Ruffed lemurs are diurnal and arboreal quadrupeds, often observed leaping through the upper canopy of the seasonal tropical rainforests in eastern Madagascar. They are also the most frugivorous of the Malagasy lemurs, and they are very sensitive to habitat disturbance. Ruffed lemurs live in multi-male/multi-female groups and have a complex and flexible social structure, described as fission-fusion. They are highly vocal, and have loud, raucous calls.
Ruffed lemurs are seasonal breeders and highly unusual in their reproductive strategy. They are considered an "evolutionary enigma" in that they are the largest of the extant species in Lemuridae, yet exhibit reproductive traits more common in small, nocturnal lemurs, such as short gestation periods (~102 days) and relatively large average litter sizes (~2–3). Ruffed lemurs also build nests for their newborns (the only primates that do so), carry them by mouth, and exhibit an absentee parental system by stashing them while they forage. Infants are altricial, although they develop relatively quickly, traveling independently in the wild after 70 days and attaining full adult size by six months.
Threatened by habitat loss and hunting, ruffed lemurs are facing extinction in the wild. However, they reproduce readily in captivity, and have been gradually re-introduced into the wild since 1997. Organizations that are involved in ruffed lemur conservation include the Durrell Wildlife Conservation Trust, the Lemur Conservation Foundation (LCF), the Madagascar Fauna Group (MFG), Monkeyland Primate Sanctuary in South Africa, Wildlife Trust, and the Duke Lemur Center (DLC).
Anatomy and Physiology Edit
Ruffed lemurs are the largest extant members of the family Lemuridae, with an average head-body length between 43 to 57 cm (17 to 22 in) and a total length from 100 to 120 cm (39 to 47 in), while ranging in weight from 3.1 to 4.1 kg (6.8 to 9.0 lb). The thick, furry tail is longer than the body, averaging 60 and 65 cm (24 and 26 in) in length and is used primarily for balance while moving through the trees. Ruffed lemurs exhibit neither sexual dimorphism nor sexual dichromatism, and females have three pairs of mammary glands.
Ruffed lemurs are characterized by their long, canine-like muzzle, which includes a significant overbite. The face is mostly black, with furry "ruffs" running from the ears to the neck. Depending on the species, these ruffs are either white (V. variegata) or deep reddish (V. rubra). Likewise, the coloration of the fluffy fur also varies by species, while the coloration pattern varies by subspecies in the black-and-white ruffed lemur. There are also intermediates in color variation between the two species. As with all lemurs, the ruffed lemur has special adaptations for grooming, including a toilet-claw on its second toe, and a toothcomb.
Ruffed lemurs are considered arboreal quadrupeds, with the most common type of movement being above-branch quadrupedalism. While in the canopy leaping, vertical clinging, and suspensory behavior, are also common, while bridging, bimanual movement, and bipedalism are infrequently seen. When moving from tree to tree, ruffed lemurs will look over the shoulder while clinging, launch themselves into the air, and twist mid-air so that their ventral surface lands on the new tree or limb. Suspensory behavior is more common in ruffed lemurs than in other lemur species. When ruffed lemurs come down to the ground, they continue to move quadrupedally, running with bounding hops and the tail held high.
Being highly arboreal and the most frugivorous of the lemurs, they thrive only in primary forest with large fruiting trees, where they spend most of their time in the upper canopy. By spending the majority of their time in the crown of tall forest trees, they are relatively safe from predators such as the fossa.
Ruffed lemurs are active primarily during the day (diurnal), during which time they feed primarily on fruits and nectar, often adopting suspensory postures while feeding. The seeds of the fruit they eat pass through their digestive tract and are propagated throughout the rainforests in their feces, helping to ensure new plant growth and a healthy forest ecosystem. These lemurs are also significant pollinators of the traveller's tree (Ravenala madagascariensis). Without destroying the inflorescence, they lick the nectar from deep inside the flower using their long muzzles and tongues, collecting and transferring pollen on their snouts and fur from plant to plant. This relationship is thought to be a result of co-evolution.
