根田鼠幼体食物选择的社群学习

社群学习为动物的一种可塑性表型行为,能使动物获得适应于栖息地的行为模式.本文在实验室条件下,通过自助餐式食物选择实验,测定栖息于青藏高原高寒草甸生态系统的根田鼠断乳幼体间食物选择的社群学习模式.结果表明,同伴对其学习个体的食物选择具有显著的作用(P<0.001).学习个体对同伴已觅食食物的摄入量占其总摄入量的71%以上.在多同伴及单同伴与学习个体相互作用4 h后,同伴对学习个体的食物选择的学习具有显著的作用(P<0.01),而在24 h后,同伴对学习个体食物选择的作用则消失.多同伴与单同伴对学习个体的食物选择作用的差异不显著(P>0.05).熟悉同伴对学习个体的食物选择具有显著的效应(P<0.01),而陌生同伴对学习个体的食物选择则无显著作用(P >0.05).     

单宁酸对根田鼠断乳幼体生长和存活的影响

在食物中含10％和20％蛋白质条件下,测定了单宁酸对根田鼠幼体在断乳后20d内的生长和存活的影响。结果表明,食物中含蛋白质为10％的条件下,摄食含3％和6％单宁酸食物的试验个体生长速率分别为-0．135g/d和-0．25g/d,食物利用效率均显低于对照组,断乳后20d内平均存活天数较对照组分别下降26．23％和49．36％。在食物蛋白质为20％的条件下,摄食含3％和6％单宁酸食物的试验个体生长速率分别为0．134g/d和-0．116g／d,摄食6％单宁酸食物的试验个体食物利用效率显低于摄食3％单宁酸食物的试验个体和对照组个体,断乳后20d内的平均存活天数较对照组下降39．41％,摄食3％单宁酸食物的试验个体较对照组略有下降,但不显。上述结果验证了单宁酸能显影响植食性小哺乳动物生长和存活的假设。     

母体密度应激与球虫感染对子代根田鼠免疫力的影响

免疫功能是影响动物个体适合度的重要因素之一,也是防御病原体入侵的重要途径,对动物的生存至关重要。种群密度与寄生物感染都能影响动物的免疫功能。本实验通过2×2析因实验设计,测定了母体密度应激+球虫感染、母体密度应激+未球虫感染、未母体密度应激+球虫感染、未母体密度应激+未球虫感染等4个处理对根田鼠粪便皮质酮、球虫感染率、白细胞总数、各型白细胞的百分比、淋巴细胞亚型计数（CD4,CD8计数）等指标。结果表明,高密度母体应激处理可显著降低CD4数量、CD4/CD8比例、淋巴细胞数、嗜酸性粒细胞数、白细胞数,母体应激与球虫的耦合可使上述免疫指标进一步降低,说明母体密度应激和球虫感染对于根田鼠的免疫具有负的叠加效应。     

根田鼠母体捕食应激对其雌性子代雄性化效应的研究

本研究了根田鼠母体捕食应激对其雌性子代雄性化的效应。母体捕食应激使雌性子代在鼻端探究、生殖区探究、试图探究和爬跨及尾随等性行为中花费的时间最多,阴道开口时间显延迟,生殖器与肛门间距离显增大,而母体食物限制和断乳应激子代则未明显呈现上述特征。母体捕食应激使其雌性子代显地降低对雄性个体的性吸引力。因此,母体捕食应激使雌性子代在性行为、形态特征及性吸引力方面呈现雄性化效应,主要归结于捕食应激引起母体内分泌的改变所致;此效应仅产生于胚胎性分化的特定关键时期。全结果检验了田鼠类母体捕食应激对其雌性子代性分化有显影响的假设。     

