Session 6: The Lemurs

1.  Key Concepts:

The lemurs are considered by many the most basal of all primates.  They are limited to Madagascar and represent a radiation of primates occurring in the absence of anthropoids.  Thus, the Lemurs represent a perfect natural experiment for evolution in the absence of anthropoids.

2.  Terms & Definitions:

Anthropoids -

Belonging or pertaining to the primate suborder Anthropoidea, characterized by a relatively flat face, dry nose, small immobile ears, and forward-facing eyes, comprising humans, apes, Old World monkeys, and New World monkeys.

Torpor - 

A state of reduced metobolic activity; often associated with hibernation or estivation.

Frugivorous - 

Fruit eating.

Folivorous - 

Leaf eating.

 

3.  Taxonomy of the Lemurs:

 The Lemurs:

The lemurs are small, generally cathemeral, primates which live in small groups and are endemic to Madagascar.  Olfactory communication plays a major role, and scent marking is extremely important.  All lemurs have a rhinerium, or wet nose, to increase sensitivity to chemical cues and scent glands.

Madagascar:

Endemic to Madagascar, the lemurs are especially sensitive to habitat degradation.  Habitat degradation on Madagascar has been severe and substantial.  Very little forest cover remains, less than 10% remains in most places, and desertification has widely occurred.  This has drastically limited the range of lemurs throughout the island. Most populations remaining today are probably relict populations/species so most behavioral patterns are likely reflective of historical adaptive functions. 

The Lemuriformes:

Although there are only five extant genera of Lemuriformes, there is a huge taxonomic variation within the lemurs.  This is despite extreme habitat loss and limited range.  The five genera are:

• Lemurida
• Indriidae
• Cheirogaleidae
• Lepilemuridae
• Daubentoniidae

Hapelemur:

The Hapelemurs, or the bamboo lemurs, specicalize on bamboo, both in diet and habitat choice.  Although they can be monogamous, the hapelemurs can also be polygynous or polyandrous.  They will supplement their diet with insects and fruits.

Photo by skinnyde. Some rights reserved.

Indri Propithecus:

The Indris are the largest of the remaining lemurs, with the largest about the size of a house cat.  They are extremely specialized for locomotion in the trees and are exclusively arboreal.  They are excellent leapers and clingers.  When the Indris do come to the ground, they hop sideways.  Typically, groups consist of one male, one female, and offspring or multi-male, multi-female, and offspring groups.  The groups are typically small, and female dominance is extreme.  Male is almost 100% responsible for maintaining social contact, and females will displace males in feeding.

Photo by banoffi. Some rights reserved.

Sifaks and Indris:

The Indris and Sifaks fill the niches in Madagascar that are filled by anthropoids in other areas of the world. 

• Indri--two adult groups, territorial vocalizations, female dominance, gibbon convergent?
• Frugivorous/Folivorous.
• Indri calls: http://www.gozen.demon.co.uk/godric/lemgall.html.
• Propithecus multi-female/ multi-male groups.
• High mortality rates.
  

Lemur catta:

Photo by Christine Wainwright. Some rights reserved.

Varecia, Lemur, Eulemur:

Can be diurnal, nocturnal, or cathemeral. They live in fission/fusion groups that break into male-female pairs.  Most live in small groups.

Photo by Skip the Budgie. Some rights reserved.

The diurnal lemurs:

• Lemur catta:
• • Multi-female. Multi-male groups.
  • Hyper seasonality and the window of reproduction.
  • Female dominance and male-male competition for spatial access.
    

• Varecia vareagatta:
• • Fission-fusion grouping and communities.
  • Male-female spatial associations.
    

• Eulemur mongoz:
• • Two-adult groups and multi-adult groups.
  • Ecologically mediated grouping patterns.
  • Male-female bonds.
    

4.  Lemur catta: an example of female dominance

  Lemur catta lives in multi-female/multi-male groups.  Two to three days a year, females are receptive .  Within this period, each female has approximately 24 - 36 hours when they are able to be fertilized.  Females that reproduce early or late have a near 0% chance of reproductive success.  This results in a clear female dominance sociallly and in access to resources, but this occurs in the months leading up to this small reproductive window.  During this time, males are completely subserviant to females.  During the pre-reproducing window, males gorge themselves to maximize time and space around females.  There is extremely high competition for females.  Competition exists in the form of scent-marking and displays. 

Due to the hyper constraint of seasonality and the cost of lactation, females have evolved an intensely short period of reproductive success.  Male subservience is actually a mating strategy to maximize male reproductive output via male investment in offspring.  Spatial dynamics also influence the male strategy of favoring and interacting with offspring.

5.  Additional Information:

Primates in Perspective.  2007.  eds.  C. J. Campbell, A. Fuentes. K. C. MacKinnon, M. Panger, and S.K. Bearder.  Oxford University Press. 

Chapter 4:  Lemuriformes - Gould & Sauther