Two rabbit survey routes were established along Jornada Basin roads
in 1996; one in black grama grassland and the other in creosotebush
shrubland. These routes were chosen to pass through habitat
resembling the vegetation at grassland and creosotebush sites in the
Small Mammal Exclusion Study. Quarterly surveys are conducted on
these roads at or near the full moon to measure the density of
rabbits in the two vegetation types. Each route is about 6 miles
long.
Night-time road surveys are conducted during or near a full moon
event (+/- 3 days) in winter (January/February), spring (April/May),
summer (July/August), and autumn (October/November). The counts can
be conducted during the full moon in either month of each season,
depending on when the weather is best. The portion of road surveyed
through the creosotebush environment (Route 1) runs 6.2 miles (9.98
kilometers) across the east bajada of the Dona Ana Mountains
(dominated with creosotebush with scattered mesquite), from the
USDA, JER south entrance on Jornada Road at the rock pillars, to the
power-line road, past the C-GRAV and C-SAND sites, to the Weather
Trailer gate. The grassland portion of the road (Route 3) runs 6.3
miles (10.14 kilometers) from South Well to USDA Pasture 13, along
the west boundary of Pasture 13, then along the north boundary of
Pasture 13 to Jornada Road at the "wind tunnel" site. One
open bed pickup truck is driven approximately 12 miles per hour
along each road route. The driver (data recorder) of the truck sets
the trip odometer to zero at the start of each of the road segments
(creosotebush and grassland). Two people (observers) in the back of
the truck scan each side of the road for rabbits, each using a
100,000 candle-power spotlight. The observers shine the light beam
in a 90 degree arc from the road ahead to the area perpendicular to
the truck. The observers should watch for rabbits, and the reddish
reflection of rabbits eyes in the light. Each time a rabbit is
observed, the truck stops, and the observer guides the truck to a
position perpendicular to the rabbit. The observer then calls out
information to the driver who records the following information in
the data book:
In addition, the data recorder must record the road mileage from the
odometer for the START and END points as well as the mileage and
time for the GATE that is passed through along each route. The terms
START, END, and GATE are entered into the species field on the data
sheet. At the start of each route, Comments must be made by the data
recorder on the Moon Phase (full moon) at the beginning of the first
route. Weather conditions (for example, scattered high clouds,
mostly clear, no wind) should be commented on at the beginning and
end of each route since wind and cloud cover conditions may change.
NOTE: Rabbit surveys are conducted only when the moon is full, the
skies are mostly clear, and winds are light (less than 10 mph).
NOTE: Bushnell Yardage Pro Compact 800 rangefinder (laser
rangefinder) used beginning January 2002.
For more detailed methods, see the rabbit survey protocol document
included with this data package
("Rabbit_Survey_Protocol.pdf"). This study is ongoing.