Dear Readers, I have always been fascinated by the way that animals seek out particular plants or other substances when they feel ill, and use them to self-medicate. Lots of grazing animals do this, and chimpanzees were observed to apply small, winged insects to one another’s wounds, though scientists are unsure whether this is because of chemicals in the bodies of the insects (such as formic acid) or just as a caring gesture. Pregnant elephants in Kenya are thought to eat particular leaves to induce birth, and female lemurs eat leaves that kill parasites and encourage milk-production. But in New Scientist this week, there’s the first case that I’ve heard about of a creature using plants to treat a sexually-transmitted disease.
Great Bustards are amongst the world’s largest flying birds. They used to be native to the UK, until the last one was shot in 1832, but a population of about 40 have been reintroduced to Salisbury Plain, where they benefit from it being Ministry of Defence land which is off-limits to most people. The birds are a real success story – their numbers have been boosted over the years by eggs collected from larger populations abroad (n the wild, they live mostly in Spain and Portugal), but now it’s hoped that they will be self-sustaining going forward. You can watch a short snippet about the reintroduction below – I love the way that humans have to wear ‘dehumanisation suits’ to stop the birds becoming accustomed to people.
As you can see, Great Bustards are impressive birds, especially in the breeding season, when the males gather in leks. The display includes throat-puffing, tail-flashing, and rather importantly for our discussion, revealing the cloaca (the multipurpose orifice which in birds serves for excretion, egg-laying and reproduction), which the female apparently peruses with some interest. Before the breeding season, the males snack upon blister beetles (which contain some very nasty chemicals, but which are thought to reduce parasites). The males also seem to eat common poppy (Papaver rhoea) and purple viper’s-bugloss (Echium plantagineum), plants which have little nutritional value and which are actually toxic, just before they start to breed. Scientists from the Spanish Natural Research Council in Madrid took extracts from these two plants, and tested them against three parasites that can be transmitted during sexual contact – a protozoan, a worm and a fungus. The plants killed up to 98% of the protozoans and up to 81% of the worms, while the viper’s-bugloss had a moderate effect on the fungus, killing over 50%. It may be that when the females inspect the males, they are looking for signs of the infections that the pathogens cause.
Breeding is a very exhausting time, particularly for male animals like the Great Bustard. Only ten percent of males actually find a mate, but those that do are very successful, mating with at least five females. Parasites are more likely in animals that are already under the weather, and once an infection starts, it can make the animal appear dishevelled, and impact on its energetic display. it’s perhaps no wonder that Great Bustards seem to have hit on a way to make sure that they’re in tip-top condition for the breeding season.
You can read the whole report here.
So, as usual, this is a positive story for Friday, both about the Salisbury Plain Great Bustards (who appear to be on track to be the first successful re-establishment of a population of the species anywhere in the world) and on the subject of the mysterious world of animals and their ability to heal themselves. We clearly have much to learn by paying attention to animal behaviour.