Joshua Tree National Park (Part 2)

White-Throated Woodrat - Neotoma albigula

It’s time to share the rest of the story about the week I recently spent with the museum’s science team a week ago. Some people choose their route on trips based on the path of least resistance. I try to find the path of most enjoyment. There are three viable paths to Cottonwood Spring. The most used is a freeway dominated route of 174 miles (near Riverside, CA) that is 10 minutes faster than the more scenic roads I like through Borrego Springs, which is about 30 miles shorter. The third route option combines more freeways, but is also scenic and goes through Anza, CA. Though the time and distance data for the third route were slightly better for the route through Anza, I wanted to look for Round-Tailed Ground Squirrels at the Borrego Sink. So I chose the route through Borrego Springs.

I know very little about the Round-Tailed GS, but I’m told they live in Creosote brush dunes at the bottom of Borrego Springs (the Sink). I wandered the area afoot for an hour and a half, but no furry critters were seen. Pictures of burrows were also requested for the Mammal Atlas, but since I couldn’t be sure which burrows belongs to the squirrels (the Desert Kangaroo Rat digs similar burrows), I photographed all the burrows I could find. I could let the science team decide what was usable and what was not. I’ve since been told that Round-Tailed Squirrels prefer the hottest weather and may stay in their burrows if the weather is not sufficiently hot.

The next leg of my journey took me along the northwestern shore of the Salton Sea, though not near enough to hunt birds. The sea rests at the juncture of the Coachella and Imperial Valleys and smack dab in the center of the San Andreas Fault. Both the north end (Coachella) and the south end (Imperial) of the sea are well developed agriculturally. The Imperial side is dominated by a wealth of row crops, but the Coachella side is primarily date palm fields. The town of Mecca sits at the north end of the Salton Sea where the Whitewater River ends its journey from the southern slopes of San Gorgonio Mountain north of Palm Springs. I found a back country road from Mecca to Cottonwood Spring called Box Canyon Road and it provided a path which allowed me to avoid ALL freeways to my destination.

My previous post explained the rhythm of work while doing the scientific chores that the survey required. The first day’s traps brought back to camp had the most subjects of any day’s collection. After we gathered our first images and specimens, the remaining days were spent targeting more specific subjects.

One of the more difficult ID problems with southern California rodents is to distinguish between the Long-Tailed Pocket Mouse and the Desert Pocket Mouse. There is much overlap in the diagnostic characteristics for these two creatures, and the most reliable features are not revealed without dissecting the animal. The length and shape of the ears is one outward feature that is used. The Desert PM has shorter, more rounded ear and the Long-Tailed PM has longer, more pointed ears. Unfortunately some of the Desert PM’s ears are longer than others and some of the Long-Tailed PM’s are shorter. We took a few additional subjects to illustrate this point.

I knew we were missing the White-Throated Woodrat images for the Mammal Atlas and would pester Scott each afternoon when he was heading into the field to place traps asking him to bring me this creature (almost in jest). On the final day of our expedition my request was fulfilled. Compared to the small pocket mice and other mice that were brought in during the week, the woodrat was a behemoth, easily 20-30 times the size of its smaller relatives. I was using a fixed focal length macro lens to photograph these subjects, and I was forced to position myself much further back from this subject than any of the others from this week. After getting as many full body shots as I felt necessary, Scott held the animal so we could photograph it’s underside for the diagnostic white fur on the throat. This provided assurance of the correct identification, as the Desert Woodrat is very similar to this species.

The team will head out again next week on another expedition to Joshua Tree NP. This trip will center near Pinyon Wells. Below are some of the images captured during the trip to Cottonwood Spring: