Nature watch: flightless young and meticulous mother bats

Bats are placental mammals that have achieved true flight. After mating and fertilisation, the egg is implanted in the wall of the uterus and the foetus undergoes development over a gestation period. After birth, the young are protected and given shelter, suckled, and possibly instructed before weaning and eventual independence. Within this period, bats show considerable variation in behaviour which is generally linked to climate and feeding habits. This article explains the behaviour associated with different breeding systems in different climatic regimes

Echolocation: the strange ways of bats

Bats are capable of avoiding obstacles that they encounter, even in complete darkness. This is because they emit ultrasound (high frequency sound) and analyse the echo produced when the sound hits objects on their path. This article describes the hunting flight of bats and how echolocation is useful in prey capture. Prey capture without the aid of echolocation by some bats is also described

Seasonal changes in the precision of the circadian clock of a tropical bat under natural photoperiod

The emergence and returning activity patterns of a colony of microchiropteran bats Hipposideros speoris, under natural light-dark cycles keep pace with the timings of sunset and sunrise respectively. The onset of emergence flight occurred at different environmental twilight intensities which vary over the seasons. The seasonal changes of phase relationship between the onset and end of flight activity to sunset and sunrise respectively are discussed. As a result ψ-onset, ψ-end, and ψ-midpoint all undergo marked seasonal variations and the values obtained are well in accordance with the seasonal rule of Aschoff. The changes in the timing of onset and end of activity reflect the changes in the duration of activity time of the colony. The activity time is positively correlated with the duration of night time. The possible involvement of the 'non-parametric' action on the entrainment of this colony is briefly discussed

The use of acoustical cues for prey detection by the Indian false vampire bat, Megaderma lyra

1. The response of the echolocating bat, Megaderma lyra, was tested to different kinds of prey in an outdoor cage. The bats caught larger flying insects (moths, beetles, grasshoppers, and cockroaches) on the wing and also picked up arthropods (solifugid spiders, beetles and cockroaches) and small vertebrates (mice, fishes, frogs and geckoes) from the ground. After touching the prey with the muzzle, the bats were able to differentiate between species. Scorpions and toads were not taken by M. lyra. 2. In lighted and in dark conditions, M. lyra detected and caught prey only when it moved. Dead frogs briskly pulled over the floor were also detected and caught, whereas stationary dead frogs were disregarded by the bats (Table 1). 3. When dead frogs were pulled over the watered surface of a glass plate to eliminate noises by motion, the motion no longer alarmed the bats. From the results of these experiments it was concluded that M. lyra detects prey on the ground by listening to the noise of the moving target only, and not by echolocation (Table 1 C, Fig. 1). Furthermore, M. lyra were not attracted by frog calls. 4. M. lyra differentiated between palatable frogs and non-palatable toads only after touching the prey with the muzzle. 5. Experiments with freshly killed frogs coated with toad secretions or covered with toad skins indicate that M. lyra differentiates between frogs and toads by chemical means. There was no evidence that these prey were differentiated by means of echolocation

Comparison Among Original AHP, Ideal AHP and Moderate AHP Models

Decisions always involve getting the best solution, selecting the suitable experiments, most appropriate judgments, taking the quality results etc., using some techniques. Every decision making can be considered as the choice from the set of alternatives based on a set of criteria. The analytic hierarchy process (AHP) is a multi-criteria decision making and is dealing with decision-making problems through pairwise comparisons. This paper is concerned with the moderate AHP decision model is always the same as the original AHP decision model. It does not violate the rule itself

Private Out-Domination Number of Generalized de Bruijn Digraphs

Dominating sets are widely applied in the design and efficient use of computer networks. They can be used to decide the placement of limited resources, so that every node has access to the resource through neighbouring node. The most efficient solution is one that avoids duplication of access to the resources. This more restricted version of minimum dominating set is called an private dominating set. A vertex v in a digraph D is called a private out-neighbor of the vertex u in S (subset of V(D)) if u is the only element in the intersection of in-neighborhood set of v and S. A subset S of the vertex set V (D) of a digraph D is called a private out-dominating set of D if every vertex of V − S is a private out-neighbor of some vertex of S. The minimum cardinality of a private out-dominating set is called the private out-domination number. In this paper, we investigate the private out-domination number of generalized de Bruijn digraphs. We estabilsh the bounds of private out-domination number. Finally, we present exact values and sharp upperbounds of private out-domination number of some classes of generalized de Bruijn digraphs

Donald Redfield Griffin: the discovery of echolocation

The puzzle as to how bats navigate without colliding with obstacles and hunt tiny mosquitoes in complete darkness remained unanswered for nearly 140 years after Lazzaro Spallanzani, who proposed at the close of the 18th century that bats possess a 'sixth sense' for orientation. Donald Griffin solved the puzzle in 1938 with the help of world's first ultrasound microphone devised by the American physicist G W Pierce. Griffin called this sixth sense 'echolocation', which enables bats and marine mammals such as whales, dolphins and porpoises to lead active lives under the cover of darkness. In this article we describe the life of Donald Griffin and how he proved the existence of echolocation in bats

