September Portal update

In September, I returned to Portal bringing with me the newest Ernest lab member, Erica Christensen. It was a bit cooler than usual for mid-September, but overall, a great time of year to be in the desert. We captured 263 rodents, most of which are still represented by the desert pocket mouse (Chaetodipus penicillatus) and Merriam’s kangaroo rat (Dipodomys merriami). It’s much less buggy than other years, and it was a really pleasant weekend. No complaints about desert fieldwork in the fall!

Merriam’s kangaroo rat.

A small kangaroo rat warms up in my pocket before being released. Sometimes after a cool night, rodents need a little help in the morning.

Erica helps process a cactus mouse (Peromyscus eremicus).

We found this guy, jumping spider Phidippus octopunctatus, on a shrub while exploring the area surrounding the site.

We didn’t conduct a formal plant survey this fall due to logistical constraints, but many flowers were blooming in September. Here is a small perennial, Zinnia grandiflora.

The desert pocket mouse continues its takeover at Portal

After trapping rodents August 26-28, it looks like the desert pocketmouse (Chaetodipus penicillatus, pictured below) is continuing do really well, as almost all the other species appear to be doing not-so-well, at least at our site!

Above, the desert pocket mouse is in a plastic bag (photo by S. Cobbold), before we take its measurements. Since we never know what is going to be inside a trap, putting it in a clear plastic bag before handling it gives us a chance to take a look at the animal and to get a good grip on it so it doesn’t escape. Sometimes we catch larger rodents (which can bite!) or other non-rodent animals (which could be venomous!).

Portal has been known for having very high diversity of rodents compared to many other locations; however, if someone had just begun trapping there this year, they would have concluded otherwise. For over a year now, we have been mostly capturing the desert pocket mouse and Merriam’s kangaroo rat (Dipodomys merriami), with only a handful of other species present (i.e. one or two grasshopper mice (Onychomys spp.), Ord’s kangaroo rat (Dipodomys ordii), or cactus mouse (Peromyscus eremicus). This month, there were ONLY Desert pocket mice and Merriam’s kangaroo rat and not a single individual of another species! I think this may be the only time this has ever happened in Portal Project history.

Stephanie Cobbold, a  graduate student at Utah State University in the Jim MacMahon lab, helped out with trapping this month. She studies the sensitivity of species traits to habitat characteristics using spider communities, and we spent our free time looking for spiders, scorpions, and other small arthropods. Since there is a lot of vegetation right now, we saw lots of interesting webs and also saw a scorpion capturing a smaller scorpion! If you’re interested in this side of desert life, check out her great blog post on the spiders of Portal Arizona!

Above: Stephanie Cobbold learns the differences between handling spiders and rodents!

 

Summer in the desert

One thing that makes traveling to Portal each month so interesting is the speed at which the desert landscape can change. Southeastern Arizona has recently been in a major drought, but the arrival of summer monsoon rains seems to have helped green things up, at least temporarily.

Below, the first photo was taken on July 2, 2011 and the second photo was taken August 6, 2011. During that month approximately 11.4 cm of rain fell and transformed the dry, dusty ground into a carpet of green seedlings and flowers.

Some areas were covered in orange flowers (e.g., summer poppies, orange flame flower, and showy flame flower), purple flowers (e.g., silverleaf nightshade) and large caterpillars were abundant (I think mostly Sphinx moths).

In addition to the growth of new plant life, the summer rains have also led to flooding in the Chircahua Mountains where the fire left slopes unstable and vulnerable to washing away. Some of the forest roads remain closed and a short drive into Cave Creek Canyon makes it easy to see areas where the forest floor is buried under mud and debris washed down by flash flooding. Some locals, bloggers Azure Gate and Cave Creek Ranch, have posted updates and photos on conditions in the area.

In addition, the dry soil conditions and lack of vegetation on the bajada and in the valley seem to have allowed for increased erosion at our site as well. The gravel roads leading towards the Portal Project were washed out in places and erosion around the fenced plots meant that some gates were left > 12 cm above the actual soil surface or buried underneath mud and debris; both scenarios making it difficult or unlikely for rodents to actually find and use the gates. I’ll have to work at maintaining these gates over the next month as more rains are likely to occur.

Luckily, I had lots of help digging out rodent gates and collecting data by Elita Baldridge, a Ph.D. student in Ethan White’s lab who came to help out before we both headed to present at ESA after field work was finished.

I continue to be amazed at the “sea” of desert pocket mice (Chaetodipus penicillatus) that seem to be taking over–we’re even encountering control plots, where kangaroo rats should be dominant, with no kangaroo rats at all! Amazing.

Oh, and speaking of amazing…

Portal lives: a long awaited update

While I’ve been busy shirking my blogging duties over the past year, many people have been busy keeping Portal up and running. After we ran out of NSF funding last summer to fund research collection at the site, we were able to keep collecting data bi-monthly for the rest of 2010 on a shoestring budget and with a lot of help from Portal volunteers past and present. Luckily for us, rodent numbers remained extremely low throughout 2010 so maintaining rodent exclosures was not problematic, even with the decrease in trapping frequency. In addition, we were able to secure some funding for the next two years and began trapping each month again in January 2011. There is not a lot of money for incidentals, so we are continuing to use a combination of pit-tags and ear tags for individual markers until they run out and are keeping our fingers crossed that the trap shed and other necessary supplies can last a few more years.

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Trapping this year has been interesting–dealing with record cold temperatures, smoke from the Horseshoe 2 forest fire in Cave Creek Canyon, and a very pesky pack rat that seems intent on living in our trap shed and destroying as many trap box shoulder straps as possible. The spring and winter were extremely dry, combined with record-low temperatures in February, and there was almost no spring germination. Consequently, this past winter, rodent numbers once again dropped extremely low (20-30 rodents in the entire site!), but enough survived the last year to reproduce this spring and our numbers this summer have been >100 rodents on site. This is still a very small number compared to more productive summers only a few years ago and we have also seen a drastic change in species diversity at the site compared to a few years ago. We are currently capturing only 4 species–Merriam’s kangaroo rat (Dipodomys merriami; common), Ords kangaroo rat (Dipodomys ordii; rare), desert pocket mouse (Chaetodipus penicillatus; very common), Bailey’s pocket mouse (Chaetodipus baileyi; very rare), and southern grasshopper mouse (Onychomys torridus; common). In 2011, it seems like we are drowning in desert pocket mice (Chaetodipus penicillatus). In fact, there are plots where kangaroo rats (Dipodomys spp.) should be “king” and instead, we are ONLY catching desert pocket mice! Its all very surprising, but perhaps that is what makes Portal so interesting.