东方田鼠社群气味对家族群成员个体觅食行为的影响

东方田鼠家族群成员个体的觅食行为是否因食物斑块存有家族群自身及非亲缘家族群气味而发生变异,进而影响其摄入率。在新鲜马唐叶片构建的均质密集食物斑块上,分别配置家族群自身巢垫物及非亲缘家族群巢垫物作为社群气味,测定东方田鼠家族群在食物斑块觅食时,其成员个体觅食行为的序列过程及参数,检验家族群自身气味及非亲缘家族群气味对成员个体觅食行为的影响。结果表明,家族群自身气味能显著地缩短本群成员个体的觅食决定时间,通过减少成员个体的嗅闻及直立扫视动作时间比例、增大一般扫视、盯视及静听动作时间比例,降低觅食中断时间比例,提高其摄入率;而非亲缘家族群气味则能显著地延长家族群成员个体的觅食决定时间,通过增大家族群成员个体的嗅闻和一般扫视动作时间比例、减小直立扫视、盯视及静听动作时间比例,增大觅食中断时间比例,降低其摄入率。结果揭示,熟悉的社群气味会促使觅食活动中的家族群成员个体,在监测环境风险时,将精力更多地用于观察和监听群内其他成员个体的行为及其发出的警报信息,以便在有效规避环境风险的同时减缓个体间因干扰性竞争对觅食活动所造成的不利影响;而陌生的社群气味会迫使成员个体,将精力由依赖群内其他成员个体的行为转向凭借自身直接警觉周围环境。     

视野受阻对东方田鼠觅食行为的影响

植食性小型哺乳动物的觅食行为是对特定生境的适应性产物。食物斑块周边植被对动物视野遮挡是否通过作用于其觅食活动中的警觉而影响摄入率。采用新鲜白三叶叶片构建东方田鼠密集均质食物斑块,以牛皮纸模拟食物斑块周边植被遮挡田鼠视野,测定其在食物斑块上的觅食行为序列过程及行为参数,检验食物斑块周边植被高度对东方田鼠摄入率的影响。结果发现,个体在不同程度视野受阻条件下食物摄入率无显著差异。分析觅食行为参数动态发现,在不同视野受阻条件下,个体能通过调整各采食回合内警觉行为动作的发生频次和持续时间,维持觅食回合内总的觅食中断时间的稳定,进而保证进食时间的稳定。东方田鼠在不同程度的视野遮挡条件下均能通过行为变异和优化使摄入率保持稳定。结果亦充分说明,东方田鼠在警觉强度上的变化不能反映觅食中断所带来的食物收益减损的代价,但觅食活动中各警觉动作的持续时间的变异却能够明确指示个体摄入率的动态变化,因此,以觅食活动中警觉引起的觅食中断时间代价为线索,检验其对摄入率的影响,是评价植食性小型哺乳动物在不同生境觅食适应性策略的有效的方法。     

捕食风险对东方田鼠功能反应格局的作用

植食性哺乳动物对食物斑块的选择和利用不仅取决于食物的可利用性,且与觅食环境潜存的各种风险紧密关联。捕食风险是否通过作用于动物觅食活动中的警觉影响其功能反应格局。在新鲜白三叶叶片构成的各类食物密集斑块上,测定东方田鼠觅食行为,建立功能反应模型,检验捕食风险对其功能反应格局的作用。结果发现,捕食风险能显著地延长东方田鼠的觅食决定时间,但其摄入率保持稳定,功能反应构型亦未发生改变,仍为Ⅱ型功能反应;除了对照组个体的采食时间随叶片大小增大无明显变动规律外,处理组个体的采食时间及对照组和处理组个体的处理时间、觅食中断时间均随叶片大小及口量的增大呈线性增高趋势,处理组个体的觅食中断时间明显大于对照组个体的;对照组和处理组个体的采食率均随叶片大小及口量呈非线性渐近递减趋势,但处理组个体的采食率较对照组个体的略有降低。结果揭示,在捕食风险压力下,虽然上述觅食参数变异能潜在地降低摄入率,但个体能通过改变觅食活动中各种警觉行为动作如降低嗅闻和静听监视动作的发生频次,增大视觉监视动作比重,以此缓冲捕食风险压力,维持摄入率。摄入率测定值与模型预测值的线性回归极显著,表明,功能反应模型具有良好的预测性。在可利用植物密集斑块,动物觅食活动中的警觉能缓冲捕食风险压力;动物摄入率是由植物大小调控的口量决定的,且受采食与处理食物竞争及觅食中断的制约;其功能反应仍属Ⅱ型功能反应。     

