Nut predation and dispersal of Harland Tanoak Lithocarpus harlandii by scatter-hoarding rodents

Plants that use the propagule to co-opt animals as dispersal agents must balance the costs of seed predation with the benefits of dispersal. Successful post-dispersal germination is a key metric that reflects these costs and benefits. By tracking individual nuts with coded tin-tags over 3 years (2000–2003), this study quantified nut predation and dispersal of harland tanoak (Lithocarpus harlandii) by seed-caching rodents in a subtropical evergreen broadleaved forest in the Duiangyan Region of Sichuan Province, Southwest China. We found that tanoak seedlings established from rodent-generated caches in the primary stands over a 12-month post-dispersal period. Our results indicate that seed-caching rodents are effective dispersers of tanoak nuts, but dispersal effectiveness varies among years and stands, probably due to mast seeding of harland tanoak or community-level seed availability according to the predator satiation hypothesis. Some nut traits in tanoak species, e.g. large seed size, hard nut husk, lower tannin and mast seeding, are important characteristics for seed dispersal by scatter-hoarding rodents, compared with oak species with higher tannin content.     

Scatter-hoarding rodents use different foraging strategies for seeds from different plant species

Seed predation and dispersal by scatter-hoarding rodents are key processes that determine seed survival, and thus, plant regeneration within forests. For decades, there has been much debate on the important effects of seed size (one of the most important seed traits) on rodent foraging preference. Furthermore, the possible selective forces in the evolution of seed size may be influenced by primary selectivity and how rodents treat seeds after harvesting. In this study, different-sized seeds from four species (Pinus armandii, Pinus densata, Abies sp., and Viburnum sp.) harvested by scatter-hoarding rodents were studied in an alpine forest in Southwestern China for two consecutive years. Our results showed that seed size influenced rodent foraging preferences, with bigger seeds being preferred over smaller seeds, within and across species. Rodents only removed and cached the larger seeds of P. armandii, and ate the seeds of the other three species in situ. Rodents are purely seed predators for these three species. For the cached seeds of P. armandii, significantly positive correlations were observed between seed size and dispersal distance among both primary and secondary cached seeds in 2006, but not in 2005. Our results indicate that among many coexisting species with widely different-sized seeds, scatter-hoarding rodents played important roles in the seed dispersal of the big-seeded species alone. This caching behavior could offset the limited seed dispersal of large-seeded and wingless species (P. armandii), in comparison with that of small winged seed species (P. densata and Abies sp.) and frugivore-dispersed species (Viburnum sp.).     

Seed dispersal anachronisms: rethinking the fruits extinct megafauna ate

Background

Some neotropical, fleshy-fruited plants have fruits structurally similar to paleotropical fruits dispersed by megafauna (mammals >10³ kg), yet these dispersers were extinct in South America 10–15 Kyr BP. Anachronic dispersal systems are best explained by interactions with extinct animals and show impaired dispersal resulting in altered seed dispersal dynamics.

Methodology/Principal Findings

We introduce an operational definition of megafaunal fruits and perform a comparative analysis of 103 Neotropical fruit species fitting this dispersal mode. We define two megafaunal fruit types based on previous analyses of elephant fruits: fruits 4–10 cm in diameter with up to five large seeds, and fruits >10 cm diameter with numerous small seeds. Megafaunal fruits are well represented in unrelated families such as Sapotaceae, Fabaceae, Solanaceae, Apocynaceae, Malvaceae, Caryocaraceae, and Arecaceae and combine an overbuilt design (large fruit mass and size) with either a single or few (<3 seeds) extremely large seeds or many small seeds (usually >100 seeds). Within-family and within-genus contrasts between megafaunal and non-megafaunal groups of species indicate a marked difference in fruit diameter and fruit mass but less so for individual seed mass, with a significant trend for megafaunal fruits to have larger seeds and seediness.

