Investigating the effects of management practice on mammalian co-occurrence along the West Coast of South Africa.

The subtle and cascading effects (e.g., altered interspecific interactions) that anthropogenic stressors have on local ecological assemblages often go unnoticed but are concerning given their importance in ecosystem function. For example, elimination of buffalo from the Serengeti National Park is suggested to have driven increased abundance of smaller antelope as a result of release from competition. The perceived low abundance of small antelope in the contractual Postberg section of the West Coast National Park (the park) has been an ongoing management concern which has been anecdotally attributed to predation by a mesopredator (the caracal, Caracal caracal). However, we hypothesized that the historical overstocking, and consequent overgrazing by larger-bodied managed ungulates would influence small antelope abundance. Using camera traps, we investigated species co-occurrence and temporal activity between small antelope, managed ungulates and caracals in Postberg as well as another part of the park (Langebaan) and a farm outside of the park. Results suggest that small antelope and managed ungulates have a high degree of temporal overlap (Δ = 0.74, 0.79 and 0.86 for the farm, Langebaan and Postberg respectively), while temporal partitioning between small antelope and caracal is apparent (Δ = 0.59). Further, small antelope and managed ungulates appear to occur independently of one another (SIF = 0.91-1 across areas). Managed ungulates were detected almost three times more frequently on fallow lands when compared to the more vegetated sites within the park suggesting that segregated food/cover resources allow for independent occurrence. Small antelope had a much higher probability of occurrence outside of the protected area (e.g., ψ = 0.192 and 0.486 for steenbok at Postberg, Langebaan compared to 0.841 on the farm), likely due to less variable (more intact) habitat outside of the protected area. There is not sufficient evidence to currently warrant management intervention for predators. The small size of the protected area provides limited scope for spatial replication thus reducing possibilities to infer the cause and effect for complex interactions (which would historically have taken place over much larger areas) with negative implications for adaptive management. We recommend continued monitoring over multiple seasons and a wider area to determine the spatial information requirements to inform management of small protected areas.

Widespread anticoagulant poison exposure in predators in a rapidly growing South African city.

Anticoagulant rodenticides (ARs) are used worldwide to control rodent populations. ARs bioaccumulate across trophic levels and threaten non-target wildlife. We investigated the prevalence of AR exposure in seven predator species in the rapidly developing Greater Cape Town region of South Africa - a mosaic of natural, urban, and agricultural areas within a global biodiversity hotspot. We focused sampling on caracals (Caracal caracal, n = 28) as part of a larger caracal ecology study, but also opportunistically sampled Cape Clawless otters (Aonyx capensis, n = 9), large-spotted genets (Genetta tigrina, n = 4), honey badger (Mellivora capensis, n = 1), water mongoose (Atilax paludinosus, n = 1), small gray mongoose (Galerella pulverulenta, n = 1), and Cape Eagle owl (Bubo capensis, n = 1). We tested livers from all species, and blood from ten caracals, for eight AR compounds to assess prevalence and amount of exposure for each compound. We used generalized linear models to test spatial, demographic, and seasonal risk factors for ten measures of AR exposure in caracals. We detected at least one of the four most toxic AR compounds in six species. Exposure was high for caracals (92%) and all species combined (81%). For caracals, proximity to vineyards was the most important AR exposure risk factor. Vineyards in Cape Town do not use ARs to protect their vines but do host commercial hospitality structures where ARs are used. Vineyards may thus link caracals that forage within vineyards to the rat poisons used in and around their commercial structures. Residue levels were unexpected in large-spotted genets and Cape Clawless otters, suggesting invertebrate vectors. ARs may present a cryptic threat to populations already vulnerable to increasing habitat loss, vehicle collisions, poachers and fire. Targeted mitigation should include a mix of environmentally responsible policies that reduce AR use, particularly in areas near wildlife habitat.