Bats in riverine forests and woodlands: a latitudinal transect in southern Africa

Abstract

Using captures in mist nets and monitoring echolocation calls, we quantified bat distribution and activity and measured insect abundance as numbers of insects attracted to black lights at 15-min intervals. These data were collected simultaneously at pairs of sites in riverine and dry woodland savannah along a transect of ca. 350 km from north to south in the Kruger National Park, South Africa. The sites were situated in the north, central, and south of the park and data were collected in January 1993. Our study involved 18 sites, three pairs each in the areas of the Luvuvhu, Letaba, and Sabie rivers. Half of the sites were in riverine woodland, the others in dry woodland. No statistical association exists between bat captures and either bat activity or insect abundance. Bat activity, however, was related significantly to insect abundance. Although bats were significantly more abundant (captures) in riverine habitats than in dry woodland savannah, comparisons of bat diversity and evenness (rarefaction curves, species abundance curves, and Whittaker plots) showed no differences between these habitats. The data neither demonstrate a decline in bat diversity away from the equator nor suggest specific bat communities associated with riverine habitats. The data do demonstrate the important influence of insects on the activity patterns of insectivorous bats.

Bats and Water: Anthropogenic Alterations Threaten Global Bat Populations

“…Differences in species richness and diversity between riverine and savannah habitats were not the same in the two regions. In the Kruger National Park, there was no difference in bat species richness or evenness between riverine habitat and savannah (Rautenbach et al 1996). In contrast, at another site in Swaziland, the riverine habitat had higher species richness and diversity (Monadjem and Reside 2008).…”

“…For example, in two regions in southern Africa, bat abundance was higher in riverine habitat than in adjacent, dryer savannah (Rautenbach et al 1996;Monadjem and Reside 2008). Differences in species richness and diversity between riverine and savannah habitats were not the same in the two regions.…”

“…In contrast, at another site in Swaziland, the riverine habitat had higher species richness and diversity (Monadjem and Reside 2008). In both regions, the two assemblages differed in the relative densities of the various species, with the savannah assemblages forming a subset of the riverine assemblages (Rautenbach et al 1996;Monadjem and Reside 2008). This reinforces the notion that bat assemblages in less mesic regions are extensions of bat assemblages in more mesic regions, but that not all species are inclined to make use of less mesic habitats when conditions are favorable.…”

“…Furthermore, calm surface water provides a less cluttered acoustic signal return from the echolocation pulses (Mackey and Barclay 1989;Siemers et al 2001), and there is some evidence, at least for echolocating bats, that activity over calm pools of water is higher than that over fastflowing riffles (von Frenckell and Barclay 1987). Bat activity in a transect from dry woodland savannah to riverine habitat in southern Africa was correlated with insect abundance-both bat activity and insect abundance were higher in riverine habitat (Rautenbach et al 1996) suggesting that bats were attracted to this habitat because of the feeding opportunities it provided.…”

Habitat use and nocturnal activity of lesser short‐tailed bats(Mystacina tuberculata)in comparison with long‐tailed bats(Chalinolobus tuberculatus)in temperate rainforest

“…Influence of ambient temperature on foraging activity Ambient temperature and invertebrate activity are consistent predictors of bat activity (e.g., Anthony et al 1981;Audet 1990;Maier 1992;Rautenbach et al 1996;Hayes 1997). Minimum temperatures influence bats' physiologically, making activity uneconomic below certain thresholds.…”