Conclusions/Significance

Megafaunal fruits allow plants to circumvent the trade-off between seed size and dispersal by relying on frugivores able to disperse enormous seed loads over long-distances. Present-day seed dispersal by scatter-hoarding rodents, introduced livestock, runoff, flooding, gravity, and human-mediated dispersal allowed survival of megafauna-dependent fruit species after extinction of the major seed dispersers. Megafauna extinction had several potential consequences, such as a scale shift reducing the seed dispersal distances, increasingly clumped spatial patterns, reduced geographic ranges and limited genetic variation and increased among-population structuring. These effects could be extended to other plant species dispersed by large vertebrates in present-day, defaunated communities.     

Diplochory in western chokecherry: you can��t judge a fruit by its mesocarp

Western chokecherry (Prunus virginiana var. demissa, Rosaceae) is dispersed by frugivorous birds and carnivores, but it has large seeds that are potentially attractive to rodents that could act as seed predators and dispersers. Here, we quantify the benefits of primary dispersal by birds and secondary dispersal by scatter-hoarding rodents. In the fall, avian frugivores (mostly American robins, Turdus migratorius, and cedar waxwings, Bombycilla cedrorum) consumed 87% of the fruit crop and dispersed 67% of the fruit crop away from parent plants. Rodents removed 89% of seeds that simulated bird-dispersed seed rain from transects in riparian zones and 58% from transects in upland habitats. Rodents scatter-hoarded 91.6% of the seeds they removed, burying most in small caches (two to eight seeds) 8?C25?mm deep. About 39% of the seeds in spring caches produced seedlings. Inside rodent-proof exclosures, 52.1% of seeds buried to simulate rodent caches produced seedlings, 29.7% of which were still alive after 1?year. In contrast, only 3.8% of seeds placed on the soil surface, simulating dispersal by avian frugivores, produced seedlings. Seed dispersal by frugivorous birds likely contributes to colonization of unoccupied habitat through long-range dispersal and to escape from distance-dependent seed mortality near the parent plant. Despite seed losses, rodents offer short-range seed dispersal and bury seeds in more favorable sites for germination, improving seedling emergence and establishment. The combined mechanisms of seed dispersal significantly enhanced chokecherry seedling recruitment by providing more dispersal-related benefits than either frugivorous bird or scatter-hoarding rodents could provide alone.     

The Comparative Effectiveness of Rodents and Dung Beetles as Local Seed Dispersers in Mediterranean Oak Forests

The process of seed dispersal of many animal-dispersed plants is frequently mediated by a small set of biotic agents. However, the contribution that each of these dispersers makes to the overall recruitment may differ largely, with important ecological and management implications for the population viability and dynamics of the species implied in these interactions. In this paper, we compared the relative contribution of two local guilds of scatter-hoarding animals with contrasting metabolic requirements and foraging behaviours (rodents and dung beetles) to the overall recruitment of two Quercus species co-occurring in the forests of southern Spain. For this purpose, we considered not only the quantity of dispersed seeds but also the quality of the seed dispersal process. The suitability for recruitment of the microhabitats where the seeds were deposited was evaluated in a multi-stage demographic approach. The highest rates of seed handling and predation occurred in those microhabitats located under shrubs, mostly due to the foraging activity of rodents. However, the probability of a seed being successfully cached was higher in microhabitats located beneath a tree canopy as a result of the feeding behaviour of beetles. Rodents and beetles showed remarkable differences in their effectiveness as local acorn dispersers. Quantitatively, rodents were much more important than beetles because they dispersed the vast majority of acorns. However, they were qualitatively less effective because they consumed a high proportion of them (over 95%), and seeds were mostly dispersed under shrubs, a less suitable microhabitat for short-term recruitment of the two oak species. Our findings demonstrate that certain species of dung beetles (such as Thorectes lusitanicus), despite being quantitatively less important than rodents, can act as effective local seed dispersers of Mediterranean oak species. Changes in the abundance of beetle populations could thus have profound implications for oak recruitment and community dynamics.     

