Posts Tagged ‘Dipodomys’

Adventures with Giant Kangaroo Rats

June 25, 2012

No, there are no Giant Kangaroo Rats at Portal – but there are a few pockets where they occur in California. In late May, I travelled to the Carrizo Plain National Monument with graduate researcher Tim Bean (who visited the Portal site in December 2011) to work on his project with Giant Kangaroo Rats (GKR; Dipodomys ingens). Tim is studying the relationship between habitat quality and species distribution models and has 8 trapping grids located throughout the Monument in locations predicted to be great for GKR and poor for GKR.

CPNM

This area of Carrizo is probably more like the historic landscape. Here we captured 3 species of Kangaroo Rat: Giant, Short-nosed, and Heerman’s.

Carrizo itself is the largest remaining “intact” piece of San Joaquin Valley desert-grassland; most of the valley was converted to agriculture in 20th century. Carrizo escaped irrigation because of it’s higher elevation, out of the Central Valley. It’s home to a suite of threatened & endangered species, such as the San Joaquin Kit Fox, Blunt Nosed Leopard Lizard, San Joaquin Antelope Squirrel and a suite of unique plant species.

GKR is the largest species of Dipodomys and is federally and state endangered due to extreme habitat loss. It is estimated that the population in Carrizo Plains NM was down to a few hundred in the early 1980s, but is now estimated to be somewhere in the tens to hundreds of thousands – so it appears the GKR story may have a happy ending. There are a few other remnant populations of GKR, but Carrizo is (by far!) the largest of them.

Here I’m holding a Giant Kangaroo Rat for scale – watch out! They scratch with their sharp little claws! Also, note the awesome field biologist vest.

A close up of a Giant Kangaroo Rat.

brome grass hay piles

GKR make large ‘hay piles’ of brome grass seeds on top of their mounds. It is unknown if the seeds remain in these ‘open’ caches, or if they are later removed to a burrow or pit cache.

Because of their sensitive status and relatively high capture rates, we conducted the field work all night, in the dark. Carrizo NM gets quite hot during the day, and we didn’t want to risk killing any rodents in heated up metal Sherman traps (extra-long). In most of Tim’s trapping grids, we only captured GKR (and a few late-evening antelope ground squirrels). At a few sites, however, that seem to represent more undisturbed Carrizo Plain habitat, we also captured Short-nosed Kangaroo Rats (Dipodomys nitratoides) and Heerman’s Kangaroo Rats (Dipodomys heermani) (both still larger than the Merriam’s and Ord’s we capture at Portal; 80-100 grams).

A Short-nosed Kangaroo Rat.

At the sites predicted to be poor GKR habitat, we mostly captured small pocket mice such as the California Pocket Mouse (Chaetodipus californicus) and the San Joaquin Pocket Mouse (Perognathus inornatus).

San Joaquin Pocket Mouse – it’s cute and orangey! A weird side note is that they smell kind of sweet, like kettle corn… CAUTION: Don’t try this at home. In order to avoid disease, you should never sniff dusty rodents or any dusty place they may have defecated.

A juvenile California Pocket Mouse at a “poor” GKR trapping site.

California Pocket Mice have stiff, white, spiny hairs on their rears.

February trip

March 8, 2010

Last month, the site received a lot of rain (approx 3 1/2 inches), which appears to be changing conditions quickly. Rodent numbers are increasing again (up to 31!) and many are already showing signs up becoming reproductive.  Mostly, we caught Merriam’s Kangaroo rat and Grasshopper mice. The dust has settled and the winter annual community appears to be doing well–some of the plots look quite green! We had lots of help this time with NMSU Las Cruces volunteers Dr. Karen Mabry, her field technician Andrew Henterly, and grad student Jane Smith, from another lab.

banner tailed hflbanner-tailed kangaroo rat on plot 23.

cave creek canyon and plotsA view of Cave Creek Canyon and the plots in the morning.

December/January Rodents

January 20, 2010

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…

dipodomys tracks

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.

sunset

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.