不同季节长爪沙鼠同生群的繁殖特征及其在生活史对策中的意义

通过剪趾和染毛双重标志的重捕跟踪途径, 结合行为观测研究了栖息于内蒙古农牧交错区草地生境的长爪沙鼠种群繁殖格局。按同生群分组分析的结果显示春季(4～5 月) 出生的雄鼠当年能达到性成熟的个体仅占34.6 % , 性成熟发育历期为3 个月, 其繁殖平均结束时间比越冬鼠早近1 个月。6 月以后出生的雄鼠当年达不到性成熟。达到性成熟的当年雄鼠在繁殖期结束前多数又转入性休止状态。当年雌鼠性成熟历期约2.5 月龄, 初次产仔时间在3.5 月龄左右。6 月份以后出生的雌鼠当年不参加繁殖。各同生群雌鼠1 年中最多产仔次数有差异,越冬鼠可产3～4 窝。4～5 月份出生的雌鼠当年可产1 窝。长爪沙鼠当年生雌、雄鼠非同步发育以及由性成熟的当年鼠与越冬鼠构成的繁殖格局有利于维持家群个体的适合度, 是该鼠生活史对策的重要特征之一。     

内蒙古农牧交错带长爪沙鼠种群存活的季节格局及其动态机制

了解动物种群存活特征以及相关环境因子对其变化的独立或整合作用过程,有助于阐明动物种群动态的生态学机制。长爪沙鼠（Meriones unguiculatus）是分布于我国北方典型草原、荒漠草原及其毗邻的农牧交错带的优势鼠种之一。2000年10月至2004年10月通过标志重捕法研究了栖息于内蒙古农牧交错区草地生境的种群动态。本文通过MARK软件包中的CJS和MS模型分析了长爪沙鼠半自然围栏种群表观存活率（Φ,简称存活率）的性别（g）差异和年龄（as）特征表现及其季节变化格局,并对种群存活变化的密度和气候效应加以分析,旨在检验长爪沙鼠种群存活显示季节变化特征,并受密度制约和气候条件反馈调节的假设。结果发现,长爪沙鼠种群存活率初始最优模型Φ(t)p(g*t)中重捕时序（t）效应显著（ANODEV,F _27,47 =11.05,P <0.001）,月季效应最优模型Φ(month)p(g*t)也显示存活率 季节变化明显（ANODEV,F _5,69 =31.69,P <0.001）,总体呈现从春季到冬季经历下降再升高的“V”字型动态模式。在无环境因子限制条件下,雌鼠（0.788±0.013）和雄鼠（0.781±0.013）存活率差异不明显;存活率年龄差异表现明显的季节特征（ANODEV,F _5,246 = 67.85,P < 0.001）,繁殖消耗在一定时期影响成年个体的存活。长爪沙鼠种群存活的季节格局反映其生活史对策中适应高纬度气候和食物等资源季节波动的重要特征。进一步统计发现种群存活率受密度制约、与降水负相关,其中密度制约效应具有一定的时滞,降水作用是即时的,上述效应的作用强度在雌、雄鼠的存活反应上有所差异。这些结果暗示密度制约整合水热条件介导最适栖息地环境变化,引发雌、雄鼠存活率差异性反应,进而影响其它种群参数变化,调节种群增长。这可能是北半球高纬度地区小哺乳动物种群调节的一个重要机制。     

大沙鼠对栖息地的选择

根据地形特点和植被状况在调查地共划分出５类生境,大沙鼠最适生境为白刺＋盐爪爪＋红柳半固定沙丘。另外,大沙鼠对栖息地的选择有明显的季节差异,在春季大沙鼠多栖息于白刺＋盐爪爪半固定沙丘;秋季,又向盐爪爪＋裸露土岗生境迁移。食物条件、地形特点和植被覆盖度是影响大沙鼠栖息地选择的三个重要因素。     

