School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales 2006, Australia.
Department of Biology, Geology & Physical Sciences, Sul Ross State University, Alpine, TX 79832, USA.
Biol Lett. 2019 Aug 30;15(8):20190462. doi: 10.1098/rsbl.2019.0462. Epub 2019 Aug 14.
A male cane toad (Rhinella marina) that mistakenly clasps another male (rather than a female) in a sexual embrace (amplexus) can be induced to dismount by a male-specific 'release call'. Although that sex-identifying system can benefit both males in that interaction, our standardized tests showed that one-third of male cane toads did not emit release calls when grasped. Most of those silent males were small, had small testes relative to body mass, and had poorly developed secondary sexual characteristics. If emitting a release call is costly (e.g. by attracting predators), a non-reproductive male may benefit by remaining silent; other cues (such as skin rugosity) will soon induce the amplexing male to dismount, and the 'opportunity cost' to being amplexed (inability to search for and clasp a female) is minimal for non-reproductive males. Hence, male toads may inform other males about their sexual identity only when it is beneficial to do so.
一只雄性甘蔗蟾蜍（Rhinella marina）错误地将另一只雄性（而不是雌性）抱住进行交配（拥抱），可以通过雄性特有的“释放叫声”来诱导其离开。尽管这种性别识别系统在这种相互作用中对双方都有利，但我们的标准化测试显示，三分之一的雄性甘蔗蟾蜍在被抓住时不会发出释放叫声。大多数沉默的雄性体型较小，睾丸相对于体重较小，且第二性征发育不良。如果发出释放叫声是有代价的（例如吸引捕食者），那么一只非繁殖的雄性可能会通过保持沉默而受益；其他线索（如皮肤粗糙度）将很快诱导拥抱的雄性离开，而对于非繁殖的雄性来说，被拥抱的“机会成本”（无法寻找和抱住雌性）是最小的。因此，雄性甘蔗蟾蜍可能只会在对其有利的情况下，向其他雄性通报自己的性别身份。
