Echolocation behaviour of Megaderma lyra during typical orientation situations and while hunting aerial prey: a field study

Abstract

Bats modify the structure and emission pattern of their calls to cope with the functional constraints of a given echolocation situation. As a consequence, the flexibility in sonar call use affects the potential niche use of a species. The present paper addresses call use in Megaderma lyra, a species with a short, broadband multiharmonic basic call, in typical orientation situations, when emerging from and re-entering a day roost, in cruising flight and when passing through vegetation, and during the pursuit of tethered, flying insects. While call duration and emission rate were adapted to the four orientation situations, call spectral composition was similar in these situations, except that bats emitted calls containing more harmonics when re-entering the roost. These moderate call modifications may be accounted for by the observation that M. lyra stayed close to landscape elements even in open habitats. Although M. lyra is a typical gleaner, all tested bats approached flying insects, guided by sonar calls of significantly decreasing duration and pulse interval, and of increasing sweep rate. Before capture, peak frequency was lowered from call to call. The spontaneous approaches towards flying insects with systematic changes in call pattern suggest regular aerial hunting in this species.

Chiropteran diversity in the peripheral areas of the Maduru-Oya National Park in Sri Lanka: insights for conservation and management

“…Human-occupied landscapes usually contains forest preserves, mature woody vegetation, and buildings, therefore, may provide shelters for bat roosting compared to agricultural landscapes under intensive commercial farming which may lack a diverse array of roosting sites (Gehrt and Chelsvig 2003). Microclimatic stability and thermoregulatory advantages, protection from inclement weather and predators, nursing young, and grooming are some benefits conferred from roosting sites; social behaviors, such as determination of hierarchies, competition, cooperation, and recruiting females into “harems” are also critical ethological elements of roost selection (Campbell et al 2006; Chaverri and Kunz 2010; Lewis 1995; Schmidt et al 2011; Storz and Kunz 1999; Tan et al 1997). Selection of optimal roost have profound fitness consequences for bats as roost conditions cater to their diversified functional attributes, physiological optima, life-history specifications, and social integrity (Campbell et al 2006).…”

“…Although bats in general are known to occupy a diverse range of habitats for roosting, studies conducted in Sri Lanka have mostly reported caves as suitable roosting sites (Kusuminda et al 2013; Rubsamen et al 2004; Yapa and Ratnasooriya 2006; Yapa 1992). Although behavior, echolocation, and trophic ecology of bats have been satisfactorily explored in Sri Lanka (Neuweiler et al 1987; Pavey et al 2001; Schmidt et al 2011), much remain unknown about selection of roosting sites and habitat associations. Thus, surveying roosting sites helps understanding habitat associations of bats in areas of interest.…”

Evolutionary escalation: the bat–moth arms race

“…A feeding buzz (i.e. echolocation call rates of >100 calls s −1 , and ≥200 calls s −1 in some species; see Glossary) has been described for almost all bats studied when taking airborne prey, a rare exception being the primarily substrate gleaning bat (see Glossary) Megaderma lyra from the ancient, species-poor family Megadermatidae (Schmidt et al, 2011). During the terminal subphase of a feeding buzz (often referred to as buzz II), species in the sister LDC bat families Vespertilionidae and Molossidae drop the peak frequency of their echolocation calls by an octave and, consequently, roughly double the breadth of their sonar beam Ratcliffe et al, 2013).…”

Managing Clutter in a High Pulse Rate Echolocation System

“…A common-sense rule is that the next pulse should not be emitted until all perceptible echoes from the previous pulse have died out. In the majority of situations, bats appear to avoid this pulse-echo ambiguity, or “aliasing.” Studies of big brown bats navigating in extremely cluttered environments, however, show cases where bats appear to tolerate such aliasing to sample the environment at a high-rate (Petrites et al, 2009 ; Schmidt et al, 2011 ).…”