Females of the great bustard, Otis tarda. Credit: Carlos Palacín
Key Points:
- Researchers have shown that great bustards favor two specific plant species that have been shown to kill parasites in vitro.
- Corn poppies, or Papaver rhoeas, are used in traditional medicine, but purple viper’s bugloss is toxic to humans.
- The plants are especially important to males during mating season, when much of their energy is expended.
A new study has added even more intrigue to the Otis tarda, or great bustard. Not only are they the heaviest birds living today capable of flight, but researchers have shown that they actively seek out two plants with compounds that can kill pathogens. They may thus be a rare example of a bird that uses plants against disease—that is, self-medication.
For the study, published in Frontiers in Ecology and Evolution, researchers collected a total of 623 droppings from female and male great bustards, including 178 during the mating season in April. Under a microscope, they counted the abundance of recognizable remains (tissue from stems, leaves, and flowers) of 90 plant species that grow locally and are known to on the bustards’ menu.
The results showed that two plant species are eaten by great bustards more often than expected from their abundance: corn poppies (Papaver rhoeas) and purple viper’s bugloss (Echium plantagineum).
The authors isolated water- and fat-soluable compounds from both plant species and determined their chemical identity with GC-MS and HPLC-MS. They focused on lipids, volatile essential oils, and alkaloids, produced by many plants as defense against herbivores. For example, they found that corn poppies are rich in bioactive alkaloids like rhoeadine, rhoeagenine, epiberberine, and canadine.
The researchers then tested the activity of the isolated molecular fractions against three common parasites of birds: the protozoon Trichomonas gallinae, the nematode Meloidogyne javanica, and the fungus Aspergillus niger.
The results show that extracts from both plants are highly effective at inhibiting or killing protozoa and nematodes in vitro, while purple viper’s bugloss is also moderately active against fungi.
In traditional human medicine, corn poppies are used as a pain reliever, sedative, and immune booster. Purple viper’s bugloss, however, is toxic for humans if eaten in great quantities.
The team says more work needs to be done, but they conclude that great bustards are prime candidates for birds that seek out specific plants to self-medicate.
“The ultimate proof of self-medication requires experimental protocols developed in the biomedical, veterinary, and pharmacological sciences,” said Luis M Bautista-Sopelana, a staff scientist at the National Museum of Natural Sciences in Madrid, and the study’s first author. “Until then, we continue with our fieldwork. For example, quantifying the prevalence of remains of corn poppies and purple viper’s bugloss and pathogens in fecal droppings across different populations of great bustards could falsify our hypothesis of self-medication in this species.”
Information provided by Frontiers.
