females with an active CL did not respond to usual dosages of PGF2 alpha warrants further investigation.     

The role of the uterus in regulation of heat duration in cycling rats

These experiments examined the effects of hysterectomy on heat duration and on the reinduction of estrous behavior by progesterone (P) following the termination of spontaneous heat in 4-day cycling rats. Hysterectomy did not affect the onset of estrus but prolonged heat duration. The average duration of sexual receptivity for hysterectomized (H) and sham-hysterectomized (SH) rats was 18.2 and 13.0 hr, respectively. Furthermore, H animals injected with either 0.5 mg P within 2 hr, or 4.0 mg P 24 hr following the termination of natural estrus showed significantly higher lordosis and solicitation responses than SH rats similarly treated. These behavioral findings were correlated with the level of hypothalamic progestin receptors. That is, H animals had a significantly higher concentration of progestin receptors than SH rats immediately following the termination of spontaneous heat and also 24 hr later. Both in estrous-cycling rats and in gonadectomized animals treated with estradiol benzoate (EB), hysterectomy resulted in higher serum estradiol (E2) levels. The results of these experiments suggest that prolongation of the period of sexual receptivity and the facilitated behavioral responses to P following the cessation of estrus in hysterectomized animals may be due to a lowered clearance rate of circulating estradiol which presumably enhances the estrogen conditioning of the neural substrates.     

A comparison of the estrous behavior of Holstein-Friesian cows when cubicle-housed and at pasture

This study compared estrous behavior of dairy cows kept in cubicle housing and fed a total mixed ration diet (HOUSED treatment) with that of cows kept at pasture with concentrate supplementation (PASTURE treatment). Behavior was compared both in the 48 h around standing estrus and during the standing estrus period. The 23 spring-calving Holstein-Friesians in each treatment were observed directly three times per day for nine weeks. The occurrence of nine selected behaviors associated with estrus was recorded during 20 min observation sessions. Twelve standing estrus events from each treatment were selected for analysis of the frequency of these nine behaviours over the 48 h around standing estrus. Milk progesterone profiles were used to confirm the dates of standing estrus events. Attempting to mount other cows, sniffing the anogenital region of other cows, resting the chin on other cows, receiving chin rests and head-to-head butts all showed significant changes in frequency in the 48 h around standing estrus in both treatments, reaching a peak during standing estrus (P ≤ 0.05). Mounting other cows increased significantly in the PASTURE treatment around standing estrus (P < 0.001), but not in the HOUSED treatment. The frequency of ano-genital sniffs received by the animals in the PASTURE treatment also increased significantly around standing estrus (P < 0.01) but not in the HOUSED treatment. When the animals were in standing estrus there was a significantly higher frequency of standing to be mounted in PASTURE than in HOUSED cows (median (q1, q3) PASTURE = 2.5 (1.0, 3.0), HOUSED = 0.0 (0.0, 1.0)) (P < 0.01), but no difference in the frequency of the other eight sexual behaviors recorded. HOUSED cows did not exhibit the same increase in mounting during the standing estrus period as PASTURE cows and received fewer mounts in observation sessions during standing estrus. These results have implications for the use of estrus detection systems that rely solely on mounting behavior in cubicle-housed dairy cows.     

Mating patterns in the golden lion tamarin (Leontopithecus rosalia): continuous receptivity and concealed estrus

Sociosexual behavior was monitored on a daily basis for 3 months in 5 pairs of golden lion tamarins (Leontopithecus rosalia). Urine samples were collected daily from each female and urinary estrogen cycles were determined by radioimmunoassay. Mounts and copulations were observed during all phases of the estrogen cycle. Peaks or regular cycles in sexual behavior were not documented. There were no significant changes in affiliative behavior by females or males that were associated with changes in urinary estrogen values. A negative relationship between pair bond duration and frequency of sexual interactions was observed: newly established pairs exhibited 2-6 times more frequent sexual behavior than a long-established pair. The lack of a conspicuous sexual signal in female golden lion tamarins may be related to a pattern of continuous sexual receptivity. Both reproductive patterns, concealed estrus and continuous receptivity, are explicable in relation to either monogamous or polyandrous mating systems.     

