Curious Conservation: Increased Population Leads to Higher Monkey Mortality

You might think that my first post on this blog would be about frogs, but I am starting with the articles I wrote on my London Student blog, Animalia, so here's a story about monkeys instead

Brachyteles hypoxanthus by Paulo Chaves

Conserving endangered animals is never easy, but few people expect the difficulties to increase with supposed success. This, however, seems to be what has happened with a population of monkeys in Brazil. There were just 60 northern muriquis (Brachyteles hypoxanthus) in this population at the beginning of the project in 1983, and there are now 300. A fantastic result, you would assume, but according to a paper by Karen Strier and Anthony Ives from the Department of Anthropology of the University of Wisconsin-Madison, it is now that the real problems have begun.

With the increase in population size, there has also been a rise in mortality. Ideally, larger populations spread out to occupy a larger space, but here habitat fragmentation has prevented dispersal, so the density of the population has increased. This is often accompanied by a rise in mortality, as resources like food and shelter become more limited, until the population stabilises.

The northern muriqui population, however, didn’t stabilise because the females remained very fertile, while mortality in prime-age males continued to rise. It turned out that both of these were linked to a new behaviour in the muriquis of spending less time in the trees and more on the ground. This increased female fertility because there was more food around, and male mortality because they were more vulnerable to predators.

Without this study, it might have been assumed that the slowed growth rate was down to limited resources, which could have led to the rather ineffectual tactic of providing more food. It shows then the importance of 'checking your facts', as it were, and not making assumptions based on other animals, as well as raising hopes for this interesting but threatened animal.

NB. As a side note, you might be more familiar with the name woolly spider monkey than muriqui, but since they are neither woolly monkeys nor spider monkeys, I have stuck with muriqui.

Here's the original article as published on the London Student: http://www.london-student.net/science/blogs/anamalia/the-curious-conservation-of-the-mariquis-monkey/