杂色山雀的反盗食贮食策略

盗食现象在贮食动物中非常普遍,种内竞争者或种间竞争者的盗食是贮藏食物丢失的主要原因之一,同时也是贮食动物贮食行为不断进化的重要选择压力,开展反盗食贮食策略的研究有助于阐释贮食行为进化的原因和对贮食鸟类的保护。杂色山雀(Parus varius)秋季有明显的贮食行为,贮食方式为分散贮食。通过人为投食的方法,以投食点为中心,根据贮食点距投食点距离远近设定了被盗高风险区、被盗中风险区和被盗低风险区,研究杂色山雀个体在无潜在盗食者和有潜在盗食者的情况下,在上述3个风险区贮食比例的变化,探讨杂色山雀个体基于自身以及周围环境条件,在权衡取食及贮藏过程中时间及能量的花费和收益后,其反盗食贮食策略的选择。40只杂色山雀个体贮食策略的统计结果表明,不论潜在盗食者出现与否,杂色山雀个体贮食的总体趋势大致相同,即主要将食物贮藏在中风险区,而高风险区和低风险区贮食比例较低;比较种间和种内潜在盗食者出现的情况下与无潜在盗食者时,杂色山雀个体在各贮食风险区的贮食策略:种间及种内潜在盗食者的出现,都会引起被盗高风险区贮食比例降低(种间潜在盗食者:F=3.174,P0.05;种内潜在盗食者:F=90.475,P0.05),低风险区贮食比例上升(种间潜在盗食者:F=220.440,P0.05;种内潜在盗食者:F=15.651,P0.05);但种间潜在盗食者出现时,杂色山雀个体在被盗中风险区的贮食比例降低(F=143.749,P0.05),而种内潜在盗食者出现时,杂色山雀个体在被盗中风险区贮食比例不变(F=0.776,P0.05),即杂色山雀个体对种间潜在盗食者的出现更加敏感,防范盗食的投入更大。此外,分别比较无潜在盗食者、有种间潜在盗食者和有种内潜在盗食者存在的情况下,雌雄杂色山雀个体在各贮食风险区的反盗食贮食策略,发现其结果也明显不同。无潜在盗食者和种内潜在盗食者出现时,雄性杂色山雀为预防灾难性盗食发生而付出的努力较雌性个体高(无潜在盗食者:高风险区t=4.962,df=16.546,P0.05;中风险区t=﹣0.890,df=29.255,P0.05;低风险区t=﹣2.166,df=30,P0.05。有种内潜在盗食者:高风险区t=﹣0.152,df=29,P0.05;中风险区t=2.352,df=19.568,P0.05;低风险区t=﹣2.287,df=19.563,P0.05);种间潜在盗食者出现时,雌雄杂色山雀反盗食贮食策略趋于一致(高风险区t=1.361,df=29,P0.05;中风险区t=﹣0.194,df=21.529,P0.05;低风险区t=﹣1.599,df=29,P0.05)。     

动物怎样找回贮藏的食物？

进化中，贮食者只有比不贮食的动物更有可能找到那些贮藏食物时，贮食行为才能成为一种进化稳定策略。本文综述了关于动物找回贮藏食物的假说及其实验验证。寻找贮藏食物时，穴蜂利用贮存地点附近的标志物的空间排列来定位。鸟类的嗅觉不发达，它们主要靠记忆埋藏地点的视觉信息找回埋藏的食物。啮齿动物和犬科动物主要靠嗅觉找回贮藏的食物。记忆埋藏地点对于灰松鼠、更格卢鼠，美洲赤狐和红松鼠也很重要。     

基于贮食行为的鸟类社会认知研究进展

贮食是动物应对环境变化和不可预测性而进化出的有效生存对策,认知则是当前鸟类学研究的热点问题之一。目前鸟类贮食行为中的认知研究多集中在空间认知,而社会认知研究相对滞后。对于贮食物种而言,储藏食物被盗现象非常普遍,为了避免被盗食,贮食者不仅要有发达的空间认知能力去记忆贮食地点,同时还需要极强的社会认知能力处理与盗食者的关系,可见社会认知在鸟类的贮食行为中扮演着重要角色。本文将从鸟类贮食的社会关系认知以及社会地位认知两个方面,对鸟类贮食行为中的社会认知研究进行综述,以期为后续鸟类社会认知研究提供借鉴和参考。     

