Motivational Systems in Muroid Rodents

The motor patterns of patrol/marking include locomotor activities, sniffing, various kinds of scent-marking, and active secretion of pheromones. Motor patterns of scent-marking are particularly variable among muroid rodent species.

As described by Shillito [1963], it is possible to distinguish two aspects of locomotion activated by patrol/marking. The first, which may be called simply "locomotion," is relatively undirected. The second, which may be called "approach locomotion" is directed specifically towards other animals or inanimate objects. Whereas the first has no releasing or directing stimuli, the second is released and directed by specific stimuli from objects encountered in the environment.

Approach locomotion usually leads to another motor pattern of patrol/marking which may be called "stop-and-sniff' [Lehman and Adams, 1977; Welker, 1964]. This motor pattern, which is usually released when the animal reaches the object or animal that it has approached, includes an inhibition of further locomotion, sweeping of the vibrissae, and sniffing. Along with locomotion and approach locomotion, the stop-and-sniff motor pattern is usually taken for granted in studies of exploratory behavior of muroid rodents.

Urine-marking has been described by Grant and Mackintosh [1963] in R norvegicus and M musculus, and called the "crawl-over" motor pattern in their inventory of the social acts of laboratory rodents. Urine-marking has also been reported in P maniculatus [Eisenberg, 1962], T leucogaster and Ae chrysophilus [Choate, 1972], C glareolus [Mironov, 1976], Cr gambianus [Ewer, 1967], N alexis [Stanley, 1971], and Rh opimus [Goltzman et al, 1977]. Its existence is debatable in Mer unguiculatus [Daly, 1977]. The urine-marking of R norvegicus has been quantified by measuring the accumulation of substances deposited during this motor pattern on a petri dish which the animal marks with a motor pattern called "crawl-over-dish" [Adams, 1976].

Perineal drag, vaginal-marking, or anal-marking have been reported in a number of muroid rodent species. These motor patterns may be difficult to distinguish, and perineal drag, in some cases, may not be differentiable from urine-marking. Perineal drag has been described in R norvegicus [Calhoun, 1962, p 154], Rh opimus [Goltzman et al, 1977], N alexis [Stanley, 1971], and three species of Neotoma [Howe, 1977]. Eisenberg [1967] also reported perineal drag from all of the muroid rodent species which he studied, including four species of Peromyscus, two of Meriones and Gerbillus, and one of Tatera and Pachyuromys. Vaginal marking has been specifically studied in female Me auratus [Johnston and Lee, 1976], and anal-marking has been reported in the muskrat, Ond zibetica [Darchen, 1964].

The motor pattern of ventral-rub was described in Mer persicus, and called "bauchreiben" [Eibl-Eibesfeldt, 1951]. Since that time it has also been described in R rattus [Ewer, 1971], Ps obesus [Daly and Daly, 1975], Rh opimus [Goltzman et al, 1977], various species of Meriones including unguiculatus [Thiessen and Yahr, 1977], tristami [Thiessen et al, 1973], and hurrianae [Eisenberg, 1967], and various species of Neotoma, including fuscipes [Linsdale and Tevis, 1951 ], cinerea [Egoscue, 1962], and mexicana, albigula, and stephensi [Howe, 1977]. In most of these species, it is associated with development of midventral sebaceous glands. The development of similar glands in other muroid rodent species including certain species of Rattus [Rudd, 1966; Quay and Tomich, 1963] and Peromyscus [Doty and Kart, 1972] would lead one to expect to see ventral-rub motor patterns in these species, but data are not yet available.

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