Behavioral correlates of physiological estrus in cheetahs

Historically, the cheetah (Acinonyx jubatus) has been known for its poor reproductive performance in captivity. Although breeding success has improved over the past decade, the percentage of breeders in the captive population is still low and successful propagation unpredictable. Estrus in this species has been reported as “silent” by some, therefore contributing to breeding problems by making appropriate timing of pair introductions difficult. To investigate whether any observable behavioral changes may be associated with estrus, we carried out quantitative behavioral observations and concomitant noninvasive monitoring of estradiol metabolites excreted in feces of 14 captive female cheetahs for periods of 5–22 consecutive weeks. We found that changes in fecal estradiol concentrations correlated significantly with variation in the occurrence of several types of behaviors, including rolling, rubbing, sniffing, vocalizing, and urine spraying. However, the number and types of correlated behaviors varied across females, revealing no single behavior indicative of estrus, but rather a constellation of behaviors that increased in frequency when estradiol concentrations were elevated. There was no significant difference in the overall average estradiol concentrations or peak values of the females that had previously mated and conceived compared to those of the females that had failed to breed. Successful breeders appeared to show significantly higher rates of rubbing and rolling than nonbreeders. However, rates of rubbing, rolling, and urine spraying also were found to increase with age, and older individuals were more likely to have bred. The results of this study indicate that estrus in the cheetah cannot be regarded as “silent” since the frequencies of some behaviors appear to covary with fluctuating estradiol levels. However, behavioral monitoring of estrus may nevertheless be difficult and time-consuming due to individual variation and subtle changes in behavioral frequencies rather than changes in the types of behaviors displayed. Zoo Biol 17:193–209, 1998. © 1998 Wiley-Liss, Inc.     

Decreased LH pulsatility during initiation of gonadotropin superovulation treatment in the cow: evidence for negative feedback other than estradiol and progesterone

LH pulse secretion is suppressed during superovulation of cattle. The objective of this study was to determine how soon after initiation of superovulation treatments this suppressive effect occurs, and to test the hypothesis that decreased LH pulsatility is not related to changes in circulating estradiol or progesterone. Heifers (n = 7/group) were injected with eCG (FOLLIGON: a single injection of 2,500 IU) or twice daily injections of decreasing doses of FOLLTROPIN-V (total equivalent of 280 mg of NIH-FSH-P1) or F.S.H.-P (total equivalent of 28 mg of Armour standard) or saline (time controls), starting on Day 10 (Day 0 = estrus). Blood samples were taken every 10 min for 12 h intervals on the day prior to first injection, at 8 to 20 h and 32 to 44 h after initiation of gonadotropin treatment, and also during prostaglandin (PG)-induced luteolysis. A simple method based on robust statistics and on graphical representations of time series was developed to characterize LH pulses. There was a significant interaction between time and treatment for mean LH, estradiol and progesterone when control and treated groups were analyzed together, and no interaction when only the gonadotropin groups were analyzed together. When compared to pretreatment values, pulse frequency of LH was significantly reduced (P<0.05) in each treatment group, 8 to 20 h and 32 to 44 h following initiation of gonadotropin treatment. Mean LH concentrations were also reduced 32 to 44 h following initiation of treatments (P<0.05). Mean estradiol concentrations increased two to threefold at 8 to 20 h following initiation of superovulation treatments (P<0.05). Progesterone concentrations also increased by 20 or 44 h. There was no significant correlation between estradiol or progesterone and LH pulse frequency, amplitude and mean concentrations at any time in control or superovulated animals. This study demonstrates that superovulation treatment in the cow causes a rapid decrease in pulsatile release of LH and suggests that this effect is not mediated through the negative feedback actions of estradiol and progesterone.     

Application of noninvasive techniques to monitor reproductive function in a brown hyena(Hyena brunnea)

Estrus in a 10-yr-old brown hyena was described by monitoring urinary steroid metabolites. These studies were repeated the succeeding year and combined with ultrasonography, vaginal cytology, and laparoscopy to further aid in identifying natural and induced estrus. Collection of semen from a 14-yr-old male brown hyena was accomplished by electroejaculation. Use of frozen semen once during natural estrus and again during estrus induced with follicle stimulating hormone (FSH) did not result in pregnancy. Further studies with this animal indicate that stimulation with gonadotropin releasing hormone (GNRH), rather than FSH, may be the more appropriate treatment for stimulating ovulation in canids or related species. While this study did not result in conception, a significant step toward that end was realized by utilizing urinary estrogen to monitor the estrus cycle.     

Patterns of circulating gonadotropins and ovarian steroids during the first periovulatory period in the developing sheep.

