Sifakas are diurnal and spend almost all of their time in the trees (2). The majority of behavioural studies of this species have been carried out on Milne-Edward's sifaka and these are thought to be broadly similar for the 3 other subspecies (2). These sifakas occur in multi-male, multi-female groups of between 3 and 8 individuals (4), who occupy large, exclusive territories that are depicted by scent-markings at the boundaries. Births for Milne-Edward's sifaka occur in May and July although those for other subspecies may take place later in the year (4). A female will give birth to a single offspring every couple of years; the infant initially clings to its mothers belly before transferring to her back after a month (4). Sexual maturity is reached at 4 to 5 years of age and, whilst males disperse, females remain within their natal group and are the dominant sex in the group (4). Sifakas move through the trees by vertical clinging and leaping (2). Feeding takes place at all levels of the canopy, predominately on leaves, although fruit, young shoots and flowers may also be eaten in season (2). Individuals may alight on the ground to search for fallen fruit and to engage in play-fighting, some sifakas have also been seen to eat soil, possibly in an effort to rid themselves of toxins (4).

The diademed sifaka is one of the largest lemurs, with a lustrous, silky coat. These lemurs have long powerful legs and grasping hands and feet, which allow them to leap from one vertical trunk to another in their arboreal habitat. The species is currently thought to be composed of 4 distinct subspecies, each of which is very different in appearance (4). The diademed sifaka (Propithecus diadema diadema) from which the species name is derived is one of the most attractive and largest of the sifakas. The coat is white on the head with a dark crown; the rest of the body varies in shades of grey except for the rich golden-orange of the arms and legs, and the hands, feet and face, which are black (4). Perrier's sifaka (P. d. perrieri) in contrast, is the smallest of the 4 subspecies and the dense coat is completely black (4). Milne-Edward's sifaka (P. d. edwardsi) has soft chocolate-brown fur with a creamy-white saddle on the lower back, and piercing orange-red eyes, which stand out against the dark face (4). The long, sleek, creamy-white coat of the silky sifaka (P. d. candidus) is also striking; the face is usually black and the eyes orange-red, although some individuals lack dark pigment giving their skin a pink tinge (4).

This species occurs throughout eastern Madagascar from about the Mangoro and Onive Rivers north to the Mananara Nord River. Its occurrence between Antainambalana River near Maroantsetra and Mananara Nord River, as reported by earlier authors (e.g., Petter et al. 1977) has not been confirmed in recent years. At the southern limit of its range there seems to be a clinal gradient between P. diadema and P. edwardsi (Andriaholinirina and Rabarivola 2004). Ranges from 200-1,625 m.

Propithecus diadema, like all lemurs, occurs only in Madagascar. Although all sifakas occur on the eastern side of the island, each of the four described subspecies has a distinct range (Garbutt, 1999).

Biogeographic Regions: ethiopian (Native )

Other Geographic Terms: island endemic

The diademed sifaka is found in eastern Madagascar, in a range that extends from the Mananara River in the south to the northern tip of the island (3). Within this area the 4 subspecies appear to occupy non-overlapping ranges with Milne-Edwards sifaka in the south and Perrier's sifaka in the north; occupying the most restricted area (4). P. d. diadema has the largest range of the four, situated between Milne-Edward's sifaka and the silky sifaka (4).

Members of the genus Propithecus reach lengths between 450 and 550 mm, with the tail adding an additional 432 to 560 mm. Propithecus diadema weighs between 5 and 7 kg.

Each subspecies is phenotypically unique. Propithecus diadema diadema is often reported to be the largest extant lemur. These animals have a white head, grey shoulders, tail, and back, and golden limbs. Propithecus diadema edwardsi is almost completely grey/black, with a white back. Propithecus diadema candidus has almost completely white pelage with tints of grey. Propithecus diadema perrieri is completely black. All subspecies have dark naked faces and red-orange eyes.

