2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Gerald Carter, a researcher at the Smithsonian Institute for Tropical Research in Panama, and his colleagues from Germany and America, have found that vampire bats can "insure risks" in the event of the loss of a breadwinner. Females make friends for themselves and feed them, so that later, in times of famine and in the absence of their main friend, the mother, they helped them to survive. The research is published in Biology Letters.
Vampire bats are a subfamily of leaf-nosed bats that feed on blood. These are small mammals, the body length of which is no more than nine centimeters. They live in the tropics and subtropics of America and are nocturnal, and during the day they sleep - some singly, and some in large colonies of thousands of individuals.
They are considered the only true warm-blooded parasites and subsist on birds and mammals. Echolocation does not work very well for them, and they find the victim mainly by listening to her breathing in the dark. Vampire mice not only fly, but also run pretty fast on the ground. Having discovered with the help of infrared receptors the least protected area of the victim's skin (for example, an ear or withers in a mammal or a comb in a chicken), they cut it with the upper large incisors, as a rule, without even waking the animal up (their saliva contains anesthetic and anticoagulant substances), and, curling their tongue into a tube, suck his blood. Literally two minutes after the start of eating, their excretory system also begins to work, excreting the plasma of the drunk blood from the body in a very liquid trickle. Otherwise, the well-drunk animal could not fly away later.
Vampire mice are pretty social animals. They cannot survive without food for more than two or three days, and it is common for females to feed each other with blood “mouth to mouth”. At the same time, they do not like greedy comrades, and do not share with them themselves. The strongest bonds are formed between mothers and daughters, but many mice feed non-close relatives too. Since this behavior is contrary to evolutionary considerations of caring for their own genes, scientists decided to investigate this phenomenon in more detail. In previous work, they had already found out that friends do help hungry females, and that the generous get more food than the greedy, but it was unclear how important the role of the main breadwinner, the mother, was.
Adult females of Desmodus rotundus from a colony containing about three dozen individuals were taken in turn and not fed for 24 hours. After that, such a hungry mouse was returned to the colony, after removing from there its closest relative, the breadwinner, and the behavior of other mice in relation to it was observed. Mice that had many friends handled the situation better than greedy mice and received much more food. At the same time, when the main breadwinner was in place, their friends fed them a little less, and here even the opposite mechanism was observed: the most socially active mice received less food from their neighbors (but they were fed by their mother). Thus, feeding the girlfriends turned out to be a mechanism of adaptation in case the next of kin disappeared.
This type of evolutionary adaptation is called "risk insurance", and is found among many species: for example, some plants deliberately leave seeds that do not germinate for a long time in the soil, which may die or be eaten, but during a drought, if the seedlings die, then such non-germinating seeds help plants survive after bad times. Female baboons, who have lost a close female relative, begin to pay more attention to their other females of the flock, hoping if something happens to get support in return. About human populations, there are also a number of works showing that people living in poor social conditions tend to make more friends, and in good ones they often give preference to quality over quantity. Such evolutionary adaptations, which have only an indirect effect on caring for their own genes, can have a significant impact on the structure of a population.
You can read about how vampire mice tasted human blood here.