The reciprocal pilferage hypothesis argues that, despite the occurrence of pilferage, scatter-hoarding behaviour could evolve if cache loss is compensated by gains pilfered from others. However, this model has not been strictly tested because of the difficulty associated with tracking caches, including ownership, over long periods. Using infrared radiation cameras, we tracked caching of Juglans regia seeds by groups of two Pere David's rock squirrels, Sciurotamias davidianus, within a large natural enclosure. Our goal was to quantify how squirrels responded to the presence of a conspecific when seed hoarding and pilfering and test the reciprocal pilferage hypothesis. We found that the numbers of seeds harvested from the seed sources and pilfered from conspecifics was initially low, increasing as seeds were removed and then dropping off once few seeds remained at the seed sources. Additionally, the number of seeds scatter hoarded increased with a decreasing number of seeds remaining at the sources. Seeds harvested from the source and pilfered from competitors were at first cached randomly within the enclosure and then centralized to the low-competition area near the nest as seed sources declined. Overall, pilferage was not high. The proportions of seeds pilfered did not vary between conspecifics and were positively correlated with each other over trials. More seeds were harvested from the seed sources than pilfered by competitors at the early stage of hoarding. These results suggest that, under conspecific competition, squirrels appeared first to compete for food at the sources, then for caches with each other as food sources decreased, and finally cache ownership became relatively stable. Squirrels compensated for cache loss by both harvesting food from the sources and pilfering caches from its competitor. The amount of seeds gained from pilfering was sufficient to replace pilfered caches, supporting the reciprocal pilferage hypothesis.

中文翻译：

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散布囤积松鼠对同种偷窃的反应：互惠偷窃假说的检验

互惠窃取假说认为，尽管发生了窃取，但如果缓存损失由从他人那里窃取的收益来补偿，则分散囤积行为可能会演变。但是，由于与长期跟踪缓存（包括所有权）相关的困难，该模型尚未经过严格测试。使用红外辐射相机，我们跟踪了两只佩雷大卫岩松鼠 Sciurotamias davidianus 在一个大型天然围栏内对胡桃种子的缓存。我们的目标是量化松鼠在种子囤积和偷窃时如何对同种物种的存在做出反应，并测试相互偷窃假设。我们发现从种子来源收获和从同种窃取的种子数量最初很低，随着种子被移除而增加，然后一旦种子源中剩余的种子很少就会下降。此外，随着源头上剩余种子数量的减少，散播的种子数量增加。从源头收获并从竞争对手那里窃取的种子首先被随机缓存在围栏内，然后随着种子来源的减少而集中到巢穴附近的低竞争区域。总体来说，盗窃率不高。被盗种子的比例在同种之间没有变化，并且在试验中彼此呈正相关。在囤积初期，从种子来源收获的种子多于竞争对手窃取的种子。这些结果表明，在同种竞争下，松鼠首先出现在源头上争夺食物，然后随着食物来源的减少，彼此的缓存，最后缓存所有权变得相对稳定。松鼠通过从源头收获食物和从竞争对手那里偷窃来弥补缓存损失。从偷窃中获得的种子数量足以取代被偷走的藏匿处，支持互惠偷窃假说。