炔雌醚对内蒙古农牧交错带长爪沙鼠种群繁殖的影响

炔雌醚对一些鼠类种群具有良好的控制效果。为探究炔雌醚对长爪沙鼠Meriones unguriculataus种群繁殖的影响,于2006年5—8月在内蒙古锡林郭勒盟白音锡勒牧场农牧交错带展开了炔雌醚对长爪沙鼠野生种群繁殖的控制实验。设置了投药区和对照区,5月初进行投药,实验期间采用夹线调查法逐月对样地内的长爪沙鼠进行系统的取样调查,分析炔雌醚对长爪沙鼠种群繁殖的影响。结果显示:在投药之后的6—8月,投药区成体鼠的子宫坏死率分别为75.3%、61.5%和48.7%,与对照区差异有高度统计学意义(P0.01);投药区成体鼠的怀孕率下降,与对照区差异有高度统计学意义(P0.01);投药区的胎仔数显著低于对照区(P0.05)。综上表明,炔雌醚对农牧交错带长爪沙鼠种群繁殖的控制具有良好的效果。     

炔雌醚对长爪沙鼠种群数量和性比的影响

炔雌醚是一种激素类新型鼠类不育剂,已有研究表明,炔雌醚对某些鼠类种群繁殖具有良好的控制成效。为检验新型不育剂对长爪沙鼠种群的控制效果,2006年5月在内蒙古锡林郭勒盟锡林浩特市农牧交错带开展了炔雌醚对野外长爪沙鼠种群的控制实验,本次实验设投药区和对照区2个组别,5—8月开展逐月的夹线调查以及四分之一圆洞口计数法,对样地内长爪沙鼠进行系统的追踪调查,分析炔雌醚对长爪沙鼠种群数量以及种群性比的作用。结果显示:投药1个月之后,投药区雌鼠比例(16.3%)不及对照组雌鼠比例(51.9%)的三分之一,投药区的雌鼠比例(16.3%)仅为雄鼠比例(83.7%)的五分之一;与对照区相比,投药区长爪沙鼠的密度下降达60%以上。这表明:炔雌醚对野外长爪沙鼠种群的不育控制具有良好效果,且炔雌醚对长爪沙鼠的种群性比影响很大,过量投放炔雌醚可造成雌鼠死亡,单独使用炔雌醚可降低野外不育剂的药物成本。     

EP-1 不育剂对长爪沙鼠野生种群增长的控制作用

长爪沙鼠在内蒙古地区的分布非常广泛,长期以来由其造成的“鼠害” 不仅给农牧业生产带来危害,而且还传播疾病。2009 年3 ～ 10 月,在内蒙古鄂尔多斯荒漠草原,利用复合不育剂左炔诺孕酮- 炔雌醚(EP-1)
对长爪沙鼠野生种群进行了不育控制试验研究。结果表明,复合不育剂EP-1 对长爪沙鼠种群结构和种群密度均有显著影响,在5 月和6 月两个繁殖高峰期,不育剂EP-1 显著降低了幼体出生的数量,实验区与对照区幼体组
成差异和成体组成差异均达到极显著(P < 0.01)。在8 ～ 10 月,实验区和对照区种群结构组成中,幼体之间、成体之间差异均达到显著和极显著(P < 0.05, P < 0.01)。在整个发育生长期,实验区长爪沙鼠幼体种群从6 月
份开始出现,9 月达到数量最高值,幼体种群全年呈现下降趋势。而对照区幼体种群从5 月份开始出现,且数量在5 月份达到全年的最高值,幼体种群与实验区相反呈增长趋势。实验区种群总体数量全年呈下降趋势,而对
照区相反,呈增长趋势。因此,复合不育剂EP-1 显著降低了长爪沙鼠种群的繁殖率、幼体出生比例和种群密度,可以对长爪沙鼠野生种群起到有效的繁殖控制作用,进而降低该鼠对农牧业生产的危害和对人类疾病传播
的风险。     

