Archive for June, 2012

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.

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