Diademed Sifaka, Propithecus diadema
DIADEMED SIFAKA
Propithecus diadema
Geographic Distribution and Habitat
Diademed sifakas naturally occur along the northeastern coast of Madagascar. The Onive River is a geographical barrier and limits the sifaka’s range in the south. The diademed sifakas are thought to be the most widely distributed sifaka species. However, this does not necessarily mean that there are a lot of diademed sifakas in the wild, but that they have been seen (at one time) throughout their range in Madagascar. As a result, scientists are not sure where their northern limit is. Currently, habitat loss could be the main factor that prevents sifakas from being found in the northernmost part of the country.
The classification of diademed sifakas is a complex and disputed topic. There are two schools of thought regarding this matter. The first believes that there is a group of “diadem” sifakas consisting of four distinct species, while the second argues that there are four subspecies of diademed sifakas. These sifakas are also known as “eastern sifakas” and are allopatric. This means that they are separated geographically and usually do not come into contact with each other. They can be visually distinguished by their different coat colors and patterns. However, when habitats become fragmented, these allopatric sifakas can overlap. In the wild, diadem sifakas and Milne-Edwards sifakas have hybridized, creating offspring from the two species or subspecies that have mated.
Size, Weight, and Lifespan
Diademed sifakas are an exception to the general rule that female sifakas are larger. Both males and females of this species weigh about the same, ranging between 11 to 13 pounds (5-6 kg). Their head-to-body length measures between 19.7 to 21 inches (50-53 cm), while their tails are relatively shorter, measuring 17.7 to 19 inches (45-48 cm).
Based on the lifespan of closely related species, diademed sifakas have an approximate lifespan of 27 years.
Appearance
Diademed sifakas are considered one of the most striking sifakas with their patchwork of rusty-brown, black, gray, and white fur. They are one of the larger sifakas with noticeably longer and silkier fur all over their body. Dark gray fur covers the back of their head and nape, becoming a gray-silver color along the upper back and shoulders. The silver fur fades to a rusty brown on their lower back and white on the back of their thighs and hind quarters. Their face is dark gray which looks naked, but is covered in fine fur. In contrast to the darker parts of their head and back, their forehead, cheeks, and throat are covered with white fur. They are called “diademed” (diadem meaning crown) because the dark patch on their head and contrasting white fur on their face make it look like they are wearing a crown. Researchers have recorded a melanistic diademed sifaka, a genetic mutation where excess melanin is produced, resulting in a sifaka covered in completely dark brown fur.
Diademed sifakas have strong legs, long arms, and naked hands and feet. Their large eyes face forward and are reddish-brown. Their tails are shorter than their bodies, unlike other sifakas.
Diademed males and females look similar and can be difficult to distinguish. However, male sifakas have a chest gland that gives their fur a reddish-brown stain, which females do not have. The amount of secretions produced by the gland increases with age and dominance, meaning that the size of the chest stain can be used to identify the more dominant male.
Diet
They are referred to as frugo-folivores because they eat mostly leaves, but supplement their diet with fruits when possible. Leaves can be protein-rich but they are generally low in sugars which is why folivores have to eat a lot of leaves to obtain enough energy for their daily activities. Sifakas have specialized teeth and digestive systems to help them chew and process these high-fiber foods. Their digestive tract is about 14 times the length of their body! The long intestines allow chewed leaves to spend more time in the gut with digestive enzymes so that the system can extract the maximum amount of nutrients from the leaves. The intestinal tract is coiled in their body, which makes sifakas sensitive to changes in their diet.
In the wild, they show a preference for fruits and flowers. Researchers discovered that diademed sifakas use their sense of smell to forage for seasonal flowers that grow under the leaf litter. The flowers have a strong smell that attracts the sifakas, who then proceed to smell and investigate the forest floor (which is not normal behavior for primates that forage leaves from trees) until they find and eat the flowers.
Primatologists often refer to seasonal scarcity of preferred food (e.g. non-fruiting or dry season) as the “lean season” when sifakas have to rely on more abundant, lower-energy foods, such as leaves. During the lean season, diademed sifakas rely on a species of mistletoe (a partially parasitic plant) that bears fruits in low rain conditions. However, mistletoes are not evenly distributed in the forest and can be difficult to find, which makes them an unreliable food source. Fruits and flowers, in general, are not as abundant as leaves, and sifaka’s adaptations to digest leaves allow them to get enough nutrition to thrive in their environment.
Behavior and Lifestyle
Sifakas are famously called “dancing lemurs” because of their unique way of skip-hopping on the ground. They hold out their arms for balance and bounce and hop forward on their long hind legs. Otherwise, sifakas are mostly arboreal (tree-dwelling). These large sifakas are quite athletic and graceful as they leap through the forest. They move about the canopy by clinging vertically to trees and leaping from one tree to another, sometimes as fast as 18 miles per hour (30 km/hr).
