Great bustards seek out plants to stop disease.
Published January 4, 2023 11:11AM EST
Great bustards look somewhat like really big geese. They have broad chests, thick necks, and distinctive turned-up tails. They can weigh as much as 40 pounds (18 kilograms) and are believed to be the heaviest bird in the world. The heaviest recorded great bustard weighed 21 kilograms (46 pounds).
These massive birds may be staying healthy by self-medication, new research finds. The birds appear to be actively searching for two plants that contain compounds that can kill pathogens. Researchers say it’s an example of possible self-medication.
Their findings were published in the journal Frontiers in Ecology and Evolution.
Great bustards (Otis tarda) are classified as vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.
First author Luis M. Bautista-Sopelana, a staff scientist at the National Museum of Natural Sciences in Madrid, and co-author Azucena González-Coloma, a researcher at the Institute of Agricultural Sciences in Madrid, spoke to Treehugger about their research.
Treehugger: Why do you find great bustards so interesting?
Luis M. Bautista-Sopelana: The study of wildlife feeding confronts you with paradoxical situations: Why do animals ingest plants or other animals with little nutritional value but a certain degree of toxicity? Exploration, learning, mistakes, etc. These are the standard answers. But when you observe that the prevalence of these elements in the diet is not tiny, you scratch your head and begin to doubt the routine explanations. If, in addition to studying the diet in the laboratory, you spend days in the field studying the behavior of bustards, you could observe that some elements of the diet are ingested for a non-nutritional purpose. And so, the research begins. You then read the scientific literature on self-medication in apes, insects, etc., and you realize two things: You have found a vein of knowledge to exploit, and there are methodological limitations that forestall you from drawing conclusive explanations at the same level as in biomedical and veterinary sciences.
Azucena González-Coloma: Also, the fact that poisonous insects were found in dead male bustards and are part of their diet inspired this work. We published a previous work on this topic.
How can self-medicating be an important and unique behavior?
Bautista-Sopelana: Self-medication in wildlife is important because it highlights that animals fight against their maladies with ad hoc behaviors like ingesting plants and animals with compounds active against maladies. But our findings do not report a unique behavior. Other bird species use plants for self-medication—for example, Psittaciformes [parrots], blue tits, Darwin’s finches, etc. Birds anoint themselves with many other items with anti-parasite properties, including millipedes, caterpillars, beetles, and plant materials.
Azucena González-Coloma: Our team is not the first to discover that wildlife can self-medicate with plants against parasites. Plants hold secondary compounds (SC) against herbivores. Some of those SCs are active against parasites and other pathogens. For example, nematicidal activity has been reported for extracts of corn poppy leaves against M. javanica. Minor alkaloids included roemerine, with reported antibacterial, antifungal, and anthelmintic activities. Furthermore, alkaloids such as allocryptopine, potopine, and berberine were nematicidal against Strongyloides stercolaris larvae. Besides, flavonoids may reduce oxidative stress and enhance immunity, so birds eat them presumably as a prophylactic drug against pathogens. Polyphenols regulate immune and inflammatory responses during enteric bacterial and parasitic infections in livestock, and organic acids can significantly reduce microbial contamination in turkeys.
Why are these findings important? What are the next steps in your research?
Bautista-Sopelana: These findings show that there are unexpected ways to research new medical compounds. There could be compounds that pass unnoticed to laboratory researchers while the wildlife routinely seeks them. Our next steps are collecting fresh droppings in several well-separated populations. Quantifying the prevalence of weeds and pathogens in the droppings will allow us to establish a statistical continuum pattern between healthy and sick populations. Genetic identification of weeds and parasites in fecal droppings is feasible, which would speed up the research. A statistical correlation between plants and parasites across droppings can make self-medication most concrete, though a correlation does not prove it beyond doubt. As already stated, the ultimate proof of self-medication requires experimental protocols developed in the biomedical, veterinary, and pharmacological sciences.
González-Coloma: We will also examine some plants selected by the bustards in more detail, as our analyses have only captured the tip of the chemical iceberg. In addition, the abundance of secondary compounds changes seasonally and geographically, so further chemical analysis is mandatory.