Ontogeny of sounds in the echolocating bat Hipposideros speoris

1. Young Hipposideros speoris emit multiharmonic sounds in groups of three to four notes. Newborns emit a relatively uniform pattern of FM- and FM/CF/FM-sounds. From ten days of age onwards the initial sound (first note) of a group is a FM-sound whereas the successive ones are CF/FM-sounds of consistently higher frequencies. At prevolant and volant stages of the bat's development most of the sound energy is concentrated in the second harmonic which is raised to the frequency range of the adults' CF/FM-sounds (127-138 kHz). Subsequently other harmonics disappear. 2. Harmonic components are suppressed or filtered out when they fall in a frequency range of approximately 65-75 kHz. This was found for bats of different ages regardless which fundamental frequency the suppressed harmonic components corresponded to, indicating a mechanical filtering process. These measurements coincide with the absence of the first harmonics in the same frequency range in the sounds of adults. 3. Temporal sound emission patterns were measured for bats of different ages. There was an increase in sound duration and an increase in the number of sounds (notes) per group as the bat matured to adulthood. 4. The sound emission of juveniles aids mothers in finding their young ones. Mothers located their infants even when the juveniles were displaced far from where they were left behind by their mothers. Behavioral experiments under both natural and captive conditions showed that the sound emission of young ones attracts mothers but do not give sufficient cues to allow the mother to discriminate their own from a group of young. 5. The ontogeny of the two types of sounds (CF/FM and complex harmonic FM) of adult Hipposideros speoris is discussed and compared with the vocalisations of other bat species

Movement as a specific stimulus for prey catching behaviour in rhinolophid and hipposiderid bats

1. The echolocating 'long CF/FM-bat'Rhinolophus rouxi and the 'short CF/FM-bats'Hipposideros bicolor andHipposideros speoris were tested for catching responses to moving and non-moving targets. 2. Under our experimental conditions (freshly caught caged bats in a natural environment)Rhinolophus rouxi and Hipposideros speoris only responded to insects of any sort that were beating their wings. The bats showed no reactions whatsoever to nonmoving insects or those walking on the floor or the sides of the cage. 3. Hipposideros bicolor responded in the same way as the above species to wingbeating insects but in addition also attacked walking insects. In 27 presentations 15 walking insects were caught (Fig. 2). 4. Rhinolophus rouxi, Hipposideros speoris and Hipposideros bicolor also detected, approached and seized tethered cockroaches hanging from the ceiling when these were vibrating up and down (Fig. 3). This indicates that any oscillating movement and not specific aspects of wing beating were the key releasers for catching behaviour in all three species. However, a wing beating insect is strongly preferred over a vibrating one in all three species (Fig. 4). 5. Rhinolophus rouxi, Hipposideros speoris and Hipposideros bicolor attacked and seized a dead bait when it was associated with a wing beating device (Fig. 1). All three species responded effectively to beat frequencies as low as 10 beats/s (peak-to-peak amplitude of the wing excursion 20 mm). For lower frequencies the response rates rapidly deteriorated (Fig. 5). 6. Horseshoe bats no longer responded to wing beats of 5 beats/s when the wing beat amplitude was 2 to 1 mm or to wing beats of 2 to 1 beats/s when the amplitude was 3 mm or lower (Fig. 6). This suggests that the speed of the wing is a critical parameter. From these data we infer that the threshold for the catching responses is at a wing speed of about 2 to 1 cm/s. 7. In horseshoe bats (experimental tests) and the two hipposiderid species (behavioural observations) one single wing beat was enough to elicit a catching response (Fig. 8). 8. It is concluded that 'long' and 'short' CF/ FM-bats feature a similar responsiveness to fluttering targets. The sensitivity to oscillating movements is considered as an effective detection mechanism for any sort of potential prey

Development of wing morphology in the Indian pygmy bat Pipistrellus mimus

The growth and development of the wing parameters of the Indian pygmy bat Pipistrellus mimus was studied under natural conditions. Newborn young were marked with nontoxic coloured paint and were later marked with split rings. The wingspan and wing area showed linear growth until the age of five weeks, after which the rate of growth decreased. The observations on flight showed that at the age of 19 days the young were able to flutter their wings, at the age of 22 days they flew for a short distance and at the age of 29 days they exhibited sustained flight. The development of wing loading and aspect ratio are also presented. The decrease in wing loading as the bat grows is discussed as an advantage to sustain flight. The aspect ratio showed a high degree of scatter at early stages of life which decreased at the later period of growth. In general the development of wing morphology of P. mimus is similar to that of other vespertilionid bats