黑线仓鼠种群年龄组成及其数量季节消长的研究

本文对黑线仓鼠的上臼齿磨损程度进行了系统观察,共采标本553只,结合生殖系统的解剖记录,确定以右侧上臼齿的磨损程度将黑线仓鼠划分为5个年龄组。探讨了年龄与体长、体重及繁殖力的相互关系,以及种群数量季节消长与气候条件及种群结构的关系。结果表明,黑线仓鼠年龄越大,雌鼠的繁殖力越高,但平均怀仔量并不随年龄增大而增加。体重、体长不易作为划分黑线仓鼠年龄组的指标。种群数量与大降雨量呈明显的负相关,但种群的年龄结构对数量消长起着主要作用。     

佛坪自然保护区羚牛的种群数量与结构特征

１９９６年对佛坪自然保护区内的羚牛种群进行了数量调查,结果表明,保护区内羚牛的数量为４３５～５２７只,种群密度达到１．２９～１．５６只／ｋｍ２。羚牛种群的成体雌雄个体之比约为１∶０．５,明显地偏向雌性。在羚牛种群中幼仔占１２．２４％,亚成体占３５．０３％,成年雄性个体占１７．３３％,成年雌性个体占３５．４０％。该羚牛种群在１９９１年至１９９６年间的年均增长率为１８．４８％,明显高于１９８４至１９９１年间羚牛种群的年均增长率。保护区周边地区的生境不断丧失,迫使羚牛向保护区境内迁移,是保护区内羚牛种群数量在短期内迅速升高的原因。     

山东阳谷县黑线仓鼠种群数量预测预报

作者于１９８２－１９９２年对山东省阳谷县黑线仓鼠的种群数量作了调查,并应用逐步回归分析法预报了阳谷,薛城１９９３年３月份,５月份、８月份和１１月份黑线仓鼠的鼠害发生程度,预报值与实测值基本相符。     

应用马尔可夫链模型预测长爪沙鼠和黑线仓鼠种群数量

依据1984～2004年21年在呼和浩特郊区对长爪沙鼠(Meriones unguiculatus)和黑线仓鼠(Cricetulus barabansis)种群数量动态的调查数据,结合优选法(0.618法),应用加权马尔可夫链预测模型,建立了长爪沙鼠和黑线仓鼠种群数量预测模型。应用此模型分别预测了长爪沙鼠和黑线仓鼠2004年的种群数量,预测值与实测值相符,预测准确。同时,预测了未来三年(2005～2007年)长爪沙鼠和黑线仓鼠的种群数量。结果表明,此方法计算简便、准确、可靠,为鼠类种群数量的预测提供了新的方法。     

Jolly-Seber法对大仓鼠和黑线仓鼠种群若干参数的估算

本文利用Jolly-Seber法估算了1986和1988年河北省饶阳县大仓鼠和黑线仓鼠的种群大小、存留率等参数。结果表明,大仓鼠的存留率比黑线仓鼠小,而且和密度负相关。大仓鼠和黑线仓鼠对铁丝活捕笼均不存在非等捕性。该方法对大仓鼠和黑线仓鼠种群参数估计是可行的。     

安徽淮北农区三种鼠的种群数量动态与年龄结构的关系

本文对安徽省淮北农业区的黑线姬鼠、大仓鼠和黑线仓鼠的种群数量及与年龄组成变化的关系进行探讨。结果表明,其各鼠的年龄组成在每年的不同时段内的变化有一定的规律:各鼠主要繁殖群体的年龄组也是有区别的,如黑线姬鼠和黑线仓鼠主要是成年Ⅱ组,大仓鼠主要是成年Ⅰ组。如果种群中幼年组+亚成年组+成年Ⅰ组的比例高时,则当年数量就可能较高,如果种群中成年Ⅱ组和老年组的比例较高时,当年数量则低。     

呼和浩特地区黑线仓鼠种群动态研究

1984—1989年,每年3—11月中旬在呼和浩特郊区定点调查,共捕获黑线仓鼠2920只,本文分析了该鼠每年的种群数量变动和年龄结构,用臼齿咀嚼面磨损程度划分年龄组,研究种群年龄结构。种群数量年际变化较大,季节变化也较明显,一般年有两个繁殖高峰和数量高峰(后峰8—10月,前峰5—6月)。每年3—10月为繁殖期,平均每胎产仔6.2±0.1只,各年间繁殖有一定差异。     