荒漠破碎化生境中长爪沙鼠集合种群野外验证研究

近年来,人类活动和自然干扰,导致内蒙古阿拉善荒漠区生境的破碎化,出现了长爪沙鼠在不同斑块间的不连续分布,每一斑块内可能存在一个局域种群,而集合种群建立的前提条件,是局域种群斑块状分布在离散的栖息地环境中。2002~2012年每年的4~10月,在阿拉善荒漠区禁牧、轮牧、过牧和开垦4种人为不同利用方式形成的生境斑块中,采用标志重捕法对长爪沙鼠（Meriones unguiculatus）种群进行定点监测。通过分析长爪沙鼠种群动态,计算各局域种群的灭绝风险,利用Spearman秩相关系数检验种群动态的空间同步性,同时以种群周转率对长爪沙鼠扩散能力进行评估,以检验阿拉善荒漠区长爪沙鼠种群空间结构是否具有经典集合种群的功能。结果表明：（1） 不同生境斑块可被长爪沙鼠局域种群占据,11年间捕获长爪沙鼠2~7次不等;（2） 长爪沙鼠所有局域种群均具有灭绝风险,在轮牧区和禁牧区灭绝率高达1.000 0,开垦区灭绝率最低,也达到0.333 4,而本研究期间最大局域种群（2008年过牧区,26只/hm²）,在2010年发生了局域灭绝;（3） 不同生境斑块间没有明显的空间隔离而阻碍局域种群的重新建立,长爪沙鼠扩散能力较强,绝大部分月份的种群周转率在50.0%以上,特别是周转率达到100.0%的月份较多;（4） 不同生境斑块间仅轮牧区和禁牧区中长爪沙鼠种群密度显著正相关（P<0.05）,而其他生境斑块间相关性均不显著（P >0.05）,长爪沙鼠局域种群整体显示出明显的非同步空间动态。阿拉善荒漠区长爪沙鼠种群满足作为经典集合种群物种区域续存的4个条件,具有作为研究小哺乳动物集合种群的潜在价值。     

炔雌醚对内蒙古农牧交错带长爪沙鼠(Meriones unguiculatus)家群大小和巢域行为的影响

为检验施用炔雌醚对农牧交错带长爪沙鼠家群大小与巢域行为的影响,于2006年5月至9月对内蒙古锡林郭勒盟锡林浩特市农牧交错区域分布的长爪沙鼠家群使用炔雌醚进行种群不育控制实验。分设投药区和对照区两个组别,分别于5月、7月与9月份采用1/4样圆面积有效洞口计数法,随机选取24个长爪沙鼠家群,调查对照区域和投药区内沙鼠的家群洞口数量以及家群大小。另在对照区和投药区,随机测定了30个沙鼠的家群活动范围,对比使用炔雌醚前后长爪沙鼠巢域平均半径和活动面积的影响。结果为:对照区家群平均洞口数58个,投药区仅23个,在炔雌醚投药区长爪沙鼠家群受炔雌醚影响,洞口数仅为23个,表明其对长爪沙鼠家群大小控制效果显著。投药区内长爪沙鼠家群密度在投药后连续下降,最大下降幅度较对照区家群密度低70%,表明炔雌醚对长爪沙鼠的家群密度影响较大,可显著降低长爪沙鼠家群密度(P<0.05)。炔雌醚对长爪沙鼠家群平均半径和活动面积的研究结果显示,施用炔雌醚后家群巢域半径与活动面积均显著缩小(P<0.05),与对照区巢域平均面积相比缩小15%、平均活动半径缩小30%。通过以上结果可得出:单独施用炔雌醚对控制野外长爪沙鼠家群以及降低长爪沙鼠巢域、活动面积效果显著。炔雌醚可有效降低农牧交错带长爪沙鼠种群数量和有效活动范围,这对于农牧交错带的鼠害防控,同时降低鼠源性疾病,包括鼠疫的传播都有一定的意义。     

