Communal nesting in yellow-bellied marmots [Elevage au nid communautaire chez les marmottes à ventre jaune].

Résumé

In our study area in the East River Valley, Gunnison Country, Colorado, female yellow-bellied marmots (Marmota flaviventris) produced 233 litters of young in 178 colony-years (a colony-year is one colony syudied in one year) at 7 research sites (=colonies) from 1962 to 1992, inclusive. Fifty-six litters (24.0%) were weaned by females living in the same burrow system. Of 25 instances of communal nesting, six involved three females and the remaining nineteen involved two females. Kinship of the communally-nesting females was known in 21 instances, eight involved litter mate sisters, seven, mother : daughter pairs, five, a mother : daughter : sister trio, and one, nonlittermate sisters. Young freely intermingled at emergence and no behavioral discrimination could be detected among the young or between the young and adult females. Space-use overlap between the adult females and young and among the young suggested that the adults and young formed one social group of closely-related kin. Communal nesting was not necessarily associated with communal nursing. Each adult female was injected with an unique antigen, such as Limulus hemocyanin, turkey egg albumin, and porcine thyroglobulin. Females formed large titers of antibodies. Blood samples were collected from the young and screened for antibodies. In one year, one young was detected with two antibodies, which indicated that she nursed more than one adult female. However, for three instances of sisters : sister communally nesting pairs, there was no evidence that a young nursed more thant one female. Thus, we conclude that communal nesting does not imply communal nursing.