A telemetric thread tag for tracking seed dispersal by scatter-hoarding rodents

The seeds of many tree species are dispersed more than once, and this secondary seed dispersal is believed to enhance seedling recruitment. However, the effectiveness of secondary seed dispersal has rarely been assessed because it is difficult to track seeds until they die or germinate. We describe a new technique that uses thread tags attached to radio transmitters (telemetric thread tags) to track long-distance multistep seed dispersal by scatter-hoarding rodents. These telemetric thread tags can be turned off with a magnet and are reactivated when the seed moves. This method allows for seed tracking with minimal cache disturbance or distance bias, over long time spans, multiple seed movements, and with few effects on animal behavior. We used telemetric thread tags to track seed dispersal of the palm tree Astrocaryum standleyanum in a Neotropical forest, and achieved near-complete recovery of dispersed seeds tracked over distances as far as 241?m. We were also able to record the recovery time and fate of cached seeds without disturbing caches. Neither the removal rate nor the dispersal distance differed between seeds with telemetric thread tags and thread-tagged seeds. We conclude that telemetric thread tags can be used to document secondary seed dispersal by scatter-hoarding animals with unprecedented efficacy and precision. Given the size of these tags relative to the size of seeds and their dispersers, this method is applicable to the majority of tree species that are secondarily dispersed by scatter-hoarding mammals.     

Effects of seed size on dispersal distance in five rodent-dispersed fagaceous species

We studied the effect of seed size on dispersal by comparing dispersal distances in five rodent-dispersed fagaceous species (Lithocarpus harlandii, Quercus variabilis, Q. serrata, Cyclobalanopsis glauca, Castanopsis fargesii) with different seed size. We tracked individual seeds with coded tin-tags in two stands over 3 years in a subtropical evergreen broadleaved forest in the Dujiangyan Region of Sichuan Province, Southwest China. Our seed tracking data indicate that dispersal distances (including mean, maximum and distribution range) of seeds in primary caches and of seeds eaten after dispersal significantly increased with seed size, for both stands and all years. In addition, larger seeds (L. harlandii and Q. variabilis) were re-cached more often than smaller ones, which further reduced the relative density among caches and extended dispersal distances. Our findings indicate that greater dispersal distances for larger seeds might benefit the evolution of differences in seed size, and that scatter-hoarding might be advantageous for rodent-dispersed tree species.     

Directed vertebrate-mediated seed dispersal of a fleshy-fruited amaryllid in a heterogenous habitat

Most plants with fleshy fruits have seeds that are ingested by animals, but a less well-understood mode of seed dispersal involves fleshy fruits containing seeds that are discarded by frugivorous animals because they are too large or toxic to be ingested. We studied the seed dispersal biology of Haemanthus deformis, an amaryllid lily species found in a mosaic of bush clumps in a grassland matrix in South Africa. We asked whether seed dispersal is directed in and among bush clumps and whether germination and survival are greater for seeds dispersed to bush clumps than for those dispersed into grassland. Using camera trapping, we found that fruits are consumed mainly by birds and rodents. The pulp was removed from the seeds which were then discarded without ingestion. While many seeds were dispersed close to the parent plant, most (c. 78.5%) were dispersed further than 1 m away from the parent plant. Longer distance dispersal resulted mainly from birds flying off with fruits in their bill or from rodents engaging in scatter-hoarding behavior. Seedling survival was most successful within bush clumps as compared to grasslands and shade was identified as a primary requirement for seedling survival. Seeds from which the fruit pulp had been removed germinated faster than those in intact fruits. Haemanthus deformis deploys a system of directed seed dispersal, whereby both birds and rodents contribute to the dispersal of seeds within patchy bush clumps that are favorable for seedling survival.     

