In Aesop's fables, the stories of urban mice and country mice teach us that rural mice can live a luxurious and diverse life in the city, but they face a variety of deadly dangers, while the villages are boring but safer. But in reality, an animal study has overturned the idea that urban frogs are not only more attractive to the opposite sex but also safer than those living in rural areas.
The protagonist of this study is Túngara frogs, a tropical creature that is distributed in rural and urban areas. This is an attraction for the animal behavior ecologist Wouter Halfwerk of Free University in Amsterdam. He was wondering how urban life affects animal communication and whether animals are responding to the city not only through learning but also through natural evolution.
Dr. Halfwerk and colleagues began recording the sounds of male frogs in Latin America when attracting females. In a paper published in the journal Nature Ecology and Evolution, the team recorded frog calls in 11 locations, including urban areas and nearby woodlands. In contrast, urban frog songs are more complex and more frequent than forest frog songs. In addition, forest frogs stop singing faster than city frogs when human observers approach.
Afterward, the researchers continued to observe the effects of frog singing in 22 locations. In general, frog calls can attract females, but they also attract hunters and parasites. Dr. Halfwerk used image monitoring to observe the number of female frogs and hunters and collected parasitic blood-sucking samples with insect traps. In all three cases, forest frogs were more noticeable than urban frogs.
However, in contrast, forest frogs attract more attention from hunters and parasites. When researchers used two-speaker experimental devices to provide a choice for female frogs, it was found that the urban frog's voice was more attractive to females. After summing up the experiment, the team assumed that compared with forest frogs facing predation or parasitism, urban frogs will face threats such as humans, but the dangers are always small, therefore they can release louder songs. Also, urban frogs face more competition than those in rural, and males need more complicated and varied songs to win female attention.
This raises the question: Is the male adjusting his behavior according to the situation, or is the evolution of urban frogs different from that of forest frogs? The researchers collected frogs from cities and suburbs separately and placed them elsewhere, sometimes at similar locations to their original lives, sometimes in completely different types of locations. As a result, urban frogs can adjust their voices in response to the dangers of forest life, but forest frogs cannot perform courtship games under the bright lights of the city.
Obviously, forest frogs have not evolved to adapt to the new environment. Stuart West, a professor of evolutionary biology at Oxford University, did not participate in the study, but he said the study subtly stated: "Human activities have a huge impact on the environment in which animals live. This study shows that it can even affect the behavior of males to attract spouses." Therefore, in the frog world, urban frogs can afford to be more gentle and sexy because the suburbs of South American are more dangerous than the city for them.