MILNE-EDWARDS'S SIFAKA

Propithecus edwardsi

Geographic Distribution and Habitat
Like all species of lemurs, the Milne-Edwards’s sifaka, also known as the Milne-Edwards’s simpona, is found only on the island of Madagascar. They inhabit both continuous and fragmented primary and secondary rainforests along a strip of southeastern Madagascar at elevations of 1,967–5,250 ft (600–1,600 m). Their home ranges can be approximately 49–124 acres (20–50 hectares) and they often have only a small overlap with neighboring groups.

Their behavior and ecology are studied by scientists in their habitat in the Ranomafana National Park in Madagascar.

Milne Edwards sifaka range, IUCN 2020

Size, Weight, and Lifespan
Milne-Edwards’s sifakas are one of the largest species of lemur and show no significant sexual dimorphism. Males and females reach roughly the same head and body length of, on average, 19 in (48 cm) and a tail length of around 17.7 in (45 cm). Canine length is about 3–3.5 in (8–9 cm) in both sexes. On average, females weigh 12.5 lb (5.7 kg) and males weigh 12.1 lb (5.5 kg).

These sifakas live to around 20 years in the wild, although infant survival is low and many individuals die before adulthood.

Appearance
​The Milne-Edwards’s sifaka is a large-bodied lemur with dark brown to black fur. They have white patches on their flanks (sides) and their backs, forming a “saddle” shape, which is sometimes bisected with a dark line of fur running along the spine. They have dark faces and dark hands and feet, which are specialized for clinging to trees with prehensile thumbs and toes, as well as sharp nails. They have round, orange eyes and, like all lemurs, a tooth comb that’s specialized for grooming.

Photo credit: Charles J Sharp/Creative Commons

What Does It Mean?

Diurnal:
Active during daylight hours.

Estrus:
A recurring period of sexual receptivity and fertility in many female mammals.

Harem:
A group of females guarded by a male, who prevents other males from mating with them; an animal group consisting of one or two males, a number of females, and their offspring. The dominant male drives off other males and maintains the unity of the group. If present, a second male is subservient to the dominant male.

Infanticide:
The killing of young offspring by a mature animal of the same species.

Sexual dimorphism:
Distinct difference in size or appearance between the sexes of an animal in addition to difference between the reproductive organs themselves.

Tooth-comb:
The incisors on the lower front jaw of some animals are grouped as if to form a comb. The tooth-comb is used by these animals to groom and clean their fur or hair.

Visit the Glossary for more definitions

Diet
The majority of the Milne-Edwards’s sifaka’s diet consists of seeds, leaves, and fruits. Fruit makes up approximately 20–30% of their diet; leaves make up around 25–50%. They prefers young leaves to mature leaves and will also occasionally ingest soil and fungi. Their food sources vary throughout the year and fruits and seeds are more available in the wet season. They exhibit some dietary flexibility, but also rely on a relatively small number of plant species to make up the main part of their diet.

Behavior and Lifestyle
Milne-Edwards’s sifakas are diurnal and spend about 30% of their day foraging, although this changes with season and food availability. They spend around 40% of their day resting and about 5% engaging in social activities, such as grooming or play. Groups tend to travel between 2,297 and 2,625 feet (700–800 m) per day. The main mode of locomotion is vertical leaping and clinging to trees. Climbing occasionally occurs, as does bipedal walking, but this is rare.

At night they sleep in trees high up in the canopy, sometimes up to 26 ft (8 m). They will sometimes reuse sleeping sites, but often there are long periods between visits.

They exhibit mutual grooming between unrelated group members, although females prefer to groom their own offspring rather than unrelated juveniles and infants. Intragroup aggression is more common between unrelated individuals than related individuals.

Daily Life and Group Dynamics 
Milne-Edwards’s sifaka groups are female dominated, with females winning the majority of male-female conflicts, although, in general, aggression rates are relatively low in this species. Female dominance is common in lemur species, but rarer among other primates.

Milne-Edwards’s sifakas exhibit an unusually flexible social system compared to many other primates. They might live in harems, multi-male/multi-female groups, male-female pairs, and single-female/multi-male groups. Even more remarkably, the same individuals may engage in different social systems each year. Researchers aren’t yet sure what causes the different social systems to form, although it’s possible that environmental factors, such as food availability, may have an influence. None of the different social systems appear to be more beneficial than the others for infant survival. Regardless of social system, groups tend to contain only a small number of juveniles and infants, often just one or two.

Upon reaching sexual maturity at around 3.5 years of age, males and females can either remain in their natal group or disperse to a new group. Consistent with the notion that dispersal is to prevent inbreeding, individuals seem to only remain to reproduce in their natal group when there is an unrelated member of the opposite sex. Individuals can delay dispersal from their natal group until they are 6 or 7 years of age.

When either males or females immigrate into a new group, it is common for them to commit infanticide—that is, to kill existing infants in their new group. Infanticide by males brings females into estrus quicker so that the immigrating male can produce his own offspring with the resident female(s); infanticide by females seems to result in the emigration of the infant’s mother, which then allows the female immigrant to become the new breeding female of the group.

Communication
Olfactory communication is generally important to lemurs, and the Milne-Edwards’s sifaka is no exception. Both sexes secrete a substance from their anal glands that they then rub onto a substrate, usually a branch, to mark it with their scent. Males also have a gland in the middle of their chests that secretes a substance with which they may also scent mark branches. Males generally scent mark twice as frequently as females, and more dominant females mark more than lower-ranking females.