The only other animals with which these animals might be confused are indris. However, sifakas have a very long tail, which distinguishes them from short-tailed indris.

Range mass: 5 to 7 kg.

Range length: 450 to 550 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Habitat and Ecology

Systems

• Terrestrial

Sifakas generally inhabit mid-altitude rainforests. These animals mainly occur at elevations above 800 meters. The range of P. diadema candidus extends into montane rainforest. Rainfall in sifaka habitat is variable, from 2000 to 4000 mm per year, with most rainfall occurring during the summer months (December through March) (Wright, 1995; Garbutt, 1999).

Range elevation: 800 (low) m.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: rainforest ; mountains

Predominantly inhabits primary and montane rainforest, although Perrier's sifaka is also found in dry-deciduous forest (4).

Propithecus diadema is herbivorous, eating only leaves, flowers, fruits, and young shoots. Approximately 25 species of plants are consumed in each of the two subspecies that have been studied (P. diadema edwardsi and P. diadema diadema). Propithecus diadema edwardsi has also been seen eating soil, possibly to detoxify plant poisons or to supplement their diet with trace elements (Garbutt, 1999).

Plant Foods: leaves; fruit; flowers

Primary Diet: herbivore (Folivore , Frugivore )

As frugivores, these animals probably help to disperse seeds. As potential prey items, they may impact predator populations.

Ecosystem Impact: disperses seeds

Individuals of all ages and both sexes are subject to predation. No documented cases of predation by reptiles or raptors exist, but suspected avian predators include Madagascar harrier-hawks and Henst's goshawks. The main predators of P. diadema are probably fossas, an ambush predator that takes advantage of any opportunities available.

Two alarm vocalizations are given in response to predators. The ground predator call is a "tzisk-tzisk-tzisk", and the aerial predator call is a "honk-honk-honk" (Wright, 1988, 1995; Garbutt, 1999; Mittermeier, 1994).

Known Predators:

• Cryptoprocta ferox
• Polyboroides radiatus
• Accipiter henstii

As in all primate species, communication is rich and varied. Vocalizations are used mainly in maintaining group cohesion. Two alarm vocalizations are given in response to predators. The ground predator call is a "tzisk-tzisk-tzisk", and the aerial predator call is a "honk-honk-honk" (Wright, 1988, 1995; Garbutt, 1999; Mittermeier, 1994).

Scent marking is common, and males scent mark twice as often as females. Scent marking frequency doubles when approaching the territorial boundaries (Wright, 1988, 1995; Garbutt, 1999; Mittermeier, 1994).

In addition to vocal and chemical communication, these animals use tactile communication, in the form of grooming, play, and aggression. Tactile communication is likely to be of high importance between mothers and their offspring, as well as between mates.

Although not specifically reported for these animals, we may assume that, like other diurnal primates, they use visual signals in their communication also. These include but are not limited to facial expressions and body postures (Nowak, 1999).

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

The longevity of this species has not been reported. However, an individual of another species in the genus, Propithecus verreauxi, is reported to have lived beyon 23 years on captivity (Nowak, 1999). It is likely that P. diadema is capable of reaching similar ages.

Observations: Not much is known about the longevity of these animals. In the wild, they have been shown to live up to 21 years with no signs of reproductive senescence except for a slight increase in mortality with age (Pochron et al. 2004). Dental senescence has also been described in animals with more than 18 years of age. Considering the longevity of similar species, it has been estimated that they may live more than 27 years in the wild (King et al. 2005), which is possible but awaits confirmation.

Our current understanding of the mating system of this species is limited. Mating occurs between resident males and resident females, with no recorded cases of invading males successfully copulating. There is a hierarchy system for mating, and it seems that only the dominant male copulates with the females. Submissive males may show aggression and attempt to keep the dominant male from mating.

