Abstract: Invasive plants can have profound impacts through altering the behaviour of native animals; the consequences of these behavioural changes resound from the level of individual native species to whole ecosystems and the people who inhabit them. Prickly pear cacti (Opuntia sp.) are one of the world’s most pervasive plant invaders: they are invasive in arid regions throughout the world, including in East and Southern Africa, Australia, the Mediterranean, and parts of South-East Asia. Several species of Opuntia are invasive in Laikipia County, Kenya: a key stronghold for biodiversity which hosts vital populations of endangered mammals including Grevy's zebra (Equus grevyi) and reticulated giraffe (Giraffa reticulata). Therefore, understanding Opuntia's impact on Laikipia's mammals is an urgent priority.
As Opuntia profoundly alters the physical structure and resource availability of the habitat, behavioural changes - particularly changes to habitat-use - potentially comprise a key aspect of Opuntia's effects on mammals in Laikipia County. Consequently, we aimed to explore the impacts of Opuntia on mammalian habitat use by quantifying the relationship between Opuntia and the occupancy and temporal patterns of activity of eight key mammal species, and to examine how these effects varied with spatial scale.
We found that the direction and magnitude of Opuntia’s effects on occupancy and activity varied among mammal species and depended on the spatial scale of the Opuntia covariate. Our key findings include negative relationships between broad-scale Opuntia volume and the occupancy probability of reticulated giraffe (Giraffa reticulata). We also observed generally positive effects of Opuntia on the occupancy and activity of elephants (Loxodonta africana), olive baboons (Papio anubis), and vervet monkeys (Chlorocebus pygerythrus), which are all thought to be important dispersal agents for the Opuntia. These results have important implications for the conservation of endangered mammal species in the region, the future spread of Opuntia through seed dispersal, and interactions between wildlife and local communities.
