The silky sifaka (''Propithecus candidus'') is a large
lemur
Lemurs ( ) (from Latin ''lemures'' – ghosts or spirits) are wet-nosed primates of the superfamily Lemuroidea (), divided into 8 families and consisting of 15 genera and around 100 existing species. They are endemic to the island of Madagas ...
characterized by long, silky, white
fur. It has a very restricted range in northeastern
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...
, where it is known locally as the ''simpona''. It is one of the rarest mammals on Earth. The silky sifaka is one of nine
sifaka
A sifaka (; ) is a lemur of the genus ''Propithecus'' from the family Indriidae within the order Primates. The name of their family is an onomatopoeia of their characteristic "shi-fak" alarm call. Like all lemurs, they are found only on the isl ...
species (
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''Propithecus''), and one of four former
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all specie ...
of
diademed sifaka
The diademed sifaka (''Propithecus diadema''), or diademed simpona, is an endangered species of sifaka, one of the lemurs endemic to certain rainforests in eastern Madagascar. Along with the indri, this species is one of the two largest living l ...
(''P. diadema''). Studies in 2004 and 2007 compared external proportions, genetics, and craniodental anatomy supporting full species status, which has generally been accepted.
The silky sifaka has a variable social structure, and lives in groups of two to nine individuals. It spends most of its day feeding and resting, though it also devotes a considerable amount of time to social behaviors, such as playing and grooming, as well as travelling. Females occasionally take priority over males during feeding. Like other eastern sifakas, it consumes mainly leaves and seeds, but also fruit, flowers, and even soil on occasion. It is a
seasonal breeder
Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ...
and only mates one day a year during the start of the rainy season. As with other sifaka species, nonmaternal infant care is common. Group members of all ages and both sexes often groom, play with, occasionally carry, and even nurse infants that are not their own. The silky sifaka vocalizes frequently despite its moderately sized vocal repertoire consisting of seven adult calls. Like all other lemurs, it relies strongly on
scent
An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...
for communication. Males frequently
scent-mark on top of scent marks made by other group members, particularly females. Males also gouge trees with their
toothcomb
A toothcomb (also tooth comb or dental comb) is a dental structure found in some mammals, comprising a group of front teeth arranged in a manner that facilitates grooming, similar to a hair comb. The toothcomb occurs in lemuriform primates ( ...
(a special arrangement of the bottom, front teeth) prior to chest scent-marking. This chest marking results in males having brown-stained chests, the only visible trait that can be used to distinguish between adult males and adult females.
The species is only found within a few protected areas in the rainforests of northeastern Madagascar, with the majority of the remaining population in
Marojejy National Park
Marojejy National Park () is a national park in the Sava region of northeastern Madagascar. It covers and is centered on the Marojejy Massif, a mountain chain that rises to an elevation of . Access to the area around the massif was restricted t ...
and
Anjanaharibe-Sud Special Reserve. A few groups have also been found in the
Makira Forest Protected Area, the Betaolana Corridor, and some unprotected forest fragments. The silky sifaka is hunted throughout its range as no local ''
fady'' (taboo) exists against eating this species. Habitat disturbance, such as
slash-and-burn agriculture
Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden. The method begins by cutting down the trees and woody plants in an area. The downed veget ...
(''tavy''),
illegal logging of precious woods (particularly
rosewood
Rosewood refers to any of a number of richly hued timbers, often brownish with darker veining, but found in many different hues.
True rosewoods
All genuine rosewoods belong to the genus ''Dalbergia''. The pre-eminent rosewood appreciated ...
) and fuel-wood, also occurs within the protected areas where it is found.
Etymology
The name "sifaka" is a reference to a common general alarm
vocalization given by western dry forest sifakas in which they emit an explosive, hiss-like "shee-faak" call several times in succession. On the east coast, local residents refer to the larger-bodied
diademed sifaka
The diademed sifaka (''Propithecus diadema''), or diademed simpona, is an endangered species of sifaka, one of the lemurs endemic to certain rainforests in eastern Madagascar. Along with the indri, this species is one of the two largest living l ...
as ''simpona'', a name which refers to the species' sneeze-like "zzuss" alarm vocalizations. The calls are emitted in a variety of stressful circumstances such as presence of humans, falling trees, terrestrial predators, and after aggression between group members. The
specific name, ''candidus'', is Latin for "white", while the specific name of the
taxonomic synonym
The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently.