Effects of seed size of wind-dispersed pines (Pinus) on secondary seed dispersal and the caching behavior of rodents

Seeds and nuts dispersed by scatter-hoarding animals are relatively large compared to propagules dispersed by other means. Possible selective forces in the evolution of large seed size include the selectivity of foraging animals and the ways that food-storing animals treat seeds and nuts after harvest. Treatment by rodents, primarily yellow pine chipmunks ( Tamias amoenus ), of four species of pine seeds that vary in size was studied in the Carson Range of western Nevada. The pines, lodgepole pine ( Pinus contorta , 8.7 mg), ponderosa pine ( P. ponderosa , 55 mg), Jeffrey pine ( P. jeffreyi , 157 mg), and sugar pine ( P. lambertiana , 213 mg), produce winged seeds that are initially wind-dispersed but are gathered by rodents and cached in the soil. Radioactive scandium-46 was used to follow the fates of seeds of all fours species placed around three source trees during autumn 1998 to 2000. Rodents gathered the seeds of all four species, but they took fewer of the lodgepole pine seeds and only six lodgepole seed caches (n=2106 total caches) were found during the three years. Among the other three species, number of seeds per cache decreased with increasing seed mass. However, the product of number of seeds per cache and seed mass was similar for all species. Sugar pine seeds were cached slightly deeper than ponderosa and Jeffrey pine seeds. For the species examined, seed size appeared to have had little effect on several other attributes, including mean dispersal distance, substrate choice, and microhabitat choice. Large size decreases wind dispersibility of pine seeds, but secondary dispersal by scatter-hoarding rodents compensates for poor wind dispersal so that total dispersibility of large-seeded pines is not compromised.     

啮齿类对植物种子的传播作用

种子植物是固着生活的有机体 ,如果能成功地将种子扩散到适宜的生境 ,将会在生存竞争中获得优势。在长期的进化过程中 ,不同的植物依赖不同的媒介传播种子 ,如风传播 ,水传播 ,或自身的力量传播 (重力、弹爆力等 )。在很多情况下也依靠动物完成种子扩散 ,即所谓的动物传播。根据依赖的动物对象不同可以分为蚁传播 ,鸟传播 ,哺乳类传播 ,以及鱼传播 ,爬行类传播等。哺乳类中传播种子的类群主要包括翼手类 ,灵长类和啮齿类。由于能够飞行 ,热带食果实的蝙蝠(属翼手类 )对种子的传播作用最明显 ,研究得也最多 ,源于蝙蝠类的传播特称为ｃｈｉｒ…     

Role of small rodents in the seed dispersal process: Microcavia australis consuming Prosopis flexuosa fruits

Understanding the functional role of animal species in seed dispersal is central to determining how biotic interactions could be affected by anthropogenic drivers. In the Monte Desert, mammals play different functional roles in Prosopis flexuosa seed dispersal, acting as opportunistic frugivores (endozoochorous medium‐sized and large mammals) or seed hoarders (some small sigmodontine rodents). Our objective was assessing the functional role of Microcavia australis, a small hystricognathi rodent, in the fruit removal and seed deposition stages of P. flexuosa seed dispersal, compared to sympatric sigmodontine rodents. In situ, we quantified fruit removal by small rodents during non‐fruiting and fruiting periods, and determined the distance seeds were transported, particularly by M. australis. In laboratory experiments, we analysed how M. australis stores seeds (through scatter‐ or larder‐hoarding) and how many seeds are left in caches as living seeds, relative to previous data on sigmodontine rodents. To conduct field studies, we established sampling stations under randomly chosen P. flexuosa trees at the Ñacuñán Man and Biosphere Reserve. We analysed fruit removal by small rodents and seed dispersal distance by M. australis using camera traps focused on P. flexuosa fruits covered with wire screen, which only allowed entry of small animals. In laboratory trials, we provided animals with a known number of fruits and assessed seed conditions after removal. Small rodents removed 75.7% of fruit supplied during the non‐fruiting period and 53.2% during the fruiting period. Microcavia australis and Graomys griseoflavus were the main fruit removers. Microcavia australis transported seeds to a mean distance of 462 cm and cached seeds mainly in scatter‐hoards, similarly as Eligmodontia typus. All transported seeds were left in fruit segments or covered only by the endocarp, never as predated seeds. Microcavia australis disperses P. flexuosa seeds by carrying fruits away from a source to consume them and then by scatter‐hoarding fruits and seeds.     