围栏条件下母体密度应激对根田鼠 F1代性器官指数的影响

为探讨自然条件下母体密度应激对根田鼠F1代性器官指数的影响,通过在围栏内建立不同密度的母体种群获得相应的F1代个体,以此建立了不同密度的子代种群,并测定了母体种群建群者的血浆皮质酮含量,将建立子代种群后剩余的F1代个体带回实验室饲养.实验结束后,测定了全部F1代个体的性器官指数及皮质酮含量.结果表明,高密度母体种群建群者的皮质酮含量显著高于低密度母体种群建群者;出生于高密度母体种群的F1代个体处于高密度子代种群,其性器官指数显著低于出生于低密度母体种群且处于低密度子代种群的F1代个体,而皮质酮含量显著高于后者;出生于高密度母体种群的F1代个体处于低密度子代种群,其性器官指数及皮质酮含量与出生于低密度母体种群且处于低密度子代种群的F1代个体间无显著差异.此外,实验室饲养条件下,出生于高密度和低密度母体种群的F1代个体间的睾丸指数无显著差异.本研究结果说明,在根田鼠种群中,单一的母体密度应激对子代的性器官指数无影响,但生前应激子代在性成熟后,当再次遭遇密度应激时,其性器官指数显著降低,母体密度应激和当前环境对种群的未来繁殖能力具有耦合效应.     

围栏条件下母体社群应激对根田鼠子代免疫力的影响

为探讨自然条件下母体社群应激对根田鼠子代免疫力的影响,在野外围栏建立高密度和低密度根田鼠种群,将围栏出生的F1代幼体在室内饲养至性成熟后,测定其血清抗匙孔血蓝蛋白抗体的IgG水平、血液学参数和脾脏指数,以及种群建群者的血浆皮质酮含量.结果表明,高密度种群建群者的皮质酮含量高于低密度种群建群者.子代个体的各类血细胞的数量无差异.高密度种群子代的IgG含量低于低密度种群的子代,但脾脏指数高于后者.上述不同免疫参数结果相互印证说明,高密度种群引起的母体社群应激对子代免疫力有抑制作用.此外,本文探讨了母体应激效应的概念和生态学意义及其在种群调节中的作用.     

放牧对布氏田鼠主要食物选择的影响

动物的食物选择受食物资源量、质量和喜好度决定。尽管放牧可减少鼠类的喜食植物的数量和质量,但其如何影响鼠类的食物选择尚不清楚。本研究于2014年5月至10月,在内蒙古锡林郭勒盟锡林浩特市毛登牧场的大型试验围栏内进行了布氏田鼠的食物选择实验。利用大型实验围栏内5年连续放牧处理所构建的植被变化条件,采用扣笼试验,调查了布氏田鼠对其三种主要植物的取食情况。研究发现：连续放牧后,糙隐子草的盖度增加,而羊草、克氏针茅盖度降低;糙隐子草的盖度显著高于羊草、克氏针茅,成为各季节的优势植物种类。放牧对布氏田鼠取食羊草、克氏针茅和糙隐子草的绝对取食频次均无显著影响。在季节上,布氏田鼠对克氏针茅和糙隐子草的取食在三个季节均无差异,但布氏田鼠对羊草取食的绝对频次夏季显著高于春季和秋季;布氏田鼠对三种植物的喜好程度依次为羊草>克氏针茅>糙隐子草,但季节和放牧因素对布氏田鼠对这三种植物的喜好度无显著影响。结果表明,布氏田鼠的食物选择及食物组成相对稳定,表现为其对放牧或季节因素造成的喜食植物资源量的变化具有很好的适应性,推测是其调整取食努力来实现食物组成的平衡。     

根田鼠母体捕食应激对其子代运动及探究行为的作用

本文研究了根田鼠母体捕食应激对其子代运动及探究行为的作用。母体自妊娠中期至分娩期间,每天被短暂且重复地暴露给艾鼬。分娩后,对母体及其子代正常饲养。在子代性成熟后,分别测定其运动和探究行为。母体捕食应激显著降低子代的运动时间和频率。在探究行为中,母体捕食应激子代的探究潜伏期和探究时间均显著大于对照子代;其次,母体捕食应激雌性子代的探究次数显著小于对照。另外,个体的运动水平以及探究潜伏期和探究次数均存在性别差异。本研究结果表明,田鼠类母体捕食应激对其子代运动和探究行为有显著的抑制作用,由此可能对子代适合度,乃至种群波动产生负效应。     

食物多样性对布氏田鼠幼体存活率和生长率的影响

为探明食物多样性对植食性小型哺乳动物种群的影响,以羊草、克氏针茅、紫花苜蓿、沙葱和阿氏旋花5种实验地常见的草本植物,组成不同食物多样性的食谱,饲喂布氏田鼠幼体,探究布氏田鼠幼体的存活率和生长率对不同食物多样性的响应.结果 表明:(1)随着食物多样性种类的增加,布氏田鼠幼体存活率显著提高(P＜0.05).与单一食物组相比...     