* In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Lin ...
''sericeus'' is derived from the Greek word for "silk".
Taxonomy
The silky sifaka was initially described in 1871 by French naturalist
Alfred Grandidier
Alfred Grandidier (20 December 1836 – 13 September 1921) was a French naturalist and explorer.
From a very wealthy family, at the age of 20, he and his brother, Ernest Grandidier (1833–1912), undertook a voyage around the world. At first ...
in a formally published letter to French zoologist
Alphonse Milne-Edwards
Alphonse Milne-Edwards (Paris, 13 October 1835 – Paris, 21 April 1900) was a French mammalogist, ornithologist, and carcinologist. He was English in origin, the son of Henri Milne-Edwards and grandson of Bryan Edwards, a Jamaican planter who se ...
. Grandidier's description was based on his own observations north of
Antongil Bay
''Helodranon' Antongila'' (Bay of Antongila), more commonly called Antongil Bay in English, is the largest bay in Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no ...
in the last few months of 1870. He then named the species ''Propithecus candidus'' due to its white color, which he likened to that of
Verreaux's sifaka
Verreaux's sifaka (''Propithecus verreauxi''), or the white sifaka, is a medium-sized primate in one of the lemur families, the Indriidae. It lives in Madagascar and can be found in a variety of habitats from rainforest to dry deciduous forest ...
(''Propithecus verreauxi''), but without the dark fur on its head or the ash-colored spot on the back. The first specimen was obtained in 1872 and provided by a "Monsieur Guinet", a planter from
Sambava
Sambava is a city and commune (commune urbaine; mg, kaominina) at the east coast of northern Madagascar. It is the capital of Sambava District and Sava Region. The population of the commune was 84,039 in as of the 2018 commune census.
Infrast ...
. The specimen allowed both Grandidier and Milne-Edwards to more thoroughly describe the species based on its skin,
coat
A coat typically is an outer garment for the upper body as worn by either gender for warmth or fashion. Coats typically have long sleeves and are open down the front and closing by means of buttons, zippers, hook-and-loop fasteners, toggles, ...
, and skull. Upon those findings, they changed the name to ''P. sericeus.'' Upon further review in 1875, Grandidier demoted the silky sifaka to a variety or "race" of the diademed sifaka. By the time German zoologist
Ernst Schwarz standardized
lemur taxonomy in 1931, ''P. sericeus'' had become a taxonomic synonym for the species, with the original name, ''Propithecus candidus'', taking
priority.
![Pd candidus AGrandidier](https://upload.wikimedia.org/wikipedia/commons/9/96/Pd_candidus_AGrandidier.jpg)
Schwarz placed all sifakas into two species, the larger diademed sifaka from the
eastern rainforests and the smaller Verreaux's sifaka from the
dry forests
The tropical and subtropical dry broadleaf forest is a habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive ...
and
spiny forests of the west and south. At the time, both species comprised four
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all specie ...
, and the silky sifaka was listed as ''P. diadema candidus'', a subspecies of the diademed sifaka. In his 1982 book ''
Primates of Madagascar'', anthropologist
Ian Tattersall
Ian Tattersall (born 1945) is a British-born American paleoanthropologist and a curator emeritus with the American Museum of Natural History in New York City, New York. In addition to human evolution, Tattersall has worked extensively with lemur ...
upheld this classification. When anthropologist
Colin Groves
Colin Peter Groves (24 June 1942 – 30 November 2017) was a British-Australian biologist and anthropologist. Groves was Professor of Biological Anthropology at the Australian National University in Canberra, Australia.
Education
Born in Englan ...
reviewed the taxonomy in his book ''
Primate Taxonomy
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including human ...
