圈养亚洲象尿液中雌二醇和孕酮含量的周期性变化

针对北京动物园2头圈养雌性亚洲象从未动情的现象,本研究于2003年12月至2005年3月,采用放射性免疫分析法测定了2只不动情象与另一只已受孕象尿液中孕酮和雌二醇的变化,并结合国内外研究探讨圈养亚洲象不动情的原因,为圈养象机构提供相应的繁殖管理建议。研究结果表明,受孕雌象在分娩前一周左右孕酮含量突然升高,后在很短时间内降低,分娩后也维持在较低水平;雌二醇含量分娩前维持在较高水平,分娩前一周骤降,并保持较低水平至本研究结束。非动情象尿液中孕酮和雌二醇水平都显著低于受孕象相应的激素水平,且无明显的波动,推测其卵巢不具活性,导致孕酮与雌二醇水平不具波动性,是这2头圈养雌象未见动情现象的主要原因。     

重复遭遇战对雌性黑线仓鼠生理状态的影响

以独居型啮齿动物——黑线仓鼠(Cricetulus barabensis)为对象,主要测定了与优势-从属关系有关的体重、生理状态和粪便激素变化规律相关的参数。野生成年仓鼠捕获于鲁西南山区农田并于实验室内单独饲养。按照陌生和体重匹配的原则配对,实验动物在中立竞技场中每天进行15 m in的遭遇战并收集粪便,连续28 d。以攻击行为、防御行为、社会行为、非社会行为确定个体的优势-从属地位。用于实验的动物共33只。行为实验结束后,将动物解剖,确定其繁殖及生理状态。结果表明:4周重复遭遇战期间,(1)优势雌体体重显著增加;(2)肾上腺指数显著降低;(3)雌体肾上腺指数与卵巢指数无显著的相关关系;(4)雌体粪便皮质醇及雌二醇含量随时间表现出明显的波动,但优势与从属个体间差异不显著;(5)优势雌体的粪便雌二醇含量与皮质醇含量呈显著的正相关关系。研究结果提示,重复遭遇战未影响雌体的存活及潜在繁殖能力,这可能与黑线仓鼠的独居生活方式有关。     

小熊猫繁殖周期血清雌二醇和孕酮含量变化

为研究小熊猫繁殖周期血清雌二醇、孕酮含量变化规律,采用化学发光免疫分析法连续16 次测定了2只成体雌性小熊猫血清雌二醇和孕酮含量变化,历经发情间期、发情期和两次妊娠期;连续9次测定了7只小熊猫妊娠期的孕酮含量变化。结果:(1)发情间期,小熊猫血清雌二醇的水平一直维持在低水平(基础水平),进入发情前期,血清雌二醇水平明显升高,在发情期一直维持高水平,配种后迅速降至基础水平; (2)小熊猫血清孕酮含量在发情间期和发情期均维持在较低水平,直至发情期过后才出现升高,在妊娠期一直维持高水平,峰值出现在5 月;(3)发情的小熊猫不论妊娠与否,在妊娠期内血清孕酮含量均维持在高水平。研究表明:小熊猫血清雌二醇、孕酮含量变化能直接反映其繁殖规律,雌二醇对启动雌性小熊猫季节性繁殖起重要作用;在妊娠期内小熊猫血清孕酮含量升高不能作为判断小熊猫妊娠的标准;雌性小熊猫在妊娠期有假孕现象。     