动物贮食行为及其生态意义

动物贮存食物，以调节食物的时空分布，度过食物缺乏期。贮食行为是一种特化的采食行为。现已发现上百种鸟类和哺乳类动物贮存食物。植食动物贮藏植物繁殖体，促进了植物的扩散。于是，植物与贮食动物形成了一种协同进化关系。这种关系是自然界互惠关系（ｍｕｔｕａｌｉｓｍ）的一种类型。     

动物分散贮食行为对植物种群更新的影响

分散贮食是许多动物取食行为策略的重要组成部分。对以植物种子为主要贮食对象的动物来说,种子内营养物质含量、种子大小以及种子内次生化合物的含量等因素都直接影响动物的贮食行为。动物偏爱贮藏个体较大的种子,大种子多被搬运并分散贮藏在远离种源的地方,而小种子则多被就地取食,以补充动物贮食过程中的能量消耗。贮食动物主要通过空间记忆、特殊路线以及贮藏点周围的直接线索等途径重新获取贮藏点内食物。在重取过程中,一些贮藏点被遗忘,其中的种子成为植物种群更新的潜在种子库。因此,分散贮食动物不仅是种子捕食者,还是种子传播者,它们对植物种子的捕食、搬运和贮藏,影响了植物种子的存活和幼苗的建成,从而在一定程度上影响植物种群的更新、分布。植物种群为了促进种子的传播,在进化过程中逐渐形成了形式多样的适应性策略,降低种子的直接被捕食率,提高种子的被贮藏率。研究动物分散贮食行为对植物种群更新的影响,将有助于理解贮食动物与植物之间的互惠关系,从而认识贮食动物种群在生态系统中的作用,为生物多样性的保护提供科学依据。     

贮食过程中的优化问题

动物贮食的每一环节都存在如何减少能量消耗，收获较多能量的问题。分散贮藏和集中贮藏是动物贮食的两种极端空间配置，贮食动物从保证日后的食物来源和节约采食能量消耗来选择适当的埋藏密度。实验证明贮藏方式是可塑的。贮藏食物习性是遗传的，而分散贮藏与集中贮藏是受环境影响的表现形式。     

啮齿动物的分散贮食行为

食物贮藏是许多动物重要的适应性行为,分散贮藏的食物以植物种子为主。每个贮藏点贮藏数量不等的食物项目。啮齿动物分散贮藏食物之后,可降低食物被其他个体获取的机率,提高对食物资源的控制能力,最终有利于自身的生存和繁殖成功。植物种子被贮藏之后,可减少非贮食鼠类对种子的取食。同时,合适的微生境和埋藏有利于种子萌发、幼苗建成和植物的更新;使植物的分布区得以扩展。探讨啮齿动物的分散贮食行为,能够更好地理解食物贮藏在啮齿动物生活史中的作用,进一步认识鼠类和植物的相互关系以及不同啮齿动物在群落形成中的潜在作用。本综述了啮齿动物分散贮食的研究进展,并提出今后工作中的几点建议。     

植物大年结实及其与动物贮食行为之间的关系

大年结实(mast seeding)是多生年植物种群周期性同步大量繁殖的一种自然现象。大年结实作为植物适应环境条件、提高繁殖能力的一种策略而备受关注, 但其驱动机制和进化意义尚存在较大争议。在依赖动物扩散种子的植物中, 大年结实被认为是一种调控动物贮食行为、提高种子扩散效率, 并最终增加繁殖成功率的一种策略; 动物介导的植物间互作可能是促进植物共存的进化驱动力。本文简要梳理了大年结实现象的各种假说, 提出了一个包括气候、资源、动植物互作的理解大年结实机制的概念框架, 并着重讨论了大年结实和动物贮食行为之间的关系及其进化和生态意义。建议未来研究需要借助长期生态监测和分子生物学方法, 揭示植物大年结实与动物贮食行为之间的生态与进化过程。     

