Russet Mouse Lemur (Microcebus rufus)


MORPHOLOGY:
The russet mouse lemur has a relatively shorter tail than the Microcebus murinus (Martin, 1972). The males of this species have a mean body mass of 50 grams and the females have a mean body mass of 49 grams (Harcourt, 1987). This species has a pelage color which is brown to reddish brown dorsally and ventrally it is gray at the base of the hair and white, off-white, or pale at the tips (Tattersall, 1982). On the face there is a white or off-white stripe running down the muzzle between the eyes (Tattersall, 1982). The cheeks are rufous in color and the throat is pale (Tattersall, 1982). The ears are naked and are shorter as compared to Microcebus murinus (Tattersall, 1982). This species has two pairs of mammae, one pectoral and one inguinal (Tattersall, 1982).

RANGE:
The russet mouse lemur is found in Eastern Madagascar and lives in the coastal rainforests (Martin, 1972). This species is found in both primary and secondary rainforests (Harcourt and Thornback, 1990).

This species found in the following protected areas in Madagascar (Harcourt and Thornback, 1990):

ECOLOGY:
The russet mouse lemur undergoes torpor during the dry season with males more likely not to undergo torpor much like the gray mouse lemur (Atsalis, 1998a). This species sleeps in tree holes or makes nests during the day (Martin, 1972). This species is found most often in edge habitat, e.g. streamsides, and secondary bamboo forests (Duckworth et al., 1995). The russet mouse lemur is primarily a frugivore which is unusual because its small size would suggest it would be primarily a insectivore (Atsalis, 1998b). Some of the fruits this species consumes includes: Medinilla, Ficus, Rhipsalis, Viscum, Psychotria, and the most important fruit source being from members of the genus Bakerella which are mistletoes (Atsalis, 1999b). Three species of Bakerella are eaten including the species Bakerella clavata and Bakerella grisea (Atsalis, 1999b). Bakerella, an epiphytic semiparasite endemic to Madagascar, is the most important food source and it is also consumed when fruit availability is relatively low (Atsalis, 1999b). Bakerella has a high fat and fiber content which would explain why members of this genus would be an important food source (Atsalis, 1999b). The russet mouse lemur also consumes insects, flowers, buds, and gum (Atsalis, 1999b). Of the flowers this species consumes includes the species Weinmannia bojeriana and members of the genus Micronychia (Atsalis, 1999b). The insects consumed includes those from the following orders: Coleoptera, Orthoptera, Hymenoptera, Heteroptera, Diptera, Lepidoptera, Homoptera, Siphonoptera, and Ephemeroptera, with Coleoptera being the order from which the species are eaten (Atsalis, 1999b). Of the Coleopterans eaten include members from the following families: Tenebrionidae, Scarabidae, Cerembicidae, Curculionidae, and Gryllidae (Atsalis, 1999b). Harste et al. (1997) found a different dietary pattern for the russet mouse lemur as compared to Atsalis (1999b). It was found that during the late-dry and early-wet seasons insects were the preferred food source over fruits and Orthopterans were the preferred insect order (Harste et al., 1997).

Home ranges for this species overlap, and males might be migratory in their behavior (Atsalis, 2000). Males may have larger home ranges than females (Atsalis, 2000). The home range of this species may be influenced by the distribution of high-lipid fruits, which is a preferred food source (Atsalis, 1999b).

LOCOMOTION:
Martin (1972) described the russet mouse lemur as using the following forms of locomotory patterns:

SOCIAL BEHAVIOR:
The males of this species have ranges which overlap those ranges of females and other males (Atsalis, 1999a). Usually a couple of central males will have territories that overlap a few females while on the fringes there will be peripheral males (Martin, 1972). Play occurs between the mother and her juveniles and includes the young chasing their mother and also where the juveniles would jump on the tail or hands of the mother (Glatston, 1979). The russet mouse lemur is a solitary forager (Fleagle, 1988).

VOCAL COMMUNICATION:
distress call: This is emitted by the infant (Glatston, 1979). The infant will emit this it is out of contact with the mother and away from the nest (Glatston, 1979). Sick infants will produce this call (Glatston, 1979).This call is high in pitch and piercing, which rises in frequency from 12 to 15 Hz, and are given at a rate of 300 per minute (Glatston, 1979).

purr: This call is given by the infant and sounds like a feline purr (Glatston, 1979). In a 1 to 2 day old infant this call consists of isolated clicks which are a burst of noise that ranges in frequency from 0 to 16 Hz (Glatston, 1979). As the infant ages the clicks increase to irregular bursts at a rate of 900 per minute (Glatston, 1979). This call is also found in adults where it is heard during bouts of allogrooming (Glatston, 1979).

elimination call: This is a soft bird-like call given by infants when they urinate or defaecates (Glatston, 1979). This call has a frequency between 0 and 10 Hz, and as the infant develops the call changes in frequency to be centered between 0 and 2 Hz and between 18 and 24 Hz (Glatston, 1979). A trill is also heard to be incorporated into this call (Glatston, 1979).