Mating System: polygynous

The best data on reproduction exists for P. diadema edwardsi, but data for other subspecies suggest that they are similar. Copulations occur in summer, in the months of December and January. Gestation period is around 180 days (approximately six months). Females give birth to one or two offspring in the winter months (May, June, July).

Offspring are carried by their mother. The young may nurse up to the age of 2, although by this time, mother's milk does not provide them with a substantial amount of their nutrition. Sexual maturity is reached at four years for females and five years for males. Birth rates are approximately 0.5 offspring per female per year (Wright, 1995; Garbutt, 1999).

Breeding interval: Females are able to produce offspring every two years.

Breeding season: Copulations occur in summer, in the months of December and January

Range number of offspring: 1 to 2.

Average gestation period: 180 days.

Range weaning age: 24 (high) months.

Average age at sexual or reproductive maturity (female): 4 years.

Average age at sexual or reproductive maturity (male): 5 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 145 g.

Average gestation period: 157 days.

Average number of offspring: 1.

Average age at sexual or reproductive maturity (male)

Sex: male: 913 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 1186 days.

Offspring initially cling to the mother's belly, switching to her back at around one month of age. Nursing begins to decrease from the age of two months, although the process of weaning is protracted. At six months of age, less than half of the offspring's diet consists of the mother's milk. At one year of age, suckling during the day ceases. Suckling during the night, however, may continue until the infant is two years old.

In addition to food, the mother provides her young with protection, grooming, and socialization.

The role of males in parental care has not been described.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female); extended period of juvenile learning

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 2000
  Critically Endangered
• 1996
  Endangered
• 1990
  Endangered
  (IUCN 1990)

Both P. diadema candidus and P. diadema perrieri are given IUCN critically endangered status. All subspecies are threatened by habitat destruction. This occurs mainly in the form of slash-and-burn agriculture, but also as timber extraction. Most are also hunted for food, even in protected areas. All subspecies occur in at least one protected area.

In response to these threats, several reserves have been established within the last few decades. Also, campaigns to educate locals and find better methods of agriculture have been persued (Wright, 1992; Mittermeier, 1994; Garbutt, 1999).

US Federal List: endangered

CITES: appendix i

IUCN Red List of Threatened Species: endangered

Classified as Critically Endangered (CR - A2cd, B1+2c) on the IUCN Red List 2002 (1), and listed on Appendix I of CITES (6).  Subspecies: Diademed sifaka (Propithecus diadema diadema) classified as Critically Endangered (CR - A1cd); Milne-Edwards's sifaka (P. d. edwardsi) classified as Endangered (EN - A1c); silky sifaka (P. d. candidus) classified as Critically Endangered (CR - A2cd, B1+2bc); Perrier's sifaka (P. d. perrieri) classified as Critically Endangered (CR - A2cd, B1+2c) (1).

Population

Population Trend

Major Threats

Habitat destruction is the major cause of the decline of the diademed sifaka. Primary forests are being cleared to make way for agriculture, for the extraction of timber and for charcoal production (4). Some subspecies may also be hunted for food in parts of their range and deliberate fires further encroach on what is an already highly- fragmented habitat (4). Perrier's sifaka is the most endangered of the diademed sifakas, and possibly the most endangered of all the lemurs; estimates in 1998 put the population at around 2,000 individuals with none in captivity (5).

Conservation Actions

All of the diademed sifaka subspecies occur in a least one protected range; P. d. diadema has been confirmed from at least 5, whilst Perrier's sifaka is thought to be found only within the Analamera Special Reserve (4). Further research and protection is needed if these appealing and interesting primates are to be saved from extinction.

There is no known negative economic effect of this species on humans.

The existence of this rare and endemic species, as well as the rest of Madagascar's unique flora and fauna, has stimulated a large amount of ecotourism for the area. This, along with the establishment of several reserves in Madagascar's remaining forests, has helped to bolster the economy of a severely depressed nation (Wright, 1992).

Positive Impacts: ecotourism