Animal contests are energetically costly, but injuries are said to be rare. In gladiator frogs, the males possess a spine beneath their pollex (i.e., prepollex) that can be used as weapons and frequently leave scars during contests over spawning areas. Knowing how scars are made, and how scars are distributed among individuals, might prove valuable to address the costs and benefits of fighting. Here, we studied the gladiator frog Boana curupi in a Neotropical stream to (1) assess the rarity of the contested resource, (2) assess how spines are used during contests, and (3) test how the quantity of scars on males’ backs correlate to their morphology. We found only four spawning areas in ~ 1 km of stream. And when males engaged in physical fights, they stroke the rival on their backs with the prepollex. Scars on males’ back are thus caused by the prepollex. Both results explain the high frequency of injuries: 90.7% (29 of 32 males) presented scars. Furthermore, the amount of injuries on a male’s back increased with the weight of the male, but not its body size. Therefore, heavier individuals are sustaining more injuries than lighter individuals, hinting that heavier individuals fight more frequently and value reproduction more than lighter individuals.

中文翻译：

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与疤痕作斗争：较重的角斗士青蛙比轻质的青蛙受伤更多

动物比赛的能量消耗很大，但是据说很少发生。在角斗士青蛙中，雄性在其花粉之下有一根脊柱（即前花粉），可以用作武器，并在产卵区比赛中经常留下疤痕。知道如何制造疤痕，以及如何在个体之间分配疤痕，可能对解决战斗的成本和收益很有帮助。在这里，我们研究了斗士青蛙Boana curupi（1）评估争夺资源的稀有性，（2）评估在比赛中如何使用刺，以及（3）测试男性背部疤痕的数量与形态之间的关系。我们在〜1 km的溪流中仅发现了四个产卵区。当雄性进行肉搏时，他们会用前花粉抚摸对手。因此，男性背上的疤痕是由前花粉引起的。两项结果均说明受伤的频率很高：90.7％（32名男性中的29名）出现了疤痕。此外，男性背部的受伤程度随男性的体重而增加，但不随其体型而增加。因此，较轻的人比轻的人承受的伤害更多，这表明较重的人比轻的人更频繁地战斗并重视繁殖。