The Social Organisation of the Fat-Tailed Dwarf Lemur, <I>Cheirogaleus medius</I> (Lemuriformes; Primates)

Completed Research Project

Title / Titel: The Social Organisation of the Fat-Tailed Dwarf Lemur, Cheirogaleus medius (Lemuriformes; Primates)

Original title / Originaltitel: The Social Organisation of the Fat-Tailed Dwarf Lemur, Cheirogaleus medius (Lemuriformes; Primates)

Summary / Zusammenfassung: The strictly nocturnal dwarf lemurs (genus Cheirogaleus) are extraordinary among primates in showing extensive torpor phases of up to six months during the dry season in the austral winter which are thought to be an adaptation to seasonal variation in food availability. To survive this period of inactivity, the animals store fat and as a result show extreme seasonal variation in body weight. Because of these torpor phases, the animals have only few months to reproduce and rear offspring. The effects of torpor and seasonal variation in body weight on the social life of the fat-tailed dwarf lemur (Cheirogaleus medius) have been investigated during a 20-month field study that was carried out at the Forestry Station of Ampijoroa in northwestern Madagascar. Results of this study revealed a dispersed monogamous social organisation for C. medius. All studied groups contained one adult pair and their offspring from one or more birth seasons. Members of agroup regularly sleep together, which might be an important means of social contact. In groups containing more than one offspring, brothers and sisters had the closest relationship. The adult pair remains together within the same home range for more than one season and presumably for life. There is a correlation between paternal investment and monogamy in primates, and paternal investment with males carrying infants has been reported in several monogamous primates. However, in dwarf lemurs (and other small nocturnal prosimians) the females do not usually carry their offspring continuosly either but cache or park them. An imbalance between male and female investment persists as females invest considerable energy in their offspring during gestation, birth and lactation. It should therefore be expected that a C. medius male somehow invests in his mate and offspring in another matter. Trapping results showed that adult males emerge from torpor earlier than females and offspring, even though food is still scarce. The subsequent weight-loss in adult males after they leave torpor suggests that this behaviour is energetically costly. It is known from non-primate mammals which undergo torpor (woodchucks, dormice and ground squirrels) that males emerge earlier from torpor than females. Because these males hibernate alone, they must come above ground to compete for estrous females in order to maximise their breeding success. However, in species where males and females hibernate together as in some marmots, males do not emerge earlier than females. Hence there must be another reason for the C. medius males to emerge torpor before the females. Observations suggest that males patrol a home range, thus guaranteeing its integrity for the coming season and ensuring a good food supply for their families. Such male behaviour increases the likelihood of his offspring and that of his mate's survival while at the same time it optimises his mate's reproductive success and thus his own reproductive potential. The high energetic costs endured by the male justify the classification of this behaviour as a form of paternal investment.

Publications / Publikationen

Mueller, A.E. (1998): A preliminary report on the social organisation of Cheirogaleus medius (Cheirogaleidae; Primates) in north-west Madagascar. Folia Primatologica 69: 160-166.

Mueller, A.E. (1999): Aspects of social life in the fat-tailed dwarf lemur (Cheirogaleus medius): Inferences from body weights and trapping data. American Journal of Primatology 49: 265-280.

Mueller, A.E. (1999): Social organization of the fat-tailed dwarf lemur (Cheirogaleus medius) in northwestern Madagascar. In: New Directions in Lemur Studies. (Rakotosamimanana, B.; Rasamimanana, H., Ganzhorn, J.U. & Goodman, S.M., eds.). Kluwer Academics/Plenum Publishers: New York, pp. 139-158.

Mueller, A.E. (1999): The Social Organisation of the Fat-tailed Dwarf Lemur, Cheirogaleus medius (Lemuriformes; Primates). PhD Thesis, University of Zuerich.

Mueller, A.E. & Thalmann, U. (2002): The biology of the fat-tailed dwarf lemur (Cheirogaleus medius E. Geoffrey 1812): New results from the field. Evolutionary Anthropology 11, Supplement 1: 79-82.

Jolly, C.J., Philips-Conroy, J.E. & Mueller, A.E. (2003): Trapping. In: Field and Laboratory Methods in Primatology. (Setchell, J.M. & Curtis, D.J., eds.). Cambridge University Press: Cambridge, pp. 110-121.

Mueller, A.E. & Thalmann, U. (2004): Sleeping site use and social contacts in the fat-tailed dwarf lemur (Cheirogaleus medius) in north-west Madagascar. Folia Primatologica 75: 309.

Weitere Informationen

Keywords / Suchbegriffe: Primates, Lemuriformes, lemurs, strepsirrhines, Madagascar, nocturnal prosimians, Cheirogaleus medius, dwarf lemur, Cheirogaleidae, radio-tracking, social organisation, solitary species, field study, trapping

Project Leadership and Contacts / Projektleitung und Kontakte

Dr. Alexandra Mueller (Project Leader)

amueller@wb.uzh.ch

Other Links to external Webpages: http://www.aim.uzh.ch

Funding Source(s) / Unterstützt durch: Others
A.H. Schultz Foundation, Family Vontobel Foundation, Goethe Foundation, G. & A. Claraz Donation, Swiss Academy of Natural Sciences (SANW)

In Collaboration with / In Zusammenarbeit mit

Dr. Urs Thalmann Anthropological Institute and Museum University of Zurich Winterthurerstrasse 190 8057 Zurich	Switzerland
Departement des Sciences de la Terre University of Mahajanga BP 652 Mahajanga 401 Madagascar
Prof. Dr. Robert D. Martin The Field Museum Chicago, IL 60605-2496	United States

Duration of Project / Projektdauer: Sep 1995 to Jul 1999