Scientists have recently made new developments on a frog that appears to have thumb-like projections for fighting with males and mating with females. The frog, which is found on the Amami and Ryukyuk islands of Japan, seems to have knife-like spikes that come off like thumb-like projections. This unique project is found on the front of both forearms of the frog, also known as Otton frog or Babina subaspera.
Dr. Noriko Iwai, a professor at the University of Tokyo who was involved in the study, has proposed that the thumb-like projections are crucial during the mating season of the frogs. She believes the projections are used to grab and hold onto females during mating. In addition, she also thinks they spikes are important in fights with other males, which often take place during mating season in order to gain the affection of females in the group.
Iwai has reported in the Journal of Zoology that the males use the spiky projections to wrestle and stab other competing male frogs while fighting. Despite believing the spikes developed primarily for mating purposes, Iwai said it is obvious that the frogs also use them for fighting. In fact, she said that when handling a male, the frog would try to jab its handlers with the spikes. Additionally, Iwai reported that most of the male frogs’ spikes had signs of combat, including extensive scarring.
“While the pseudo-thumb may have evolved for mating, it is clear that they’re now used for combat,” Iwai explained in a statement. “The males demonstrated a jabbing response with the thumb when they were picked up, and the many scars on the male spines provided evidence of fighting.”
Despite the seemingly brutal nature of the thumb-like projections, Iwai insisted that the spikes do not cause death in the fighting frogs. Instead, the frog being attacked is shielded by a special patch of skin that is located on the side of the frog, protecting it from the enemy’s spikes. This is fairly unique to the Otton frog as many others, such as the gladiator tree frog (Hypsiboas rosenbergi), cause deadly injuries to their enemies during fights.
“It seems that the intensity of combat in Otton frogs is finely balanced so as not to result in critical or mortal injuries, yet it remains aggressive enough to establish a clear victor,” Iwai wrote in a paper published online in the Journal of Zoology.
While seemingly tough, Otton frogs are not immune to danger. In fact, they are currently part of the endangered species list. Their placement on the list is due to many things including destruction of habitat, construction, river development, and their number one predator: the mongoose.
Since the mongoose was introduced to the Otton’s frog’s natural habitat in Amami Oshima and Kakeromajima, Japan, the frog population has taken a big hit. Those looking to see the Otton frog in action could find them on the islands either in evergreen forests with broad leaves, or in small pools of water during mating season.