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I was very interested to find that right-hand use was more common among the lemurs in my study. Humans are mostly right-handed, so it could make sense that lemurs would also be this way, but there's previous research on lemurs where left-hand use was actually more common than right-hand use.
I also thought it was very interesting that in my initial analysis, biological sex was a significant predictor of hand use, but when I just looked at the grasping data, biological sex wasn't significant. Switching from looking at all of my data to just grasping eliminated 1/6 of my data, so maybe it was the result of a small sample size. I would be surprised if grooming, walking, and landing were sex-linked but grasping wasn't.
Sifakas used their left hands a lot more than the ring-tailed and mongoose lemurs. This is similar to what I expected based on past readings but still fascinating. Why do sifakas use their left hands more?
If I were to continue this research, I would want to collect a lot more data. This study took place over a 10-week internship, so my opportunities to collect data were limited. Many of the focal lemurs were resting a lot or did not forage much, so the available data from some individuals were scant. I also tried to collect data on foot use as well as data on behaviors such as grooming and landing, but I wasn't able to collect enough to do a thorough analysis. I would also want to include more lemurs to have a larger sample size. I did not have a large enough sample size to observe, for instance, if 10% of sifakas exhibit a left-hand preference.
Most previous research on limb preferences in non-humans uses manipulation. My study design instead uses observations of natural behaviors. This can provide many benefits because I am not requiring animals to move in unnatural positions or accidentally making them use a certain limb. However, there are also many challenges. When a lemur grabs a branch, for instance, I don’t know whether it was because it was their "preferred" side, or if it was because the branch just happened to be closer. Also, if a lemur was grasping a branch with one hand and eating with the other, I don’t know whether the eating hand was their "preferred" hand or it was the one grasping the branch. Behavior is dynamic and can be difficult to measure!
Another potential issue is that an animal also could have had pain or limited mobility on one side of the body, causing them to mostly reach with their non-preferred hand. None of the lemurs in my study were reported to have any pain or mobility problems, but it's still something to think about!
A major limitation of my study was that not all of the focal subjects were in free-ranging enclosures. Only 2 free-ranging mongoose lemurs were available, so I had no choice but to observe 2 that were in indoor enclosures. Thrax and Gisela were in free-ranging enclosures at the beginning of the study but were later moved indoors before I was able to observe them.