292 Notocitellus annulatuswithin its habitats, including various agricultural crops. It is
agile and can often be sighted in trees, usually a few meters
off the ground. N. annulatus vocalizes and quickly seeks shel-
ter in the presence of intruders. Breeding occurs during the
dry season (between December and June), but little is known
about the reproductive behavior of the ring-tailed ground
squirrel. The baculum is rather unique among this group of
ground squirrels, with a short broad spoon-shaped distal end,
lined with a single row of toothlike projections. Predators are
not reported for this species, and the only parasite observed
from N. annulatus is the botfl y (Cuterebra).general references: Álvarez-Castañeda, Castro- Arellano,
Lacher, et al. 2008a; Best 1995h.Otospermophilus Brandt, 1844
This genus contains three species.
Otospermophilus atricapillus
W. Bryant, 1889
Baja California Rock Squirrel
description: The Baja California rock squirrel is recog-
nized by a dark triangular patch on the back of the head, the
neck, and the anterior portion of the back. Hairs on the pos-
terior end of the body and the tail are dark at the base and a
pinkish buff color at the tip. This species has a whitish eye
ring. It is distinguished from O. variegatus by the dark trian-
gular patch on top of the head and between the shoulders,
and from O. beecheyi by the longer tail and the marginally
smaller head/skull.
size: Female—HB 231.2 mm; T 196.5 mm; Mass 350.0 g.
Male—HB 237.8 mm; T 192.6 mm; Mass 505.0 g.
Sex not stated—HB 300.0 mm; T 235.0 mm.distribution: This species’ range extends along the east-
ern edge of southern Baja California and central Baja Cali-
fornia Sur (México). The entire area of its geographic range
is less than 5000 km^2 , but it is highly fragmented.geographic variation: None.conservation: IUCN status—endangered. Population
trend—declining.habitat: This species is found in volcanic mountains with
desert shrub vegetation. Dominant plant species typically
found within its habitat includes several cacti—cardon
(Pachycereus pringlei), choya (Opuntia cholla), and pitaya (Le-
maireocereus thurberi and Machaerocereus gummosus)—and
other desert plants such as mesquite (Prosopis julifl ora), palo
blanco (Lysiloma candidum), torote (Bursera cerasifolia), and
ashy limberbush or lomboy (Jatropha cinerea). The Baja Cali-Otospermophilus atricapillus. Photo courtesy Eric Mellink.