E. rufifrons have evolved separately from other primates and they can be important species to study in order to better understand social cognition rules in evolution (Schnoell and Fichtel 2012).
E. rufifrons are classified as cathemeral which means that they are active at various times during the day and night depending on social interactions or foraging needs (Schnoell et al. 2014). This may allow them to readily adapt to their environment and may have allowed them to colonize western and eastern Madagascar.
Individuals tend to keep within a 15 m radius of their group members (Schnoell and Fichtel 2012) and these groups tend to include an average of only 2-3 females (Pflϋger and Fichtel 2012). The group sizes are very small (about 10 individuals per group) but this low number of females gives an uneven sex ratio within the group. During the dry season in Madagascar, food and other resources tend to be limited. This limitation may play a role in keeping lemur group sizes so small (Kappeler and Fichtel 2012). Lemurs have been observed to evict members from their group in order to maintain their group size (Kappeler and Fichtel 2012).
Groups are organized under a mostly egalitarian social structure (Schnoell and Fichtel 2012). This means that there is not much linear dominance nor dominance based on sex. After a conflict in the group, E. rufifrons soon reconcile in order to reduce the probability of the conflict reoccurring (Pflϋger and Fichtel 2012).E. rufifrons spend most of their time in close proximity to one another, which allows for a great deal of social interaction (Schnoell and Fichtel 2012.
Studies have shown that they are able to use information from other group members in order to learn new foraging methods (Schnoell and Fichtel 2012). Once they have learned a new technique and the majority of the group is using this technique, the rest of the group tends to adopt this technique as they observe other individuals performing it (Schnoell and Dittmann 2014).
Females have been noted to have a higher success than males when learning to obtain rewards from boxes during research studies (Schnoell and Fichtel 2012). Females also have been found to initiate group movements more frequently than males (Pyritz et al. 2011). Males and females tend to have equal aggression levels with no sexual difference between aggression scores.
Interestingly, Schnoell and Fichtel (2012) found that E. rufifrons tend to watch non-related individuals more often than related individuals when learning a social task. This could negatively impact the species because it may be more beneficial to observe related species than non-related species when relying on social learning (Schnoell and Fichtel 2012). Perhaps these unique social dynamics may be at least partly to blame for the decline in the number of E. rufifrons.
E. rufifrons have been observed producing many types of close calls depending on the type of situation. These calls include: grunts, long grunts, hoos and meows. The majority of their vocalization includes grunts. They tend to produce this call in order to keep the group together and to avoid separation of the group. As more of the group separates, the more frequently the grunt calls occur. Along with keeping the group together, grunts are used to keep the peace within the group since the grunt represents harmless intentions (Pflϋger and Fichtel 2012). On the other hand, Pflϋger and Fichtel (2012) found that hoo calls were commonly given during rest. These calls are suggested to be important in reducing conflict within the group, allowing the individuals to focus their energy elsewhere, such as on foraging (Pflϋger and Fichtel 2012).
Conservation Status:
According to IUCN Red List of Threatened Species, E. rufifrons is listed as near- threatened. IUCN lists E. rufifrons as near threatened because the number of individuals has declined by 20-25% over the past 24 years. Many factors are contributing to the species’ declining population, including habitat loss due to illegal logging, slash-and–burn agriculture, clearing for pastureland, and gathering wood for fuel. Other major threats to the species are hunting and trapping.Red-fronted lemur populations are expected to continue declining due to increases in habitat fragmentation and hunting (IUCN 2014).
Although some lemur species have actually benefited from light logging, E. rufifrons are negatively impacted by both light and heavy logging (Herrera et al. 2011). Their unique response to the logging may be due to the removal of the trees that produce fruits important to their diet (Herrera et al. 2011). Logging may also increase the visibility of E. rufifron to predators.
E. rufifrons individuals occupy deciduous forests of Madagascar, such as the Kirindy forest (Pyritz et al., 2011; Pfluger and Fichtel, 2012). The Kirindy forest receives about 900 mm of precipitation a year from November to March (Kappeler and Fichtel, 2012). The habitat of E. rufifrons has a cool dry season from April to October and a rainy and warm season from November to March (Pyritz et al. 2011).
