Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Conservation of raptors and vultures in Botswana : with a focus on lappet-faced vultures Torgos tracheliotos

Auteur : Garbett, Rebecca Ann

Université de soutenance : University of Cape Town.

Grade : Doctor of Philosophy 2018

Résumé
Many raptor species are in steep decline across Africa. Botswana is regionally important for many of these species, including vultures, yet information on most raptors in this area is lacking. Along with the rest of the region, Botswana has seen a rise in poisoning incidences which have decimated vulture populations and threaten other scavenging raptor species. As a result, seven out of the nine sub-Saharan species of vulture are now at risk of extinction. The lappet-faced vulture Torgos tracheliotus exists at very low densities in comparison with other African vultures and in 2015 was up-listed to “Endangered” by the IUCN because of its recent rapid decline. Although it is one of the most commonly seen vultures in Botswana and is widespread across the continent, very little is currently known about its ecology. This thesis aims to provide information on how raptors and particularly vultures are faring in Botswana, the possible threats that they face in this region and how we can use ecological information to alleviate these threats by better protecting these species. I repeated transect surveys of raptors in northern Botswana that were first conducted 20 years ago to investigate changes in abundance of raptor species that were included in the original surveys. I used data for 29 raptor species to compare abundance between the two surveys and found that 14 species (48%) had experienced significant declines of between 37% and 97%, and that overall, 18 species had declined by >50% ; three of which were vulture species. When I compared the overall trend between the two surveys, I found a 40% decline in total abundance of all raptors. Only three species (all eagles) showed significant increases in abundance, but these were small (6-15%). I then went on to explore changes in abundance inside and outside of protected areas. In contrast to what was anticipated, I found that only two species showed significantly different trends (both eagles). These trends differed, with one species showing larger declines outside of protected areas than inside of them, and the other species increasing outside of protected areas but remaining stable inside of them. The findings suggest that Botswana raptor populations are declining in-line with global raptor populations and that vultures may be equally at risk in Botswana as in other parts of Africa. Protected areas do not appear to act as a buffer for declines for most raptor species, which suggests that drivers of decline are acting in equal measure inside and outside of protected areas.

Présentation

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