鼠类对辽东栎橡子的搬运

在北京东灵山地区,在灌丛、森林2 种生境类型中共设计了5 个处理,以检验种子质量、种子可视度、生境类型如何影响鼠类对辽东栎（Quercus liaotungensis）橡子的搬运。每个处理包括200 枚种子。每日检查种子状态,实验持续16 d。鼠类在几天之内将大多数种子搬运走。完好橡子比虫蛀橡子消失得快。橡子在森林生境中明显比在灌丛生境中消失的快。鼠类对放置在灌丛下方和灌丛之间的橡子的搬运速率差别不大。放置在落叶下方的橡子消失速率明显慢于地表的橡子。本研究利用半存活时间测量种子的搬运率。各处理的半存活时间范围是0. 6 ～ 8. 6 d。各处理的橡子搬运率均较高,这说明鼠类有能力在种子下落到冬季来临的2 个月时间内,搬运绝大多数的橡子。实验说明,鼠类是辽东栎橡子重要的捕食者和扩散者。     

啮齿动物和鸟类对东灵山地区辽东栎种子丢失的影响

20 0 0年 8月中旬至 10月上旬 ,在北京东灵山地区小龙门林场选取两块辽东栎分布近似而坡向不同的样地 ,并对样地内种子库与啮齿动物的种群数量变化进行了调查。结果表明 ,两块样地种子雨持续 4 0天左右 ,且种子下落趋势基本一致 ,高峰期都集中在 9月中旬 ,不同坡向的种子产量差异显著。在两样地随机各设置 2 4个种子方形收集器 (0 5m2 )和 2 0个地表样方 (1 0× 0 5m2 )调查种子产量。通过比较收集器内壳斗和种子数量 ,发现二者无显著差异 ,说明鸟类对林冠层种子丢失作用不明显 ;而收集器和地表样方种子数量差异显著 ,表明辽东栎种子库扩散主要由林中啮齿动物完成。标记重捕发现辽东栎林中啮齿动物群落包括大林姬鼠 ,社鼠 ,棕背鼠平和花鼠 ,其中大林姬鼠为优势种 ,占群落的 77.2 %。     

啮齿动物的贮藏行为与植物种子的扩散

绝大多数啮齿动物一方面取食大量的植物种子和果实,另一方面通过其贮食行为将植物种子和果实搬运到远离母树的地点,即扩散,并将它们分散埋藏在落叶下或浅表的土层中,从而影响种子和果实的时空分布,最后导致幼苗在有利的条件下发生和建成,实现植物更新。啮齿动物与植物种子和果实之间已广泛形成了互惠或协同进化的关系。啮齿动物的贮食行为主要通过以下几个过程对植物种子和果实的扩散产生影响：选择、搬运和埋藏以及随后对种子和幼苗存活和死亡的影响等。本综述了啮齿动物对植物种子和果实贮藏的研究结果,以期为进一步开展啮齿动物的贮食行为在植物种子和果实的扩散中的作用的研究提供参考。     

The Interplay among Acorn Abundance and Rodent Behavior Drives the Spatial Pattern of Seedling Recruitment in Mature Mediterranean Oak Forests

