Troop fission in wild ring-tailed lemurs (Lemur catta) at Berenty, Madagascar.

A detailed fission process in a wild ring-tailed lemur (Lemur catta) troop was observed at Berenty Reserve, Madagascar. The troop fission occurred as follows: 1) During the birth season in 2000, two adult females (mother and daughter) were evicted as a result of "targeted aggression" (i.e., intense and persistent aggressive behavior toward particular individuals). 2) Two adult and three immature females in the same kin group as the evicted females spontaneously immigrated into the new group. 3) A male immigrated into the new group 1.5 months later. 4) The new troop successfully established its own home range. This report exemplifies three characteristics of troop fission in ring-tailed lemurs. First, targeted aggression initiated the fission process. Second, the troop females divided along matrilineal lines. Finally, no male played a specific role in the fission process.

Ichino S 《AMERICAN JOURNAL OF PRIMATOLOGY》

Attacks on a wild infant ring-tailed lemur (Lemur catta) by immigrant males at Berenty, Madagascar: interpreting infanticide by males.

An orphaned infant ring-tailed lemur (Lemur catta) was attacked persistently by immigrant males and disappeared with severe wounds at Berenty Reserve, Madagascar. Prior to the attacks, two troop members disappeared. On 20 November 1998, the only resident male in Troop C2B disappeared suddenly. After the disappearance, nine males from three neighboring troops approached, but only six males continued to shadow the troop. Of the females, the one lactating female attacked the males the most frequently. On 21 January 1999, the lactating female disappeared and her infant was orphaned. Subsequently, five attacks on the infant by immigrant males were observed for five consecutive days from January 23 to 27. The aggression was persistent and specifically targeted the infant, suggesting that the attacks were purposeful aggression, rather than redirected or accidental aggression. The primary attacker was the most dominant of the immigrant males, and mated with females in the next mating season.

Ichino S 《AMERICAN JOURNAL OF PRIMATOLOGY》

Intra-troop affiliative relationships of females with newborn infants in wild ring-tailed lemurs (Lemur catta).

Nakamichi M ，Koyama N 《AMERICAN JOURNAL OF PRIMATOLOGY》

Demographic and life-history patterns in a population of ring-tailed lemurs (Lemur catta) at Beza Mahafaly Reserve, Madagascar: a 15-year perspective.

Over 15 field seasons (1987-2001), we collected census and life-history data on a population of individually identified ring-tailed lemurs at the Beza Mahafaly Reserve, Madagascar. No significant difference was found in population size over the study period, though a marked decline in the population occurred following a 2-year drought. The population rebounded rapidly after the immediate postdrought period. There was nearly a complete replacement of individuals over the study period. Average group size is 11.5 animals, and adult male to female sex ratio is 0.92. Most females reproduce annually, and the average fecundity rate is 84.3%. The greatest variability in fecundity is found among old females. We suggest that ring-tailed lemur females follow an "income breeding" strategy, i.e., females use maximum resources during reproduction rather than relying on fat stores, as do "capital breeders." Infant mortality to 1 year of age in a nondrought year is 52%, higher than infant mortality in small to medium-sized anthropoids. The oldest known female was 18 years old in 2001. We suggest that 18-20 years may represent the maximum life-span for wild ring-tailed lemurs. Because males regularly emigrate from the population, we have no data regarding male life-span; however, there is some indication that males do not survive as long as females. Group fission has occurred three times: twice from one parent group living in the driest area of the reserve, with the most dispersed food resources. We suggest that the reproductive strategy that has evolved in this species, wherein females reproduce early in life and annually until old age, is a response to the unusual climate and environmental conditions under which Lemur catta has evolved.

Gould L ，Sussman RW ，Sauther ML 《AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY》

Population and social dynamics changes in ring-tailed lemur troops at Berenty, Madagascar between 1989 - 1999.

Koyama N ，Nakamichi M ，Ichino S ，Takahata Y ... -  《PRIMATES》