The Importance of Acacia Trees for Insectivorous Bats and Arthropods in the Arava Desert

Abstract

Anthropogenic habitat modification often has a profound negative impact on the flora and fauna of an ecosystem. In parts of the Middle East, ephemeral rivers (wadis) are characterised by stands of acacia trees. Green, flourishing assemblages of these trees are in decline in several countries, most likely due to human-induced water stress and habitat changes. We examined the importance of healthy acacia stands for bats and their arthropod prey in comparison to other natural and artificial habitats available in the Arava desert of Israel. We assessed bat activity and species richness through acoustic monitoring for entire nights and concurrently collected arthropods using light and pit traps. Dense green stands of acacia trees were the most important natural desert habitat for insectivorous bats. Irrigated gardens and parks in villages and fields of date palms had high arthropod levels but only village sites rivalled acacia trees in bat activity level. We confirmed up to 13 bat species around a single patch of acacia trees; one of the richest sites in any natural desert habitat in Israel. Some bat species utilised artificial sites; others were found almost exclusively in natural habitats. Two rare species (Barbastella leucomelas and Nycteris thebaica) were identified solely around acacia trees. We provide strong evidence that acacia trees are of unique importance to the community of insectivorous desert-dwelling bats, and that the health of the trees is crucial to their value as a foraging resource. Consequently, conservation efforts for acacia habitats, and in particular for the green more densely packed stands of trees, need to increase to protect this vital habitat for an entire community of protected bats.

A whispering bat that screams: bimodal switch of foraging guild from gleaning to aerial-hawking in the desert long-eared bat

“…It is therefore possible that O. hemprichii enters different habitats with artificial irrigation or attacks different prey and then adopts a different foraging mode in times of scarcity of its typical prey. Indeed, O. hemprichii in the region are typically found in natural habitats and rarely in artificial habitats such as the date palms and village gardens where we recorded (Hackett et al, 2013). Additionally, on moonlit nights, adult common yellow scorpions (Buthus occitanus israelis) are less active, and those that are active tend to ambush from under vegetation (Skutelsky, 1996).…”

“…Otonycteris hemprichii Peters 1859 is a desert passive gleaner that feeds primarily on non-aerial arthropods in dry, sparsely vegetated environments (Arlettaz et al, 1995;Gharaibeh and Qumsiyeh, 1995;Fenton et al, 1999;Korine and Pinshow, 2004;Holderied et al, 2011;Hackett et al, 2013). As with most gleaning species, it has long ears, low wing loading and a low aspect ratio (Gharaibeh and Qumsiyeh, 1995).…”

The Buzz of Drinking on the Wing in Echolocating Bats

“…We only recorded at sites in Israel whose bat fauna was well known and made of a limited (<10) number of species whose call structure did not overlap between each other (Hackett et al. ).…”

The use of Vocalizations of the Sambirano Mouse Lemur (Microcebus sambiranensis) in an Acoustic Survey of Habitat Preference

“…We attached the acoustic recorder to a tree at the recording site at a height of 1.0–1.5 m above the ground so that the chance of device tampering by rats and other small ground-dwelling animals was minimal, an approach used by Hackett et al (2011). The acoustic recorder produced stereo files at a 48-kHz sampling rate, 16-bit resolution, resulting in 320 kbps WAV audio files, an approach that has worked successfully in other acoustic surveys of terrestrial organisms (Baldo and Mennill 2011).…”

“…If a species can be identified through its vocal acoustic properties, bioacoustic surveys can be used to investigate species-specific vocal activity (Terry et al 2005). Bioacoustic surveys are a noninvasive method of obtaining vocalization activity data and have been used successfully in studies of birds (Baldo and Mennill 2011; Dawson and Efford 2009), bats (Hackett et al 2011; Obrist 1995), frogs (Love and Bee 2010; Penny et al 2014), and marine habitats (Jolly and Hampton 2011). Such surveys are ideal for investigating animal habitat preference, population distributions within tropical forests, and the influence of habitat on animal vocal repertoires (Drew 2014).…”