盗蜜行为在植物繁殖生态学中的意义

在动植物的相互关系中,盗蜜行为被认为是一种不同于普通传粉者的非正常访花行为。动物之所以要采取这种特殊的觅食策略,有假说认为是由访花者的口器和植物的花部形态不匹配造成的,也有认为是盗蜜行为提高了觅食效率从而使盗蜜者受益。在盗蜜现象中,盗蜜者和宿主植物之间的关系是复杂的。盗蜜对宿主植物的影响尤其是对其繁殖适合度的影响归纳起来有正面、负面以及中性3类。与此同时,盗蜜者的种类, 性别及其掠食行为差异不仅与生境因素密切相关,而且会对宿主植物的繁殖成功产生直接或间接的影响。另外,盗蜜者的存在无疑对其它正常传粉者的访花行为也产生一定的影响,从而间接地影响宿主植物的繁殖成功, 而植物在花部形态上也出现了对盗蜜现象的适应性进化。作者认为, 盗蜜是短嘴蜂对长管型花最有效的一种掠食策略, 它不仅增加了盗蜜者对资源的利用能力, 而且由于盗蜜对宿主植物繁殖成功的不同的影响使其具有调节盗蜜者和宿主之间种群动态的作用, 两者的彼此适应是一种协同进化的结果。     

啮齿动物对植物种子的多次贮藏

啮齿动物对种子的多次搬运和贮藏是极为复杂的行为过程,既是对自己贮藏物进行管理、防御竞争者盗食的一种策略,也是盗食其它个体贮藏物的一种食物利用方式。此外,啮齿动物多次贮藏种子的过程实际上也是植物种子的多阶段扩散过程,因而对植物更新产生重要影响。本文综述了啮齿动物对植物种子多次贮藏的研究进展,分析了多次贮藏种子的原因,并从啮齿动物与植物的相互关系上探讨其生态学意义。     

Reciprocal pilferage and the evolution of food-hoarding behavior

Current theories of food-hoarding behavior maintain that hoardingcan be adaptive if a hoarder is more likely than any other animalto retrieve its own caches. A survey of the literature indicatedthat the hoarder often has a recovery advantage when searchingfor items it has stored, but levels of cache pilferage are oftenso high (2–30% per day) that at least for some long-termfood hoarders, the caching animal is unlikely to recover a significantamount of its stored food. Except in a few cases (acorn woodpeckersand beavers), kin selection cannot explain the high levels ofpilferage observed. We suggest that some small solitary animalswith overlapping home ranges (e.g., most rodents, chickadees,and tits) are able to tolerate high levels of cache pilferage.Pilferage is not as damaging to these animals as it might otherwisebe because many interspecific and all intraspecific cache pilferersalso cache food. These or similar food caches can be pilferedlater by the original food hoarder. In other words, pilferingin these species is often reciprocal, and because it is reciprocal,it can be tolerated. We argue that caching systems based onreciprocal pilfering can be stable and are not necessarily susceptibleto "cheaters," animals that pilfer food but do not scatter hoardfood themselves, and we introduce a model of food hoarding tosupport this argument. These food-caching systems based on reciprocalpilfering resemble cooperative behavior, but the behavior isactually driven by the selfish interests of individuals. Thistheory of scatter-hoarding behavior based on reciprocity hasimportant implications for the ways that food-hoarding animalsinteract with inter- and intraspecific competitors.     

Scatter‐hoarding and cache pilfering of rodents in response to seed abundance

Seed caching and reciprocal cache pilferage play an important role in the coexistence of food‐hoarding animals. Understanding what affects seed caching and how cache pilferage occurs is an important question in seed dispersal ecology. However, tracking seed fate and cache pilferage presents substantial practical difficulties. Siberian chipmunks Tamias sibiricus always remove the entire pericarp when scatter‐hoarding acorns of Mongolian oak Quercus mongolica, whereas wood mice Apodemus peninsulae often store whole acorns in their caches. These differences in behavior provide an opportunity to investigate unilateral cache pilferage of T. sibiricus from A. peninsulae in response to seed abundance. In this study, tagged acorns were released at the peak and end periods of seed rain from Q. mongolica. This allowed us to investigate seed caching and unilateral cache pilferage at different seed abundances. We found that a higher proportion of acorns were cached at lower level of seed abundance (toward the end of seed rain), mainly because T. sibiricus rather than A. peninsulae scatter‐hoarded significantly more acorns at this time. Cache distances decreased with increasing seed abundance, indicating that acorns were cached further away and into smaller caches at lower seed abundance. Unexpectedly, unilateral cache pilferage by T. sibiricus was not significantly influenced by seed abundance—remaining at around 28% during both periods of high and low seed abundance.     