This report provides evidence that an increment in serum gonadotropin levels occurs at puberty in the sheep and that this reflects the critical hormonal event culminating in first ovulation in this species. Blood samples were collected from 6 female lambs at 4-h intervals for a period of approximately 2 mo around the expected time of puberty (32 wk of age) until behavioral estrus was observed and ovulation was verified by assay of serum progesterone. Patterns of circulating LH, FSH, progesterone, and estradiol concentrations were characterized during the peripubertal period for each lamb. A rise in serum levels of both LH and FSH began approximately 7-10 days before the first preovulatory surge of gonadotropins. Although the increase in gonadotropin levels occurred gradually over several days, serum estradiol levels rose only during the final 40-60 h prior to the preovulatory surge of gonadotropin. Serum progesterone profiles revealed, however, that normal (14-16-day) luteal phases were induced in only 2 of 6 females as a result of the first surge. In four lambs, a short luteal phase of 2.5 days' duration occurred, which was followed by another estradiol rise and a preovulatory surge that then resulted in a full luteal phase of 14 days' duration. These data demonstrate clearly that the precipitating event at puberty in the female sheep is an increase in circulating gonadotropin levels and that the estradiol secreted from the newly stimulated follicle provides the signal for the first preovulatory surge.     

Differential estradiol requirement for the induction of estrus behavior and the luteinizing hormone surge in two breeds of sheep

For a better understanding of the mechanisms that lead to the preovulatory GnRH/LH surge and estrus behavior, the minimum estradiol (E) requirements (dose and duration) to induce each of these events were determined and compared between two breeds of ewes having either single (Ile de France) or multiple (Romanov) ovulations. The ewes were initially studied during a natural estrus cycle, and were then ovariectomized and run through successive artificial estrus cycles. For these artificial cycles the duration and amplitude of the follucular phase E increase were manipulated by E implants. Under all conditions, the onset of estrus behavior was similar in the two breeds, although its duration was longer in Romanov ewes. While a moderate E signal (6 cm for 12 h) induced an LH surge in 10/10 Ile de France ewes, a larger E signal (12 cm for 12 h) was minimally effective in Romanov ewes (4/10). Additional studies revealed that a small E signal (3 cm for 6 h) induced full estrus behavior in all Romanov ewes but was completely ineffective in Ile de France animals (0/10). Higher doses and mostly longer durations of the E signal (12 cm for 24 h) were required to induce a surge in all the Romanov ewes. These results demonstrate a clear difference in the E requirement for the induction of estrus behavior and the LH surge between breeds of ewes that have different ovulation rates. These data provide compelling evidence that, in one breed, the neuronal systems that regulate both events require different estrogen signals.     

Chronic stress, hormone profiles and estrus intensity in dairy cattle

The objectives of the present study were to determine if lameness, a model for a natural chronic stressor, affects hormone concentrations in milk prior to estrus and/or the subsequent expression of estrus in the postpartum period. Dairy cows>20 days postpartum were scored for lameness and observed for estrus intensity using a weighted scoring system (>100 points=estrus=Day 0). Increasing lameness score was not associated with daily profiles of milk progesterone (throughout Days -18 to 0), estradiol (Days -6 to 2) or cortisol (Days -18 to 2) around estrus, maximum estradiol values or estradiol concentrations on Day 0. However, post hoc pair wise comparisons revealed that prior to estrus, severely lame cows had lower maximum progesterone concentrations compared to nonlame cows (1.3+/-0.1, 1.2+/-0.2, 0.7+/-0.1 ng/ml milk; P=0.042). Furthermore, severely lame cows expressed behavioral estrus with lower intensity (284+/-128 points, n=9) compared to moderately lame (662+/-310 points, n=9) or nonlame animals (583+/-275 points, n=18; P=0.05 and P=0.02, respectively). Resting concentrations of cortisol (Days 20-80 postpartum) did not vary between days postpartum or lameness score. The incidence of behavioral estrus was not affected by increasing lameness score, as 54.2%, 56.2% and 50.0% periods with low progesterone were associated with spontaneous estrus expression, respectively. Concluding, in this biological model of chronic stress, lameness did not affect the incidence of behavioral estrus but did reduce estrus intensity once ovarian cyclicity had resumed after calving. This reduced intensity of estrus was associated with lower maximum progesterone values prior to estrus but not abnormal daily cortisol or estradiol values in milk.     

Evaluating the utility of an accelerometer and urinary hormone analysis as indicators of estrus in a Zoo-housed koala (Phascolarctos cinereus)

Induced ovulators, such as the koala, do not always have overt signs of estrus, which makes pairing these animals for breeding purposes difficult to achieve in a zoo setting. This study examined the possibility of using alternative methods to behavioral sampling and weight fluctuations for monitoring estrus in a female koala of reproductive age. We attempt to gain an improved understanding of koala estrus and enhance our ability to detect it by combining a noninvasive technique for hormone analysis with a newer method for recording activity level. The findings suggest that activity levels were accurately measured using an accelerometer and increased activity was associated with one estrus behavior, bellowing. Weekly weight declines occur with increases in activity registered from the accelerometer. We also validated an assay to detect progesterone and estradiol in female koala urine in an attempt to detect an estrus spike. However, neither urinary concentrations of estradiol nor progesterone was associated with behavioral cues of estrus in our subject. We suggest that increased female activity, bellowing, and weight loss all indicate a pro-estrus state that requires proper male stimulation in order to achieve a full estrus display. Zoo Biol 28:59–68, 2009. ©2008 Wiley-Liss, Inc.     