东方田鼠警觉对其功能反应的作用格局

植食性哺乳动物功能反应描述了摄入率与植物可利用性变量的动态关系。动物警觉因占用了处理食物时间即觅食中断时间而延迟与下一口食物相遇,引致摄入率降低,进而对功能反应构型产生影响。在新鲜白三叶叶片构成的各类食物密集斑块上,测定东方田鼠觅食行为,建立功能反应函数模型,检验觅食中断对功能反应的作用格局及机制。结果发现,除小叶片斑块觅食中断时间在觅食活动中所占的比例较低外,在大、中型叶片斑块的觅食中断时间比例均达到15.42%-26.82%;尽管,觅食中断使摄入率降低了33%,但东方田鼠功能反应仍为Ⅱ型功能反应。除东方田鼠采食时间及觅食回合时间随叶片重增大保持相对稳定外,处理时间及觅食中断时间均随叶片重增大呈线性递增趋势;采食时间、处理时间及觅食中断时间随口量的增大呈线性递增趋势;采食率随叶片重和口量增大呈指数递减趋势。研究结果揭示,东方田鼠因警觉引起的觅食中断事件是导致采食率及摄入率降低的主要因子。摄入率测定值与模型预测值的线性回归极显著(P < 0.01),表明,新建立的功能反应模型具有良好的可预测性。推测,东方田鼠因警觉引起采食率及摄入率减小的代价,是以延长觅食时间来补偿的。研究结果充分验证了,在可利用性植物密集斑块,由植物大小调控的动物口量决定其摄入率,且受采食和处理食物竞争及觅食中断的制约,其功能反应为Ⅱ型功能反应的假说。     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0％单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0%单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。     

植食性哺乳动物能量收益增长减速机制的检验

能量收益函数描述了植食性哺乳动物在植物斑块的食物摄入量与在斑块停留时间的函数关系,为觅食生态学理论的重要组成部分。在新鲜白三叶叶片构成的各类叶片斑块上,测定东方田鼠的觅食行为,建立其能量收益函数模型,分析植食性哺乳动物能量收益增长减速的机制。研究结果表明,东方田鼠觅食大叶片时,叶片干物质收益与停留时间呈非线性渐进函数关系,能量收益函数为渐进函数;觅食中、小型叶片时,叶片干物质收益与停留时间呈线性函数关系,能量收益函数为线性函数;没有检测到东方田鼠的能量收益动态呈分段线性函数或S型函数增长。东方田鼠在大、中型叶片斑块觅食时,随停留时间的增大,口量呈线性或指数递减,而处理时间则呈线性或指数递增,采食时间、间隔时间及咀嚼频次保持相对稳定,瞬时摄入率呈减小趋势;东方田鼠在小叶片斑块觅食时,觅食行为参数口量、摄入率、采食时间、间隔时间、处理时间及咀嚼频次均保持相对稳定。研究结果充分验证了,植食性哺乳动物在消费植被过程中,大型可利用性植物减少,受植物大小调控的动物口量减小,处理时间增加,引起瞬时摄入率降低,导致其能量收益增长减速的假说。     

植食性哺乳动物能量收益函数模型的预测性及适用性

以东方田鼠喜食的白三叶叶片作为食物,在保持叶片生物量不变的条件下,改变叶片大小,配置东方田鼠觅食的各类食物大小异质斑块,测定东方田鼠觅食的行为。通过比较几种植食性哺乳动物能量收益函数模型的预测性,评价其适用性。结果发现,没有检测到东方田鼠食物摄入量动态呈S型能量收益函数增长。线性函数模型能准确地预测东方田鼠在中、小型食物斑块的停留时间;在大型食物斑块,尽管,分段线性函数及渐进函数均能很好地拟合东方田鼠的食物摄入量动态,但仅分段线性函数模型能准确地预测其停留时间。线性函数模型及分段线性函数模型是在功能反应机制模型-口量模型基础上建立的,反映了调节摄入率动态的机制,为机制性模型。因此,此2种模型是在口量及摄食站尺度上,探讨动物在食物斑块的能量收益动态及停留时间;而渐进函数模型及S型函数模型均为实验性模型,是在斑块尺度上预测动物能量收益动态及停留时间,未能反映动物摄入率动态,故其预测效果较差。由于此4种模型均未考虑动物在食物斑块搜寻食物及非觅食活动如警觉和逃跑等花费的时间,因而,限制了模型的广泛应用。建议,发展新的模型,促进觅食生态学斑块模型理论研究的深入发展。     