They are diurnal, or mostly active during the day, which is when they forage for food. They spend their nights huddled together high in the trees, which gives them some protection from their main nocturnal predator, the fossa.
They are territorial and will defend their resources from immigrating males or troops by emitting loud calls and showing aggressive behaviors.
Diademed sifakas are considered by some to be the prettiest of the sifakas because of the colorful coat which is a patchwork of white, rusty browns, black, and silver.
They have keen senses of smell which they use to root out flowers that grow under the leaf litter.
They have a unique vocabulary of vocal sounds, including a “Zzuss” sneeze-like sound that warns others when a fossa is nearby.
Diademed sifakas cover long distances while they search for food, typically ranging from 0.3-0.6 miles (500-1000 m) per day. During the wetter seasons, when fruits are more plentiful, the sifakas tend to travel greater distances in search of their preferred fruits. In contrast, during the drier months, they rely more on leaves which are more readily available in a smaller area, thereby reducing the need to travel long distances to find adequate food. Sifakas can maintain large home ranges of 81-197 acres (33-80 hectares), but in fragmented habitats, they are forced to restrict their movements to smaller areas.
Sifakas feed during the early hours of the day and spend the afternoons resting or sleeping. This conserves energy during the hottest part of the day and gives their body the time to process the difficult-to-digest leaves.
They live in female-dominant groups of 2 to 9 individuals, consisting of multiple males and females. The groups are dominated by females, who have access to the best food options before males. Female sifakas also tend to win the most aggressive interactions with males. When the group travels from one food patch to another, females lead the group.
Interactions within the troop are usually peaceful and the dominance hierarchy within the group tends to be stable with older females being the most dominant. However, when two groups encounter each other, the interactions are vocal and aggressive and the larger troop usually drives off the smaller one.
Diademed sifakas are an expressive species and use different vocalizations to communicate with one another. These calls can trigger specific behavioral responses in other individuals of the same species. The name “sifaka” originates from their most common vocalization, which is a rapid “Shee-fauk” sound. Apart from this, diademed sifakas make several unique calls, including the open-mouthed, medium-pitched “lost call” and the high-pitched “chatter-squeal.”
When sifakas spot an aerial or flying predator, such as an eagle, they emit a specialized loud “roar” that triggers members of the troop to hide in the lower tree canopy. Ground predators, such as the fossae, cause sifakas to give a “kiss-sneeze” (or “Zzuss”) type alarm call that warns troop members to be on high alert and choose higher escape routes and even higher sleeping sites on days when ground predators have been spotted frequently.
Smell, or olfaction, is an important means of communication for sifakas. Like other lemuriformes, sifakas’ noses remain visibly wet all the time. The moisture keeps their noses humid and sensitive which helps them pick up traces of smells in their environment. Sifakas have scent glands on different parts of their body which they rub against branches and trunks of trees. Additionally, they also use urine to mark trees. Sifakas’ scent glands and urine contain a complex combination of microbes (e.g. bacteria) and hormones that provide information about the identity of the individual (are they an adult, male, or female) and information about their health (a healthy individual would be large and capable of making a lot of strong-smelling secretions). Scent marking is often used to communicate territorial boundaries, whether females are ready to mate, or the presence of a troop. So, when sifakas mark trees, it is like they leave a sticky note for other sifakas to read and decide whether they want to hang around, mate, or leave.
Both male and female sifakas have anogenital glands under their tail, near their reproductive organs. Only males have a sternal gland on their chest which stains the chests of males. During mating season, females mark more often with their anogenital gland which has more secretions related to reproduction, and males mark more with their chest glands.
Sifakas tend to live in multimale-multifemale troops with females being the most dominant and males forming a dominance hierarchy only among other males. However, their social organization is dependent on the availability of food, the quality of their habitat, and the general population numbers of sifakas in the area. Some have noted that the Milne-Edwards sifaka (which belongs to the diadem group or a diademed subspecies) can live in pairs or uni-male groups. The behavior of sifaka females and males must be studied further to determine if there are any social rules followed or if their environment influences their interactions.
Sifakas have a slow reproductive rate with a female giving birth once in about 2 years. One reason for this is that sifaka reproduction is dependent on the season. Mating season usually occurs in December-January which is in the rainy season and, therefore, fruits are more available. And the young are born between May and July which overlaps with when mothers fall back on eating more protein-rich leaves.
They also take a long time to develop hormonally, which contributes to their slow reproductive rates. Sifakas take between 4-6 years to become sexually mature, but mating may occur well after that age. When sifaka females are in estrus (hormonally ready to mate), they secrete a pink-colored substance from their genitalia (reproductive organ). This pink color visually signals her readiness to mate with the males, who then start producing more testosterone. Researchers suspect that her estrus period only lasts for a day which means the window to mate and become pregnant is small. Different females in the troop may come into estrus on different days.
