Male European frogs, to access females, harass, intimidate and force them to copulate. These efforts can cause reproductive failure in both individuals and cost the lives of the females. Previously, they were thought to be passive and unable to resist male coercion, but oran investigation recently published in the scientific journal Royal Society Open Science shows that females have different strategies to avoid males that they have not chosen.
When reproductive interests or strategies between males and females differ, it can lead to sexual conflict. During the short breeding season, which lasts two weeks in spring, the sex ratio is usually skewed with a large majority of males. This causes many individuals to congregate and fight among themselves for a female. Given this scenario, “they end up losing, since many times they die by drowning due to the group of up to eight frogs that are placed on them,” explains Iñigo Martínez-Solano, from the Department of Biodiversity of the National Museum of Natural Sciences. These accumulations are known as mating balls.
Scientist Carolin Dittrich from the Konrad Lorenz Institute of Ethology in Vienna collected 96 female and 48 male common frogs during the breeding season. She placed a male alongside two females of different sizes in a box with five centimeters of water and allowed them to move freely for an hour while she videotaped their behavior. The males did not take the hint of rejection, but the researcher detected that the females made evasive maneuvers to push them away.
Among mate avoidance strategies, the most common was rotation, where the female attempts to rotate on her own axis to escape the male’s grasp. The second is to protest. Dittrich describes this action as a “deep, low-frequency” growl, in what he believes is an imitation of the release calls that males produce when fighting each other. They may also make a higher frequency sound described as a “chirp.”
The final and “most surprising” behavior was tonic immobility, what we understand by playing dead. Females rigidly extend their arms and legs away from their bodies to feign death for several minutes. In one of the videos analyzed, a male is seen dragging a female who remains motionless. After releasing her, the female maintains the position until the male turns around and then she swims away from him. This is quite unusual behavior.
Traditionally, it is associated with tonic immobility as a strategy to avoid predation, but in a mating context it has only been observed in spiders or dragonflies “as a defense of last resort,” notes the researcher. The maneuvers, often used in combination, worked. Of 54 females grabbed by a male, 25 managed to shake them off and escape. The highest success rate was for smaller females because it is easier for them to escape from the male’s clutches. Although this study was conducted in a laboratory, Dittrich believes that female frogs would exhibit similar behavior in the wild.
Rejection by females is a matter of preference. Many times they simply choose not to mate with the first male that latches on to them, but rather with the one with the deepest song or the one with the largest size. Some, after being rejected, intercept the females by surprise to try their luck again, but this grab does not guarantee fertilization. If the female does not accept, that is when they implement escape strategies. “We have seen cases in which females carry a male on their back for days and even weeks, waiting for a larger male or the one they prefer,” says Martínez-Solano. Unlike females, they do not seem to be very selective. They capture randomly and do not show preferences in terms of female body size. Their aggressive behavior is due to the short breeding season.
Dittrich believes that these strategies had not been detected because previous research tended to focus on male reproductive behavior, “but it is something that is slowly changing to also include the female perspective,” he notes. For his part, Martínez highlights that research like Dittrich’s is positive, as it contributes to the understanding of the biology of amphibians, about which “there is enormous ignorance.” Understanding them in more detail can help uncover demographic aspects and implement effective conservation measures.
The behaviors detected, the researcher emphasizes, in no way threaten the reproduction or survival of the species. But climate change does. Although it is a widespread species, populations are declining. Those who will survive are those who are best adapted or can adapt best to a changing environment. Dittrich quotes her doctoral director, Mark-Oliver Rödel: “There is nothing that frogs cannot do.”
You can follow SUBJECT in Facebook, x and instagramor sign up here to receive our weekly newsletter.
#Female #European #frogs #fake #deaths #avoid #unwanted #males