Hyper-dispersed cache distributions reduce pilferage: a laboratory study

Many animals use hoarding as a long-term strategy to ensure a food supply at times of shortage. We suggest that long-term scatter hoarders, whose caches are vulnerable to potentially high pilferage, should hoard in ways to reduce cache loss. This could be achieved by manipulating the density and dispersal patterns of caches to reduce the foraging efficiency of pilferers. This study explores the effect of distribution patterns on cache loss in the laboratory. We recorded the discovery of food items in different dispersal patterns by two bird species: coal tits Periparus ater (a hoarder) and great tits Parus major (a non-hoarder). Hyper-dispersed distributions reduced foraging efficiency because both species used systematic local search patterns. This study shows that hyper-dispersed distributions would be advantageous to hoarding animals to reduce cache loss.     

Seed caching and cache pilferage by three rodent species in a temperate forest in the Xiaoxinganling Mountains

Although differences in food-hoarding tactics both reflect a behavioral response to cache pilferage among rodent species and may help explain their coexistence, differentiation in cache pilfering abilities among sympatric rodents with different hoarding strategies is seldom addressed. We carried out semi-natural enclosure experiments to investigate seed hoarding tactics among three sympatric rodent species (Tamias sibiricus, Apodemus peninsulae and Clethrionomys rufocanus) and the relationship of their pilfering abilities at the inter- and intraspecific levels. Our results showed that T. sibiricus exhibited a relatively stronger pilfering ability than A. peninsulae and C. rufocanus, as indicated by its higher recovery rate of artificial caches. Meanwhile A. peninsulae showed a medium pilfering ability and C. rufocanus displayed the lowest ability. We also noted that both cache size and cache depth significantly affected cache recovery in all three species. T. sibiricus scatter-hoarded more seeds than it larder-hoarded, A. peninsulae larder-hoarded more than scatter-hoarded, and C. rufocanus acted as a pure larder-hoarder. In T. sibiricus, individuals with lower pilfering abilities tended to scatter hoard seeds, indicating an intraspecific variation in hoarding propensity. Collectively, these results indicated that sympatric rodent species seem to deploy different food hoarding tactics that allow their coexistence in the temperate forests, suggesting a strong connection between hoarding strategy and pilfering ability.     

Mechanisms of Cache Retrieval in the Group Nesting Southern Flying Squirrel (Glaucomys volans)

We examined the proximate mechanisms of cache retrieval in the group‐living, southern flying squirrel, Glaucomys volans, through a series of behavioral experiments conducted in a large indoor arena. The effectiveness of several retrieval mechanisms was determined including spatial memory, olfaction, random searching and a heuristic under different environmental conditions. Our goal was to elucidate the hoarding strategy of individuals in a nest group and to address whether food storing individuals possess a retrieval advantage over pilfering nestmates. A storer's retrieval advantage is necessary for scatter hoarding to be an evolutionarily stable strategy (ESS) within aggregations of unrelated individuals. Our previous work has shown that, G. volans lives in such groups, and consequently it was important to address the storer's retrieval advantage under a range of environmental conditions. Initially in our baseline experiment, we developed methods to eliminate olfactory‐based retrieval and to control for random searching. Subsequently, we experimentally determined the effectiveness of cache retrieval via spatial memory, a heuristic and olfaction. We examined the mechanisms of cache retrieval in three additional experiments using two independent subject populations and found that under dry, odorless conditions spatial memory was the most effective retrieval mechanism in support of a storer's retrieval advantage. In a fifth experiment we examined cache retrieval under wet environmental conditions and showed that olfactory‐based retrieval was effective and the storer's advantage was reduced. We interpret these laboratory results based on considerations of natural environmental conditions and game theory. We propose a conditional ESS strategy where animals store and retrieve their own caches as the primary food hoarding tactic and opportunistically pilfer caches as a secondary tactic.     

贮藏点深度、大小及基质含水量对花鼠找寻红松种子的影响

2012年8-10月,在黑龙江省伊春市带岭林业局东方红林场,通过人工围栏控制实验,研究了贮藏点深度、大小及基质含水量对花鼠找寻红松种子的影响。发现：(1) 埋藏深度显著影响花鼠对贮藏点的找寻率,埋藏深度为 1 cm 和 2 cm 的找寻率显著高于 4 cm 和 6 cm。(2) 埋藏点大小对花鼠发现种子也有显著影响,埋藏点越大,花鼠发现贮藏点的比例越高。(3) 高的基质含水量利于花鼠找寻贮藏点。结果表明,围栏条件下食物贮藏点深度、大小及基质含水量的改变能显著影响花鼠对贮藏点的找寻。     