Jolly - Seber 法估算长爪沙鼠种群参数的适用性探讨

以2000 年6 月～10 月群居性长爪沙鼠野生种群的标志重捕资料为依据, 采用Jolly - Seber 模型估算了该鼠种群参数, 结果表明, 长爪沙鼠个体间具等捕性(Leslie 法检验) , 研究期间取样个体的重捕率平均为89.7 %(77.4 % ～ 100 %) ; 参数估计结果具有合理的生物学意义, 认为采用该模型估算长爪沙鼠种群参数是适用的。     

长爪沙鼠肥满度的年龄和季节特征

采用胴体重(去除内脏的体重,记为WN)替代传统计算公式中的体重(W)建立肥满度指标K′＝100WN／L^3(g／cm^3)对长爪沙鼠肥满度的年龄和季节变化特征进行研究。结果显示：该鼠肥满度年龄组间差异显,末成年个体的肥满度明显高于成年个体;各性别年龄组肥满度季节变化明显,趋势基本一致,春季高、夏季最低、秋季又行育肥。在春夏季繁殖期(8月以前),雌鼠的肥满度大于雄鼠。成年雌鼠秋季育肥时间晚于其他个体组。长爪沙鼠肥满度的年龄差异和季节变化反映了该鼠在不同生活时期对环境的生理适应特征和对策。此外,各月肥满度与当月及其后第4个月的夹捕率存在一定的相关关系,提示该指标在短期预测长爪沙鼠种群数量方面可能有其参考价值。     

Population structure and reproductive biology of Pygospio elegans (Polychaeta: Spionidae) on an intertidal sandflat, Firth of Forth, Scotland

Abstract. The population structure and reproductive biology of a population of the spionid polychaete Pygospio elegans was studied at Drum Sands, Firth of Forth, Scotland, between March 1997 and February 1998. P. elegans was numerically dominant at the site and exhibited a population density increase through the sampling period. The population showed a seasonal pattern with two acute periods of recruitment during the year, one in spring and one in winter. Planktotrophic larvae were the only larval type produced throughout the sampling period. Larvae were released at the 3–5 setiger stage and settled at a size of 18–22 setigers. The spring recruits grew at a rate of 23 setigers per month, reaching sexual maturation size during September of the same year. The adult sex ratio was female-biased throughout the study period (mean = 2.99:1 ± 0.51). When female:ripe male sex ratios were highest (summer and fall), the proportion of females brooding larvae decreased suggesting that sexual reproduction is seasonal. Asexual reproduction was not observed in the population of P. elegans on Drum Sands. These findings suggest that a high degree of variability is a trait of the reproductive biology of P. elegans. .     

Delayed female reproduction in equilibrium and chaotic populations

Behavioural and life history polymorphisms are often observed in animal populations. We analyse the timing of maturation and reproduction in risky and resource-limited environments. Field and laboratory evidence suggests that female voles and mice, for example, can adjust their breeding according to the level of risk to their own survival and to survival probabilities and recruitment of young produced under different environmental conditions. Under risky or harsh conditions breeding can be postponed until later in the current breeding season or even to the next breeding season. We develop a population dynamics and life history model for polymorphism in reproduction (co-existence of breeding and non-breeding behaviours) of females in an age-structured population, with two temporally distinct mating events within the breeding season. We assume that, after overwintering, the females can breed in spring and again in summer or they can delay breeding in spring and breed in summer only. Young females born in spring can either mature and breed in summer or stay immature and postpone breeding over the winter to the next breeding season. We show that an evolutionarily stable breeding strategy is either an age-structured combination of pure breeding behaviours (old females breed and young delay maturity) or a mixed breeding behaviour within age-classes (a fraction of females breed and the rest of the age class postpones breeding). Co-occurrence of mixed reproductive behaviour in spring and summer within a single breeding season is observed in fluctuating populations only. The reproductive patterns depend on intraspecific, possibly interspecific, and ecological factors. The density dependence (e.g. social suppression) and predation risk are shown to be possible evolutionary mechanisms in adjusting the relative proportions of the different but co-existing reproductive behaviours.     