The patterns of seedling recruitment in animal-dispersed plants result from the interactions among environmental and behavioral variables. However, we know little on the contribution and combined effect of both kinds of variables. We designed a field study to assess the interplay between environment (vegetation structure, seed abundance, rodent abundance) and behavior (seed dispersal and predation by rodents, and rooting by wild boars), and their contribution to the spatial patterns of seedling recruitment in a Mediterranean mixed-oak forest. In a spatially explicit design, we monitored intensively all environmental and behavioral variables in fixed points at a small spatial scale from autumn to spring, as well as seedling emergence and survival. Our results revealed that the spatial patterns of seedling emergence were strongly related to acorn availability on the ground, but not by a facilitationeffect of vegetation cover. Rodents changed seed shadows generated by mother trees by dispersing most seeds from shrubby to open areas, but the spatial patterns of acorn dispersal/predation had no direct effect on recruitment. By contrast, rodents had a strong impact on recruitment as pilferers of cached seeds. Rooting by wild boars also reduced recruitment by reducing seed abundance, but also by changing rodent’s behavior towards higher consumption of acorns in situ. Hence, seed abundance and the foraging behavior of scatter-hoarding rodents and wild boars are driving the spatial patterns of seedling recruitment in this mature oak forest, rather than vegetation features. The contribution of vegetation to seedling recruitment (e.g. facilitation by shrubs) may be context dependent, having a little role in closed forests, or being overridden by directed seed dispersal from shrubby to open areas. We warn about the need of using broad approaches that consider the combined action of environment and behavior to improve our knowledge on the dynamics of natural regeneration in forests.     

济源太行山区鼠类对三种林木种子的扩散和贮藏

对取食种子的动物而言,种子的选择、扩散以及随后的处理是一个复杂的过程。为了解济源太行山区鼠类对不同种林木种子的选择和扩散策略的差异,于2011 年9 月10 日至11 月8 日,选取山杏、桃和栓皮栎3 种林木种子,将种子标记后,释放于次生林中,以5 d 间隔,调查并记录种子命运。结果表明: (1)大林姬鼠和岩松鼠是该地区主要的种子取食者和扩散者; (2)3 种种子的扩散速率明显不同,栓皮栎种子扩散速率最快(中位存留时间8. 6 d),其次为山杏种子(中位存留时间20. 9 d),桃种子扩散速率最慢(中位存留时间37. 5 d); (3)鼠类倾向于取食栓皮栎种子(55.0%) , 埋藏山杏种子(62. 0% ),但忽略桃种子(原地存留率99. 0% );(4)88. 6%的山杏和78. 8% 的栓皮栎种子被贮藏在灌丛下方、树干基部周围和石块旁边等生境中,而仅有4 3% 的山杏和9.1% 的栓皮栎种子被贮藏于裸地中;(5)鼠类将山杏种子搬运到更远(3. 4 ± 2. 1 m,mean± SE,n =63)处贮藏;而栓皮栎种子的搬运距离则相对较近(2. 5 ± 2. 4 m,n = 57)。结果显示:鼠类对不同种植物种子具有明显的取食、贮藏偏好和不同的贮藏策略。     

Teasing Apart the Effects of Seed Size and Energy Content on Rodent Scatter-Hoarding Behavior

Scatter-hoarding rodents are known to play a crucial role in the seed dispersal of many plant species. Numerous studies have indicated that both seed size and the energy content of seeds can affect rodent foraging behavior. However, seed size is usually associated with energy content per seed, making it difficult to isolate how seed size and energy affect rodent foraging preferences. This study used 99 treatments of artificial seeds (11 seed sizes×9 levels of energy content) to tease apart the effect of seed size and energy content on rodent seed-caching behavior. Both seed traits showed significant effects, but their details depended on the stage of the rodent foraging process. Seeds with higher energy content were harvested more rapidly while seed size only had a modest effect on harvest rate. However, after harvesting, seed size showed a much stronger effect on rodent foraging behavior. Rodents’ choice of which seeds to remove and cache, as well as seed dispersal distance, seemed to reflect an optimal seed size. Our findings could be adapted in future studies to gain a better understanding of scatter-hoarding rodent foraging behavior, and the co-evolutionary dynamics between plant seed production and seed dispersers.     