'' in 2001, he also upheld the subspecies status of the silky sifaka because variations in fur coloration between the available specimens suggested converging similarities with the diademed sifaka's coloration. Groves later noted that the coloration of the two species did not overlap, suggesting that the populations were distinct.
In 2004,
Mayor
In many countries, a mayor is the highest-ranking official in a municipal government such as that of a city or a town. Worldwide, there is a wide variance in local laws and customs regarding the powers and responsibilities of a mayor as well ...
''et al.'' showed that despite having a similar
karyotype
A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...
(the number and appearance of
chromosome
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins ar ...
s) of 42 chromosomes (2n=42), the silky sifaka was distinct from the diademed sifaka. This was shown through genetic tests (
D-loop
In molecular biology, a displacement loop or D-loop is a DNA structure where the two strands of a double-stranded DNA molecule are separated for a stretch and held apart by a third strand of DNA. An R-loop is similar to a D-loop, but in this ca ...
sequencing) and by comparing external proportions. For example, the silky sifaka has a shorter tail. Their analysis indicated a closer relationship with
Perrier's sifaka (''Propithecus perrieri'').
Russell Mittermeier
Russell Alan Mittermeier (born November 8, 1949) is a primatologist and herpetologist. He has written several books for both popular and scientist audiences, and has authored more than 300 scientific papers.
Biography
Russell A. Mittermeier is ...
and colleagues followed by adopting the full species status of the silky sifaka for the second edition of ''
Lemurs of Madagascar'' in 2006. Although Groves maintained the silky sifaka as a subspecies in the 3rd edition of ''
Mammal Species of the World
''Mammal Species of the World: A Taxonomic and Geographic Reference'' is a standard reference work in mammalogy giving descriptions and bibliographic data for the known species of mammals. It is now in its third edition, published in late 2005, ...
'' in 2005, he recognized it as a distinct species in 2007 by acknowledging the work of Mayor ''et al.'' and also noting the additional distinction that the silky sifaka has relatively long
molar teeth
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone ...
compared to the length of its toothrow. Despite the promotion to full species status, the silky sifaka is still considered to be a member of the ''P. diadema'' group of four closely related, large-bodied, eastern-rainforest sifakas. The other three members of this group are the diademed sifaka, Perrier's sifaka, and
Milne-Edwards' sifaka
Milne-Edwards's sifaka (''Propithecus edwardsi''), or Milne-Edwards's simpona, is a large arboreal, diurnal lemur endemic to the eastern coastal rainforest of Madagascar. Milne-Edwards's sifaka is characterized by a black body with a light-colo ...
(''Propithecus edwardsi''). The species status of the silky sifaka, as well as other sifakas, does not have universal support: in 2007, Tattersall argued against species distinctions within ''Propithecus'', claiming the decisions were made prematurely.
In 1974, Tattersall spotted what he thought was a color variant of the silky sifaka north of
Vohemar
Vohemar ( mg, Vohimarina or ''Iharan̈a'' ) is a coastal city and commune ( mg, firaisana) in northern Madagascar. It belongs to the Districts of Madagascar, district of Vohemar District, Iharana, which is a part of Sava Region. The population ...
in northeast Madagascar. Describing it as such eight years later in ''The Primates of Madagascar'', he not only cited its mostly white fur, but also uncharacteristic traits such as a patch of orange on its crown and tufted ears. It was not observed again until 1986, when a team led by paleoanthropologist
Elwyn L. Simons captured specimens for
captive breeding and identified it as a new species, named as the
golden-crowned sifaka
The golden-crowned sifaka or Tattersall's sifaka (''Propithecus tattersalli'') is a medium-sized lemur characterized by mostly white fur, prominent furry ears, and a golden-orange crown. It is one of the smallest sifakas (genus ''Propithecus'') ...
(''Propithecus tattersalli'') in 1988.
Geographic range and habitat
The silky sifaka is confined to a small region of northeastern Madagascar within a strip of humid forest stretching from
Maroantsetra
Maroantsetra , formerly Louisbourg, is a market town and domestic seaport in Analanjirofo Region, Madagascar, at the northern end of the Bay of Antongil. In 2005 it had a population of 42,529 people.
