However, when drawing a rectangular or circular area, as close to the space shape as possible, you find 32 mammal species instead. Of course, drawing a box or circle around the island, you capture a few sea mammal species, but that’s just some of missing species.
This situation is not only specific to this island but virtually any place / location around the globe. There is always a serious “delta” of missing data for species/observations between drawing a box or choosing place.
There are a number of things that explain the discrepancy.
First, the list of 10 is a checklist. Checklists are known to be a little buggy and are not recommended (and will be phased out at some point), plus they don’t include casual observations.
If you instead use Explore to list mammals on the island, and you allow for casual observations (because your list of 32 allows casual), then you get 20 instead of 10.
So what is missing between the 20 and the 32 from the drawn circle? It’s not just “a few sea mammal species”, the missing 12 species are 11 sea mammals and the bat that you mentioned. The sea mammals are easily explained by the difference in the shape between the two places, and the bat is missing because it is threatened and the locations are obscured, more about geoprivacy here.
In the specific case of the endemic Azores Noctule bat, it appears that all of the observations on/near Sao Miguel are obscured, perhaps due to its conservation status. As such, the automatic obscuring of the locations (to a random point in a large rectangle) necessarily causes the “accuracy” of all those sightings to exceed the limits of the place defined as Sao Miguel, so they won’t be collected in any list for the island. To be included in a checklist or any “Explore” results, both the point of an observation and the entirety of its accuracy circle must be encompassed in the defined polygon for the place. (I’m not sure I personally like the way this functions, but it is what it is.)
if you look at this set of observations, you’ll see that the others have already provided a lot of explanations for the existence of these 694 observations. the only other thing i’ll add is that there are also unobscured observations that have really big positional accuracy values which will prevent them from being found when filtering on the smaller place.
this is already done by default. but as others have noted, this won’t work if you’re filtering on a smaller custom place where the obscured coordinates fall outside the bounding box of the place. this is just how the geoprivacy functionality works.
it’s unlikely the place checklists that currently exist are going to be changed. as i understand it, there are already plans to make a new “dynamic” version of place checklists that will be similar to the dynamic life lists for users.