grunt: This call is heard in captivity by infants when they seek the feeding pipette (Glatston, 1979). This call occurs in a series and clicks may be given in association with this call (Glatston, 1979). This call has a frequency which ranges between 8 and 18 Hz (Glatston, 1979).

threat call: This call starts out as a hoarse growl which develops into a series of sharp barks that have a frequency which increases from 5 Hz to 13 Hz then decreases again (Glatston, 1979). During this an individual will adopt horned ears position of the ears (Glatston, 1979). This call is also known as the contact rejection call (Petter and Charles-Dominique, 1979).

soft squeak: This call is given by males and serves to give the location of the caller (Glatston, 1979). This call is similar to the trill given by the gray mouse lemur (Glatston, 1979). This call occurs in the 12-24 Hz frequency range (Glatston, 1979). OLFACTORY COMMUNICATION:
urine washing: This is when the hand and foot of the same side are raised and urine is deposited on the hand from the penis or the clitoris (Glatston, 1979). Then the foot is rubbed over the hand rapidly and then both hand and foot are replaced to the substrate (Glatston, 1979). This process is repeated, alternating the different sides of hand and foot, while the individual moves along a branch (Glatston, 1979). For the gray mouse lemur this is the most frequent method of scent marking using urine (Glatston, 1979). Females do this at a higher frequency than males, but this behavior decreases in frequency during estrus (Glatston, 1979). This communicates territorial demarcation (Glatston, 1979).

rhythmic micturation: During this the body is lowered to the substrate and a thin trail of urine is deposited as the individual moves forward by a wriggling motion (Glatston, 1979). Females do this at a higher frequency than males, but this behavior decreases in frequency during estrus (Glatston, 1979). This communicates territorial demarcation (Glatston, 1979).

deliberate discharge: This is when a large amount of urine is intentionally sprayed on to a branch (Glatston, 1979). Females do this at a higher frequency than males, but this behavior decreases in frequency during estrus (Glatston, 1979). This communicates territorial demarcation (Glatston, 1979).

mouth-wiping: This is when the corner of the mouth, the face, and occasionally the head are rubbed on a branch (Glatston, 1979). In this behavior of depositing glandular secretions, saliva may also be deposited (Glatston, 1979). Females will increase this behavior during estrus (Glatston, 1979). This behavior increases in frequency by the male when the female is in estrus (Glatston, 1979). This communicates territorial demarcation (Glatston, 1979).

anogenital-rubbing: This is when an individual will lower the hind quarters and drag the anogenital region along the substrate depositing glandular secretions (Glatston, 1979). Females will increase the frequency of this behavior during estrus (Glatston, 1979). This communicates territorial demarcation (Glatston, 1979). This form of scent marking may also provide information on the reproductive condition of the female during the breeding season (Glatston, 1979).

VISUAL COMMUNICATION:
defense threat: This is where the mouth is open, the lips are covering the teeth, the eyes are open, and the ears are spread back (Glatston, 1979). When the threatening stimulus comes closer the eyes begin to become more narrow and the ears take on the back and folded position (Glatston, 1979).

defensive attack: This behavior usually follows defensive threat (Glatston, 1979). When a threatening stimulus would approach the individual gives threat calls and rears up on the hind legs while clenching the fists (Glatston, 1979). The mouth is open, the teeth bared, and the ears are in the back and folded position right before an individual will bite the threatening source (Glatston, 1979).

swaying posture: In this display the body is held low against the substrate with the front half of the body swaying from side to side (Glatston, 1979). Occasionally the head is turned side to side during this display (Glatston, 1979). This display is seen when an individual is presented with a novel object (Glatston, 1979).

cringing body posture: This display is only performed by the male and this is where the male would be in hunched position, sitting down, with the ears in the back and folded position and the eyes partially closed (Glatston, 1979). This is seen by males when introduced to non-estrus females and seems to function in inhibiting aggression from the female (Glatston, 1979).

tail-lashing: This is when the tail is vigorously moved up and down (Glatston, 1979). This behavior is seen during mating by the male as he approaches the female to mount her (Glatston, 1979). This display is also seen by immature females when they would approach a male (Glatston, 1979).

spread ears: This is when the ears are fully extended being parallel to the vertical plane of the face (Glatston, 1979). This behavior is seen during confident approaches, attacks, and chases (Glatston, 1979).

horned ears: This is where the ears are facing to the side at an angle to the respect of the vertical plane of the face ranging to the perpendicular to the vertical plane of the face (Glatston, 1979). This behavior is seen in situations of great caution or uncertainty, for example during female-female introductions, male-female fights following introduction, and during threat calls (Glatston, 1979). This behavior is also seen when the male will investigate the scent mark of a female, and the corners of the mouth are pulled back during this situation (Glatston, 1979). The more alarmed an individual is the more erect the ears become (Glatston, 1979).

back and folded position: This is when the ears are folded back against skull (Glatston, 1979). This behavior occurs during times of great alarm and fear (Glatston, 1979). A male will perform this when persistently threatened by a female and this behavior is often associated with cringing body posture, defensive threat, and defensive attack (Glatston, 1979). A female who is subordinate will perform this sniffed by a more superior female (Glatston, 1979). This ear position is also seen when an individual is taking insect prey (Glatston, 1979).