The gestation period (the time a female is pregnant) is about 6 months (179 days) and females give birth to one young at a time. Baby sifakas are born covered in pale cream fur and cling to their mother’s belly at first and eventually (by the third or fourth week) they will move to cling onto their mother’s back. Development from infant to fully independent juvenile can take a long time (1-2 years). Infants are completely dependent on their mother’s milk for nutrition and protection.
By the time the baby is six months old, they will get half of their nutrition from plants but may continue to feed on their mother’s milk when they are a year and a half old. Interestingly, sifaka teeth develop from baby teeth to adult teeth much faster than their body. Sifaka adults need strong teeth with a lot of ridges that can crush hard leaves throughout their lifetime. In young sifakas, the more plants they consume, the further they will move away from their mothers and the more independent they will become. Quick teeth development is an adaptation to help young sifakas become independent feeders quickly in an environment where soft foods are not always available.
When a sifaka is young (<2 years), the chances of being killed by a predator like a fossa are high. This infant mortality further slows the reproduction rate of the troop and so, in many cases, no new members are added to the troop for many years.
In many primates, usually the sub-adult male or female will leave the natal troop (where they were born) to form or find a new troop of their own. In diademed sifakas, there have been observations of both males and females dispersing from their natal troop and, in some cases, the sub-adults remain in the natal troop and find mates within the troop. There have not been any observations of mating between related sifakas (inbreeding) which indicates that this is an unlikely behavior. Experts suspect that the slow reproductive rate and small group size result in long gaps between new births and no overlap of related reproductive aged sifakas, which prevents inbreeding.
Island ecology depends on a careful balance of interactions between animals, plants, and nutrients. Any disruption in this balance usually has a relatively quick series of negative effects. Sifakas are an integral part of this island’s ecology and their activities have an effect on the plant, nutrient, and predator community in Madagascar.
As fruit eaters, sifakas disperse seeds on the forest floor which help with the regeneration of these valuable fruiting trees. The sifaka’s leaf consumption also helps plant species that compete with each other for sunlight for photosynthesis (the plant process of using sunlight to make sugars). In rainforests, tall trees can be dense with leaves that block out sunlight for smaller plants and trees. By eating large amounts of leaves, as the sifakas do, thin out the trees and allow sunlight to pass through the canopy. This allows shorter plants to access vital sunlight for their own growth. In this way, folivores (leaf-eaters) help maintain the complexity of plant life in a rainforest.
Sifakas are one of the largest prey available to predators in Madagascar, which makes them a valuable part of the survival and success of the predators on the island. Fossae are the largest native carnivore mammals in Madagascar and they can survive on the island because they have large food sources like sifakas and lemurs. Without sifakas as prey, it is unlikely that the island would be able to support a population of large carnivores like the fossa that specializes in hunting in the tree-canopy.
The International Union for Conservation of Nature lists diademed sifaka as Critically Endangered (IUCN, 2018), appearing on the IUCN Red List of Threatened Species. They have been given this designation because more than 80% of their population is expected to decrease over the next 45 years due to the threats outlined below. There are only about 1000-10,000 individuals left in the wild.
The main threat to sifakas is the rapid habitat destruction and fragmentation of rainforests. For as long as humans have inhabited Madagascar, forests have been cleared to make agricultural fields. The traditional method of slashing and burning forests deposits fertile ash on the soil that can be used to farm, but the effect is short-lived, and soon the soil becomes stripped of nutrients. When this happens farmers move on to the next forest patch to slash-and-burn. The process destroys forests and the land’s ability to regenerate. Consequently, rainforests do not exist continuously, but in patches. Animals like the sifaka have a harder time finding food and they are exposed to more human hazards such as pollution and road accidents.
Diademed sifakas adjust their diets in fragmented forests where resources are fewer. Over the years, researchers have observed that sifakas in fragmented forests tend to be smaller than the average size. So even though sifakas are capable of adjusting to fragmented and degraded habitats, the shift in diet may have negative effects on the reproduction and health of these primates with their delicate digestive system.
On a smaller and more local scale, hunting has disrupted sifaka populations as adult sifakas are the most likely to be hunted. Removing a healthy individual from the population, coupled with the sifakas’ slow development and reproduction, results in a population that cannot grow and replenish itself.
The diademed sifaka is listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. This is the highest level of international protection against trafficking the species.
Diademed sifakas are protected in Madagascar and national parks where hunting, logging, mining, and agriculture are prohibited. These are also the main ways to protect their habitat.
Many private organizations such as Madagasikara and Madagascar Fauna & Flora help protect habitats, provide resources for locals and researchers to work in local resource conservation, and educate the public on lemurs and sifakas.
There have been efforts to translocate diademed sifakas from fragmented forests to more intact habitats to increase their survival and reproductive success. When whole families or troops were translocated together to the new forest, the sifakas survived and even gave birth to infants.
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Written by Acima Cherian, February 2024