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Sparrows, unlike other animals, do not use smell when choosing a partner with a different immune system. This is the conclusion of a study in which researchers from the National Museum of Natural Sciences (MNCN-CSIC) and the Rey Juan Carlos University (URJC) participate. published in the magazine Plos One, the work lays the foundations for improving and refining the role of smell in the sexual selection of birds.
Animals choose their partner based on, among other things, the mechanism of the immune system responsible for recognizing pathogens. In this way, they seek to find a partner whose system is as different from theirs as possible, since this will benefit their offspring, because it gives them the opportunity to face more diseases. It has already been shown that some groups, such as mammals, use smell to distinguish differences in this system. However, after studying a population of sparrows Passer domesticus During the breeding season, the researchers have been able to conclude that this species does not use smell in its selection.
"The importance of these results lies in the fact that they allow us to improve future experiments on mate choice in birds in relation to the immune system," says MNCN researcher Annie Machordom. "After ruling out this pathway, a large number of possibilities open up regarding other mechanisms responsible for this mate selection, because there must be another way in which the sparrows detect the most compatible system for them in their companions," adds Luisa Amo, researcher of the URJC.
Immune recognition system in birds
Birds, like many other animals, have a pathogen and parasite recognition system that helps them avoid catching the infections they are exposed to on a daily basis. in the sparrows, Passer domesticusFor example, avian malaria is very common, so a good resistance against this disease is a great advantage. During the breeding season, sparrows will seek to improve immunity in their offspring, choosing a partner with an immune system that is compatible with theirs, thus creating greater resistance to pathogens in their offspring and reducing the chances of contracting avian malaria or other infections.
"The importance of these results lies in the fact that they allow us to improve future experiments on mate choice in sparrows and on the immune system of birds," says MNCN researcher Annie Machordom. "After ruling out this route, a large number of possibilities open up regarding other mechanisms responsible for this mate selection, because there must be another way in which the sparrows detect the most compatible system for them in their companions", concludes Luisa Amo, researcher of the URJC.
Know animal behavior
To study animal behavior, experimental studies are often used, in which subjects are subjected to different situations created to observe and analyze their responses.
In this case, the researchers carried out a behavioral study in an olfactometry chamber, a mechanism that allows exposing the birds only to olfactory stimuli from pairs. The olfactometry chamber consists of a rectangular box divided into three parts, in which the scent donor sparrows are placed at the ends of the box, and in the central part the experimental sparrow, which is of the opposite sex to the odor donors. smell. "What we did was expose the experimental sparrow to the odor of the donor sparrows for 5 minutes, and then the doors in the central part were opened so that it could choose one odor or another," Amo details. The experiment was repeated with 151 individuals in the chamber, both male and female, and the results showed that the choice of sparrows based on scent was random, that is, the birds did not choose a partner with a more compatible immune system, therefore what cannot be attributed to smell influences that selection.