实验检验东方田鼠学习能力的性别差异

东方田鼠选择从禾本科植物叶片的不同部位采食会引起食物摄入率的巨大差异,这项具有明显的认知和学习行为的觅食活动是否存在性别差异。在由带两片叶的新鲜马唐茎秆配置的密集食物斑块上,测定东方田鼠觅食马唐叶片的行为序列、过程及参数,检验其在学习能力上的性别差异。结果表明,雌鼠和雄鼠的觅食决定时间尽管均随觅食学习天数的增加而减小,但雌鼠的觅食决定时间显著地高于雄鼠的;雌鼠和雄鼠均由从对叶片部位无差别选择和采食转向偏爱从叶片基部采食。学会这项采食技能后,雌鼠从叶片基部采食的选择指数显著地高于雄鼠的;二者的摄入率均随觅食学习天数的增加极显著地增大,但雌鼠的摄入率却极显著地高于雄鼠的。研究结果充分验证了提出的假设:雄鼠较雌鼠能更快地习得从禾本科植物叶片的基部采食和收获食物;但当二者习得这项采食技艺后,雌鼠较雄鼠能获得更高的食物摄入率;同时也说明,新建立的评价小型植食性哺乳动物认知和学习能力的实验方法,具有可靠的有效性和实用性。     

根田鼠几种觅食功能反应模型的比较

植物组织空间排列对植食性哺乳动物功能反应的作用,是觅食生态学的热点问题之一。以新鲜紫花苜蓿叶片为食物,改变苜蓿叶片大小调控根田鼠口量,改变叶片间距调控叶片密度,设置叶片空间异质性斑块。在空间异质性斑块上测定根田鼠的觅食行为及其参数,检验植食性哺乳动物4种功能反应模型的预测性。除复合模型参数Rmax、h和Vmax及口量模型参数Rmax的最大似然估计值与测定值近似外,其它模型参数的估计值与测定值均存在较大差异。根田鼠摄入率测定值与4种模型预测值的线性回归均显著(P0.01),但与复合模型预测值的线性拟合效果最佳。表明,复合模型能很好地解释根田鼠觅食与行走的竞争对摄入率调节的动态。根田鼠复合模型存在调节其功能反应机制转变的距离临界值(d)。叶片间距大于该值时,叶片密度调节摄入率;叶片间距小于该值时,口量调节摄入率。结果充分地验证了提出的特定假设:在植物密集条件下,植物大小能调节植食性小型哺乳动物根田鼠的摄入率;在植物稀疏条件下,植物密度调节其摄入率。     

鄱阳湖围垦区藕塘越冬白鹤的时间分配与行为节律

2016年12月—2017年3月,采用瞬时扫描法研究了鄱阳湖围垦区藕塘生境中白鹤Grus leucogeranus越冬期的行为,共扫描2560次,23219只次,包括18031只次成鹤和5188只次幼鹤。结果表明,觅食(41.78%)、警戒(25.02%)、修整(15.00%)和休息(10.84%)是白鹤越冬期的主要行为。与自然生境相比,藕塘生境中白鹤主要采取多休息和修整的策略来节省能量支出。成鹤的觅食行为(35.29%)显著低于幼鹤(62.42%)(F_(1,12)=45.977,P0.01),警戒行为(28.66%)则显著高于幼鹤(10.26%)(F_(1,12)=38.975,P0.01)。家庭群成鹤觅食行为(43.96%)极显著高于非家庭群成鹤(27.04%)(F_(1,12)=60.169,P0.01)。家庭群成鹤需要喂食幼鹤,它们花费更多的时间觅食弥补能量的消耗。行为节律上,白鹤各时段觅食行为占总行为的比例均较高,11:00—11:59出现明显高峰,占总行为的48.64%。警戒行为无明显的低谷和高峰。成鹤在各时段的觅食行为比例均明显低于幼鹤,成鹤和幼鹤的觅食曲线变化趋势相似,即觅食比例的升高和降低比较同步。成鹤在各时段的警戒行为和修整行为比例均明显高于幼鹤,成幼鹤的休息行为比例在各时段差别不大,均在14:00—14:59有个明显的高峰。家庭群成鹤的觅食行为比例几乎在各时段均明显高于非家庭群,家庭群成鹤的修整行为和休息行为在大部分时段均低于非家庭群成鹤。因此家庭群成鹤采取多取食,少休息和修整的策略提高自身的适合度,同时保证对后代的抚育。     

