Monday, September 29, 2014

A lack of results, it happens.

Earlier this month, I attended the American Society of Primatologists annual meeting to present a paper. One of the talks I attended that I really quite enjoyed was given by Jessica Rothman, "Within-Species Variability in the Microhabitats of Mountain Gorillas (Gorilla beringei): Implications for Nutrient Balancing."  As I'm sure you've guessed from the talk title, Rothman, a nutritional ecologist at the CUNY in NYC, studies mountain gorillas, the fuzziest of the gorillas. Mountain gorillas are primarily folivores, meaning their diet is composed largely of leaves and herbaceous matter. There are very few mountain gorillas left in the wild and there are none in captivity, so of course Rothman studies the ones remaining in the wild.
Male mountain gorilla

Rothman noticed that the gorillas would sometimes bypass or ignore foods that they would stop and feed on at other times. She wanted to know why. Why would the gorillas pass up foods in one instance only to stop and feed on the same type of food in other instances? Some days gorillas will feed on these plants all day and other times they will travel right by them. That seems a little odd, doesn't it?

Sounds like a great question to me! To answer her question, Rothman collected lots of plant samples and recorded information about the microhabitat in which those samples were found. Variables she looked at included altitude, slope angle, topographic position, and areas of the park zoned for human use. She looked to see if gorillas stopped to consume plants at say a lower altitude for example and ignored the ones at a higher altitude, or if perhaps gorillas ignored foods in human-use areas and stopped to feed on the same plants outside of these areas.

Next, foods were analyzed for their nutritional value. The amount of sugar, protein, and fiber in each sample was determined as what the amount of tannins, bitter tasting compounds produced by plants that deter animals from feeding on the plant. Perhaps foods found in areas outside of human use are of higher nutritional quality than foods found inside areas that humans frequent.

Unfortunately, there were no real significant differences in any of the nutrients or tannins with respect to the microhabitat variables Rothman and colleagues looked at, especially when one considers what gorillas would be able to detect in terms of nutrients. 

Photo by Dylan Walters
Rothman found lots of nutritional variability within microhabitats, including variability within a single month, but as Rothman said, we're not yet able to explain this variability or were not asking the right questions.

This may seem like a disappointing result, and in ways it is. Of course as scientists, we like to ask questions and then have a concrete answer. We want to be able to say, "Gorillas are avoiding plants in high altitudes because the nutritional content of those plants is lower" for example, but that's not what was found. The reality is that sometimes we can't find a correlation, a connection or relationship between two or more things showing interdependence (note this connection or relationship is not necessarily causation), or an answer to our original question. Maybe we're looking at the wrong variables, maybe we're missing some key part of the puzzle, maybe there isn't a link there at all, or maybe our methodology isn't quite the best way to answer the question we're asking. This happens to all scientists regardless of the field.

A lack of correlations or findings is not a waste of time or complete loss though. New questions can present themselves or a new approach may suddenly become clear. And it's important to remember that we do learn from studies where no correlations are found. Scientist still need to publish their results and share them with others.

Food for thought: Why do scientists still need to publish studies where no correlations are found? Why is it important to share these results?

More food for thought: Can you think of how Rothman might use different methods to answer this question? What else might be causing gorillas to pass the same foods at some points in time and stop and feed on them at other times?

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