圈养林麝社会等级与粪样类固醇激素水平的关系

动物社群的社会等级可对个体的资源分配、社群稳定及个体的行为对策产生重要影响,圈养动物的类固醇激素水平与饲养管理有关,可反映动物的社群紧张水平。深入理解圈养动物的社会等级与其类固醇激素水平的关系是进行濒危动物迁地保育和成功驯养的基础。2018年6月15日—8月15日,用焦点取样法对四川马尔康林麝繁育场的25头林麝进行了冲突行为取样及社会等级计算,采用放射免疫分析法检测了同期粪样的类固醇激素水平,分析了林麝社会等级与粪样皮质醇、睾酮及雌二醇水平的关系。结果表明:低等级雌麝的雌二醇水平(289.037±59.710 pg·g^-1,n=11)显著高于高等级雌麝(45.670±27.283pg·g^-1,n=6)(P<0.05),低等级雄麝的睾酮水平(3.863±1.538 ng·g^-1,n=3)和高等级雄麝(8.017±1.295 ng·g^-1,n=5)无显著差异(P>0.05);低等级雄麝(37.891±7.564 ng·g^-1,n=3)和雌麝(37.262±1.544 ng·g^-1,n=11)的皮质醇水平与高等级雄麝(29.947±2.441 ng·g^-1,n=5)及雌麝(37.478±4.628 ng·g^-1,n=6)间的差异不显著(P>0.05)。不区分性别,低等级林麝的皮质醇水平(37.397±1.826 ng·g^-1,n=14)和高等级个体(34.055±2.886ng·g^-1,n=11)间无显著差异(P>0.05)。研究结果表明,圈养林麝雌体的社会等级与其粪样雌二醇水平呈负相关,低等级雌麝的粪样雌二醇水平显著高于高等级雌麝。在麝类驯养实践中,可监测雌麝的社会等级和粪样雌二醇水平变化,预测雌麝的行为健康及繁殖成效。     

不同社群条件下雄性布氏田鼠的行为

实验室内观察了布氏田鼠雄性个体之间在3 种不同社群条件下(社群1:2 只雄鼠;社群2:2 只雄鼠与1只非动情雌鼠,社群3:2 只雄鼠与1 只动情雌鼠)的相互行为,结果显示:(1)在嗅闻行为上,不论优势雄鼠还是从属雄鼠在3 组间都存在显著差异,它们的嗅闻频次都是在社群3 中最少、在社群2中居中,在社群1中嗅闻频次最多;(2)在攻击行为频次上,不论是优势雄鼠还是从属雄鼠在3 组中都不存在显著差异;(3)在上跳频次上,优势雄鼠在各组间存在显著差异,从属雄鼠在各组间不存在显著差异; (4) 在自我修饰行为频次上,不论是优势雄鼠还是从属雄鼠,在3 组之间不存在显著差异;(5)在相互友好行为上,3 组间存在显著差异。其中社群2 中的雄性之间的友好行为频次最高,社群3 中次之,社群1 中最低。结果表明,雄性之间的攻击行为并不因为雌性的存在而增强,反而会可能减少,我们推测这可能因为雄性要花费更多的时间用于社群探究和交配,从而减少了雄性之间的斗争。     

雄性麋鹿的交配机会、社会等级和皮质醇水平

我们在北京麋鹿苑研究了发情期雄性麋鹿的社会行为、社会等级和血清皮质醇水平,并分析了三者间的相互关系。按照雄性麋鹿的行为,将雄性麋鹿分为优势群和从属群。优势群包括群主和挑战者,从属群包括单身汉和被淘汰群主。使用SJ—Ⅰ型事件记录器进行常规行为取样,用放射免疫分析法测定血清皮质醇含量。发现：(1)优势雄鹿的发情行为频次明显高于从属雄鹿;(2)攻击行为的发生频次在两组间无显著差异;(3)血清皮质醇含量在两组间也无显著差异。由此我们认为,发情期雄性麋鹿的社会等级序位影响许多行为的表达,优势雄鹿成功交配的机会比从属雄鹿多。而攻击行为和肾上腺皮质醇的分泌与社群等级无明显相关,可能是麋鹿在圈养状态下的一种适应策略,这将有利于缓解发情期雄鹿的紧张,从而允许更多的能量投放在发情交配上。     