Sex differences in giraffe foraging behavior at two spatial scales

We test predictions about differences in the foraging behaviors of male and female giraffes (Giraffa camelopardalis tippelskirchi Matchie) that derive from a hypothesis linking sexual size dimorphism to foraging behavior. This body-size hypothesis predicts that males will exhibit specific behaviors that increase their dry-matter intake rate relative to females. Foraging behavior was examined at two hierarchical levels corresponding to two spatial and temporal scales, within patches and within habitats. Patches are defined as individual trees or shrubs and habitats are defined as collections of patches within plant communities. Males were predicted to increase dry-matter intake rate within patches by taking larger bites, cropping bites more quickly, chewing less, and chewing faster. Within habitats, males were expected to increase intake rate by increasing the proportion of foraging time devoted to food ingestion as opposed to inter-patch travel time and vigilance. The predictions were tested in a free-ranging population of giraffes in Mikumi National Park, Tanzania. Males spent less total time foraging than females but allocated a greater proportion of their foraging time to forage ingestion as opposed to travel between patches. There was no sex difference in rumination time but males spent more time in activities other than foraging and rumination, such as walking. Within patches, males took larger bites than females, but females cropped bites more quickly and chewed faster. Males had longer per-bite handling times than females but had shorter handling times per gram of intake. Within habitats, males had longer average patch residence times but there was no significant sex difference in inter-patch travel times. There was no overall difference between sexes in vigilance while foraging, although there were significant sex by habitat and sex by season interactions. Although not all the predictions were confirmed, overall the results agree qualitatively with the body-size hypothesis. Sex-related differences in foraging behavior led to greater estimated intake rates for males at the within-patch and within-habitat scales. Received: 20 November 1995 / Accepted: 5 November 1996     

Sex-Related Differences in the Trade-Off between Foraging and Vigilance in a Granivorous Forager

The relationship between intake rate and food density can provide the foundation for models that predict the spatiotemporal distribution of organisms across a range of resource densities. The functional response, describing the relationship between resource density and intake rate is often interpreted mechanistically as the relationships between times spend searching and handling. While several functional response models incorporate anti-predator vigilance (defined here as an interruption of feeding or some other activity to visually scan the environment, directed mainly towards detecting potential predators), the impacts of environmental factors influencing directly anti-predator vigilance remains unclear. We examined the combined effects of different scenarios of predation risk and food density on time allocation between foraging and anti-predator vigilance in a granivorous species. We experimentally exposed Skylarks to various cover heights and seed densities, and measured individual time budget and pecking and intake rates. Our results indicated that time devoted to different activities varied as a function of both seed density and cover height. Foraging time increased with seed density for all cover heights. Conversely, an increased cover height resulted in a decreased foraging time. Contrary to males, the decreased proportion of time spent foraging did not translate into a foraging disadvantage for females. When vegetation height was higher, females maintained similar pecking and intake rates compared to intermediate levels, while males consistently decreased their energy gain. This difference in anti-predator responses suggests a sexually mediated strategy in the food-safety trade-off: when resource density is high a females would adopt a camouflage strategy while an escape strategy would be adopted by males. In other words, males would leave risky-areas, whereas females would stay when resource density is high. Our results suggest that increased predation risk might generate sexually mediated behavioural responses that functional response models should perhaps better consider in the future.     