根田鼠栖息地选择的影响因素

2002 年7～9 月在中国科学院海北高寒草甸生态系统定位站地区对根田鼠的栖息地选择进行了研究。对根田鼠栖息地利用强度变量(一定面积内的跑道长度、跑道分叉数、洞口数) 与12 个栖息地特征变量进行多元线性逐步回归分析表明: 显著影响跑道长度的变量为灌丛高度、竞争性啮齿类、电线杆、早熟禾、围栏、灌丛间距和双子叶植物生物量; 显著影响跑道分叉数的变量为灌丛高度、竞争性啮齿类、电线杆、早熟禾和围栏; 显著影响洞口数的变量为灌丛高度、土壤含水率和围栏。对影响利用强度变量的因素进行综合生态学分析表明,在小生境尺度上, 研究期间影响根田鼠栖息地选择的因素主要为捕食风险和种间竞争, 食物资源和土壤硬度也有一定程度的影响。     

捕食和食物交互作用条件下根田鼠季节性波动种群攻击水平及其行为多态性分析

在捕食和附加食物交互作用条件下,以恐吓、进攻、追逐、争斗及回避5类行为为变量,以恐吓、进攻、追逐计数之和的平均值作为攻击水平,测定根田鼠种群不同波动时期成体的攻击水平.发现根田鼠的攻击性与种群波动时期之间,存在明显的关联.统计分析结果表明,在种群3个波动时期,4种处理种群两性攻击型个体比例差异显著.除预防捕食者无附加食物（-P,-F）种群的雌体外,其它处理种群增长期和高峰期雌性和雄性攻击型个体的比例高于其衰减期.其中,预防捕食者附加食物（-P,＋F）种群、-P,-F种群及未预防捕食者附加食物（＋P,＋F）种群,雄性攻击型个体的比例均为增长期＞高峰期＞衰减期;在未预防捕食者无附加食物（＋P,-F）种群,雄性攻击型个体比例为高峰期＞增长期＞衰减期.各处理种群雌性攻击型个体比例的格局与雄体的不同.其中,-P,＋F种群及＋P,＋F种群为增长期＞高峰期＞衰减期,＋P,-F种群为高峰期＞增长期＞衰减期,而-P,-F种群攻击型个体比例为高峰期＞衰减期＞增长期.虽不同处理种群雌体及雄体的5类行为变量与种群密度的相关性不一致,而具有明显攻击性的恐吓、进攻及争斗3类行为则分别与种群密度呈显著或极显著的线性正相关关系,其结果与Chitty多态行为假设预测的一致;验证了所提出的特定假设：种群外部因子捕食和食物交互效应介导的攻击行为选择,是引起田鼠类种群季节性波动的主要内部因子.     

Insights on zinc regulation of food intake and macronutrient selection

Zinc (Zn) is an essential trace element required for human beings and animals. This divalent cation is involved in many physiological functions, including immune and antioxidant function, growth, and reproduction. Deficiency of Zn produces several pathological disorders and abnormalities in its metabolism, such as anorexia, weight loss, poor efficiency, and growth retardation. Although it has been known for more than 50 yr that Zn deficiency regularly and consistently causes anorexia in many animal species, the mechanism that causes this phenomenon still remains an enigma. The present review describes recent research investigating the relationship between Zn deficiency and the regulation of food intake, as well as macronutrient selection.     

Mechanisms of food selection in Daphnia

A conceptual behavioural and mechanistic Holling-type model of food selection in Daphnia pulicaria is derived from SEM observations with animals feeding on mixtures of spherical-cylindrical diatoms, oblongate green algae, and filamentous cyanobacteria, as well as ultrafine particles. The algae used were Stephanodiscus hantzschii (<- 6 µm length), Monoraphidium setiforme ( 20 µm), and Oscillatoria aghardii (strands, >- 80 µm). Cell (strand) selection can occur at any or all of three stages: (i) interception from the feeding currents, (ii) collection and channeling to the food groove, and (iii) compaction and transport to the mouth. During each stage, given equal initial cell densities, elongate cells are more likely to escape collection than spherical cells and are more likely to be rejected. In addition, filaments require increased handling time at stages (ii) and (iii) and promote entanglement with limb 5 and the postabdominal claw. Food is collected primarily with the aid of limbs 3 (and 4), but limbs 1 and 2 also intervene. Neither the leaky sieve hypothesis alone nor any other single-process hypothesis explains the observations on examined in corpore positions, morphology, and derived movements of the feeding limbs. Attachment and mucus appear to be important for the ingestion of bacteria and ultrafine particles.The model is consistent with many experimental results of differential feeding by Daphnia pulicaria on mixtures of variously shaped algae and other observations on Daphnia feeding behaviour. The paradigm of invariate, nonselective feeding by Daphnia is rejected.     