E. rufifrons have a dispersal range of about 6 km from where they were born or raised and their home range can be up to 100 ha (Delmore et al. 2013). Pyritz et al. (2011) found that E. rufifrons individuals tend to increase their daily range during the rainy season (November- March).
The separation of the eastern and western population of E. rufifrons, due to fragmentation, may make it difficult for the two populations to interact. The species may therefore benefit from corridors to allow them to freely move between the two populations. Another barrier that separates E. rufifrons populations are the large number of rivers that run through Madagascar. Building rope bridges over the rivers, would allow separated populations to interact, might increase the genetic diversity of the group and overall fitness. Since habitat destruction and overexploitation are a problem, creating national parks and reserves are another important way to protect these animals and prevent their extinction.
A nuclear DNA sequence can be found at Genbank accession number KF708137 (Markolf et al. 2013).
Female E. rufifrons are identified by black colored fur on the top of their heads, above and below their eyes, and on their muzzles. On average, females tend to have a body mass of 1.96 kg, skin-fold thickness of 5.31 mm, tail length of 54.76 cm, and an upper canine height of 8.48 mm (Delmore et al. 2011).
Male E. rufifrons are identified by dark muzzles, white colored patches above their eyes, gray body color and reddish-brown, bushy fur on the top of their heads. On average, males tend to have a body mass of 1.82 kg, skin-fold thickness of 6.41 mm, tail length of 53.13cm, upper canine height of 10.40 mm, and relative testes volume of 4.31 mm3/kg (Delmore et al. 2011).
E. rufifrons lack a precise grip, which results in a reduced ability to manipulate objects in comparison to other primates (Schnoell and Fichtel 2012). They are considered a medium size primate. E. rufifrons are quadrupedal which allows them to move quickly in the trees, where they spend most of their time (Schnoell et al. 2014).
E. rufifrons have been observed on both the western and eastern coasts of Madagascar. Their range extends southward from the Tsiribihina River to the Fiheranana River. In the east, they occur near the Mangoro River and the Onibe River and extend as far south as the Andringitra Massif (Mittermeier et al. 2008).
The mating season of E. rufifrons is usually May to June, which is early in the dry season of Madagascar. Females reach sexual maturity between 2-4 years old. Once a year, they give birth to a single offspring about 4 months after fertilization. This birth is usually at the peak of the dry season (Pyritz et al. 2011). It is interesting that females give birth during the dry season because food resources would be low. Conducting a future study on infant mortality rates could help determine whether this timing contributes to the species’ population decline.
Once the offspring are born, they express the male phenotype. It is not until 3-4 months of age that the female juveniles start to express the female phenotype. Mother E. rufifrons carry around their offspring until they reach 12 weeks of age (Kappeler and Fichtel 2012).
Members of the genus Eulemur are known as true lemurs and they make up the “brown lemur complex.” The brown lemur complex includes twelve species: E. albifrons, E. sanfordi, E. fulvus, E. rufus, E. rufifrons, E. cinereiceps, E. collaris, E. rubriventer, E. mongoz, E. coronatus, E. flavifrons, and E. macaco (Markolf and Kappeler 2013).
In the past E. rufifrons was thought to be a subspecies of E. rufus (Mittermeier et al. 2008). However, Markolf and colleagues (2013) gave evidence that E. rufifrons significantly differs from E. rufus in fur coloration, genetics, and acoustic parameters.
E. rufifrons are frugivores, meaning they forage primarily for fruits such as oranges and mangos (Herrera et al. 2011; Schnoell and Fichtel 2012). Most of their foraging occurs in the trees by pulling branches towards their mouth and obtaining fruit orally (Schnoell et al. 2014). By using their mouths to gain purchase on the fruit, they free one hand to stabilize them on the branch of the tree.
The fossa (Cryptoprocta ferox), a large carnivore, is the greatest known predator of E. rufifrons (Kappeler and Fichtel 2012). Other predators include harrier hawks (Polyboroides radiates), feral canines (Canis familiaris), and Malagasy ground boas (Acrantophis madagascariensis; Pyritz et al. 2011).
