64 Home Ranges and Resources in Baboons

Key Idea: Baboon troops occupy home ranges that overlap but have distinct core areas. Olive baboon troops in Africa each occupy distinct home ranges. The home range is the area regularly utilised by the troop, and it provides all the resources the troop needs for its survival. Home ranges differ from territories in that they may overlap in places and are not necessarily defended. The size of the home range reflects the quality of its resources.

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Scale

Baboon home ranges in Nairobi Park

5 km

Key

Sleeping trees Home ranges (each range shown by a different dash pattern) Core areas

Nairobi Park boundary

This map shows the boundaries of home ranges of different olive baboon troops living in the Nairobi Park, Kenya. Each has its own resident population of baboons that can range from 20-80 in number. Savannah-dwelling baboons spend more time on the ground than do most other primates and have one of the largest home ranges, averaging 20 km2. Baboons may travel up to 4 km a day in search of food. Most of the troop's activity is concentrated in the core area (which is like a territory). This area contains the best food sources, and more importantly, water holes and trees for sleeping in at night. Although olive baboons spend nearly all of their day on the ground, they always return to the safety of the trees before dusk to sleep.

1. Why would baboons defend the core areas aggressively?

2. (a) How many home ranges are represented on the map above?

(b) Contrast the distribution of home ranges and core areas of neighbouring troops. Suggest a reason for the difference:

3. The table below summarises troop size and home range size in various baboon troops in Africa. Use the information in the table to describe how the environmental factors affect the home range of baboons:

Region Home range size (km2) Average troop size Habitat Yearly rainfall (mm)

Bole Valley, Ethopia 1.1 20 Mixed forest and grassland 2000 Ishasa, Uganda 4.0 60 Forest and shrub-land 1200 Gilgil, Kenya 19.7 49 Open grassland and shrub-land 750 Laikipia Plateau, Kenya 43.8 100 Dry grassland 500