History
Maurice Benyovszky arrived in Maroant ...
in the south to the
Andapa Basin and the
Marojejy Massif in the north.
Marojejy National Park
Marojejy National Park () is a national park in the Sava region of northeastern Madagascar. It covers and is centered on the Marojejy Massif, a mountain chain that rises to an elevation of . Access to the area around the massif was restricted t ...
represents the northern limit of its current distribution, although historical sifaka range maps created by Grandidier and Milne-Edwards in the late 19th century show the silky sifaka as far north as the
Bemarivo River, north of
Sambava
Sambava is a city and commune (commune urbaine; mg, kaominina) at the east coast of northern Madagascar. It is the capital of Sambava District and Sava Region. The population of the commune was 84,039 in as of the 2018 commune census.
Infrast ...
. The
Androranga River may represent the northwestern range limit within the
Tsaratanana Corridor. The southern limit of its range appears to be the
Antainambalana River
''Antainambalana'' (Also known as Antainambalan on some maps) is a river in the region of Analanjirofo in north-eastern Madagascar. It flows down from the highlands to flow into the Bay of Antongil and the Indian Ocean near Maroantsetra.
History
...
, within the
Makira Conservation Site. It is not known if the silky sifaka has ever ranged as far south as the
Masoala Peninsula. As of 2009, new observations of a few groups of the silky sifaka in unprotected forest fragments adjacent to northeastern Makira (
Antohaka Lava and
Maherivaratra) may slightly enlarge the known geographic range of this species. The presence of the silky sifaka has been documented within Marojejy National Park,
Anjanaharibe-Sud Special Reserve, the
Makira Forest Protected Area, the
Betaolana Corridor, and the Tsaratanana Corridor. In 2008, 16 groups were discovered in western Marojejy near Antsahaberoaka.
The silky sifaka tends to be found at higher elevations than any of the other sifaka species and also occupies the greatest range of elevations for the group. In Marojejy National Park and Anjanaharibe-Sud Special Reserve, where most of the remaining groups exist, it is not found below of elevation and not above . However, at its southernmost location in Makira (Andaparaty), several groups inhabit forest fragments at an unusually low elevation of . The silky sifaka inhabits three types of elevation-specific habitats: primary
montane rainforest,
sclerophyllous forest, and the most elevated portions of low
ericoid bush. How sensitive the silky sifaka is to disturbance or whether it avoids habitat edges ("edge-intolerant") or is more edge-tolerant like the diademed sifakas is unknown. Like other rainforest sifaka species, it seldom crosses unforested regions between forest fragments.
In the Anjanaharibe-Sud Special Reserve, the silky sifaka is
shares the same geographic range as the
white-fronted brown lemur (''Eulemur albifrons'') and an all-black population of
indri
The indri (; ''Indri indri''), also called the babakoto, is one of the largest living lemurs, with a head-body length of about and a weight of between . It has a black and white coat and maintains an upright posture when climbing or clinging. ...
(''Indri indri''). In Marojejy National Park, it is sympatric with the white-fronted brown lemur. In 2008, the silky sifaka was suggested to be sympatric with the
red ruffed lemur
The red ruffed lemur (''Varecia rubra'') is one of two species in the genus ''Varecia'', the ruffed lemurs; the other is the black-and-white ruffed lemur (''Varecia variegata''). Like all lemurs, it is native to Madagascar. It occurs only in the ...
(''Varecia rubra'') near Maherivaratra and Andaparaty.
Description
The silky sifaka is one of the larger sifaka species, with a head-body length of , a tail length of , a total length of , and a weight of . As its common English name suggests, its long, white
fur has a silky texture. Not all individuals are completely white: some have silver-gray or black tints on the crown, back, and limbs. The base of the tail ("pygal region") can be yellow. The ears and face are hairless, and the skin may be a mix of pink and black, completely black, or completely pink. The tips of the ears protrude slightly above the fur on the rest of the head. Its eyes have a deep orange-red coloration. Its appearance is distinctive, and since no other sifakas share its range, it is not easily confused with other lemur species.
