Hunting as an evolutionary factor. Birds are getting smarter
People have always hunted animals. Previously, in order to get food for yourself. Now in most cases of sports interest. One of the most attractive objects for hunters to pursue are birds. Moreover, modern scientists believe that hunting may well be one of the factors of evolution, the influence of which leads to the appearance of more intelligent individuals with a larger brain size than their ancestors. The difference in size is not too large, but perhaps it plays a role in the survival of birds.
Scientists made their conclusions by studying the behavioral characteristics of the bird population in Denmark. The work is also interesting in that it clearly demonstrates that brain size is an important factor in the development of mental abilities.
According to John Marzluff, a specialist in wild animals and an expert on cognition in ravens, the new work “expands the boundaries of cognition and shows that the mind is a significant factor in nature, over which man gradually seizes power”. Marzluff is a biologist from the University of Washington in Seattle, he has nothing to do with the recently published work of Danish specialists.
The fact that fishing and hunting are important factors in modern evolution, no one argues. For example, due to the constant catch of the largest individuals of zander, the population of this fish species living in the Finnish archipelago has changed. Sudak began to fade. And not because fishermen catch large individuals, preventing young individuals from developing. No, catch rules are respected here. The problem is that the fishermen catch the largest individuals in the population, which leads to the offspring of the genes of not such large fish. It is interesting that puberty in this zander population occurs earlier than dozens of years ago.
Not only man is an evolutionary factor. For example, terrestrial predators like arctic foxes or polar bears also "make" their victims grow wiser from generation to generation. A recent study showed that sea ducks, where birds with large heads predominate in a flock, can provide better protection than schools where there are more ducks with small heads. In this case, scientists did not measure brain size, but made the assumption that the size of the head in this case is directly related to the size of the bird's brain.
Is all this true for hunter people and their flying victims? To find out, Anders Pape Møller, evolutionary biologist at the University of Paris-South XI, decided to check the brain sizes of 3781 birds of 197 species that fell into the hands of taxidermists (an expert on stuffed animals) in Denmark from 1960 to 2015. Among other species, there are pheasants, partridges, black grouse, magpies, and gray crows. According to Danish law, taxidermists must record the date and cause of death of any animal from which they make a stuffed animal. Co-author of the study, Johannes Erritso, a taxidermist and ornithologist from the Christian Research Center for Birds in Denmark, performed an autopsy of each bird. At the same time, he noted the mass of each instance, and also weighed the extracted brain. Scientists also recorded the state of the bird's body, and the age at which the bird died.
As it turned out, 299 or 7.8% of the 3781 birds studied were shot. Birds with a small brain (compared to the size of the whole body) died more often from gunshot wounds than birds with a brain, the size of which was larger in relation to the size of the body. It was also noted that the victims of hunters more often became large birds (this is a convenient target) and males (in most cases they have a brighter color).
As it turned out, the likelihood that a hunter will shoot a bird with a brain larger in body size is much less than the inverse probability. Experts noted an almost 30-fold difference. The results are published in Biology Letters. This dependence can be traced regardless of the health of the bird, body weight, gender, and belonging to a particular species. Hunters, according to the results of the study, involuntarily force the birds to evolve, destroying members of the population with a small brain. Representatives of the same species of birds with a large brain, according to Danish scientists, are smarter than other relatives, so they successfully avoid hunters and traps.
Scientists compared the size of other organs of birds - the heart, liver, lungs and found out that only the size of the brain of those birds that have been hunted for a long time has changed. “This means that hunting has a very specific effect on the brain of birds, and only on it,” Moliere says.
According to him, hunters do not set themselves the task of finding and shooting a bird with a small head. It's just that birds with a smaller brain are not so successful in avoiding hunters. “They have a longer reaction. Between the moment the hunter is discovered and the danger is understood, such birds spend more time than their more intelligent relatives. ”
Now experts are testing their hypothesis by studying curlews and snipe, hunting for which has been banned for five years in Denmark. Scientists want to compare specimens of birds that in previous decades fell into the hands of taxiderms with modern representatives of these species.
The results of the study interested many other scientists, including Susan Healy of the University of St. Andrews. Healy conducted about 50 studies during his work, the purpose of which was to find out the relationship between the brain size of animals and the behavioral characteristics of various representatives of the same animal species, including cunning, sexual preferences, and a tendency to migrate. Significant results from this work were not .
The work of Danish scientists raises a few more questions. For example - is the evolution of the birds that man hunts long and irreversible in time? How will all this affect the hunt itself in the future? And how does this affect the relationships between natural predators and their prey - isn't it becoming harder to hunt the latter first? It is still difficult to answer all these questions, so you have to wait for the results of new studies.