Refuge or predation risk? Alternate ways to perceive hiker disturbance based on maternal state of female caribou

Human presence in natural environments is often a source of stress that is perceived by large ungulates as an increased risk of predation. Alternatively, disturbance induced by hikers creates a relatively predator‐free space that may serve as a refuge. We measured the behavioral responses of female caribou to disturbance associated with the presence of hikers during summer in the Gaspésie National Park. We used those data to determine whether caribou responded negatively to human activity (i.e., the predation risk hypothesis) or whether human activity resulted in a decrease in the magnitude of perceived risk (i.e., the refuge hypothesis). Female caribou with a calf spent nearly half of their time feeding, regardless of the presence of a trail or the number of hikers. They also decreased their vigilance near trails when the number of hikers increased. Conversely, lone females fed less frequently and almost doubled the time invested in vigilance under the same circumstances. However, both groups of females moved away from trails during the day, especially in the presence of hikers. We demonstrated that risk avoidance was specific to the maternal state of the individual. Lactating females accommodated the presence of hikers to increase time spent foraging and nutritional intake, providing support for the refuge hypothesis. Alternatively, lone females with lower energetic requirements and no maternal investment in a vulnerable calf appeared less tolerant to risk, consistent with the predation risk hypothesis. Synthesis and applications: Hikers influenced the vigilance–feeding trade‐off in caribou, underlining the importance of appropriate management of linear structures and human activities, especially across the critical habitat of endangered species. Even if some individuals seemed to benefit from human presence, this behavioral adaptation was not sufficient to reduce annual calf mortality associated with predation.     

Information transfer and the facilitation and inhibition of feeding in a schooling fish

Synopsis Recent studies show that fish forage actively when perceived risk is low, but decrease foraging and increase vigilance when perceived risk is high. Isolated juvenile chum salmon,Oncorhynchus keta, were visually exposed to groups of conspecifics engaged in different activities to examine their ability to gain information about foraging opportunity and risk by interpreting conspecific behavior. Isolates ate most when exposed to feeding groups, less when exposed to nonfeedig groups, and least when exposed to alarmed groups. Isolates exposed to alarmed conspecifics also spent more time motionless than did fish exposed to either feeding or nonfeeding conspecifics. These findings indicate that schooling fish gain information by interpreting conspecific behavior, and are consistent with research showing that animals balance the conflicting demands of foraging and vigilance.     

Behavioral Profiles Related to Dominance Hierarchy in Associated Foundresses of Belonogaster juncea juncea (F.) (Hymenoptera: Vespidae)

This study was conducted to examine the phenomenon of task partitioning among associations of foundresses of the primitively eusocial wasp Belonogaster juncea juncea (F.). The time–activity budget for five main behavioral categories (foraging, building, feeding, inactivity, and reproduction) for each foundress belonging to trigynic associations was recorded using the instantaneous scanning technique. After ranking the individuals on the basis of agonistic encounters, data were submitted to a canonical discriminant analysis. The results show behavioral differences between individuals of each rank. The proportion of time allocated to foraging behavior is a good rank index. The females of the first rank spent less time on foraging behavior and significantly more time (13.6% of their time) on reproductive behavior than females of other ranks. The females of the second rank also spent less time on foraging behavior and showed a tendency toward building behavior. The females of the third rank spent significantly more time (77.28% of their time) on foraging behavior. The behavioral profile of each foundress was therefore determined by its rank on the dominance scale.     

The group size effect and synchronization of vigilance in the Tibetan wild ass

Vigilance behavior is considered as an effective strategy for prey species to detect predators.An individual benefits from living in a group by reducing the time spent being vigilant without affecting the probability of detecting a predator.However,the mechanism producing a decrease in vigilance with increasing group size is unclear.Many models of vigilance assume that group members scan independently of one another.Yet in recent studies,the other 2 patterns of vigilance,coordination and synchronization,were reported in some species.In 2 summers(2018 and 2019),we studied the group-size effect on vigilance and foraging of Tibetan wild ass in Chang Tang Nature Reserve of Tibet.We also tested whether individuals scan the environment independently,tend to coordinate their scans,or tend to synchronize their vigilance.The results showed that individuals decreased the time spent on vigilance with increasing group size,while increased the time spent foraging.Group members scanned the environment at the same time more frequently and there was a positive correlation between group members'behaviors,indicating that Tibetan wild asses tend to synchronize their vigilance.