When I think about the ecosystem of places like Yellowstone, I think of majestic creatures like wolves, elk, and beaver living their lives among the iconic geysers and waterfalls. You know what creature I never think of? Vultures. They matter a lot to the ecosystem, though. They're part of a clean-up crew that is constantly working, scavenging the remains of other animals' meals and breaking down the waste into smaller bits that are ready for decomposers to move in.
The vulture is an apex scavenger. These birds are very good at their jobs; a group of them can completely clean the carcass of a large animal in less than an hour. They're built for scavenging work, too. Their heads are featherless, which reduces the amount of bacteria that would otherwise get caught in their feathers as they eat. Their stomach acid measures at a jaw-dropping 0 on the pH scale. Acid that potent destroys bacteria and other microbes in the vultures that would cause illness in other organisms.
Just how important are vultures to an area? In a word, very.
In India back in the 1990's, livestock and other domesticated animals were being treated for pain with a medication called diclofenac. Ecologists found that traces of this medicine stayed in animals' bodies even after they died. Unfortunately, the drug is toxic to vultures. When vultures ate decaying animals that had been treated with the medication, the vultures died by the millions.
With most of the vultures gone, things took a bad turn. Without the vultures to break down dead animals to prepare them for decomposition, the carcasses slowly decayed in place instead, allowing diseases to grow in them. The spread of diseases like hantavirus and leptospirosis skyrocketed - and they moved to human populations! Estimates are that hundreds of thousands of people may have died from infectious disease as a result of the missing vultures. 😔
The good news is, there are conservation efforts happening to help rebuild the vulture population in India. A ban of the drug diclofenac has helped, and dedicated vulture sanctuaries are allowing these critical scavengers to start to bounce back. They aren’t back to their original numbers, but scientists are encouraged by their population gains.
The graph below shows the changing population density of two species of vultures in and around Indian national parks. It was measured by counting the vultures seen along a stretch of road through the park.
If I brought this graph into the classroom, here are some questions I'd have to go with it:
💡What is the dependent variable for this graph? (Hint: the independent variable is the one that researchers change in a consistent way, and the dependent variable is the one they watch for results.)
💡During what year did G. indicus reach its peak? How does this compare to G. bengalensis?
💡If you were a scientist working in India, why might you be encouraged by the data shown on this graph?