Subfamily Delanymyinae
Delany's swamp mice

Delanymyinae is an Old World nesomyid subfamily consisting of just a single genus and species, Delany's swamp mice (Delanymys brooksi). (Musser and Carleton, 2005)

Delany's swamp mice are native to east central Africa, including southwestern Uganda, Zaire, Rwanda, and the eastern portion of the Democratic Republic of the Congo. (Nowak, 1999)

The preferred habitat of Delany's swamp mice is sedge marsh in montane and bamboo forests, at elevations from 1,700 to 2,625 meters. (Carleton and Musser, 1984; Nowak, 1999)

Hayman (1962), the first author to describe Delanymys, classified Delanymys with Petromyscus in the subfamily Dendromurinae, based on dental characteristics. Most authors have followed suit in uniting Delanymys and Petromyscus, despite numerous morphological differences between the two genera. For example, Petter (1967) recognized Petromyscinae as a subfamily that included both Delanymys and Petromyscus, and he placed it in the family Cricetidae. Others have classified Petromyscinae, including Delanymys, in the family Muridae (Carleton and Musser 1984, Musser and Carleton 1993). Musser and Carleton (1984) adhere to the tradition of uniting the two genera, but note that the only trait they have in common is an extra cusp on the first and second upper molars, and that they may not form a monophyletic group. Molecular evidence shows that Petromyscus is part of the clade constituting the family Nesomyidae, and though molecular studies including Delanymys are lacking, it is now considered part of the Nesomyidae as well (Jansa and Weksler 2004, Steppan et al. 2004). In their latest classification, Musser and Carleton (2005) have separated Petromyscus and Delanymys into their own subfamilies. (Carleton and Musser, 1984; Hayman, 1962; Jansa and Weksler, 2004; Musser and Carleton, 1993; Musser and Carleton, 2005; Petter, 1967; Steppan, Adkins, and Anderson, 2004)

Delany's swamp mice are small nesomyid rodents. The head and body length ranges from 50 to 63 mm, the tail length ranges from 87 to 111 mm, and the body weight is about 6 grams. The tail is about twice as long as the head and body. Delany's swamp mice have delicate, gracile bodies with long hind feet and digits. The tail is semiprehensile, and the fifth toe is semiopposable. Four of the digits on the front feet bear claws, and the hind feet have claws on all five digits. The fur on the back is russet, the chin is whitish, and the belly is a warm, buff color. The bases of the hairs are grayish. The coat is thick, soft, and woolly. The scaly, bicolored tail is covered in thin hairs, and the soles of the feet lack fur except near the bases.

The delanymyine dental formula is 1/1, 0/0, 0/0, 3/3 = 16. The upper incisors are orthodont and the upper molars lie in parallel rows. The brachydont molars have three roots in the upper jaw and two roots in the lower jaw. The first two molars are about the same size, and the third molar is about a third the size of the others. The molar surface is marked by a series of alternating cusps, and the anterior crests of the first upper molars are large and not bicuspid. The first and second upper molars have distinct mesolophs and mesostyles. There is a labial cusp on the cingulum of the first and second molars of the lower jaw, and there is no posterior cingulum of the molars of the upper jaw. The small mandible has thin coronoid processes. The rostrum is short, and the delicate skull has a high, rounded braincase. The area between the orbits is narrow to moderately wide and has smooth edges. There are no temporal ridges. The zygomatic arches are narrow and delicate, and the infraorbital foramina are relatively large. The zygomatic plates are narrow and do not extend anterior to the dorsal zygomatic roots. The incisive foramina terminate before the anterior borders of the molar rows, and the bony palate terminates in a deep V-shape before the posterior borders of the molar rows. The mesopterygoid fossa is narrow and the anterior portion is constricted, and the pterygoid fossae are long, wide, and almost flat. There are small sphenopalatine vacuities. The middle lacerate foramina are small. There is no alisphenoid strut, and the accessory foramen ovale, masticatory foramen, and buccinator foramen are all merged into a single opening. There is no stapedial foramen, and the internal maxillary artery is a branch of the internal carotid artery. The auditory bullae are relatively inflated, and there is a large opening in the lateral surface of each mastoid bulla. The soft palate has three ridges in the premolar region and four ridges in the molar region. (Carleton and Musser, 1984; Nowak, 1999)

No information is available on the lifespan of delanymyines.

Delany's swamp mice build small, round nests out of grass. Each nest has one or two entrances and is situated in a low shrub. They are nocturnal, and, as their common name would suggest, they are well-adapted for climbing, with semi-prehensile tails, long digits, and semi-opposable toes. (Carleton and Musser, 1984; Nowak, 1999)

Delanymyines have eyes and ears, so they no doubt perceive the world through vision and hearing. They probably also receive tactile and chemical signals, as do all mammals. No information is available on how these rodents communicate.

Delany's swamp mice feed exclusively on seeds. (Nowak, 1999)

There have been no reports of predation on delanymyines, nor have any anti-predator adaptations been reported. However, these mice probably remain vigilant and use their agility to escape predation. Likely predators include raptors, snakes, and small to medium-sized mammalian carnivores.

Delanymyines are primary consumers, and they are no doubt consumed by other animals, although no one has reported predation on climbing swamp mice.

There are no known negative impacts of these rodents on humans.

There are no known positive impacts of these rodents on humans, although these mice are undoubtedly integral parts of healthy ecosystems in areas they inhabit.

Delanymys brooksi is listed as endangered by the IUCN due to the destruction of habitat in its already small geographic range. (IUCN, 2004)