Both males and females in single male/single female groups scent mark more, probably to discourage other males/females from joining the group. However, they don’t scent mark more in mating season, and the presence of an infant in the group doesn’t appear to affect scent marking behaviors. Therefore, this species doesn’t seem to use scent marking for attracting mates but rather to signal status and territory.

Males also participate in tree gouging; this consists of biting a tree and removing, but not eating, its bark, and then scent rubbing the exposed area. Dominant males tree gouge more often than others and it is thought to help maintain the scent while providing a visual cue to accompany it.

In addition to olfactory communication, this species communicates vocally, using a “roaring bark” vocalization when predators are sighted, as well as contact calls and “chatter” calls.

Reproduction and Family
Milne-Edwards’s sifakas are seasonal breeders, with most infants born during winter in Madagascar (May–July). Females usually give birth to one infant after a gestation period of around 180 days.

Interbirth intervals are between 1 and 2 years, although this changes depending on how long the infant survives; females who lose their infants will be able to reproduce again more quickly. Infants are usually weaned after 5–6 months.

Sadly, infant mortality is high and as many as 50% of infants do not survive beyond their first year. In fact, only a quarter of females will survive to breeding age, which is around 3.5–4 years of age. This low survival rate is a factor that prevents large kin-bonded groups from developing, such as those seen in baboons or vervet monkeys; by the time a female reaches the end of her breeding life, she will usually only have one adult daughter surviving compared to around three in monkey species.

Photo credit: Brian Gratwicke/Creative Commons

Ecological Role
​Seeds and fruit constitute a large part of these sifakas’ diet, so they likely play an important role in seed dispersal.

Conservation Status and Threats
The Milne-Edwards’s sifaka is currently classified as Endangered by the International Union for Conservation of Nature (IUCN, 2020). Their population is currently decreasing and researchers estimate that fewer than 10,000 individuals exist in the wild. Their low survival rates combined with low reproduction rates means that this species is very vulnerable to population decrease.

Natural predators of this species are the fossa and various birds of prey. However, the gravest threats come from habitat destruction for agriculture, mining and logging, and hunting for bushmeat.

Conservation Efforts
The Milne-Edwards’s sifaka is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES). Approximately half the total population is thought to be within the protected area of Ranomafana National Park, although action is needed to protect the individuals outside of this area. Scientists recommend extending the reach of Ranomafana National Park to include unprotected populations, as well as the establishment of wildlife corridors to connect fragmented forest. More research is still needed into population size and trends.

References:

  • Gerber, B. D., Arrigo-Nelson, S., Karpanty, S. M., Kotschwar, M., & Wright, P. C. (2012). Spatial ecology of the endangered Milne-Edwards’ Sifaka (Propithecus edwardsi): Do logging and season affect home range and daily ranging patterns?. International Journal of Primatology33(2), 305-321.
  • King, S. J., Morelli, T. L., Arrigo‐Nelson, S., Ratelolahy, F. J., Godfrey, L. R., Wyatt, J., … & Wright, P. C. (2011). Morphometrics and pattern of growth in wild sifakas (Propithecus edwardsi) at Ranomafana National Park, Madagascar. American Journal of Primatology73(2), 155-172.
  • Kotschwar, M. W. (2010). Variation in predator communities and anti-predator behaviors of Milne-Edwards’ sifakas (Propithecus edwardsi) in southeastern Madagascar (Doctoral dissertation, Virginia Tech).
  • Meyers, D. M., & Wright, P. C. (1993). Resource tracking: food availability and Propithecus seasonal reproduction. In Lemur social systems and their ecological basis (pp. 179-192). Springer, Boston, MA.
  • Patel, E. (2012). Acoustic and olfactory communication in eastern sifakas (Propithecus sp.) and rhesus macaques (Macaca mullata). PhD Thesis, Cornell University.
  • Pochron, S. T., Tucker, W. T., & Wright, P. C. (2004). Demography, life history, and social structure in Propithecus diadema edwardsi from 1986–2000 in Ranomafana National Park, Madagascar. American Journal of Physical Anthropology: The Official Publication of the American Association of Physical Anthropologists125(1), 61-72.
  • Pochron, S. T., Morelli, T. L., Scirbona, J., & Wright, P. C. (2005). Sex differences in scent marking in Propithecus edwardsi of Ranomafana National Park, Madagascar. American Journal of Primatology: Official Journal of the American Society of Primatologists66(2), 97-110.
  • Pochron, S. T., Morelli, T. L., Terranova, P., Scirbona, J., Cohen, J., Kunapareddy, G., … & Wright, P. C. (2005). Patterns of male scent‐marking in Propithecus edwardsi of Ranomafana National Park, Madagascar. American Journal of Primatology: Official Journal of the American Society of Primatologists65(2), 103-115.
  • ​Wright, P., Morelli, T. L., King, S., & Pochron, S. (2009). The rules of disengagement: takeovers, infanticide, and dispersal in a rainforest lemur, Propithecus edwardsi. Behaviour146(4-5), 499-523.
  •  Alltheworldsprimates.org
  • https://www.iucnredlist.org/species/18359/16116270

Written by Jennifer Botting, PhD, February 2020