安徽淮北农区大仓鼠和黑线仓鼠种群动态的研究

1982一1988年在安徽淮北农区的调查结果表明:大仓鼠种群数量的季节消长特点是,数量高的年份出现3个波峰(即前峰、中峰和后峰),平常年份有2个波峰(中峰和后峰),数量低的年份仅1个波峰(后峰)。波峰峰度大都是后峰最高。黑线仓鼠的波峰数除个别数量高的年份有2个(前峰和中峰)外,多数年份只有1个前峰。两种仓鼠的年间数量变幅皆较明显,推测两鼠各自从一个高峰期到另一个高峰期之间需经历7—8年左右时间。繁殖期,大仓鼠为7个月(4—10月),黑线仓鼠为10个月(2—11月);两者均有两个繁殖盛期,即春峰和秋峰经相关分析,大仓鼠的年数量与年怀孕率存在密切的正相关关系,而黑线仓鼠则为年怀孕率对次年数量有明显的影响。     

甘肃鼢鼠种群动态及其影响因素的初步分析

啮齿动物种群动态及影响因素的研究是害鼠预测预报的基础。国内曾对大林姬鼠、子午沙鼠、大仓鼠、布氏田鼠、黑线仓鼠、小家鼠等种群动态及影响因素进行过研究。作者于１９９２～１９９４年,在延安树木园和富县牛武林场对甘肃鼢鼠种群动态及影响因素做了研究,现将结果报...     

滇中农区大面积灭鼠后褐家鼠种群动态的初步研究

滇中农区大面积灭鼠后褐家鼠种群动态的初步研究褐家鼠是滇中农区主要危害种类之一。我们于１９９０年１月－１９９１年１月和１９９１年５月－１９９２年７月在云南中部通海县开展周年调查,以分析全县统一灭鼠对褐家鼠种群数量的影响,现将结果报道如１．自然概况和调查...     

北京大兴地区黑线仓鼠种群繁殖生态研究

黑线仓鼠(Cricetulus barabensis)是我国华北地区广泛分布的农田主要害鼠之一。1982年9月到1985年3月,作者在北京、天津及河北省一些地区,调查了它的分布和群落结构并研究其种群生态,本文仅就北京郊区大兴县黑线仓鼠的种群繁殖问题进行讨论。     

中国哺乳类物种与科属的数量关系

利用中国三种地理类型(自然保护区、行政省和动物地理亚区)的哺乳类名录,分析物种与高等分类阶元(属、科)的数量关系,旨在为利用高等分类阶元替代物种预测生物多样性提供理论依据,研究结果显示:1)不同地理类型中物种-属-科在数量上具有相似的增长趋势,且物种-属、物种-科的数量关系呈极显著相关(P < 0.01)。利用模型对哺乳类物种与科和属的数量关系模拟,乘幂模型拟合效果最佳。2)物种在属间、科间的频次均呈非均匀分布,对结果进行拟合发现对数、乘幂、指数和线性四种模型中,乘幂模型对哺乳类物种与科和属的数量关系模拟效果最佳。综合以上内容认为,哺乳类物种与高级分类阶元在数量和频次分布上存在规律,且可用模型进行很好拟合,这种关系适用于生物多样性预测、评价和保护。     

鲁西平原黑线仓鼠种群调节机理的研究——种群密度与肾上腺、性腺重量及血浆皮质醇值之间的关系

关于种群数量波动的内在调节机制,现今已有大量的实验种群资料证明大多数小型啮齿类种群具有内部调节的反馈系统,但对自然种群的研究至今报道较少,涉及的鼠种为数不多,其中关于Christian(1964)的行为-内分泌     

桉树人工林树液流动密度随边材径向深度的变化

树液流动密度 (SFD)随边材径向深度的变化对于准确估测流经边材的树液通量是非常重要的 ,后者又制约着HeatPulse的应用精度。但迄今为止 ,只有很少的研究估计了由于SFD随径向的梯度变化而带来的误差 ,SFD沿树干径向分布规律的获得往往依靠对少数几棵树的观测资料。基于在广东雷州半岛对两块 3～ 4年生桉树 (Euca lyptusurophyllaS .T .Blake)人工林 1年的HeatPulse观测 ,探讨了对来自 39株立木大量观测资料的综合处理方法 ,发现这两个样地 (纪家和河头 )的林分中SFD随边材径向深度的变化可以用如下回归方程来描述 :纪家 :y =3.6 6 75x3 - 7.2 95 5x2 3.6 82 6x 0 .5 6 74 (R2 =0 .9391,n =80 ,P =0 .0 1)河头 :y =5 .0 0 6 2x3 - 9.116 1x2 4.4 5 4 4x 0 .4 6 34(R2 =0 .80 6 9,n =72 ,P =0 .0 1)式中 :y———某一树液感应器所测得的SFD与不同深度的 4个感应器所测得的SFD的平均值之比 ;x—某一树液感应器在边材中的深度与边材厚度之比。从形成层到心材 ,SFD最初有所增加 ,随后持续减小 ,但由于树木年龄很小 ,最大的SFD只比最小的SFD大 0 .33～ 0 .36倍。     

