The cascading effects of elephant presence/absence on arthropods and an Afrotropical thrush in Arabuko‐Sokoke Forest, Kenya

Abstract

Although studies have explored how habitat structure and disturbance affect arthropod communities, few have explicitly tested the effects of both structure and disturbance level across trophic levels and phyla. We present here the results of a study conducted in the Arabuko‐Sokoke Forest (ASF) of coastal Kenya, in which abundance of arthropods and one of their avian predators, the East Coast Akalat Sheppardia gunning sokokensis was compared in relatively undisturbed habitat (outside elephant roaming areas) and in disturbed habitat (inside elephant roaming areas). Vegetation structure in both areas was measured using several metrics, including leaf litter depth, understory vegetation density, animal disturbance and fallen log counts. Leaf litter and coleopteran abundance were higher outside the elephant roaming areas, whereas understory visibility, animal disturbance and dipteran diversity were much higher inside the elephant areas. Species composition of several arthropod taxa (e.g. Hymenoptera, Coleoptera, Diptera, Hemiptera and Araneae) was also influenced by degree of disturbance, whereas akalat abundance was inversely related to understory visibility. Our results suggest that differences in species sensitivity to habitat disturbance and vegetation structure across trophic levels should be incorporated into the management and conservation of rare and endangered species.

Forest-type preference of an Afrotropical thrush (East Coast AkalatSheppardia gunningi sokokensis) in Arabuko-Sokoke Forest, Kenya

“…Some studies have indicated that akalats need an open understory, thriving in forest areas that are not too dense but have some vegetation cover and leaf litter in which they can forage (Matiku et al 2000, Nemeth and. However, in a recent study conducted in the Mixed forest of ASF, it was found that this effect diminishes in forests that are 'too open' -specifically, akalat densities are lower in areas with little vegetation 1-2 m off the ground (Banks et al 2010). Sheppardia gunningi's preference for Cynometra forest and thicket may therefore be a function of vegetation density in the sampling areas.…”

“…More generally, studies on large herbivores indicate that they can negatively impact bird diversity and abundance, with higher densities in areas of herbivore exclusion (Ogada et al 2008). Furthermore, elephants may indirectly affect some bird populations by altering vegetation composition as well as habitat critical to the survival of arthropods important to their diets (Skarpe et al 2004, Banks et al 2010. Elephants in ASF have been contained within the reserve by an electrified fence, which was begun to be put in place approximately 10 years ago.…”

“…As S. gunningi shares habitat with these species, its population dynamics may serve as an indicator for broadly focused ongoing habitat conservation efforts in ASF, including efforts to reduce poaching of forest products. Feeding primarily on insects (with supplemental berries and seeds), S. gunningi thrives in open forest understory with some vegetative cover a few metres above the ground and ample leaf litter (Matiku et al 2000, Nemeth and; the latter has been correlated with increased beetle populations (Banks et al 2010). …”

Habitat type and altitude work in tandem to drive the community structure of dung beetles in Afromontane forest

“…Thus, understanding of the factors influencing invertebrate taxonomic richness and diversity at both local and regional scales is important for conserving biodiversity and for maintaining ecosystem services. Dung beetles are known to represent an important functional component of the animal fauna found in tropical forests (Krell-Westerwalbesloh et al 2004;Banks et al 2010) as they provide several key ecological functions such as seed dispersal, parasite suppression and dung removal (Nichols et al 2008).…”

Spider assemblages associated with leaf litter of three tree species in central South Africa (Arachnida: Araneae)

“…, 2009), habitat fragmentation (Dias et al. , 2006), habitat disturbance (Banks et al. , 2010), altitude (Sabu, Vineesh & Vinod, 2008), nutrient levels (McGlynn et al.…”