笼养雌性黑叶猴尿中性腺激素水平变化与性行为、等级序位的关系

2003年10月30日至2004年11月21日,采集了3只笼养雌性黑叶猴妊娠期和1 只笼养雌性黑叶猴发情期的晨尿,并用放射免疫分析法检测尿液中孕酮和雌二醇浓度,同时用全事件观察法观察黑叶猴的行为,分析雌性黑叶猴的行为与其尿中的性腺激素的关系。研究结果发现:1)进入妊娠期,雌性黑叶猴尿中的雌二醇浓度逐渐上升,中后期达高峰;而尿中孕酮浓度在妊娠初期仍维持在放免法的灵敏度以下,妊娠约1 个月后才升高至灵敏度以上(13.39 ng/ mgCr);2)在妊娠中期,雌性黑叶猴仍维持着较高频率的邀配行为,但与雌激素的变化无明显的相关关;3)发情期,雌猴尿中的雌二醇浓度与其邀配行为呈正相关;4)雌性黑叶猴的性激素高低与其等级序位无关,但序位高的雌猴繁殖较早。     

黑线仓鼠殴斗行为模式及其与生理状态的关系

本文以分布于鲁西南山区的黑线仓鼠雄体为对象,通过测定重复遭遇战(repeated encounters)对黑线仓
鼠体重、生理指标等参数的作用,以期阐明社群冲突(social conflict)对黑线仓鼠生理状态的影响。研究结果表
明:在4 周的重复遭遇战过程中,参与冲突个体的体重增长率略有降低,但未达到显著水平;粪便肾上腺皮质
激素(GCs)含量呈现波动性变化,在整个遭遇战过程中,优势个体与从属个体的GCs 含量交替显著升高,与
冲突时间及个体社群地位均有关;优势个体保持较高的睾酮水平,利于其增强攻击行为和获得优势地位;从属
组雄体的肾上腺显著增大,但生殖腺间差异不显著;HPA 轴对HPG 轴具有显著的抑制效应,肾上腺分泌的皮质
醇可显著抑制个体的睾酮分泌,二者呈显著的负相关关系。这些数据表明,黑线仓鼠雄体可通过斗殴行为建立
明确的优势- 从属关系,睾酮可促进个体优势地位的形成并受到肾上腺皮质醇抑制;HPA 轴对HPG 轴的抑制未
能在器官指数方面得到证实。从属个体受到胁迫,对优势雄性黑线仓鼠野外生存和繁殖有重要意义。     

圈养马麝刻板行为表达与粪样类固醇激素的关系

2017年7月1日-8月31日及2018年6月1日-7月31日,在甘肃兴隆山保护区马麝繁育中心,采用焦点取样法和连续记录法进行了圈养马麝的刻板行为取样,采集同期粪样,并用放射免疫分析法（RIA）检测粪样中肾上腺皮质醇、睾酮及雌二醇激素的水平,分析了圈养马麝刻板行为表达与上述3种激素水平的关系。结果显示,展现刻板行为的圈养马麝的皮质醇水平（111.099 ± 16.231）ng/g略高于无刻板行为表达的马麝（95.640± 9.738） ng/g,差异未达显著（P> 0.05）;展现刻板行为雄麝的睾酮水平（135.900± 21.582）ng/g略高于无刻板行为的雄麝（108.182 ± 9.689） ng/g,差异也不显著（P> 0.05）;展现刻板行为雌麝的雌二醇水平（0.445 ± 0.116）ng/g显著低于无刻板行为雌麝（10.843 ± 1.142）ng/g（P< 0.05）。研究结果表明,圈养雄性马麝的刻板行为表达与其类固醇激素水平不相关;而雌麝的刻板行为表达与雌二醇分泌显著负相关,这与其繁殖及健康状况有关。在麝类驯养实践中,可将粪样类固醇激素水平（尤其是雌二醇）作为其受胁迫水平及行为健康的监测指标。     

