Engelhardt Katharina A M, Ritchie Mark E, Powell James A
Appalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg, MD 21532-2307, USA.
Department of Biology, Syracuse University, Syracuse, NY 13244-1270, USA.
ScientificWorldJournal. 2014 Feb 4;2014:643694. doi: 10.1155/2014/643694. eCollection 2014.
Differences in body sizes may create a trade-off between foraging efficiency (foraging gains/costs) and access to resources. Such a trade-off provides a potential mechanism for ecologically similar species to coexist on one resource. We explored this hypothesis for tundra (Cygnus columbianus) and trumpeter swans (Cygnus buccinator), a federally protected species, feeding solely on sago pondweed (Stuckenia pectinata) tubers during fall staging and wintering in northern Utah. Foraging efficiency was higher for tundra swans because this species experienced lower foraging and metabolic costs relative to foraging gains; however, trumpeter swans (a) had longer necks and therefore had access to exclusive resources buried deep in wetland sediments and (b) were more aggressive and could therefore displace tundra swans from lucrative foraging locations. We conclude that body size differentiation is an important feature of coexistence among ecologically similar species feeding on one resource. In situations where resources are limiting and competition for resources is strong, conservation managers will need to consider the trade-off between foraging efficiency and access to resources to ensure ecologically similar species can coexist on a shared resource.
体型差异可能会在觅食效率（觅食收益/成本）和获取资源之间形成一种权衡。这种权衡为生态相似的物种在一种资源上共存提供了一种潜在机制。我们针对苔原天鹅（小天鹅）和号手天鹅（一种联邦保护物种）探讨了这一假设，它们在犹他州北部秋季停歇和越冬期间仅以茨藻块茎为食。苔原天鹅的觅食效率更高，因为相对于觅食收益，该物种的觅食和代谢成本较低；然而，号手天鹅（a）脖子更长，因此能够获取埋在湿地沉积物深处的专属资源，并且（b）更具攻击性，所以能够将苔原天鹅从利润丰厚的觅食地点赶走。我们得出结论，体型差异是在以一种资源为食的生态相似物种共存中的一个重要特征。在资源有限且对资源的竞争激烈的情况下，保护管理人员需要考虑觅食效率和获取资源之间的权衡，以确保生态相似的物种能够在共享资源上共存。
