Zebra-eating plants spread anthrax

Carnivorous plants have always fascinated me. So when I saw this link on Facebook a few years ago, I was quite excited! The link (and this video) claim that the bromeliad Puya chilensis eats sheep. That’s right. A plant that eats sheep! The sheep are ensnared in the plant’s thorns until they succumb to exhaustion and die, and then their rotting carcasses feed the plant. We don’t actually know that the plants have evolved to “catch” and eat mammals, of course. An alternative explanation is that sheep are just rather unintelligent. But the idea is fascinating.

Whether some plants intentionally kill mammals or not is up for debate, but plants do eat mammals. Kind of. For instance, in Namibia, zebra carcasses increase soil nutrient concentrations for at least a year after the animal dies (Turner et al. 2014), and during that initial year, grass biomass near carcasses is higher than randomly-selected carcass-free sites (Turner et al. 2014).

The higher grass biomass near carcasses causes zebra and other ungulates to be attracted to carcass sites to forage (Turner et al. 2014). You might be thinking that foraging near a dead zebra body might be a bad idea for a zebra, and you’d be right. Namibia is one location where anthrax (caused by the bacterial pathogen Bacillus anthracis) naturally infects wildlife, so contacting a carcass could mean contacting anthrax spores. And zebras should worry about more than just the carcasses; the soil, grass roots, and grass at carcass sites all harbor anthrax spores, at least for the first year after the carcass appears (Turner et al. 2014).

If visiting carcass sites exposes zebras to a potentially lethal pathogen, why don’t zebras avoid carcasses? Well, they do, but only a little bit. When a carcass is relatively fresh, zebras are less likely to visit carcass sites than control sites, but that avoidance doesn’t last until all of the anthrax has left the grass. Therefore, sexy, delicious grass may facilitate anthrax infections in zebra.

Reference:

Turner WC et al. 2014 Fatal attraction: vegetation responses to nutrient inputs attract herbivores to infectious anthrax carcass sites. Proc. R. Soc. B 281: 20141785. http://dx.doi.org/10.1098/rspb.2014.1785

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s