TACTILE COMMUNICATION:

REPRODUCTION:
The russet mouse lemur has 1-3 infants per birth with up to two births per year found incaptivity (Rowe, 1996). The mating season is from September to October and the birth season is from November to December (Rowe, 1996).

Mating occurs in the gray mouse lemur as follows: before peak receptivity during estrus of the female, the male will approach the female giving the soft squeak call and tail-lashing vigorously, and the female will respond with aggression towards the male (Glatston, 1979). When peak receptivity occurs for the female she will engage with frequent anogenital rubbing and mouthwiping, and at this time when the male approaches the female she will not act aggressively towards him (Glatston, 1979). When the male approaches the female he will sometimes sniff the flanks and the anogenital area of the female (Glatston, 1979). The will groom the female before he mounts her and will continue to groom her neck once mounted (Glatston, 1979). During mating the male will utter soft squeaks and the female is quiet except for threat calls once mating has completed (Glatston, 1979). The position the male takes during mating is that his forearms are grasping the waist of the female and the feet are either gripping the substrate or the hocks of the female (Glatston, 1979).

The birth of an infant occurs in the following manner for the russet mouse lemur: preceding birth the female will become restless and engage in bouts of self grooming and nesting behavior (Glatston, 1979). The position the female takes for delivery is that the female sits with the legs spread widely and she licks the infant as it emerges, and the female does take hold of the fetal head as it comes out (Glatston, 1979). After delivery the female will bite through the umbilical cord and continue to groom the infant (Glatston, 1979).

The russet mouse lemur infant will remain in the nest the entire time for the first three weeks of its life (Glatston, 1979). The mother only leaves the nest to fee, drink, urinate, or to defaecate (Glatston, 1979). Suckling bouts last on average for about 20 minutes (Glatston, 1979). Infant grooming by the mother is usually associated with suckling or the mother's entry into the nest (Glatston, 1979).

REFERENCES:
Atsalis, S. 1998a. Seasonal fattening and changes in activity levels in the brown mouse lemur (Microcebus rufus) in Ranomafana National Park, Madagascar. (abstract) American Journal of Primatology. Vol. 45, 165.

Atsalis, S. 1998b. Feeding ecology of the brown mouse lemur, Microcebus rufus. (abstract) Folia Primatologica. Vol. 69 (suppl 1), 406-407.

Atsalis, S.A. 1999a. Aspects of social organization in Microcebus rufus: results from a long-term mar-recapture study in Ranomafana National Park, Madagascar. (abstract) American Journal of Physical Anthropology. Suppl. 28, 85-86.

Atsalis, S. 1999b. Diet of the brown mouse lemur (Microcebus rufus) in Ranomafana National Park, Madagascar. International Journal of Primatology. Vol. 20(2), 193-229.

Atsalis, S. 2000. Spatial distribution and population composition of the brown mouse lemur (Microcebus rufus) in Ranomafana National Park, Madagascar, and its implications for social organization. American Journal of Primatology. Vol. 51, 61-78.

Duckworth, J.W., Evans, M.I., Hawkin, A.F.A., Safford, R.J., and Wilkinson, R.J. 1995. The lemurs of Marojejy Strict Nature Reserve, Madagascar: A status overview with notes on ecology and threats. International Journal of Primatology. Vol. 16(3), 545-559.

Fleagle, J. G. 1988. Primate Adaptation and Evolution. Academic Press: New York.

Glatston, A.R.H. 1979. Reproduction and behaviour of the lesser mouse lemur (Microcebus murinus, Miller 1777) in captivity. unpublished PhD. thesis, University of London.

Harcourt, C. 1987. Brief trap/retrap study of the brown mouse lemur (Microcebus rufus) Folia Primatologica. Vol. 49, 209-211.

Harcourt, C. and Thornback, J. 1990. Lemurs of Madagascar and the Comoros. The IUCN Red Data Book. IUCN, Gland, Switzerland and Cambridge, U.K.

Harste, L.V., Wright, P.C., and Jernvall, J. 1997. Microcebus rufus feeding behaviour in the south-eastern rain forest of Madagascar. (abstract) Primate Eye. Vol. 62, 6-7.

Martin, R.D. 1972. A preliminary field-study of the lesser mouse lemur (Microcebus murinus J. F. Miller 1777). Advances in Ethology. Vol. 9, 43-89.

Rowe, N. 1996. The Pictorial Guide to the Living Primates. Pogonias Press: East Hampton, New York.

Tattersall, I. 1982. The Primates of Madagascar. Columbia University Press: New York.

Last Updated: January 22, 2007.
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