Late September at Joshua Tree NP

Chaetodipus rudinoris

Last Sunday (2016-09-24) I left Poway for Cottonwood Spring in southern Joshua Tree National Park to stay with members of the museum’s science team for the week. With the San Diego County Mammal Atlas coming near the end of preparation, there were a couple of species we’d hoped to get images of and we thought we could piggy-back it onto the restudy project that has been recently undertaken by the museum.

The team was comprised of myself (for photography), Scott Tremor (science team leader), Lea Squires (biologist), and for one day, Lori Hargrove (biologist, coordinator).

The general rhythm of the expedition began with a late afternoon session of Scott and Lea setting traps to catch small rodents. Traps (called “Sherman Traps”) the team uses are amazing little collapsable aluminum boxes that pop open to a 3” x 3.5” x 12” with a spring-loaded trapdoor on one end. An animal enters the box to find the few pieces of rolled oats inside. As it reaches the full depth of the box, it steps on the trigger and the trapdoor snaps shut. Hundreds of traps are set each evening and about 20% make successful captures. At dawn the next morning all the traps would get collected. Most of the specimens are documented, marked (so recaptures could be recognised) and released. A selected few were brought back to camp for me to photograph.

While the team was out managing the traps, I would setup the ‘theater’ for the photographs. The theater stage was a glass aquarium that I broke the bottom from. By placing the enclosure on the native ground, the natural substrate presented for the subject captures to roam on. I learned to place objects inside the theater (rocks, sticks, cactus pieces, etc.) for the subjects to pose near. Placing brush and rocks behind the aquarium (terrarium) helped to complete the illusion. Rearranging the scene from time-to-time helped to give variety to the images I would capture. A screened lid with a hole cut out of the middle to introduce the subject to the stage and some lighting to sit overhead and I was ready to take pictures.

I spent afternoons and evenings sorting and grooming images while Scott and Lea prepared the specimens I’d photographed in the morning for the museum’s collections. While preparing the animal skins had an element of gruesomeness to it, there was an important scientific contribution to be appreciated. The way the team worked through the evening, and the good natured conversations that accompanied the process, reminded me of a friendly card game, or sewing circle with busy hands and witty conversation.

There were many useful images that I collected on this expedition. Today I’m sharing one of the surprise subjects that were discovered here; The Northwestern Baja Pocket Mouse. This mouse was once called the Bailey’s Pocket Mouse, but that species was recently split. We’ve not been able to locate images of the Northwestern Baja Pocket Mouse for the San Diego County Mammal Atlas, so getting good images was quite a nice surprise. We believe, but are not sure, this discovery documents the northern extent of this animal’s range. It goes to show trapping is like a box of chocolates; you never know what you’re going to get (sorry Forrest).