Effect of RFRP-3 on reproduction is sex- and developmental status-dependent in the striped hamster (Cricetulus barabensis)

RFamide-related peptides (RFRPs) are orthologous to gonadotropin-inhibitory hormone (GnIH) inhibiting gonadotropin release. There are only two RFRP sequences (RFRP-1 and RFRP-3) encoded in rodents. RFRP-3, which was considered as a hypothetical inhibitor on GnRH, shows a stimulatory effect on the male Syrian and male Siberian hamster in short days. As a dominant rodent pest in northern China farmland, the striped hamster (Cricetulus barabensis) has higher reproductive activities and could act as a model to study the mechanism of reproduction. However, the effect of RFRP-3 on the reproductive activity for the striped hamster is less understood. In the study, we cloned 643 bp RFRP cDNA from the striped hamster hypothalamus, which contained an ORF of 570 bp encoding two RFamide-related peptide (RFRP) sequences: SPAPANKVPHSAANLPLRF-NH₂ (C. barabensis RFRP-1) and TLSRVPSLPQRF-NH₂ (C. barabensis RFRP-3). We also investigated the expression variation of RFRP mRNA and GnRH mRNA in the hypothalamus from hamsters with different developmental statuses (7-week-, 13-week- and 1.5-year-olds) using FQ-PCR, in which the 13-week-old female individuals were in estrous. The striped hamsters that are 7 weeks and 1.5 years old are non-breeding individuals, and those that are 13-week hamsters have breeding phenomena. The highest hypothalamus RFRP mRNA level was found in breeding males as compared to non-breeding males. Conversely, the lowest RFRP mRNA level in the hypothalamus was observed in breeding females, with no significant level when the breeding females were compared to the 7-week-old individuals. Additionally, the investigation of GnRH expression level showed a declining expression trend across the developmental stages (7-week-, 13-week- and 1.5-year-olds) in both sexes. Significant negative and positive relationships were detected in the 13-week estrous female (r = − 0.997, P = 0.035) and the 13-week male (r = 0.998, P = 0.029) striped hamsters respectively, which suggest that RFRP-3 has inhibitory and stimulatory effects on female and male adults respectively. Our results suggest that the effects of RFRP-3 on reproduction are sex- and developmental status-dependent in the striped hamster.     

A note on the nonautonomous delay Beverton-Holt model

It is well known that the periodic cycle {x(n)} of a periodically forced nonlinear difference equation is attenuant (resonant) if av(x(n)) < av(K(n))(av(x(n)) > av(K(n))),where {K ( n )} is the carrying capacity of the environment and av(t(n)) = (1/p)∑(p?1) (i=0) ti (arithmetic mean of the p-periodic cycle {t ( n )}). In this article, we extend the concept of attenuance and resonance of periodic cycles using the geometric mean for the average of a periodic cycle. We study the properties of the periodically forced nonautonomous delay Beverton-Holt model x(n+1) = r(n)x(n)/1 + (r(n?l) ? 1)x(n?k)/K(n?k), n= 0, 1, . . . , where {K ( n )} and {r ( n )} are positive p-periodic sequences; (K ( n )>0, r ( n )>1) as well as k and l are nonnegative integers. We will show that for all positive solutions {x ( n )} of the previous equation lim sup (n→∞) (∏(n?1)(i=0)xi)(1/n) ≤ ((∏(p?1)(i=0)ri)(1/p) ? 1)(∏(p?1)(i=0)(ri ? 1))(?1/p)(∏(p?1)(i=0)Ki)(1/p). In particular, in the case where {x(n)} is a p-periodic solution of the above equation (assuming that such solution exists) and r ( n )=r>1, the periodic cycle is g-attenuant, that is (∏(p?1)(i=0)x(i))(1/p)<(∏(p?1)(i=0)K(i))(p?1) Surprisingly, the obtained results show that the delays k and l do not play any role.     

Correlation of scrotal circumference and age in American Brahman bulls

Scrotal circumference (SC) measurements were taken of 921 American Brahman bulls located on two ranches in southcentral Texas. Measurements were taken at various seasons of the year over an 11-yr time span. Body condition scores, as reflected by fat cover, and a subjective estimate of overall nutritional status were 4 or better, based upon a 1 to 9 scoring system, with 5 representing an animal with an average amount of body fat. Associated body weights were not measured and semen evaluations were not performed. Ages were calculated from exact birthdates and rounded to the nearest whole month. Ages from 8 mo to more than 36 mo were reported. SC measurements ranged from 16.0 cm to 42.5 cm. The relationship of SC and age was positively correlated (r=0.74) (P<0.0001) and could be predicted using the equation y=0.525x + 18.702 where y=SC in centimeters and x=age in months. These data provide evidence that the relationship of scrotal circumference and age of American Brahman bulls is similar to that of other cattle breeds.