根田鼠攻击行为模式及其进化稳定对策分析

在捕食和附加食物交互作用条件下 ,测定根田鼠种群攻击水平与种群参数之间的关系 ,应用对策论分析攻击行为的模式。通过观测 1 6 5对实验个体的攻击行为 ,发现体重和繁殖特征决定根田鼠个体的攻击水平。体重较大个体及繁殖个体的攻击频次最高。攻击水平的性别差异显著。Kruskal- Wallis单侧秩方差检验结果表明 ,雄体攻击水平显著高于雌体。攻击水平与种群密度呈负相关关系 ,但不显著。与留居个体比较 ,扩散个体的攻击性弱。高质量的附加食物可降低根田鼠的攻击水平 ,捕食者的存在不直接影响攻击水平。根田鼠的攻击行为属仪式化非伤害行为。ESS的鹰 -鸽对策模型分析结果与实验结果一致 :不同处理种群 ESS集的鹰型对策者比例有显著差异 ,环境条件愈差 ,取胜的价值愈大 ,种群中鹰型对策者比例愈高。有捕食者、无附加食物( P,- F)种群的环境条件最差 ,鹰型对策者比例最高 ,为 0 .4 0 ;次为无捕食者、无附加食物 (- P,- F)种群 ,为 0 .33;有捕食者、有附加食物 ( P, F)种群 ,为 0 .1 8;无捕食者、有附加食物 (- P, F)种群的环境条件最优越 ,鹰型对策者比例最低 ,为0 .1 7。验证了捕食和食物交互效应能改变田鼠类动物攻击行为格局及对策模式的假设     

The functional basis of frequency-dependent food selection

Various animals have been observed to select food in a way that changes according to the relative frequency of the different foods available. Sometimes only the strength of selection varies, its direction remaining constant, but sometimes the direction of selection also changes. Selection of a food may be more intense as that food becomes rarer, or vice versa. I discuss here the situations in which animals, particularly predators, may maximize their feeding efficiency by behaving in ways that result in frequency-dependent selection of their food. These include cases in which different types of prey occupy different ecological niches, those in which there are benefits or costs to mixed diets for the predator, those in which rarer types of prey provide easier targets, those in which the different types of prey provide unequal benefits to the animal eating them, those in which direct comparison of the benefits is possible, those in which sampling is necessary because the benefits are unknown, and Batesian and other mimicries. Frequency-dependent selection of food is likely to be common and widespread: to assume frequency independence, without testing, may often be misleading.     

Seasonal variation of feeding patterns and food selection by crop-raiding elephants in Zimbabwe

Elephants and humans are increasingly coming into conflict because of the conversion of elephant habitat into agricultural areas. In order to identify trends that influence raiding behaviour, the nutritional makeup of food items consumed by crop‐raiding elephants over a 2‐year period were analysed and a trigger for crop raiding was identified. The point at which the quality of wild grasses declines below the quality of crop species corresponded to the movement of bull elephants out of a protected area and into fields. This finding may have wider implications for developing predictive models of elephant/human interactions.     

Effects of pre-dispersal selection on offspring growth and survival in Erythronium grandiflorum

Effects of pre-seed-dispersal processes on offspring vigor were examined in Erythronium grandiflorum using manipulations of the number of pollen donors contributing to the pollen pool and comparisons of means and variances in offspring growth measurements. There were no effects of the number of donors on measures of pollen-tube growth, ovule abortion, seed set, mean seed weight, or seedling germination. Seeds from pollinations with only one donor produced corms that averaged 5% lighter after one season of growth and had lower overall survival after three years compared to corms from pollinations with either three or ten donors. Patterns of within- and among-family variance estimates for the different treatments were consistent with the hypothesis that less-vigorous offspring were eliminated prior to seed dispersal in the multiple-donor treatments. The difference in the growth of offspring from different treatments was apparently not due to pollen competition because pre-zygotic attrition of pollen tubes led to incomplete fertilization of ovules. Results from this study suggest that post-fertilization abortion of less-vigorous progeny, perhaps as a consequence of early-acting inbreeding depression, is responsible for the increase in the average vigor of offspring from multiply-sired fruits.     