While it is difficult to distinguish adult males and females in other eastern rainforest sifakas, such as Perrier's sifaka and Milne-Edwards' sifaka, gender in the silky sifaka is easily discerned due to differences in fur coloration of the upper chest. Females have white fur, while males have a large brown patch of fur that results from
scent marking
In ethology, territory is the sociographical area that an animal consistently defends against conspecific competition (or, occasionally, against animals of other species) using agonistic behaviors or (less commonly) real physical aggression. ...
with a gland on the chest and throat (the sternal gular gland). During mating season, the size of the "chest patch" increases to cover both the chest and abdomen as a result of increased scent marking.
Behavior
Until the 21st century, brief observations and lemur surveys had merely documented the presence of the silky sifaka in special reserves and national parks. More recently, a 14-month study and two short-term studies in Marojejy National Park have revealed previously unknown details about its behavioral biology, communication, and feeding ecology. The silky sifaka has a variable social structure and is known to live in
male-female pairs,
one-male groups, and
multiple-male/multiple-female groups. Group sizes range from two to nine individuals, while the
home range
A home range is the area in which an animal lives and moves on a periodic basis. It is related to the concept of an animal's territory which is the area that is actively defended. The concept of a home range was introduced by W. H. Burt in 1943. He ...
s are estimated to range from , varying in size by location.
![Silky sifaka Allocare](https://upload.wikimedia.org/wikipedia/commons/d/d1/Silky_sifaka_Allocare.JPG)
According to some studies, the silky sifaka spends most of its day resting and feeding (about 44 and 25%, respectively). It also devotes approximately 6.8% of the day to social behavior, such as
personal grooming
Grooming (also called preening) is the art and practice of cleaning and maintaining parts of the body. It is a species-typical behavior.
In animals
Individual animals regularly clean themselves and put their fur, feathers or other skin cov ...
,
social grooming (allogrooming), and play. The rest of the day is spent traveling and sleeping. Other sources report that the species divides half of the day between traveling and foraging, while the rest is spent resting. Daily foraging usually starts at dawn unless delayed by rain. Group movement is usually led by females, and groups usually travel per day, and may climb along vertical slopes. Although the species spends its time in the trees, terrestrial play is not uncommon, even among adults, with play sessions lasting 30 minutes or more. Like other sifakas, it uses a type of
arboreal locomotion known as
vertical clinging and leaping Vertical clinging and leaping (VCL) is a type of arboreal locomotion seen most commonly among the strepsirrhine primates and haplorrhine tarsiers. The animal begins at rest with its torso upright and elbows fixed, with both hands clinging to a v ...
.
Dominance hierarchies have not been documented among female sifakas, including the silky sifaka, although seasonal hierarchies are known to occur.
Aggression, which is generally infrequent, occurs primarily during feeding, where females take priority over males, although submissive signals are not always obvious.
The silky sifaka's diet is similar to that of other eastern rainforest sifakas, consisting primarily of leaves (
folivory
In zoology, a folivore is a herbivore that specializes in eating leaves. Mature leaves contain a high proportion of hard-to-digest cellulose, less energy than other types of foods, and often toxic compounds.Jones, S., Martin, R., & Pilbeam, D. ...
) and seeds (
seed predation
Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores (seed predators) feed on the seeds of plants as a main or exclusive food source,Hulme, P.E. and Benkman, C.W. (2002) "Granivory", pp. 13 ...
). It is highly varied and includes many plant species. A two-month study from the mid-2000s showed that the silky sifaka can feed on as many as 76 species of plant from 42
families
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideal ...
. Its favorites included primarily tree species, but also some
lianas. The most prominent plant families in the diet were
Moraceae
The Moraceae — often called the mulberry family or fig family — are a family of flowering plants comprising about 38 genera and over 1100 species. Most are widespread in tropical and subtropical regions, less so in temperate climates; however ...