Memory for food caches: not just for retrieval

Many animals use hoarding as a long-term strategy to ensurea food supply at times of shortage. Hoarders employ strategiesthat enhance their ability to relocate caches such as rememberingwhere caches are located. Long-term scatterhoarders, whose cacheshave potentially high pilferage rates, should also hoard ina way to reduce potential cache pilferers' ability to find caches.Previous studies have demonstrated that this could be achievedby hyperdispersing caches to reduce the foraging efficiencyof pilferers. This study investigates whether coal tits (Parusater) indeed place their caches away from existing ones. Inour experiment, birds hoarded food in 3 conditions: when cachesfrom a previous storage session were still present, when cachesfrom a previous storage session were not present anymore becausethe bird had retrieved them, and when caches from a previousstorage session had been removed by the experimenter. We showthat coal tits hoard away from existing caches and that theydo not use cues from extant caches to do this. This evidenceis consistent with the use of memory for the locations of previouscaches when deciding where to place new caches. This findinghas important implications for our understanding of the selectivepressures that have shaped spatial memory in food-hoarding birds.     

Ravens, Corvus corax, differentiate between knowledgeable and ignorant competitors

Human social behaviour is influenced by attributing mental states to others. It is debated whether and to what extent such skills might occur in non-human animals. We here test for the possibility of ravens attributing knowledge about the location of food to potential competitors. In our experiments, we capitalize on the mutually antagonistic interactions that occur in these birds between those individuals that store food versus those that try to pilfer these caches. Since ravens' pilfer success depends on memory of observed caches, we manipulated the view of birds at caching, thereby designing competitors who were either knowledgeable or ignorant of cache location and then tested the responses of both storers and pilferers to those competitors at recovery. We show that ravens modify their cache protection and pilfer tactics not simply in response to the immediate behaviour of competitors, but also in relation to whether or not they previously had the opportunity of observing caching. Our results suggest that the birds not only recall whom they had seen during caching, but also know that obstacles can obstruct the view of others and that this affects pilfering.     

Effects of food value, predation risk, and pilferage on the caching decisions of Dipodomys merriami

Animals that scatter cache their food face a trade-off betweenthe benefits of protecting caches from pilferers and the costsassociated with caching. Placing food into a large number ofwidely spaced caches helps to protect it from pilferage butalso involves costs such as greater exposure to predators. Ipredicted that animals would disperse food into a larger numberof more widely spaced caches when caching (1) a preferred foodversus a less preferred food and (2) under conditions of lowpredation risk versus high predation risk. To test these predictions,I examined the scatter-caching decisions of Merriam's kangaroorats (Dipodomys merriami). D. merriami distributed caches inclumped patterns, regardless of food preference, but they showeda tendency to invest more in a preferred food by distributingcaches more widely. Under the relative safety of the new moon,they did not disperse caches more widely, rather they partitionedthe same amount of food into a larger number of caches thanthey did under the full moon, when predation risk is higher.To examine whether their cache spacing decisions had a significantimpact on the success of cache pilferers, I measured discoveryby pilferers of artificial caches of two food types at differentcaching distances. Results indicate that the cache spacing behaviorof D. merriami functions to protect caches from pilferers, becauseincreased spacing of artificial caches decreased the probabilityof pilferage for both types of food.     

Cachers, scavengers, and thieves: a novel mechanism for desert rodent coexistence

A biologically explicit simulation model of resource competition between two species of seed-eating heteromyid rodent indicates that stable coexistence is possible on a homogeneous resource if harvested food is stored and consumers steal each other's caches. Here we explore the coexistence mechanisms involved by analyzing how consumer phenotypes and presence of a noncaching consumer affect the competitive outcome. Without cache exchange, the winning consumer is better at harvesting seeds and produces more offspring per gram of stored food. With cache exchange, coexistence is promoted by interspecific trade-offs between harvest ability, metabolic efficiency, and ability to pilfer defended caches of heterospecifics or scavenge undefended caches of dead conspecifics or heterospecifics. Cache exchange via pilferage can equalize competitor fitnesses but has little stabilizing effect and leads to stable coexistence only in the presence of a noncaching consumer. In contrast, scavenging is both equalizing and stabilizing and promotes coexistence without a third consumer. Because body size affects a heteromyid rodent's metabolic rate, seed harvest rate, caching strategy, and ability to steal caches, interspecific differences in body size should produce the trade-offs necessary for coexistence. The observation that coexisting heteromyids differ in body size therefore indicates that cache exchange may promote diversity in heteromyid communities.