Raven flies to the crow

A corpse is a dangerous thing. It attracts predators, scavengers and stinging insects; Being next to him, you can pick up some kind of infection. Social animals - ants, bees, termites, rats - try to get rid of their dead as soon as possible, destroy or burrow. However, many animals, despite the risk, not only for quite some time remain next to the dead relative, but also touch him, show aggression and even try to mate.

Cases of necrophilia were observed in the gophers of Richardson, coastal swallows, the corassed toad Rhinella Jimi, the lizard of a giant ameiva. For the description of homosexual necrophilia in Kryakwa, Rotterdam Kees Moeliker, in 2003, received the Ignobel Prize in Biology [1]. In relation to animals to their dead people, it is the sexual aspect that is especially exciting. However, having recorded cases of necrophilia, scientists cannot explain their causes and do not even know why animals touch corpses at all.

It is convenient to explore this problem on the vocational birds. They react quite violently to dead individuals of the same species (conspicifics). Scientists watched the ordinary and American voorons, as well as the California shrub soyshiks of Aphelocoma Californica, at the sight of a corpse, raise a scream - a danger signal. Other birds fly to these cries and attach their votes to the general cacophony. Raven also haunt people who touched a dead bird.

Small -sized areas, so it is easy to present a dead conspicification for them. It would be much more difficult to deliver to the right place a carcass of a dolphin. And the birds also have a bad sense of smell, and you can deceive them by slipping a taxisoderman product instead of a real corpse.

So, Professor of the University of Washington (USA) John Marzluff (John Marzluff) and his graduate student Kayli Swift studied the reaction of the American ravens Corvus Brachyrynchos to the dead relatives. The American raven is smaller than the European, the size of our gray crow, the Americans call it a crow.

Scientists were especially interested in how often crows touch corpses, why they do it, and whether this behavior can be considered ordinary [2].

Researchers worked with stuffed animals of adults and young ravens, pigeons and gray protein. All products looked very reliable. The experiments were conducted in different cities of Washington, in areas where raven couples nest. Scarecrow made from animals obtained outside the study, so that subjects of the birds could not be familiar with them. Only one incentive was presented to each pair. It was placed 35–45 m from the nest, when there were no adult birds in it. The stuffed animals were weighed down with lead or sand or attached to the cargo with a transparent fishing line so that the crows could not drag them. Kylie Swift stood in the distance and fixed everything that was happening within two hours after the first adult bird notices the stuffed animal. The distance between the observation points was at least 300 m so that one pair did not gain experience, observing the other.

It is known that crows sometimes eat dead pigeons and proteins. Researchers suggested that the birds touch the corpse, wanting to have a bite or find out something about it. The stuffed pigeons and the protein of the crows touched in about a third of cases. Most often they pecked the scarecrow, striving to get into the eye or other unprotected place. They also gently touched the corpse with a beak or foot; dragged him on the ground, grabbing his beak; They blocked, tearing out the fur, feathers, upholstery and even a limb. The contacts were briefly because the crows quickly found out that the corpse was not real. And, yes, they tried to mate with pigeons. Four times out of 153. They did not encroach on the protein.

However, the reaction of ravens to the dead relatives was different. As a rule, the bird, who saw the body, raised a scream, giving a signal of danger and shaking the other ravens that quickly flew, croaked and behaved aggressively (Fig. 1). The birds touched the scarecrow of the conspicifications in about a quarter of cases, preliminarily by equal. There were only six sexual contacts, of which four of them with a scarecrow of an adult raven and two with a stuffed young man. At the same time, the birds actively pecked the dead partner and behaved quite aggressively with him. In two cases, while one of the birds tried to master the scarecrow, the second was mated with herself [3]. However, such scandalous behavior with shouts, aggression and necrophilia took place only at the beginning of the reproduction season, in March-April.

The aggressive excitement, which was caused by the dead crows in the living, is not like attempts to satisfy hunger or to get some information about the bird's dead bird (and the ravens do not have cannibalism). And then the scientists suggested that the crows simply do not understand that they have a corpse. They see a relative who behaves strangely, and try to expel from their site, and if they succeed, then it is also a muffle at the same time.

The flattened dead bird resembles a female ready for copulation: the wings are deployed and the tail is open. Therefore, in the second experiment, the researchers suggested that the crows of stuffed animals in different poses: a corpse with diluted wings, a body with pressed wings and a standing bird, which can be mistaken for living (Fig. 2). If the crows distinguish the living and dead relatives, the main fraction of the battle and aggression will fall to the share of a standing stuffed animal. If they are interested in copulation, they will prefer a bird with spread wings, and not standing or “picked up”.

The pose of the dead raven did not affect the attitude of the living towards him. However, the birds perfectly distinguished the lying and standing stuffed animal and reacted differently to them. At the sight of those lying, they often anxiously yelling, on the standing more often they dive. Obviously, the crows perceive the corpse, first of all, as a signal of danger, and the “living” relative - as an attacker who needs to be driven away.

In this experiment, the researchers observed eight sexual contacts with the “dead” crows and four with the “living”, and in three cases, they did not yell and pecked him on a stagnant. Since all attempts to mate with dead birds took place in the spring, at the beginning of the reproduction season, and accompanied by aggression, scientists suggested that the ravens had a failure of the behavior program.

In the spring, they experience sexual arousal, to which anxiety and aggression are added that occur at the sight of dead relatives. The hormonal changes occurring during the mating period prevent some birds from adequately respond to the stimulus and cause inappropriate and inappropriate behavior, which people readily call necrophilia. Researchers believe that in fact, a corpse as a sexual object does not attract a raven, and they have no necrophilia in the human sense. To verify this hypothesis, scientists plan to determine the hormonal status of non-coo-bicrophils during the reproduction season.

Putting to dead pigeons is also the result of a malfunction of the program. Sometimes males who do not have access to females are trying to master a partner of another kind. Suddenly, the ravens also happen?

In fact, Kylie Swift and John Marzluff watched the crows perceive death. While they checked the reaction of birds to the corpse of an unfamiliar individual. But the American crows form constant couples, which persist for more than ten years, and it is possible that the reaction to the death of a familiar bird will be different. Scientists have to find out what these differences will be. They are not going to kill anyone, but will resort to sedatives. The data obtained will allow people to better understand what the death of a group or partner member means for the animal and, if it happens in captivity, help him survive the loss. So the reaction of birds and animals to the dead body is examined not for the sake of curiosity, but with good practical purpose.

Natalia Reznik

1. Moeliker C. W., The First Case of Homosexual Necrophilia in the Mallardanas Platyrhynchos (Aves: Anatidae) // Deinsea, 2001, 8: 243–247
2. Swift K., Marzluuff J. M., OcCurrence and Variabiley of Tactile Interactions Between Wild American Cross and Dead Conspecifics // Phil. Trans. R. SOC. B, 2018, 373: 20170259, DOI: 10.1098/RSTB 2017.0259
3. figshare.com/articles/video_of_tactile_interacts_between_american_crows_and_dead_conspecific_from_occ Urrence_and_variaBility_of_tactile_Interations_betWeen_wild_american_crows_and_dead_conspecifics/6392225