(20.30%),
Fabaceae (12.87%),
Myrtaceae (12.65%),
Clusiaceae
The Clusiaceae or Guttiferae Juss. (1789) (''nom. alt. et cons.'' = alternative and valid name) are a family (biology), family of plants including 13 genera and ca 750 species. Several former members of Clusiacae are now placed in Calophyllaceae ...
(10.13%) and
Apocynaceae
Apocynaceae (from ''Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison Members of ...
(9.49%). In the study, feeding upon these four plant families took up as much as 37.06% of the total feeding time for the silky sifaka: 16.09% on the fruit of ''
Pachytrophe dimepate'', 8.43% on the seeds of ''
Senna'' spp., 6.52% on the young leaves of ''
Plectaneia thouarsii'', and 6.02% on the fruit of ''
Eugenia
''Eugenia'' is a genus of flowering plants in the myrtle family Myrtaceae. It has a worldwide, although highly uneven, distribution in tropical and subtropical regions. The bulk of the approximately 1,100 species occur in the New World tropics, ...
'' spp. In sum, folivory accounted for 52% of the feeding time, while
fruit-eating accounted for 34%, and seed predation made up 11%. The consumption of flowers, as well as soil (
geophagy
Geophagia (), also known as geophagy (), is the intentional practice of eating earth or soil-like substances such as clay, chalk, or termite mounds. It is a behavioural adaptation that occurs in many non-human animals and has been documented in ...
), was rarely observed in this study. Prior to this, preliminary studies had reported that folivory accounted for 75% of the diet, while fruits and 15% was seed predation, 7% was flower consumption, and bark and soil made up the remainder.
Like all other lemurs, the silky sifaka is a
seasonal breeder
Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ...
, and are thought to
mate only one day a year during the start of the rainy season sometime in December or January. Infants are born six months later in June or July. Females typically give birth to a single infant once every two years, although births in consecutive years have been observed. Infants initially cling to the fur of their mother's chest for nearly four weeks and then switch to riding on her back. As with other eastern rainforest sifakas, the infants of this species develop rapidly. This may be due to assistance in the care of infants by all group members (known as
alloparental care)—a trait typical among all sifakas. Nonmaternal care usually takes the form of allogrooming, but also playing, occasional carrying, and in rare cases, nursing. The dispersal of offspring is thought to be similar to that of other eastern rainforest sifakas, with both males and females transferring out of the group at
sexual maturity
Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definit ...
. However, dispersal has only been observed once with a young adult male, which left his natal group and proceeded to oust an older male from a group in which he had been a member for seven years. Female dispersal and group transfer has not yet been observed.
The only documented predator of the silky sifaka, other than humans, is the
fossa, a
cat-like carnivore found only on Madagascar. Although no aerial predators are known, the silky sifaka often watches the sky and emits loud "aerial disturbance" roars at the sight of the large
Madagascar buzzard
The Madagascar buzzard (''Buteo brachypterus'') is a bird of prey which is endemic to Madagascar. It is a species from the widespread genus ''Buteo'' in the family ''Accipitridae''.
Description
The Madagascar buzzard is a typical old-world buzza ...
(''Buteo brachypterus'') and other small birds. Another, more general alarm call is the loud, sneeze-like "zzuss"
vocalization, which is emitted in response to terrestrial disturbances, calls from lost group members, and aggression by other group members. Acoustic analyses of the "zzuss" vocalization have shown that the call's
acoustic structure differs between individuals and by gender.
Adult eastern sifakas have a moderately sized vocal repertoire of about seven call types. If their vocalizations have specific or varied contexts is uncertain, and as with other primates, arousal level may play a role in the acoustic structure of its calls. Despite the limited size of the silky sifaka's vocal repertoire, it does exhibit high call rates of seven calls per hour, on average. Even infants are known to have several specialized vocalizations. The most frequently emitted silky sifaka vocalizations are low-amplitude, low-frequency, tonal "hum" and "mum" vocalizations. These contact calls are used in a variety of circumstances, including group movement, affiliation, foraging, and while resting.
