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!
Posts Tagged ‘kangaroo rat’
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!
In September 2009, a remote camera was set up near a seed tray put out by Kate Thibault and undergraduate students from Furman University who visited the site as part of their “wild semester“. Kate later strung the photos together to create this fun insight into a hungry kangaroo rat’s night. If you look close, you can also see some a grasshopper mouse (Onychomys spp.) traveling past. Footage takes place between 12:30 am and 6 am September 20th. Enjoy!
Here is the belated spring update on Portal rodents. March, April and May were all months full of flowers! In May we began seeing scorpions, Mojave rattlers, and bee swarms. The site was beautiful as all the spring flowers took off, but the rodent numbers stayed low after winter. By May, we were still just below 50 animals! In addition, it appears some changes may be occurring within the community. We haven’t captured a banner-tailed kangaroo rat since late fall and Ord’s kangaroo rat is also doing quite poorly (2 or less all spring!). Perhaps most suprisingly, Bailey’s pocketmouse, which we usually capture throughout the colder months has also nearly disappeared. Very few were seen all winter, and by spring we were only capturing 1-2 each month. Instead, the smaller Desert pocketmouse is numerically dominant, along with Merriam’s kangaroo rat. Overall diversity is currently very low. Hopefully we can continue trapping, at least in some capacity, in order to see what happens as rodent numbers slowly rebound from near zero last winter!
Conditions at Portal seem to be getting worse for the rodents. Since it is cold, the smaller species are no longer showing up in trapping censuses. Furthermore, Merriam’s kangaroo rat, seems to have nearly taken over the site, comprising more that 50% of the community (at least, of the 20 rodents caught in January). We continue to catch one or two Banner-tailed kangaroo rats each month and of course, many grasshopper mice. Ord’s kangaroo rat no longer seems to be around and Bailey’s pocketmouse is also nearly absent–only one individual made an appearance in January. It will be interesting to see what shows up as things get warmer this spring! A third seed box has disappeared, this one stolen, so off we are to find another seed box that is tough enough to withstand hungry rats, but not attractive enough to be taken…
As conditions seem to be getting worse for the rodents, the loose dust provides a good way to track use of the plots! Although we haven’t caught an individual on plot 12 for several months, it seems there is a hungry kangaroo rat trying to get in! By January, every animal traversing was leaving tracks, making it interesting to determine who/what was around.
The dust seems to be winning the battle in this photo taken on plot 12 in December. It was even worse in January, with every step leaving tracks in the dust inches deep.
Banner-tailed kangaroo rat mound on plot 23. We catch this individual nearly every month.
Ryan O’Donnell, a grad student at USU, made a 3rd appearance at Portal in December to help with trapping and to practice his wildlife photography skills.
Fantastic sunsets in January did not disappoint myself or my helper for the month, Ken Locey, a grad student in Ethan White’s lab at USU.
January saw signs of spring germination with many small plants breaking through the crust.
This fall the dramatic decline in the number of rodents caught on the Portal plots. By November, we dropped from 94 individuals in August to only 31. We remain busy keeping things running, however, especially since some very hungry rodents ate through 2 seed boxes in less than 2 months! Kate Thibault and Travis Perry, along with their field class from Furman University, joined me at the site in September and October to help with data collection. Michelle Lute, a grad student studying macaques at University of Notre Dame, joined me in November to learn something about small mammals and the desert.
The field class found this box turtle crossing the road near the site in September.
The saga of the weather station continues as we attempted to fix it this fall. After replacing it with a spare on for a month, we were able to get the data, but are still working out the bugs post re-installment.
It rained a bit almost every trip down this fall. Here are some pictures of a strange misty rain in Cave Creek Canyon during trap setting in November.
Michelle gets to know a Dipodomys spectabilis.