社群等级对金乌贼行为表型及能量代谢的影响

采用实验生态学方法,在室内水槽条件下研究了金乌贼(Sepia esculenta Hoyle,1885)繁殖过程中社群等级的形成对其行为表型和能量代谢的影响,分析测定了不同优势等级雌雄个体腕部肌肉和性腺组织中己糖激酶(Hexokinase, HK)、丙酮酸激酶(Pyruvate kinase, PK)、乳酸脱氢酶(Lactate dehydrogenase, LDH)、苹果酸脱氢酶(Malate dehydrogenase, MDH)、柠檬酸合酶(Citrate synthetase, CS)活性以及乳酸(Lactic acid, LD)含量。结果显示:(1)金乌贼繁殖期不同优势等级雌雄个体之间行为表型具有显著差异,优势雄性个体游动悬浮、争斗时间显著高于劣势个体,而优势雌性个体静止伏底时间高于劣势个体,游动悬浮时间低于劣势雌性;(2)优势雄性个体在争斗过程中主要通过无氧代谢提供能量,而处于游动悬浮状态时通过有氧代谢提供能量。主要表现在优势雄性个体肌肉中无氧代谢酶(PK、HK、LDH)活性显著高于劣势个体(P0.05),有氧代谢酶(MDH、CS)活性也显著高于劣势个体,雌性个体之间则差异不显著(P0.05);(3)繁殖期雌性个体通过减少运动量来储存能量用于产卵繁殖,主要表现在优势雌性个体肌肉中有氧代谢酶(MDH、CS)活性低于劣势个体,而在性腺中恰恰相反;(4)运动表型与能量代谢之间存在显著相关性,表现在游动悬浮时间与有氧代谢酶(MDH、CS)活性呈显著正相关(P0.001),争斗时间与无氧代谢酶(PK、HK、LDH)及乳酸(LD)含量呈显著正相关(P0.05)。结果表明,社群等级高的雄性个体运动能力强,具有较高的生存适应性。而社群等级高的雌性个体多处于静止状态,以便更好地储存能量用于繁殖。研究结果为金乌贼健康苗种培育以及规模化繁殖技术优化提供了理论依据。     

Interrelationship of serum testosterone, dominance and ovarian cyclicity status in female African elephants

The African elephant population in North American zoos is not self-sustaining, in part due to the prevalence of ovarian acyclicity. While little is known about the cause of this condition, earlier research has shown that females without cyclic corpus luteum (CL) function rank higher in the dominance hierarchy than females with cyclic CL function. The goal of this study was to measure longitudinal serum testosterone concentrations in captive female African elephants to determine if there is a relationship among serum testosterone concentrations, social dominance rank and ovarian cyclicity status. Weekly blood samples from 49 female African elephants (24 having and 25 not having cyclic CL function at 22 facilities) were collected over a 12-month period and analyzed for serum testosterone using an enzymeimmunoassay. A progesterone radioimmunoassay was used to quantify serum progestagen concentrations and categorize ovarian cyclicity status. The dominance hierarchy of individual elephants within each herd was assessed by a written temperament survey, which identified 19 dominant, 15 middle and 15 subordinate females. No clear patterns of serum testosterone secretion were observed in females with and without cyclic CL function. Furthermore, no significant relationships were found among serum testosterone concentrations, dominance rank, and ovarian cyclicity status. These data suggest that increased circulating testosterone concentrations are not associated with greater rates of ovarian acyclicity or dominance status in captive female African elephants.     

Secretory Pattern of Inhibin During Estrous Cycle and Pregnancy in African (Loxodonta africana) and Asian (Elephas maximus) Elephants

The ovary of female elephants has multiple corpora lutea (CL) during the estrous cycle and gestation. The previous reports clearly demonstrated that inhibin was secreted from lutein cells as well as granulosa cells of antral follicles in cyclic Asian elephants. The aim of this study is to investigate the inhibin secretion during the pregnancy in African and Asian elephants. Two African elephants and two Asian elephants were subjected to this study. Circulating levels of immunoreactive (ir‐) inhibin and progesterone were measured by radioimmunoassay. Four pregnant periods of an African elephant and three pregnant periods of an Asian elephant were analyzed in this study. Circulating levels of ir‐inhibin started to increase at 1 or 2 week before the ovulation and reached the peak level 3 or 4 weeks earlier than progesterone during the estrous cycle in both African and Asian elephants. After last luteal phase, the serum levels of ir‐inhibin remained low throughout pregnancy in both an African and an Asian elephant. The mean levels of ir‐inhibin during the pregnancy were lower than the luteal phase in the estrous cycle despite high progesterone levels were maintained throughout the pregnancy. These results strongly suggest that CL secrete a large amount of progesterone but not inhibin during the pregnancy in elephants. Zoo Biol 31:511‐522, 2012. © 2011 Wiley Periodicals, Inc.     

