Why are chimps hunting red colubus monkeys to death?

Time is running out for the red colubus monkey, which lives in Uganda's Kibale National Park. Chimpanzees appear to be huntings these poor guys to death. It's the first time that one primate species has overhunted another, without humans being involved.

According to census data collected between 1975 and 2007, the Ugandan red colubus monkey has seen an 89% population drop, and the hunting habits of common chimpanzees are almost entirely to blame. Disease and competition with similar monkey species have also been cited as factors, but the researchers say these still just pale in significance when compared to the effects of chimp hunting.

Indeed, these chimps seem to be actively trying to wipe out their primate brethren. The chimps generally target younger monkeys that haven't yet reached reproductive age, which means there are far fewer red colubus monkeys around who can help bring the population back. Chimpanzees have been doing very well during all this, as their population has increased by 53% over the same time period that the monkeys have nearly disappeared.

It's a good reminder that overhunting is not a strictly human practice, although we tend to be particularly adept at wiping out other species through excessive hunting. The researchers aren't sure what is driving the chimps to kill so many colubus monkeys - it's possible that other food sources decreased or that environmental shifts could have made increased hunting the most effective option.

There is a bit of good news, though - the chimpanzees seem to have seriously cut back on their hunting in recent years, which might mean the red colubus monkeys can survive after all. This means that fewer adult chimps are passing on their hunting skills to their young, which is creating generations of poor hunters, which can only help the colubus monkeys. No one is quite sure why the chimps changed their hunting patterns, but I'd like to think this is our first evidence of chimp conservationism.

American Journal of Primatology via Scientific American. Image via.