The effect of supplemental food on the growth rates of neonatal,young, and adult cotton rats (Sigmodon hispidus) in northeastern Kansas,USA

In food-limited populations, the presence of extra food resources can influence the way individuals allocate energy to growth and reproduction. We experimentally increased food available to cotton rats (Sigmodon hispidus) near the northern limit of their range over a 2-year period and tested the hypothesis that seasonal growth rates would be enhanced by supplemental food during winter and spring when natural food levels are low. We also examined whether additional food resources were allocated to somatic growth or reproductive effort by pregnant and lactating females. The effect of supplemental food on growth varied with mass and season, but did not influence the growth rates of most cotton rats during spring and winter. In winter, small animals on supplemented grids had higher growth rates than small animals on control grids, but females in spring had lower growth rates under supplemented conditions. Growth rates of supplemented cotton rats were enhanced in summer. Northern cotton rat populations may use season-specific foraging strategies, maximizing energy intake during the reproductive season and minimizing time spent foraging in winter. Adult females invest extra resources in reproduction rather than in somatic growth. Pregnant females receiving supplemental food had higher growth rates than control females, and dependent pups (≤ 1 month of age) born to supplemented mothers had higher growth rates than those born to control mothers. Increased body size seems to confer an advantage during the reproductive season, but has no concomitant advantage to overwinter survival.     

长爪沙鼠褐色脂肪组织和肝脏产热特征的季节性变化

长爪沙鼠（Meriones unguiculatus）是一种栖息于典型草原和荒漠草原非冬眠群居性的小型哺乳动物。为研究其产热功能的季节变化,我们分别在2003年秋季（9月下旬）、冬季（11月下旬）、2004年春季（3月底-4月下旬）和夏季（7月下旬）,分别测定了其体重、褐色脂肪组织和肝脏的重量、线粒体总蛋白含量和细胞色素c氧化酶活力,以及褐色脂肪组织中解偶联蛋白1（Uncoupling protein1,UCPl）的含量等。结果显示：除雄鼠的体重显著高于雌鼠外,其它各项指标均无性别差异。体重和褐色脂肪组织的重量都在冬季较高,显著高于夏季,而肝脏的重量在夏季显著高于其它季节。褐色脂肪组织和肝脏的线粒体蛋白含量和细胞色素c氧化酶活力以及UCP1含量,都在冬季较高,夏季较低。这些结果表明：在野外条件下,褐色脂肪组织和肝脏在细胞水平上产热能力的提高和UCP1含量的增加,是长爪沙鼠抵御寒冷的重要方式。     

长爪沙鼠免疫功能、体脂含量和器官重量的季节变化

小型哺乳动物的体脂含量与免疫功能有关,并受环境条件的影响。为了进一步理解野生长爪沙鼠对环境的生存适应策略,我们于2004 年夏季(7～8月)和2005年冬季(1～3月)测定了野生长爪沙鼠的体重、体脂含量和脏器重量,以及由匙孔血蓝蛋白(KLH)对雄鼠所介导的体液免疫反应。结果发现:雄鼠的胴体干重和体脂含量都显著高于雌鼠,其他各项指标无性别差异。冬季雌雄沙鼠的体重、胴体干重、体脂含量和褐色脂肪组织的湿重,以及雄鼠的睾丸湿重都显著高于夏季。脾脏的重量冬季趋于降低。处理组(注射KLH )动物血清中抗KLH 抗体的含量在冬季和夏季都显著高于对照组(注射生理盐水),且冬季处理组显著高于夏季处理组。本研究结果为动物种群调节的“冬季免疫增强假说”提供了一个新的野外例证。没有检测到免疫器官和产热器官、免疫器官和繁殖器官之间的权衡关系。     