Estrous state influences on investigative,aggressive, and tail flicking behavior in captive female Asian elephants

Females of species that live in matrilineal hierarchies may compete for temporally limited resources, yet maintain social harmony to facilitate cohesion. The relative degree of aggressive and nonaggressive interactions may depend on the reproductive condition of sender and receiver. Individuals can benefit by clearly signaling and detecting reproductive condition. Asian elephants (Elephas maximus) live in social matrilineal herds. Females have long estrous cycles (14–16 weeks) composed of luteal (8–12 weeks) and follicular (4–8 weeks) phases. In this study, we observed the behavior of four captive Asian elephant females during multiple estrous cycles over 2 years. We evaluated whether investigative, aggressive, and tail flicking behaviors were related to reproductive condition. Investigative trunk tip contacts showed no distinct pattern by senders, but were more prevalent toward female elephants that were in their follicular compared with their luteal phase. The genital area was the most frequently contacted region and may release reproductively related chemosignals. Aggression did not differ significantly with estrus; however, rates of aggression were elevated when senders were approaching ovulation and receivers were in the luteal phase. Females in the follicular phase may honestly advertise their condition. Contacts by conspecifics may serve to assess condition and reduce aggression. A behavior termed “tail flicking” was performed mainly during the mid‐follicular phase when estrogen and luteinizing hormone levels are known to spike. Tail flicking may disperse chemical signals in urine or mucus as well as act as a tonic signal that could provide a means of anticipating forthcoming ovulation by elephants and also for human observers and caretakers. Zoo Biol 27:167–180, 2008. © 2008 Wiley‐Liss, Inc.     

Use of genital inspection and female urine tests to detect oestrus in captive Asian elephants

Captive Asian elephant (Elephas maximus) populations are decreasing due to low birth rates compared to wild elephants. Improving oestrous detection in female elephants is required to ensure successful mating in captive and semi-captive herds. Responsive behaviours of eight semi-captive bull elephants to the uro-genital area (genital inspection test) or urinary pheromones (urine test) of 14 female elephants throughout the oestrous cycle were evaluated. Weekly blood samples were collected for 27 consecutive months (14 months for the genital inspection test and 13 months for the urine test) from female elephants to characterize the patterns of circulating progestagen. Responsive behaviours of bulls were compared between females in the follicular versus the luteal phase of the cycle. The sensitivity and specificity of the genital inspection test were 65% and 68%, while those of the urine test were 52% and 61%, respectively. The bulls showed significantly higher “genital inspection”, “flehmen from genital area” and “trunk on back” behaviours during the genital inspection test, and “flehmen” behaviours during the urine test in oestrous than in non-oestrous females. In sum, this study showed that monitoring sexual behaviours of Asian elephant bulls towards females or their urine can be used to detect the oestrous period. Although the sensitivity and specificity of both tests were not as high as expected, still, these methods appear to be more efficient at detecting oestrous than traditional methods based on mahout estimations of female receptivity. The use of genital inspection and urine tests may lead to more successful matings and thus to creating self-sustaining populations of captive elephants in range countries.     

