Counting technique

How does one use photos to "monitor" Grevy’s anyhow? Our field assistant, Hussein, regularly conducts surveys for zebra and livestock on Mpala. Over the course of three days, he covers as much of the ranch’s 48,000 acres as possible by driving a standardized network of roads and tracks.

Along the route, each time he encounters a group of Grevy’s, he attempts to
photograph every individual:

This is a simple task when he encounters a lone territorial male, but can become quite difficult when he stumbles upon a tightly spaced group of 20+ females and their young! He records the number of animals seen, as well as the group structure. We therefore know how many males (territorial or bachelor), females (pregnant, lactacting, or non-lactating), juveniles, and foals of different age categories there were. See for yourself how hard it can be to get a photo (and data) for every member of a group!

This isn’t the only data he collects, however. Each of these sightings is associated with a location, weather conditions, vegetation characteristics, and what the group was busy doing when they were first sighted. This teaches us about the Grevy’s habitat preferences and behavior.

All of this same habitat information is recorded for plains zebra and livestock (cattle, sheep, camels and donkeys) as well. Not only can we use this information to make comparisons across species, but we can see how Grevy’s interact with other competing grazers.


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