Geographic Range and Habitat EditLike all lemurs, this genus is found only on the island of Madagascar off the southeastern coast of Africa. Confined to the island's seasonal eastern tropical rainforests, it is uncommon to rare throughout its range, which historically ran from the Masoala Peninsula in the northeast to the Mananara River in the south. Today, the black-and-white ruffed lemur has a much larger range than the red ruffed lemur, although it is very patchy, extending from slightly northwest of Maroantsetra, on Antongil Bay, in the north down the coast to the Mananara River near Vangaindrano in the south. Additionally, a concentrated population of black-and-white ruffed lemurs, of the subspecies Varecia variegata subcincta, can also be found on the island reserve of Nosy Mangabe in Antongil Bay. It is suspected that this population was introduced to the island in the 1930s. The red ruffed lemur, on the other hand, has a very restricted range on the Masoala Peninsula.
Historically, the confluence of the Vohimara and Antainambalana Rivers may have been a zone of hybridization between these two species, although no conclusive results have indicated current interbreeding. In general, the Antainambalana River appears to isolate the red ruffed lemurs from the neighboring subspecies of black-and-white ruffed lemur, V. v. subcincta. The subspecies V. v. variegata can be found further south, and V. v. editorum is the southernmost subspecies. The ranges of these two southern subspecies overlap and intermediate forms are reported to exist, although this has not been confirmed.
The rainforests in which these animals live are seasonal, with two primary seasons: the hot, wet season (November through April), and the cool, dry season (May through October). The primary habitat for both species, at any season, is in the crowns of trees, where they spend the majority of their time 15 and 25 m (49 and 82 ft) above ground. With the seasonal availability of resources being similar regardless of location, there is little to no difference in tree usage between species. From September through April, more fruit is available, so females prefer the lianas in the crowns of trees. Both sexes prefer the lower, major branches during the hot, rainy season. The tree crowns are predominantly used from May through August, when young leaves and flowers are in abundance.
Ruffed lemurs, on average, spend 28% of the day feeding, 53% resting, and 19% traveling, although differences in resting and feeding durations have been observed between males and females, with females resting less and feeding more. They are diurnal; although peak activity occurs during the early morning and late afternoon or evening, resting usually occurs around midday. When resting, ruffed lemurs often sit hunched or upright. They are also frequently seen lying prone over a branch or sunbathing in a supine position with the limbs outstretched. When feeding, they will often hang upside-down by their hind feet, a type of suspensory behavior, which allows them to reach fruits and flowers.
Being highly arboreal, they spend the majority of their time in the high canopy throughout the day. Ruffed lemurs spend the majority of their time between 15 to 20 m (49 to 66 ft) above the forest floor, followed by 20 to 25 metres (66 to 82 ft) up, and are least frequently seen at 10 to 15 metres (33 to 49 ft). During the hot season, they will relocate to the lower canopy to help regulate their body temperature. In the cold season, ruffed lemurs are least active and may dedicate 2% of their resting time to sunbathing in order to warm up.
Long-term field research has shown that range size, group size, social systems, and territorial behavior vary widely, and may be greatly affected by food distribution and quality. It is generally agreed that the ruffed lemur social system is multi-male/multi-female with a fission-fusion society, although some populations of black-and-white ruffed lemur have been reported as monogamous. This social flexibility is suspected to improve survivability despite an inflexible feeding ecology.
Being the most frugivorous members of the family Lemuridae, consuming an average of 74–90% fruit, ruffed lemurs also consume nectar (4–21%), and supplement the rest of their diet with young leaves (3–6%), mature leaves (1%), flowers (3–6%), and some seeds. Ruffed lemurs have also been reported to come to the ground to eat fungi and exhibit geophagy.
The majority of their diet is made up of relatively few common plant species, with a few species providing more than 50% of the diet. Fig species of the genus Ficus, for example, account for 78% of the fruit consumed by red ruffed lemurs on the Masoala Peninsula. Although plant species and diets vary by location, the most common food plants reported from the field include the following:
- Ravensara (family Lauraceae)
Fruit trees do not appear to be selected by species, but by availability and accessibility of edible fruit. And despite predominance of a few plant species in the ruffed lemur diet, the remainder of their diet consists of between 80 and 132 other species from 36 plant families.
The availability of food reflects the seasonal nature of the forests in which they live. During the hot season, fruit, flowers, and young leaves are more abundant, whereas the cold, wet season offers more young leaves and flowers. Despite this, the diet changes little between seasons, except that females will consume more high-protein, low-fiber items, such as young leaves and flowers, during pregnancy and lactation in order to offset the energy costs of reproduction. Nectar is only available sporadically, yet constitutes a major food source when the flowers bloom. The nectar of the traveller's palm (Ravenala madagascariensis) is a favorite among ruffed lemurs.