球虫感染与捕食对根田鼠繁殖性能的影响

在自然界,捕食者和寄生物是两种主要的种群外部调节因子,二者的交互作用会对猎物和宿主种群波动产生深远影响。较低的球虫感染强度与捕食对根田鼠（Alexandromys oeconomus）繁殖无显著的交互作用。自然界球虫感染存在季节性变化,秋季感染强度最高。为了探究较高感染强度下,球虫与捕食对根田鼠繁殖的主效应及交互作用,本研究采用2×2析因实验设计,在野外围栏中测定了根田鼠种群肠道内寄生物的感染率和感染强度、雄性睾丸指数、睾酮水平、精子密度、精子活力以及雌性卵巢指数。结果表明,较高的感染强度下,球虫能显著抑制根田鼠的繁殖性能,但球虫感染与捕食对根田鼠的繁殖无显著的交互作用,这可能与球虫感染和捕食效应在时间上的错配有关。本研究认为,球虫感染对繁殖期小哺乳动物种群的调节作用虽有限,但其可通过与捕食者的耦合来降低宿主越冬时的存活率,进而影响宿主种群波动。     

Role of early experience in the development of preference for low-quality food in sheep

Domestic ruminant selectivity induces floristic changes in pasturelands, risking sustainability and limiting the subsequent availability of susceptible plant species. Development of preferences for species of lower nutritional quality may help to overcome those problems. In this study, we tested the hypothesis that early experience of sheep with a low-quality food (LQF) in a nutritional enriched context increases preference for LQF in adulthood. We predicted a higher proportional consumption of LQF in experienced lambs (EL) than in inexperienced lambs (IL) in choice situations involving LQF and alternative foods. Additionally, we determined intake of LQF by EL and IL at different levels of high-quality food (HQF) availability. From 60 to 210 days of age, EL were fed in separated feed bunks mature oat hay (LQF) simultaneously with sunflower meal (SM) and corn grain (CG), whereas IL were fed alfalfa hay (HQF) simultaneously with SM and CG. After exposure, EL and IL were offered LQF in free choice situations involving alternative foods, and also at five levels of HQF availability (100%, 75%, 50%, 25% and 0% of ad libitum intake). Proportional consumption of LQF was lower or similar in EL than IL. Intake of LQF was also lower or similar in EL than IL at all levels of HQF availability, except when the LQF was the only food available. Our results did not support the hypothesis that early experience with a LQF in a nutritional enriched context increases preference for LQF in adulthood. On the contrary, experience with LQF diminished subsequent preference for LQF in adulthood. It is proposed that, in the conditions of our study, continuous comparison between the LQF and the high-quality supplements (CG and SM) during the early exposure period lead to devaluation of LQF by EL through a simultaneous negative contrast effect.     

Lower foraging efficiency of offspring constrains use of optimal habitat in birds with extended parental care

After reproducing successfully, birds with extended parental care form family groups. Despite being the dominant social unit, such family groups have been reported to switch to alternative habitat earlier than adults without offspring, with potential negative carry‐over effects for the next breeding season. Here we test a proposed mechanism for this earlier habitat switch, namely a low foraging efficiency in juveniles. Such a test is best performed under controlled conditions because in the field families may occupy food patches of a different quality than singles or pairs without young. We studied this mechanism in Bewick's Swans Cygnus columbianus bewickii, which trample (or ‘treadle’) for food buried in the sediment. The gross intake rate of juveniles was as low as 60% of that of adults, depending on the burial depth of the food. Trampling effort did not differ between age classes, but differences in intake rate were related to body size, suggesting that larger or heavier birds were trampling more efficiently. Corresponding giving‐up densities in the field were calculated to be c. 60% higher for juveniles than for adults. Our findings are consistent with the hypothesis that the lower foraging efficiency of juveniles may be responsible for the segregation of family groups from adults without offspring.