A Newly Discovered Symbiotic Relationship Between Giant Cowbirds (Molothrus oryzivorus) and South American Tapirs (Tapirus terrestris) in Suriname

Abstract

Interspecific interactions are a common occurrence in nature, and, in some instances, two species form very close associations. Such symbiotic relationships vary, though, in terms of the relative advantages and disadvantages accrued by both species during interspecific interactions. Symbiotic relationships whereby both species benefit are thought to occur between oxpeckers and large mammals in Africa because while oxpeckers benefit by preying upon ticks and blood-sucking flies on the mammal's bodies, the mammals also benefit from the removal of ticks and flies. However, there is also evidence that the interactions between oxpeckers and mammals may not benefit both species because oxpeckers may not significantly reduce the abundance of ticks and may also deliberately keep wounds open, making such interactions harmful for mammals. Here, we respond to calls for further observations to help clarify the nature of such interactions by reporting a newly discovered symbiotic relationship between giant cowbirds (Molothrus oryzivorus) and South American tapirs (Tapirus terrestris) in Suriname. The cowbirds were observed feeding on ticks on the bodies of the tapirs and while it appeared that the tapirs were generally tolerant of the cowbirds, we did observe the tapirs attempting to repel the cowbirds when they appeared to target wounds on their bodies. The interactions we observed therefore appeared to benefit the cowbirds by providing them with prey and while the tapirs benefit from a reduction in tick abundance, the cowbirds did appear to target wounds on their bodies. Consequently, we tentatively conclude that the relationship between giant cowbirds and South American tapirs that we observed was beneficial to the birds and yet potentially harmful to the mammals and so further observations are needed to confirm if such interactions are context dependent. The interactions between giant cowbirds and South American tapirs provide an interesting opportunity to examine the nature of the evolutionary causes and ecological consequences of symbiotic interactions between birds and mammals.