Concentrations of steroids and gonadotropins in follicular fluid from normal heifers and heifers primed for superovulation

The concentrations of six steroids and of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in follicular fluid from preovulatory and large atretic follicles of normal Holstein heifers and from preovulatory follicles of heifers treated with a hormonal regimen that induces superovulation. Follicular fluid from preovulatory follicles of normal animals obtained prior to the LH surge contained extremely high concentrations of estradiol (1.1 +/- 0.06 micrograms/ml), with estrone concentrations about 20-fold less. Androstenedione was the predominant aromatizable androgen (278 +/- 44 ng/ml; testosterone = 150 +/- 39 ng/ml). Pregnenolone (40 +/- 3 ng/ml) was consistently higher than progesterone (25 +/- 3 ng/ml). In fluid obtained at 15 and 24 h after the onset of estrus, estradiol concentrations had declined 6- and 12-fold, respectively; androgen concentrations had decreased 10- to 20-fold; and progesterone concentrations were increased, whereas pregnenolone concentrations had declined. Concentrations of LH and FSH in these follicles were similar to plasma levels of these hormones before and after the gonadotropin surges. The most striking difference between mean steroid levels in large atretic follicles (greater than 1 cm in diameter) and preovulatory follicles obtained before the LH surge was that estradiol concentrations were about 150 times lower in atretic follicles. Atretic follicles also had much lower concentrations of LH and slightly lower concentrations of FSH than preovulatory follicles. Hormone concentrations in follicles obtained at 12 h after the onset of estrus from heifers primed for superovulation were similar to those observed in normal preovulatory follicles at estrus + 15 h, except that estrogen concentrations were about 6-40 times lower and there was more variability among animals for both steroid and gonadotropin concentrations. Variability in the concentrations of reproductive hormones in fluid from heifers primed for superovulation suggests that the variations in numbers of normal embryos obtained with this treatment may be due, at least in part, to abnormal follicular steroidogenesis.     

Gonadotropic and ovarian hormone response in dairy cows treated with norgestomet and estradiol valerate

Injection of estradiol valerate in conjunction with receiving a norgestomet ear implant (Syncro-Mate-B) reduced plasma progesterone (P<.001) and FSH (P<.02) and increased estradiol (P<.01) in postpartum cows during the treatment period. Occurrence of LH and FSH peaks (P<.05) varied between 12 and 48 hr follwing removal of SMB implants and estrous behavior was minimal. FSH was strongly correlated to LH and was inversely related to progesterone in untreated cows and to estradiol in treated cattle. Syncro-Mate-B suppressed luteal activity and peak gonadotropin release during treatment and elicited variable endocrine and behavioral response following treatment.     

Hormonal correlates of reproductive seasonality in wild female hanuman langurs (Presbytis entellus)

To date, it is not known whether the seasonal occurrence of sexual behavior and mating in free-ranging Hanuman langurs at Ramnagar, Nepal, is correlated with seasonal changes in female ovarian function, and, if so, which factor(s) triggers the onset of the reproductive period. Using noninvasive fecal hormone analysis in combination with behavioral observations, this study was carried out to: 1) investigate and characterize seasonal patterns of ovarian cyclicity and timing of conception in wild langur females living in a highly seasonal habitat; and 2) examine the relationship between seasonal patterns of ovarian cyclicity, behavioral estrus, and female physical condition. Behavioral data and fecal samples were collected during a total period of 14 months from nine females living in a multi-male group. Physical condition of the females was assessed monthly by visual inspection, using a seven-fold scale. Ovulatory cycles and timing of conceptions were identified by the measurement of immunoreactive pregnanediol glucuronide (iPdG) in extracted feces. Hormone profiles in individual females revealed a clearly seasonal distribution in the occurrence of ovulatory cycles, which were restricted to the period from July to October. The distribution of female estrus behavior showed a similar seasonal pattern, and in total 88.2% of all estrus periods observed in the focal females were accompanied by ovulation. Onset of ovarian cycles as well as mating activities were strongly correlated with the onset of the rainy season. Females conceived, on average, in their second ovulatory cycle (pregnancy length: 211.6 +/- 3.4 days), with timing of conception being confined to the months when animals showed an improved physical condition. Collectively the present data clearly suggest that in seasonally-breeding langurs at Ramnagar, ecological conditions (rainfall, food availability, and quality) influence the onset of ovulations and timing of conceptions.     