The silky sifaka uses well-developed
olfactory (smell-based) communication, as with all other
strepsirrhine
Strepsirrhini or Strepsirhini (; ) is a suborder of primates that includes the lemuriform primates, which consist of the lemurs of Madagascar, galagos ("bushbabies") and pottos from Africa, and the lorises from India and southeast Asia. Colle ...
primates. Like other eastern rainforest sifakas, it has several specialized glands for
scent-marking
In ethology, territory is the sociographical area that an animal consistently defends against conspecific competition (or, occasionally, against animals of other species) using agonistic behaviors or (less commonly) real physical aggression. A ...
, including a
sebaceous gland
A sebaceous gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest nu ...
on the chest, found only in males, and mixed
apocrine
Apocrine () glands are a type of exocrine gland, which are themselves a type of gland, i.e. a group of cells specialized for the release of secretions. Exocrine glands secrete by one of three means: holocrine, merocrine and apocrine. In apocri ...
-sebaceous glands on the
genitals
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
in both sexes. Unlike the
true lemur
True lemurs, also known as brown lemurs, are the lemurs in genus ''Eulemur''. They are medium-sized primates that live exclusively on Madagascar.
The fur of the true lemurs is long and usually reddish brown. Often, sexual dimorphism in colorati ...
s of the genus ''Eulemur'', the silky sifaka does not directly scent-mark its
conspecifics
Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species.
Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organis ...
(
allomarking), although it does scent-mark its territory. Both sexes will often
urinate while scent-marking. Males and females scent-mark in different ways: females rub their genital glands in an up-and-down motion against trees, while males may use their chest gland, genital glands, or a combination of both. Males also use their specialized
toothcomb
A toothcomb (also tooth comb or dental comb) is a dental structure found in some mammals, comprising a group of front teeth arranged in a manner that facilitates grooming, similar to a hair comb. The toothcomb occurs in lemuriform primates ( ...
to gouge trees before scent-marking with their chest—a behavior that leaves long-lasting visible marks. The gouging is thought to serve a role in communication and has no dietary component, since males do not eat the bark or tree gum.
Males scent-mark more frequently than females, as much as two or three times as often. Males also respond to female scent-marking by overmarking with their own scent glands, usually by combining chest and genital marking. They also overmark other males, although less quickly and less often. In a one-year study, males responded to 71% of the marks made by females within an average of 61 seconds while only 17% of male marks received a response from other group members. Because males overmark frequently, this results in "totem-tree marking", where certain trees become covered by male scent and gouge marks. However, no observations of widespread home-range border scent-marking have been reported. Scent-marks are usually left on trees in the core area of the home range, as opposed to the territorial boundaries.
Conservation
![Hunted Silky Sifakas](https://upload.wikimedia.org/wikipedia/commons/2/26/Hunted_Silky_Sifakas.jpg)
According to the most recent IUCN Red List assessment, the silky sifaka is
critically endangered. It is one of the rarest and most critically endangered lemurs. Its population size is estimated to range between 100 and 1,000 individuals, while the number of mature individuals is thought to be less than 250. No silky sifakas are kept in captivity, such as in zoos.
The silky sifaka is the
flagship species
In conservation biology, a flagship species is a species chosen to raise support for biodiversity conservation in a given place or social context. Definitions have varied, but they have tended to focus on the strategic goals and the socio-economi ...
for the protected areas in which it is found, particularly for Marojejy, which has recently been inaugurated as part of a
World Heritage Site
A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for h ...
cluster known as the
Rainforests of the Atsinanana.
Habitat disturbance, such as
slash-and-burn agriculture
Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden. The method begins by cutting down the trees and woody plants in an area. The downed veget ...
(known locally as ''tavy''), logging of precious woods (e.g.,
rosewood
Rosewood refers to any of a number of richly hued timbers, often brownish with darker veining, but found in many different hues.
True rosewoods
All genuine rosewoods belong to the genus ''Dalbergia''. The pre-eminent rosewood appreciated ...
