R
ocky habitatis found throughout the world,
and almost everywhere that it exists, one or more
rock-dwelling species of mammal has made a home
for itself among the crevices. In Australia, 11% of all ro-
dents and marsupials are considered to be rock-specialists
(Freeland et al. 1988). This list includes species of antechi-
nus (Parantechinus bilarniand Pseudantechinus macdon-
nellensis), rock wallabies (Petrogalesp.), wallaroos (Marco-
pussp.), and rock-rats (Zyzomyssp.; Freeland et al. 1988).
The African continent is home to another group of rock-
dwelling mammals, which includes red rabbits (Pronolagus
sp.), hyrax (Procaviasp. and Heterohyraxsp.), and dassie
rats (Petromus typicus;George and Crowther 1981; Hoeck
1989; Nowak 1991). Sixty percent of Namibia’s endemic
mammals are in fact rock-dwellers (Griffin 1998). In Asia,
rocky habitat is home to pikas (Ochotonasp.), high moun-
tain voles (Alticolasp.), and the recently rediscovered woolly
flying squirrel (Eupetaurus cinereus), whereas in South
America, chinchillas (Chinchillasp.), rock cavy (Kerodon
rupestris), and punaré (Thrichomys apereoides) are the lo-
cal inhabitants of rock outcrops (Lacher 1981; Nowak
1991; Zahler 1996; Nadachowski and Mead 1999a; Nada-
chowski and Mead 1999b; dos Reis and Pessoa 2004; Spo-
torno et al. 2004). Even on the remote island of East Plana
Cay in the Bahamas, an endangered rock-dwelling mam-
mal, the Bahaman hutia (Geocapromys ingrahami), has
managed to find a place to live (Clough 1972).
Although comparative studies have discussed similarities
among mammals that live in other types of habitat (subter-
ranean [Nevo 1979; Lacey and Sherman, chap. 21 this vol-
ume]; desert [Prakash and Ghosh 1975; Randall 1994];
aquatic [Wolff and Guthrie 1985]), few studies have sought
to elucidate similarities among taxa that live in rocky hab-
itat. One notable exception is the comparative study of
Mares and Lacher (1987), which contrasted numerous as-
pects of the ecology, morphology, and behavior of sixteen
species of rock-dwelling mammals against similar attributes
of non-rock-dwelling taxa. Mares and Lacher’s (1987) study
revealed convergent evolution among rock-dwelling mam-
mals in several traits. Morphologically, rock-dwellers tend
to have padded feet, reduced claws, and (in approximately
a third of the genera) a specialized grooming claw. Ecolog-
ically, approximately half of the rock-dwelling mammals
are arboreal; most species utilize lookout posts for predator
detection, and all species live in habitat that is patchily dis-
tributed. Behaviorally, most species have warning calls and
the majority of taxa use the disjunct rockpiles in their habi-
tat as a defensible resource. Most species also use commu-
nal defecation sites called middens, which are increasingly
being used for phylogeographic studies because they con-
tain valuable historical information on regional flora (Kuch
et al. 2002). Information on social structure was compiled
for ten of the rock-dwelling mammals. Remarkably, 90%
could be classified as social; seven species live in harems
that contain multiple females per male, and two species live
in family groups (table 35.1). The only species that was not
classified as social was the solitary American pika (Ocho-
tona princeps).
The high degree of social behavior exhibited by rock-
dwelling mammals in Mares and Lacher’s (1987) study is
of particular interest to mammalian sociobiology and war-
rants further investigation. This chapter extends the find-
ings of Mares and Lacher (1987) by addressing how living
within rock outcrops is likely to affect the social behavior