By David Western and Victor N. Mose
Preamble
The Amboseli Conservation Program (ACP) has conducted regular aerial counts of the Amboseli ecosystem and eastern Kajiado since 1973. The counts give a 50-year record of wildlife and livestock numbers in response to droughts and human settlement (Western and Mose 2021). ACP has commissioned the Department of Resource Surveys and Remote Sensing (DRSRS) to conduct similar counts since 2011. The two sets of counts have given very similar results over the period of overlap. ACP commissioned DRSRS to conduct an aerial count of eastern Kajiado to assess the impact of the 2022-2023 drought by comparing current figures with the pre-drought count of February 2022. DRSRS used ACP counting protocols (Jolly 1969, Western 1976) to ensure compatibility with earlier counts.
We had intended the count to be flown in April-May at the height of the long rains to ensure maximum visibility of animals against the greenery. A three-month delay in aircraft availability put the count off until August 29th to September 1st. The delay resulted in the count being conducted during a severe dry spell when the visibility of animals from the air falls relative to wet seasons. As a result we expect the counts to underestimate the numbers of smaller species in more scattered herds and animals blending into the background.
In the event the delay was fortuitous, despite the poorer counting conditions. During the long rains in April-May an east-west rainfall gradient saw pastures green up well to the west and south of Amboseli and recovery little to the east on Kuku and Rombo. The scattered rains drew large numbers of wildebeest and zebra across the border into Tanzania beyond the counting area. Had the count been conducted in May, few wildebeest would have been counted in the Amboseli ecosystem. The low numbers would have greatly exaggerated drought losses, By the end of August, a survey flight we conducted showed most but not all wildebeest and zebra to have returned to Amboseli.
Preamble
The Amboseli Conservation Program (ACP) has conducted regular aerial counts of the Amboseli ecosystem and eastern Kajiado since 1973. The counts give a 50-year record of wildlife and livestock numbers in response to droughts and human settlement (Western and Mose 2021). ACP has commissioned the Department of Resource Surveys and Remote Sensing (DRSRS) to conduct similar counts since 2011. The two sets of counts have given very similar results over the period of overlap. ACP commissioned DRSRS to conduct an aerial count of eastern Kajiado to assess the impact of the 2022-2023 drought by comparing current figures with the pre-drought count of February 2022. DRSRS used ACP counting protocols (Jolly 1969, Western 1976) to ensure compatibility with earlier counts.
We had intended the count to be flown in April-May at the height of the long rains to ensure maximum visibility of animals against the greenery. A three-month delay in aircraft availability put the count off until August 29th to September 1st. The delay resulted in the count being conducted during a severe dry spell when the visibility of animals from the air falls relative to wet seasons. As a result we expect the counts to underestimate the numbers of smaller species in more scattered herds and animals blending into the background.
In the event the delay was fortuitous, despite the poorer counting conditions. During the long rains in April-May an east-west rainfall gradient saw pastures green up well to the west and south of Amboseli and recovery little to the east on Kuku and Rombo. The scattered rains drew large numbers of wildebeest and zebra across the border into Tanzania beyond the counting area. Had the count been conducted in May, few wildebeest would have been counted in the Amboseli ecosystem. The low numbers would have greatly exaggerated drought losses, By the end of August, a survey flight we conducted showed most but not all wildebeest and zebra to have returned to Amboseli.
Population estimates and standard errors for all species included in the August 29th to September 2023 aerial count.
Download full report below.
| amboseli_outlook_report_september_2023.pdf |
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