) and fuel-wood, also occurs within the protected areas where it is found. Unlike the
golden-crowned sifaka
The golden-crowned sifaka or Tattersall's sifaka (''Propithecus tattersalli'') is a medium-sized lemur characterized by mostly white fur, prominent furry ears, and a golden-orange crown. It is one of the smallest sifakas (genus ''Propithecus'') ...
(''Propithecus tattersalli''), there is no local taboo (''fady'') against eating this species, and the hunting of
bushmeat is a known issue within its range. It is most heavily hunted in the northern and western parts of Marojejy, as well as other areas around the Andapa Basin. The species is restricted to of protected areas, although this may be an overestimation because in much of its range the silky sifaka is not found below in altitude, possibly due to either hunting pressure or habitat preference.
Illegal logging
Illegal logging is the harvest, transportation, purchase or sale of timber in violation of laws. The harvesting procedure itself may be illegal, including using corruption, corrupt means to gain access to forests; extraction without permission, o ...
of precious hardwoods, such as rosewood and
ebony
Ebony is a dense black/brown hardwood, coming from several species in the genus '' Diospyros'', which also contains the persimmons. Unlike most woods, ebony is dense enough to sink in water. It is finely textured and has a mirror finish when ...
, has become one of the greatest threats to the silky sifaka's habitat, especially since the
2009 Malagasy political crisis
The 2009 Malagasy political crisis began on 26 January 2009 with the political opposition movement led by Antananarivo mayor Andry Rajoelina, which sought to oust President Marc Ravalomanana from the presidency. The crisis reached its climax in t ...
. Its two largest protected areas, Masoala National Park and Marojejy National Park, have been the hardest hit. The disturbance caused by selective logging increases the likelihood of forest fires, helps
invasive species take root, impairs habitat, and causes the loss of
genetic diversity.
Local villages adjacent to its remaining protected areas adopted a two-pronged strategy towards silky sifaka conservation education. First, a "cognitive component" was implemented to increase knowledge and awareness through radio interviews, slide presentations, and the disbursement of literature in twelve primary and secondary schools. Additionally, an "emotional component" was begun to link silky sifaka conservation with positive emotional experiences, with the goal of establishing a psychological connection between the children and the lemur. To do this, groups of children were taken on three-day educational
eco-tours in Marojejy National Park. Both the teachers and the students showed interest and genuine concern about the plight of the silky sifaka.
Plans are being made to both expand Anjanaharibe-Sud Special Reserve and link existing parks and reserves in the region with
wildlife corridor
A wildlife corridor, habitat corridor, or green corridor is an area of habitat connecting wildlife populations separated by human activities or structures (such as roads, development, or logging). This allows an exchange of individuals between ...
s. These corridors include the Betaolana Corridor between Marojejy and Anjananharibe-Sud and Makira, which will connect Anjananharibe-Sud with
Masoala National Park
Masoala National Park, in northeast Madagascar, is the largest of the island's protected areas. Most of the park is situated in Sava Region and a part in Analanjirofo. Created in 1997, the park protects 2,300 square kilometres of rainforest and ...
to the south. In addition to providing additional habitat for the silky sifaka, the corridors would promote genetic exchange between currently isolated populations.
References
Books cited
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External links
Lemur Conservation FoundationRecent Research ArticleTrouble in Lemur Land by Earth Touch- Documentary Film about Silky Sifakas and Rosewood Logging
Dan Rather Reports Marojejy Documentary– a professional 50 minute HD film about illegal rosewood logging in Madagascar and the impact on the silky sifaka lemur
Silky sifaka documentary on Erik Patel's research in Marojejy N.P.Carte Blanche news program featuring the silky sifaka and illegal rosewood loggingSilky sifaka expert from Madagascar receives Seacology Prize
{{Featured article
Sifakas
Endemic fauna of Madagascar
Mammals of Madagascar
Critically endangered fauna of Africa
Articles containing video clips
Mammals described in 1871
Species endangered by slash-and-burn
Species endangered by logging for timber
Species endangered by selective logging
Taxa named by Alfred Grandidier