hi! I read your post with the ask where you said the siamang was your favorite ape, so I went to the wikipedia to read about it. it said it has an average home range of 23 hectares and a day range of 1 meter. what is the difference between an average home range and a day range? (I'm assuming it means 23 hectares over their entire lives and 1 meter in a day, but how do they get to 23 hectares when they only do a meter a day?)
This is a good question, one that I had to do some research for.
A home range refers to the area in which an animal lives and moves on a periodic basis. An example of this is if you live in a city, your home range would be the area that includes your home, place of work, closest grocery store, etc. while excluding places you only go very occasionally, like the airport. You can and still might go there sometimes, but your average day would exclude it.
Home range is calculated by documenting an animals movement over a long period of time, creating a shape that covers the space that is most frequented, and then measuring the area of that shape.
Day range refers to the average daily movement of an animal. Day range and home range can differ wildly if an animal moves around near constantly but very slowly, or if an animal mostly stays put but regularly (but infrequently) travels great distance.
The discrepancy you are seeing in siamangs is caused by the following:
The day range for siamangs is actually >1km, not 1m. I think you may have misread the Wikipedia entry, which would account for the confusion at least partially. For scale, a meter is a little over 3 feet and a kilometre is 3280 feet. Quite a big difference!
Day range often does not account for vertical exploration. If you spent the day in a very tall tree foraging, climbing, and exploring but I was tracking your movements using a GPS collar, it might look to me like you only moved a meter or two when you actually had a very active day.
Depending on the lifestyle of an animal and the way data is analyzed, the numbers can be misleading. If you spend most days only going as far as your front yard but once every two weeks you run all your errands around town, that could average out to a small number because the errand running distance is offset by the relative inactivity in the rest of your time. This is why calculating median range can give a more accurate idea if outliers are involved.
Overall, I think that misreading >1km as 1m is probably the root of your confusion with the additional caveat that vertical travels may not be accounted for and averages can look weird when animals themselves are weird.
I hope this helps! Don't be afraid to ask more questions, this was really interesting to look into.