Effects of disperser abundance, seed type, and interspecific seed availability on dispersal distance

Seed dispersal distance is influenced by a variety of seed properties and functional responses of dispersers. However, to our knowledge, how and why seed dispersal distances are determined remains poorly understood. In the present study, seeds of sympatric tree species, Pinus koraiensis, Corylus mandshurica, Corylus heterophylla, and Quercus mongolica were released to investigate the effects of rodent abundance, seed type, and seed availability on seed dispersal. Our results showed that seeds of P. koraiensis were dispersed further than those of C. heterophylla and C. mandshurica regardless of the ambient rodent and seed abundances, reflecting a consistent effect of seed type on seed dispersal distances. Seed dispersal distance was greatly facilitated by lower per-capita seed abundance (the ratio of seeds to rodents); however, seed caching and cache survival were benefited from higher per-capita seed abundance. Although seed dispersal and seed caching of a particular tree species can be enhanced by its own seed availability, no consistent influence was detected at interspecific levels, reflecting different interspecific effects of seed availability on seed dispersal of sympatric seed species. Our results provide evidences that the effect of seed availability on seed dispersal should be evaluated in terms of per-capita seed abundance and interspecific effects, rather than the independent influence of seed or disperser abundances.     

Scatter-hoarding rodents prefer slightly astringent food

The mutualistic interaction between scatter-hoarding rodents and their seed plants is highly complex yet poorly understood. Plants may benefit from the seed dispersal behavior of rodents, as long as seed consumption is minimized. In parallel, rodents may maximize foraging efficiency and cache high-quality resources for future consumption. Defensive compounds, such as tannins, are thought to be a major mechanism for plant control over rodent behavior. However, previous studies, using naturally occurring seeds, have not provided conclusive evidence supporting this hypothesis. Here, we test the importance of tannin concentrations on the scatter-hoarding behavior of rodents by using an artificial seed system. We combined feeding trials and field observations to examine the overall impact of seed tannin concentrations on rodent behavior and health. We found that rodents favored seeds with an intermediate amount of tannin (~5%) in the field. Meanwhile, in rodents that were fed a diet with different tannin content, only diets with high tannin content (25%, 15%, and 10%) caused a significant negative influence on rodent survival and health. Significant differences were not found among treatments with tannin levels of 0-5%. In contrast to many existing studies, our results clearly demonstrate that scatter-hoarding rodents prefer slightly 'astringent' food. In the co-evolutionary arms race between plants and animals, our results suggest that while tannins may play a significant role in reducing general predation levels by the faunal community, they have no precise control over the behavior of their mutualistic partner. Instead, the two partners appear to have reached an evolutionary point where both parties receive adequate benefits, with the year-to-year outcome being dependent on a wide range of factors beyond the control of either partner.     

Effects of burrow condition and seed handling time on hoarding strategies of Edward's long-tailed rat (Leopoldamys edwardsi)

Many hoarding rodents use burrows not only for dwelling and protection from natural enemies, but also for food storage. However, little is known how burrows used by scatter-hoarding animals influence their foraging behaviors. In addition, handling time for a given food item has a fundamental impact on hoarding strategies of these hoarding animals: food items with longer handling time are more likely to be hoarded due to increasing predation risk because the animals spend more time outside their burrows if they consumed such food. By providing with two types of artificial burrows (aboveground vs. underground) and two types of food items (i.e. seeds) with contrasting handling times, we investigated how burrow condition and handling time co-influence hoarding strategies of a key scatter-hoarding rodent, Edward's long-tailed rat (Leopoldamys edwardsi) in large enclosures in southwest China. We found that only a few animals larder-hoarded fewer seeds when only aboveground burrows were available, while over 80% of the animals preferred to use the underground burrows and hoard significantly more seeds in the burrows when both aboveground and underground burrows were provided simultaneously. We also found that seed handling time significantly affected hoarding strategies of the animals: they consumed and/or scatter-hoarded more Camellia oleifera seeds with shorter handling time outside the burrow, but consumed and larder-hoarded more Lithocarpus harlandii seeds with longer handling time in underground burrows. Our study indicates that both burrow types and seed handling time have important impacts on hoarding strategies of scatter-hoarding animals.