2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Male folded-faced leaf-bearer (Centurio senex).
Zoologists were the first to describe the mating behavior of folded-faced leaf-noses. Observations in the Costa Rican jungles have shown that the males of these bats are mating: they gather in certain places, sing and attract females with white masks on their faces. During the only mating recorded, the male dropped his mask. As noted in an article for PLoS One magazine, this is one of the few cases of current behavior in bats and mammals in general.
Many bats have rather expressive faces with huge ears, tiny or, conversely, large eyes and various leathery outgrowths around the mouth and nose (you can learn more about them from our mouse (fly) test). However, the folded-faced leaf-noses (Centurio senex), inhabiting Central and North South America, stand out against the background of even the strangest relatives. The foreheads of these bats are covered with deep wrinkles, and the lower part of the face of the males is covered by a leathery mask covered with white fur. At the same time, these bats do not have a nasal leaf, which is characteristic of many other representatives of the phyllostomidae family.
Little is known about the behavior and lifestyle of folded-faced leaf-noses. Previous studies have shown that these bats eat fruits (which is why they do not have a leaf on their noses that makes it easier to hunt insects using echolocation) and can even chew on hard seeds. However, other aspects of the biology of this species, for example, the characteristics of reproduction, remained poorly understood. And, among other things, the experts did not know why folded-faced leaf-noses needed their unusual masks.
A team of researchers led by Bernal Rodríguez-Herrera of the University of Costa Rica has decided to learn more about the lifestyle of folded-fronds. In the fall of 2018, they went to one of the Costa Rican biological stations located in the middle of a tropical rainforest. Finding a section of the forest where leaf-bearing males gathered at night, the authors returned to it thirteen times after sunset to record the signals emitted by the bats and record their behavior on an infrared video camera.
Interestingly, the number of males in this area gradually changed. On the fifteenth of September, when Rodriguez Herrera and his colleagues first noticed the leaf-bearers, there were seventeen of them, and by the second of October this figure had reached thirty individuals. Then the number of males began to decline, and after October 31, none of them could be found. In total, the males used 53 perches, but some of them were much more popular than others.
After sunset and until about midnight, the males spent most of the time hanging on the perches and pulling the mask over their faces with the help of their first fingers on their wings. At the same time, they periodically emitted trills and echolocation signals. The authors did not observe any conflicts between leaf noses.
When another individual approached the male hanging upside down, he flapped his wings several times with a noise, pulled his face mask higher and whistled loudly. In most cases, the visitor then flew away. Unfortunately, the quality of the video did not allow determining the sex of the individuals flying up to the males.
However, on October 10, the authors managed to capture a female that landed next to a male hanging on a branch (the researchers distinguished her by the absence of a face mask). The male immediately lowered the mask with his wings, approached the partner and started mating, holding her with his wings. Thirty seconds later, the female got worried and flew away, and the male lifted the mask and returned to the roost. Interestingly, before and during her visit, the male leaf-bearer sang, interrupting only for the time of copulation.
A) Male of folded-faced leaf-bearer with raised mask; B) He, with the mask down; C) Another individual flies up to the male hanging on the perch; D) Male before whistling.
In the opinion of the authors, they observed the mowing of folded-nosed leaf-noses. Zoologists call mating behavior in which males (less often females) of animals gather in a specific place for mating demonstrations, tournaments and the fight for partners. Most often it is noted in birds: it is enough to remember the wood grouses or black grouses. Among mammals, there are (in the broad sense of this term) males of twenty-six species, mainly artiodactyls and pinnipeds. The only bats among them are the hammerhead bats (Hypsignathus monstrosus). The behavior of seven more species of bats is either considered a gaiting without sufficient evidence, or slightly inconsistent with its classical definition.
Observations show that leaf beetles use several types of signals to attract females. To interest a potential mate at a distance, the male makes a set of several repetitive sounds. As the female approaches, the signals become more intense and end with a whistle. Perhaps the song contains information that allows female leaf bearers to judge the physical condition of males. Interestingly, males issue mating calls with masks pulled over their faces, which slightly reduces the volume of singing and affects the spectrum of available frequencies. The authors suggest that deep grooves in the forehead, which help the sounds propagate, can compensate for this deficiency.
The female, who is closer to the male, sees his white face mask, clearly visible in the dark forest. This element can also serve as an indicator of the physical qualities of an individual. The authors suggest that there are scent glands under the mask, as indicated by a number of previous observations, as well as the fact that the muzzles of the males with the masks down in the videos look wet. When the face is closed, the odorous molecules do not disperse and reach a high concentration, and when the female approaches, the male opens his face, allowing her to smell his own scent. However, it is possible that the mask serves to protect the eyes and the entire face from competitors and possible partner aggression (although all individuals in the study behaved peacefully).
Why for thirteen nights the researchers recorded only one pairing is still unclear. It is possible that only a few males are successful in attracting females and not every night. Another possible explanation is that the specialists missed most of the mating, since they had only one camera, which was directed to different perches on different nights.
The authors admit that so far they have more hypotheses than real facts. The fact is that they were afraid to disturb the leaf-bearing plants and therefore focused on observations, not experiments. Future research will help understand what signals attract females of this species and how exactly males use their masks.
The leaf-nosed family includes many amazing bats, for example. famous vampires. They are interesting not only for their blood-based diet, but also for their complex social behavior. For example, recently it was revealed that vampires who feel sick tend to communicate less with their relatives - just like people who practice social distancing.