The heaviest flying bird in the world could self-medicate with plants used in traditional medicine

If you see a great bustard (Otis tarda) in the wild, you are unlikely to forget it. Huge, colorful and impossible to confuse, they are the heaviest birds in existence today capable of flight, with the largest difference in size between the sexes. They are also “lek breeders”, where males gather at chosen sites to put on an audiovisual show for visiting females, who choose a mate based on their appearance and the quality of their show.

But now, a study in Frontiers in Ecology and Evolution suggests that great bustards have another claim to our interest: they actively search for two plants with compounds that can kill pathogens. Therefore, they may be a rare example of a bird using plants against disease, i.e. self-medication.

“Here we show that great bustards prefer to eat plants with chemical compounds with in vitro antiparasitic effects,” said Dr. Luis M Bautista-Sopelana, a staff scientist at the National Museum of Natural Sciences in Madrid and first author of the study.

Co-author Dr. Azucena González-Coloma, a researcher at the Institute of Agricultural Sciences in Madrid, said: “Buntards forage for two species of weeds that humans also use in traditional medicine. We show that both contain antiprotozoals and nematicides.” (i.e. worm-killing compounds), while the latter also contains antifungal agents.”

Humans aren’t the only species that self-medicates.

Self-medication in animals is suspected to occur, with varying degrees of confidence, in animals as diverse as primates, bears, deer, moose, macaws, bees, and fruit flies. But it is difficult to prove it without a doubt in wild animals, warned Bautista-Sopelana: “We cannot compare between control and experimental treatments. And double-blind trials or dose-effect studies, mandatory steps in human or veterinary medicine, are obviously impossible.” in wild animals”.

Classified as Vulnerable on the International Union for Conservation of Nature’s Red List of Threatened Species, great bustards breed in grasslands from western Europe and northwestern Africa to central and eastern Asia. Approximately 70% of the world population lives in the Iberian Peninsula. Females typically remain faithful to the range where they hatched for life (10–15 years), while after dispersal, males revisit the same lek site year after year. By staying (and, more importantly, pooping) in the same area for long periods of time, they risk becoming reinfected. And males need exceptional stamina during mating season, which is expected to send their immune defenses into a tailspin.

“In theory, both sexes of bustards could benefit from foraging for medicinal plants in the mating season, when sexually transmitted diseases are common, whereas males using plants with disease-active compounds may appear healthier, more vigorous and more attractive. for females.” Gonzalez-Coloma said.

Some members of the present research team have studied bustards since the early 1980s, mainly in the regions of Madrid and Castilla y León, Spain. They collected a total of 623 female and male bustard scats, including 178 during the mating season in April. Under a microscope, they counted the abundance of recognizable remains (stem, leaf and flower tissue) of 90 locally growing plant species known from the bustard menu.

Plants contain compounds that kill parasites.

Results showed that two species are eaten by bustards more frequently than expected from their abundance: corn poppies, Papaver rhoeas, and purple viper’s bugloss, Echium plantagineum.

“Buntards select poppy and purple viper bugloss mainly in the mating season, in April, when their energy expenditure is greatest. And the males, who during these months spend much of their time and energy on sexual display, prefer them more than the females. ”, Bautista-Sopelana concluded.

Of these two species, the former is avoided by cattle and is used in traditional medicine as an analgesic, sedative, and immune booster. The second is toxic to humans and livestock if ingested in large amounts. They also have nutritional value: fatty acids are abundant in poppy seeds, while blackberry seeds are rich in edible oils.

The authors isolated water- and fat-soluble compounds from both species and determined their chemical identity with gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (HPLC-MS). They focused on lipids, volatile essential oils, and alkaloids, produced by many plants as a defense against herbivores. For example, they discovered that corn poppies are rich in bioactive alkaloids such as rhoeadine, rhoeagenine, epiberberine, and canadine.

The authors then tested the activity of the isolated molecular fractions against three common parasites of birds: the protozoan Trichomonas gallinae, the nematode (parasitic worm) Meloidogyne javanica, and the fungus Aspergillus niger.

The results show that the extracts of both plants are highly effective in inhibiting or killing protozoa and nematodes in vitro, while the purple viper’s bugloss is also moderately active against fungi.

Authors Still Call For Caution

The authors conclude that great bustards are prime candidates for birds seeking specific plants to self-medicate. But more research is needed, they warn.

“The definitive proof of self-medication requires experimental protocols developed in the biomedical, veterinary and pharmacological sciences,” said Bautista-Sopelana.

“Until then, we continue with our field work. For example, quantifying the prevalence of remains of corn poppies and purple viper bugs and pathogens in fecal droppings in different populations of bustards could falsify our hypothesis of self-medication in this species.”