Reproductive ecology and territorial behavior of Boana goiana (Anura: Hylidae), a gladiator frog from the Brazilian Cerrado

ABSTRACT Anuran males and females adopt different reproductive and behavioral strategies in different contexts. We investigated the reproductive ecology and territorial behavior of the treefrog Boana goiana (B. Lutz, 1968) from the Brazilian Cerrado. We hypothesized that competitor density/proximity would increase the behavioral responses of B. goiana males, and that mating would be assortative. We also tested if the number of eggs correlates with female size and if there is a trade-off between clutch size and egg size. We conducted two territoriality experiments to test the effects of male size, competitor proximity and competitor density. Larger males called more in the presence of a second male. In the second experiment, the largest males emitted more calls and the distance to the nearest male increased as resident males called more. In both experiments, the number of calls was influenced by either male size or spacing between males. Some males behaved as satellites, probably to avoid fights. Our analyses indicate that females choose males with similar sizes to their own, corroborating our hypothesis of size-assortative mating. We found no relationships between female size and clutch size/volume, and between egg size and number of eggs per clutch. We also report multiple spawning for this species. The low incidence of physical combats and the spacing pattern indicate that this species relies almost solely on calls to resolve contests, which could be explained by low motivation, or simply because males avoid combats to decrease injury risks. Thus, acoustic or even multimodal communication seems crucial for social interactions of B. goiana.

摘要 无尾两栖类（Anuran）的雌雄个体在不同情境下会采取差异化的繁殖与行为策略。本研究针对源自巴西塞拉多稀树草原（Brazilian Cerrado）的雨蛙*Boana goiana*（B. Lutz, 1968，下称B. goiana）的繁殖生态学与领域行为展开系统调查。我们提出两项核心假设：其一，竞争者密度或空间邻近程度会强化B. goiana雄性的行为响应；其二，该物种存在体型选型交配现象。此外，我们还验证了两个科学问题：雌性体型是否与单窝产卵数量相关，以及产卵窝规模与卵粒大小间是否存在进化权衡。本研究开展两项领域行为实验，以检验雄性体型、竞争者空间距离及竞争者密度对其行为的调控作用。结果显示，当环境中存在另一只雄性时，体型更大的雄性鸣叫频次显著更高。在第二项实验中，体型最大的雄性发出的鸣叫声更多，且当定居雄性鸣叫频次提升时，其与最近雄性的空间距离也随之增大。两项实验均证实，雄性体型或雄性个体间的间距均会对鸣叫频次产生显著影响。部分雄性会以卫星雄性个体的身份活动，推测其目的是避免直接打斗。本研究的分析结果表明，雌性会选择体型与自身相近的雄性作为配偶，这一结果验证了我们提出的体型选型交配假设。我们未发现雌性体型与产卵窝大小/产卵体积之间存在显著关联，也未观测到卵粒大小与单产卵窝内卵粒数量间存在相关性。此外，本研究还记录到该物种存在多次产卵行为。该物种较低的肢体冲突发生率与空间分布模式表明，其几乎完全依靠鸣叫声来解决种内竞争冲突，这一现象可归因于较低的争斗动机，或是雄性为降低受伤风险而主动规避打斗。因此，声学乃至多模态通讯似乎对B. goiana的社会互动至关重要。