Data from: Seed ingestion and germination in rattlesnakes—overlooked agents of rescue and secondary dispersal

Seed dispersal is a key evolutionary process and a central theme in the population ecology of terrestrial plants. The primary producers of most land-based ecosystems are propagated by and maintained through various mechanisms of seed dispersal that involve both abiotic and biotic modes of transportation. By far the most common biotic seed transport mechanism is zoochory, whereby seeds, or fruits containing them, are dispersed through the activities of animals. Rodents are one group of mammals that commonly prey on seeds (granivores) and play a critical, often destructive, role in primary dispersal and the dynamics of plant communities. In North America, geomyid, heteromyid, and some sciurid rodents have specialized cheek pouches for transporting seeds from plant source to larder, where they are often eliminated from the pool of plant propagules by consumption. These seed-laden rodents are commonly consumed by snakes as they forage, but unlike raptors, coyotes, bobcats, and other endothermic predators which eat rodents and are known or implicated to be secondary seed dispersers, the role of snakes in seed dispersal remains unexplored. Here, using museum-preserved specimens, we show that in nature three desert rattlesnake species consumed heteromyids with seeds in their cheek pouches. By examining the entire gut we discovered, furthermore, that secondarily ingested seeds can germinate in the colons. In terms of secondary dispersal, rattlesnakes are best described as diplochorous. Because seed rescue and secondary dispersal in snakes has yet to be investigated, and because numerous other snake species consume granivorous and frugivorous birds and mammals, our observations offer direction for further empirical studies of this unusual but potentially important channel for seed dispersal.

种子传播是陆生植物演化进程中的关键环节，亦是陆地植物种群生态学研究的核心主题。多数陆地生态系统的初级生产者（primary producer）均通过涵盖非生物与生物运输方式的各类种子传播机制完成繁殖与种群维持。目前最常见的生物性种子运输机制为动物传播（zoochory），即通过动物活动实现种子或带果种子的扩散。啮齿动物是一类常以种子为食的哺乳动物（即食籽动物，granivores），它们在初级传播与植物群落动态中扮演着关键却常具破坏性的角色。在北美地区，囊鼠科、更格卢鼠科以及部分松鼠科啮齿动物拥有特化的颊囊，可将种子从植株来源地搬运至储粮巢穴，而这些种子往往会被啮齿动物取食，从而脱离植物繁殖体库。这些携带有种子的啮齿动物在觅食过程中常会被蛇类捕食，但与猛禽、郊狼、短尾猫等已知或被证实可作为次级种子传播者的恒温（endothermic）捕食者不同，蛇类在种子传播中的作用至今尚未得到探索。本研究依托馆藏标本证实，在自然环境中，三种沙漠响尾蛇会捕食颊囊中携带有种子的更格卢鼠。此外，通过对完整肠道的解剖分析，我们发现被二次摄入的种子可在结肠中萌发。就次级传播而言，响尾蛇的传播模式最适合被描述为双阶段传播的（diplochorous）。由于蛇类介导的种子获救与次级传播机制尚未得到研究，且诸多其他蛇类物种亦会捕食食籽或食果的鸟类与哺乳动物，本研究的发现为进一步探索这一特殊却可能极具重要性的种子传播途径提供了明确的研究方向。