היומן של maxallen

A recent observation highlighted the limitation of using geography to determine species on iNaturalist. If you take a close look at the photograph in https://www.inaturalist.org/observations/41662271 you may note that animal exhibits the characteristics of a mule deer rather than a white-tailed deer. However, the location makes it nearly inconceivable that it is a mule deer.

This is a conundrum that scientists often run into when using citizen science data. What can be inferred from a given observation, and how do you ensure the accuracy of it? It is generally more accurate to base identifications on field marks (physical characteristics) than location. This is the essence of birding and why people get so excited about rare birds showing up in odd locations. If people just ignored field marks and just considered geography, most of these rare birds would never be documented. But why do we ignore this principle with mammals?

In the deer example, as noted by @sambiology, the habitat in the photo doesn't fit north Dallas. This makes it most likely it is a mule deer and the location is simply wrong. But what happens when we know the location is accurate? Should we look at field marks or just consider geography? Take a look at 2 other observations and see what you think.

1) https://www.inaturalist.org/observations/18767407
In this case, we have what appears to be an American marten (with known location). But American martens are endangered in Wisconsin, and are unknown to occur in this area (before this observation). The field marks suggest American marten. The geography suggests it is actually a mink or fisher or some other mustelid or maybe a squirrel. Based on this observation, @lincolndurey extended the range map for American martens. But what if we had just labeled this as a squirrel and moved on without considering the field marks?

2) https://www.inaturalist.org/observations/20912284
Similar to #1, here we have what appears to be a fisher (with known location). But fishers are endangered in California and the population at the southern edge of the Coast Range is considered basically non-existent (before this observation). Specifically, the last fisher sighting this far south was made by Joseph Grinnel nearly a century ago. The field marks suggest this is a fisher. The geography suggests it is a mink or squirrel. Based on this observation, fisher researchers have extended the known range of fishers in the Coast Range of California. But what if we had just labeled this as a squirrel and moved on without considering the field marks?

Fishers (Pekania pennanti) are a forest-specialist mesocarnivore and are a species of special concern in California (CDFW 2015a, 2015b). In comparison to the Sierra and Cascade populations, the coastal population is under-studied and the southern extent of its range is not clearly documented (Zielinski et al.
1995).

We documented a fisher at the southern edge of Lake County. This is the southernmost documented fisher sighting since Joseph Grinnell. Grinnell, in his review of fisher locations in 1937, noted that fishers may extend as far south as Marin County, but had no definitive proof.

The full documentation of this sighting is available at http://publish.illinois.edu/maxallen/files/2019/01/Allen-2015-Fisher-Range-Expansion.pdf

This photo is part of our discovery of American martens on the Apostle Islands. Martens were reintroduced to the Apostle Islands by the State of Wisconsin in the 1950's, but were not seen after the 1960's. Using camera trapping over the past few years we detected American martens at 28 of 87 functioning camera trap sites on 5 of 13 monitored islands and documented the existence of American martens in APIS in Wisconsin for the first time in over 50 years.

Full story: http://publish.illinois.edu/maxallen/files/2018/11/Allen-2018-Marten-Discovery-Apostle-Islands.pdf

This observation is rather typical when investigating fresh puma (also called mountain lions) activity (using data from GPS collars). While hiking in on the nearby ridge I found an older bed (about 36 hours old) with fresh scat, evidence that the mountain lion had indeed been there. I then began searching more carefully and soon found the remains of the deer that the puma (82M) had killed and eaten. He also rested for some time while apparently grooming (note the large size of the bed compared to a sleeping bed) in a bed with a scenic view (see second photo). Note how the bed is dry while the surrounding area is wet, it had stopped raining 30 minutes before as I began my hike into the area...