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。本研究针对巴西塞拉多（Cerrado）生态区的戈氏雨滨蛙（Boana goiana, B. Lutz, 1968）的繁殖生态与领域行为展开调查。我们提出两项假说：其一，竞争者密度与空间接近程度会强化戈氏雨滨蛙雄性的行为响应；其二，该物种的交配模式存在体型选型交配（assortative mating）现象。同时我们还验证了两个科学问题：雌性体型是否与产卵数量存在相关性，以及产卵团大小（clutch size）与卵粒大小之间是否存在权衡关系。我们开展了两项领域性实验，以检验雄性体型、竞争者空间位置及竞争者密度对其行为的影响。实验结果显示，当有另一只雄性存在时，体型更大的雄性鸣叫频次更高；在第二项实验中，体型最大的雄性发出的鸣叫更多，且当定居雄性的鸣叫频次提升时，其与最近雄性的间距也会增大。两项实验均表明，雄性的鸣叫频次受自身体型或雄性间间距的共同影响。部分雄性会充当卫星个体（satellites），大概率以此避免直接打斗。分析结果证实，雌性会选择与自身体型相近的雄性，验证了我们关于体型选型交配的假说。我们未发现雌性体型与产卵团大小/体积之间存在关联，也未观测到卵粒大小与单产卵团卵粒数量之间的相关性。此外，我们还记录到该物种存在多次产卵行为。该物种物理打斗的发生率极低，且其空间分布模式表明，它们几乎完全依靠鸣叫来解决种群内的竞争冲突，这一现象可归因于较低的打斗动机，或是雄性为降低受伤风险主动规避打斗。由此可见，声学甚至多模态通讯（multimodal communication）对于戈氏雨滨蛙的社会互动至关重要。