Structure and annual increase in a population of West Greenland caribou (Rangifer tarandus groenlandicus)

• Published in: Rangifer
• Main Author: Henning Thing
• Format: Article in Journal/Newspaper
• Language: English
• Published: Septentrio Academic Publishing 1982
• Subjects: Population ecology; wild reindeer; West Greenland; Animal culture; SF1-1100; Greenland; Sisimiut; caribou; Rangifer; Rangifer tarandus
• Online Access: https://doi.org/10.7557/2.2.2.410; https://doaj.org/article/b9a5301972064462a978a81294d7b80a

During 1977-80 a large scale research program was carried out in West Greenland to study caribou ecology and population dynamics. Papers dealing with feeding ecology, range condition, calf mortality, and behaviour have been published elsewhere (Strandgaard 1980; Holt 1980; Clausen et al. 1980; Thing & Clausen 1980; Thing 1980; Roby 1980; Thing 1981; Roby & Thing 1982; Thing & Thing 1982). The present study deals with some dynamic parameters in the Sisimiut herd (Fig. 1), viz. group size, sex and age composition, calf/cow ratio, calf increment, and annual recruitment. Caribou in the Sisimiut region are mainly found in very small groups of one to five animals in most seasons. Aggregations of more than 50 animals are rarely seen except in the calving and summer seasons (Fig. 2). A distinct annual cycle is apparent in the mean group size with a steady increase from a mid winter minimum of 1.4 caribou/group towards a maximum of almost 25 caribou/group in the post-calving season (Fig. 3). The absence of important predators (especially wolves) and the fact that winter food resources in the region have been depleted seem to reduce group size. Consequently, Sisimiut caribou are characterized year round by forming very small groups as compared to most other wild Rangifer populations. Caribou cows (females 2 years + ) make up approx. 50% of the herd, while bulls (males 2 years + ) average only 10% (Fig. 4). The number of bulls in the herd shows a significant decline caused by a selective hunting pressure as well as natural winter mortality (Fig. 5). The rut takes place in October during the fall migration from the inland ranges adjacent to the Inland Ice towards the coast line. The cows are apparently served mainly by 1 1/2 and 2 year old bulls. Despite scarcity of adequate food on the winter ranges there is a high calf production. This is probably explained by excellent forage conditions on the inland range prior to and during the calving season (May - June). Calving adds as much as 40% new individuals to the ...