Estrous synchrony in a group of African elephants (Loxodonta africana) under human care

Synchrony of estrous, and consequently of conception and birth of young, may be of adaptive significance for certain mammals. Among the species in which estrous synchrony has been suspected several times are elephants, but clear evidence is still missing. We determined estrous cycles of African elephants (Loxodonta africana) (n=4) at the Vienna Zoo, Austria, between June 2003 and January 2006 by measuring serum progesterone levels from weekly blood samples. Except for the dominant female when she was intensively lactating, all animals showed clear cycles or progesterone release with a mean period of 105.3+/-15.37 days. For most of the study period, estrous cycles were asynchronous between females. However, after re-occurrence of the progesterone cycle in the dominant female following the first period of lactation, all four females showed high synchrony of progesterone release over the two subsequent cycles. Large changes in individual period lengths indicated that synchronization was due to the adjustment of cycle length in subdominants to that of the dominant female. We used a bootstrap procedure, based on resampling measured times of progesterone peaks, to determine if this apparent synchrony could have been caused by chance alone. This statistical analysis indicated that between-individual variances of the timing of progesterone peaks were much smaller that to be expected by chance (P=0.009). This finding represents the first evidence for estrous synchrony between elephants. We discuss various hypotheses to explain the biological function of cycle synchrony in elephants.     

Concentrations of progesterone,testosterone and estradiol-17β in the serum during the estrous cycle of Asian elephants (Elephas maximus)

The levels of progesterone, testosterone and estradiol-17β in serum samples from two female Asian elephants were measured for the period of 32 months from February 1987 to September 1989. Serum samples were collected weekly from unanesthetized elephants. Each elephant showed eight ovarian cycles in 32 months. Ovarian cycles, characterized by changes in concentrations of serum progesterone, averaged 16.8 ± 0.6 (mean ± SEM. n = 14) weeks in length. The changes in concentrations of testosterone in the serum showed a similar pattern to those of progesterone with a striking increase noted during the luteal phase. The highest levels of serum estradiol-17β were noted when progesterone levels showed low basal values. These results suggest that estradiol-17β may be an index of follicular maturation during the estrous cycle in Asian elephants, and that the ovaries of Asian elephants may produce testosterone in the luteal phase.     

Hormonal correlates of dominance in meerkats (Suricata suricatta)

In cooperatively breeding meerkats (Suricata suricatta), individuals typically live in extended family groups in which the dominant male and female are the primary reproductives, while their offspring delay dispersal, seldom breed, and contribute to the care of subsequent litters. Here we investigate hormonal differences between dominants and subordinates by comparing plasma levels of luteinizing hormone (LH), estradiol and cortisol in females, and testosterone and cortisol in males, while controlling for potential confounding factors. In both sexes, hormone levels are correlated with age. In females, levels of sex hormone also vary with body weight and access to unrelated breeding partners in the same group: subordinates in groups containing unrelated males have higher levels of LH and estradiol than those in groups containing related males only. When these effects are controlled, there are no rank-related differences in circulating levels of LH among females or testosterone among males. However, dominant females show higher levels of circulating estradiol than subordinates. Dominant males and females also have significantly higher cortisol levels than subordinates. Hence, we found no evidence that the lower levels of plasma estradiol in subordinate females were associated with high levels of glucocorticoids. These results indicate that future studies need to control for the potentially confounding effects of age, body weight, and access to unrelated breeding partners before concluding that there are fundamental physiological differences between dominant and subordinate group members.     

Relation between the dominance rank of female rhesus monkeys and their access to males

Systematic observations were made on 12 measures of the sexual, aggressive, and social interactions of 24 male–female pairs of rhesus monkeys in six social groups, each consisting of one male and four ovariectomized females tested in a large room. Each female in a group was treated in turn first with estradiol alone and then with estradiol and progesterone in combination. When hormone-treated, the female was also observed during pair tests with the male in the same large observation room (four males, eight females, 240 group tests, 240 pair tests). The dominance ranks of females during group tests were determined post hoc by means of the dominance index [Zumpe & Michael, American Journal of Primatology 10:291–300, 1986]. In all six groups, the most dominant female virtually monopolized the male, and the subordinate females' interactions with the male, assessed during pair tests, were almost completely suppressed during group tests. This “dominant female effect” was a robust phenomenon that depended solely on female dominance rank. It was independent of the identity and hormonal status of females and of the social preferences of males as expressed in pair tests. These findings demonstrate the existence of female mate competition in an Old World primate.