Hormonal control of proceptive and receptive sexual behavior and the preovulatory LH surge in the ewe: reassessment of the respective roles of estradiol, testosterone, and progesterone

When estrous behavior is induced in ovariectomized ewes by subjecting them to progestagen priming followed by a dose of estrogen large enough to guarantee estrus in all animals, an abnormally long period of estrus in induced, suggesting that the regime of steroid replacement needs modification. Using quantitative tests for proceptivity and receptivity, we studied the patterns of sexual behavior of intact ewes and then attempted to reproduce them in the same animals after they had been ovariectomized. We used various combinations of exogenous estrogen, androgen, and progestagen and compared the behavioral responses with an endocrine response, the preovulatory surge of luteinizing hormone (LH). In intact ewes, sexual behavior and the LH surge were closely synchronized and their characteristics differed slightly between the middle and the end of the breeding season. Proceptive behavior was not greatly affected by the frequency of tests, but the duration of receptivity was significantly reduced by frequent testing. In ovariectomized ewes, we found that: (a) progesterone priming is essential for normal patterns of receptive and proceptive behavior, and for synchronizing the behavioral and endocrine responses to estrogen; (b) androgens do not play a major role in the control of either receptive or proceptive behavior; and (c) the inclusion of a low dose of estrogen with the progestagen in the 'priming' regime improves the responses to estradiol-17 beta. Under these conditions, the timing, intensity and duration of the behavior are very close to those observed in the same ewes when they were intact and cycling spontaneously.     

Dynamics of Male–Female Multimodal Signaling Behavior across the Estrous Cycle in Giant Pandas (Ailuropoda melanoleuca)

Giant panda courtship behavior includes multimodal signaling assemblages consisting of olfactory, vocal, and postural elements. While signaling is generally conspicuous, successful copulation is inconsistently achieved in captivity, even when female behavioral and physiological data indicate that ovulation is imminent. We set out to characterize these complex patterns of social behavior by observing interactions between 26 unique pairs of giant pandas housed in adjoining pens throughout the females' reproductive cycle. We categorized social behaviors from a transactional perspective and examined social exchanges via analyses of the relative frequency of social behaviors, and via the sequential relationship between male and female social behavior. From non‐estrus to peak‐estrus, we found that the relative frequency of female affiliative and sexual behavior increased and that the relative frequency of ambivalent and aggressive behavior decreased. Male behavior was fairly constant, except for sexual behavior, which increased during peak‐estrus, when it was facilitated by female sexual behavior. Sequential analysis of social interactions showed that preceding behavior had a significant influence over the other panda's response behavior primarily during peak‐estrus, suggesting that pandas are most responsive to conspecific signaling during the peri‐ovulatory period. However, behavioral momentum was a dominant feature of the intra‐individual transitions. Females maintained sexual, ambivalent, and neutral behavior during interactions significantly more than would be expected by chance, with male behavior bearing little influence once the behavior was initiated. A similar pattern was also observed in males, who maintained affiliative, interested, and neutral behaviors. Overall, our data suggest that the multimodal signals used by giant pandas during courtship do not consistently evoke a discrete, immediate response from receivers. Instead, signals appear to advertise reproductive condition and influence potential mates over longer timeframes, suggesting the potential tonic role of communication.     

Social interactions and solitary behaviors in a pair of captive sand cats (Felis margarita)

This study examined the behavior and activity of two captive sand cats at the Washington Park Zoo in Portland, Oregon. Sex differences in behavior were examined and the direction and frequency of social interactions were determined. An attempt was made to determine behavioral signs of estrus. A scan sampling data collection technique was used to find the percentage of time spent by each cat in each behavior. Simultaneously, the frequency of social behaviors was recorded. The cats spent the greatest percentage of their time pacing and resting; social interactions occurred very infrequently. The only significant sex difference in behavior was that the male marked and urinated/defecated more than did the female. Temporal distribution in the usage of the enclosure was examined. It was found that when one cat was active, the other tended to be inactive. No overt behavioral signs of estrus were evident other than the actual observance of copulation. However, the percentage of time spent in each behavior was examined when the female was assumed to be in estrus (days when copulation was observed) versus nonestrous periods. The female was found to pace and locomote significantly more during estrous periods.