Excerpts from Jim Conrad's
from the June 9, 2007 Newsletter issued from Sierra Gorda Biosphere Reserve, QUERÉTARO, MÉXICO
EASTERN & DESERT COTTONTAILS
Often as I jog just before dawn I see rabbits hopping about grazing in the dewy grass. As with the Pauraque, whose definite identification eluded me for years, with these rabbits I'm just never sure whether I'm seeing SYLVILAGUS FLORIDANUS, the Eastern Cottontail so common in much of eastern North America, or SYLVILAGUS AUDUBONII, the more western Desert Cottontail. We're also within the distribution area of a couple of jackrabbit species, but those are such long-eared, rangy-looking and usually easily spooked species that I know I'm seeing them during my morning jogs.
In western Kansas the two cottontail species similarly overlap in distribution. A University of Kansas webpage says that "The desert cottontail is difficult to distinguish externally from the eastern cottontail, but is paler, and has longer and more thinly haired ears. Its upperparts are pale grayish brown heavily lined with black and with some yellow."
It continues, "Desert cottontails are usually found in dry, open upland habitats, whereas eastern cottontails in the same areas of western Kansas are restricted to riparian thickets along streams."
I suspect that that's also the case here -- that out in the scrub we have Desert Cottontails, but down in the lush vegetation along streams in valley floors we have Eastern Cottontails.
But, who are these black silhouettes I see in the mornings when I jog in this valley beside a manmade reservoir surrounded by scrubby slopes?
You can see if you detect obvious differences between the species. A good picture of an Eastern Cottontail is at http://www.duke.edu/~jspippen/mammals/mammals.htm.
A good picture of a Desert Cottontail is at http://wc.pima.edu/~bfiero/tucsonecology/animals/mamm_deco.htm.