Reproductive biology of Hepatus pudibundus (Crustacea: Brachyura), the most abundant crab on the southeastern Brazilian coast

This study analyzed the size at sexual maturity and reproductive period of populations of Hepatus pudibundus in three bays on the northern coast of São Paulo, Brazil. Crabs were collected monthly and the bottom-water temperature was measured at each collection point. The animals were sexed, measured for carapace width (CW), and their gonadal stages were determined. A total of 8,674 specimens were collected (2,435 males and 6,239 females). Adult males showed the highest mean CW; the size at maturity for both sexes was 32.5 mm CW. Reproduction was continuous and peaked in spring and summer, because of the greater availability of plankton food for the larvae. This pattern is typical in tropical and subtropical regions, unlike the seasonal reproduction found in temperate regions. Reproductive activity of females was not significantly correlated with bottom-water temperatures. Immatures and individuals in all stages of gonadal development were found throughout the sampling period and at all depths, probably because the species completes its entire reproductive cycle in that area.     

年龄对布氏田鼠和长爪沙鼠能量代谢的影响

能量代谢对动物的存活和繁殖等生活史特征具有重要的调控作用.布氏田鼠(Lasiopodomys brandtii)和长爪沙鼠(Meriones unguiculatus)是内蒙古草原同域分布的两种啮齿动物,前者的体重和野外寿命要明显小于后者,这符合寿命随体型增大而增加的一般规律.本研究进一步探讨了随年龄增加,两种动物的能量代谢特征的改变.发现布氏田鼠的非颤抖性产热能力随年龄增加而降低,而长爪沙鼠的非颤抖性产热能力随年龄增加而保持稳定.布氏田鼠的摄食能力和身体脂肪储备随年龄增加而降低;而长爪沙鼠摄食能力不随年龄改变,脂肪储备则随年龄增加而增加.长爪沙鼠的基础代谢水平低于布氏田鼠,其繁殖成熟时间更长.本研究推测,这些随年龄而变的生理特征反映了两种动物不同的生活史对策:布氏田鼠更倾向于尽快繁殖,其他与生存相关的生理指标随年龄增加而迅速降低,而长爪沙鼠更倾向于将能量投资到较晚期的存活和繁殖.     

Reproductive strategies and the influence of date of birth on growth and sexual development of an aseasonally-breeding ungulate: Reeves' muntjac (Muntiacus reevesi)

Unlike most species of deer, Reeves' muntjac does not have a seasonal reproductive cycle. Births are equally distributed throughout the year and, irrespective of season of birth, females start breeding when they have reached a minimum body weight of about 10 kg. A significantly smaller proportion of females is born in the autumn/winter than the spring/summer, but there is no effect of maternal age or condition on foetal sex ratios for first or subsequent pregnancies. Whilst aseasonal breeding increases female productivity, males are only able to hold territories encompassing the ranges of a number of does for a relatively short period of time. It is argued that for muntjac there is much less inter-sexual variation in lifetime reproductive success than for seasonally-breeding polygynous cervids. Hence, although muntjac are sexually dimorphic and polygynous, females do not invest preferentially in male offspring.
Young males can be fertile from 36 weeks of age, when their first antlers are still in velvet. Whilst season of birth has no effect on the rate of sexual development in females, it does for males, with autumn-born male fawns attaining sexual maturity earliest. This accelerated development occurs in the period following independence from the mother, and there is no evidence of a maternal cost in producing male fawns. Since the canine tusks are the main weapons for intra-sexual conflict, there could be clear gains in terms of reproductive success for males that attain sexual maturity, adult weight and adult tusk size quickly, even though their first antlers are much smaller than those of older bucks. The hypothesis is presented that, for muntjac, the majority of a male's lifetime reproductive success is achieved relatively early in life when the canine tusks are in pristine condition, and that bucks lose their territories, and associated access to oestrous does, once the canines are broken.