Evolutionary Characteristics Of Bats

Bats are a unique group of small mammals to have evolved wings with a well-developed ability for powered flight. They exhibit evolutionary characteristics that to a large extent are considered socially, physiologically and ecologically unique and peculiar. Bats are classified under the Order Chiroptera containing the suborders Pteropodiformes and Vespertilioniformes which consist of mega and micro bats respectively. They are the most abundant group of mammals in terms of population numbers with a great diversity of over 1000 extant species that is second only to those of the taxonomic Order Rodentia.

The wings enable bats to fly and cover long distances. As such, bats have exploited this attribute to explore a wide variety of ecosystems during feeding and migratory activities.

This accounts for their wide geographic distribution and high ecological diversity, occurring over all major continents except Antarctica and some polar regions.Their well-developed and unique socio-physiological adaptations help in enabling many bat species to thrive and successfully propagate their survival. In addition to flight ability, bats can also echolocate, show roosting behavior, enter torpor and hibernate in winter and live unusually long life spans for such smaller-sized mammals.

Bats are generally active at night and show different feeding habits, emerging from their roost sites after sunset to forage and feed on a wide variety of dietary items including insects, flower nectar, fruits, seeds, fish, frogs, small mammals as well as blood. Bats are characterized by relatively small body size which varies between 2 grams, such as the Bumblebee bat and the Golden capped fruit bat (Acerodon jubatus), the largest species of bats with a body mass of up to 1.

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The wing spans of bats generally ranges from a mere 8 centimeters to 1 meter in length. They show roosting behavior that enables them to live in a wide variety of natural structures including in caves, trees, tree hollows, the under bark of trees as well as man-made structures like house roofs, abandoned mines and bridges. In southern Africa, many efforts have been made in examining various ecological aspects, reproductive strategies, distribution and diet composition of some bat species especially in South Africa. In Namibia however, published ecological studies on bats are almost non-existent. In fact, much of what is currently known about the occurrence and distribution of bat species is largely based on records of museum specimens that were collected as far back as the late 1960s, which may not necessarily reflect the current patterns and status of bat distribution and occurrence.

The biology and ecology of many bat species in Namibia remain unexplored, let alone bat community-based studies focusing on species richness and composition at localized habitats in the different biomes. This presents a lack of scientific research and knowledge that is necessary for effective management and conservation of bats. Namibia is generally categorized as an arid landscape with certain parts largely characterized by communal land tenure systems underpinned by subsistence farming lifestyles. These, coupled with a growing population, lead to overexploitation of natural resources resulting in deforestation, wild fires and soil erosion, thereby intensifying the problem of desertification . In addition, human activities relating to agriculture, wood logging and animal farming are transforming the vegetation structure of natural habitats and consequently affect natural ecological processes.

This in turn may adversely affect species composition, richness and diversity of bats in the modified local habitats. Bats are also sensitive to changing environments and are considered suitable biological indicators of environmental quality, serving as agents for monitoring changing ecosystems. According to Lima, Varzinczak, & Passos (2016), the interactions of factors pertaining to habitat structure and seasonality influences the composition of local bat assemblages. In essence, bat communities at local scales are influenced by interacting factors, wherein availability of suitable roosts and easy access to foraging habitats with abundant food resources takes precedence. Therefore, the determination of patterns of species richness and composition in local habitats will help characterize important conservation areas of high species richness and the associated species such habitats may support.

The effective conservation of biodiversity and particularly bats may also hinge on our understanding of changing environments and how these changes affect species richness and composition of bats particularly in localized habitats. Characterizing patterns of species richness and composition of local habitats within these biomes would represent a starting point and a positive step towards understanding the biology, ecology, patterns of species occurrence and distribution of some bat species in Namibia. Moreover, bats have in recent times come under increasing attention in regard to their roles as hosts for a large number of both old and emerging zoonotic viruses that pose potential to spill over and infect humans and other animals with significant economic and public health implications. According to Calisher et al. (2006) and Smith & Wang (2013), as many as 66 viruses including Ebola virus, Hendra virus, Nipah virus and SARS-CoV have been reported to be carried by bats without showing any pathogenic effects or any symptom of the disease.

Although bats carry this important status of being hosts for viruses with significant public health impact, they are equally suitable carriers of new and emerging viruses, including the emergence of hantaviruses in Africa. Accordingly, the detection of the first novel African bat-borne Magboi hantavirus (MGBV) confirmed the status of bats as suitable hosts for hantaviruses and has drawn attention to hantaviruses and their potential public health significance on the African continent. Hantaviruses are a group of emerging viruses sharing similar antigenic and genetic properties. Hantaviruses, classified under the genus Orthohantavirus, family Hantaviridae and Order Bunyavirales, comprises of different hantavirus species (genotypes) that are traditionally named after the place where each hantavirus was first detected from their carrier hosts.

These viruses inhabit rodent, shrew and bat hosts that are dispersed and adapted to different environments across the world. The hosts excrete the hantavirus in saliva, urine and feces while infections may happen through inhalation of excreted virus-contaminated aerosols, contact with contaminated excreta, contaminated food or by bites that may occur. Human infections by the rodent borne Hantaan virus (HTNV) and the Seoul hantavirus (SEOV), as well as Puumala and Dobrava-Belgrade hantaviruses cause Hemorrhagic fever with renal syndrome (HFRS) in Asia and Europe, while the Sin Nombre (SNV) and Andes (ANDV) hantaviruses cause hantavirus pulmonary syndrome (HPS) in the Americas.

In Africa, there is a conspicuous absence of recorded cases. The extent and impact of hantavirus disease has largely remained unknown for many years, with only one isolated case of HFRS reported in Central African Republic in 1987. Although pathogenic hantaviruses are traditionally known to be carried by rodents, there is emerging evidence that shows hantavirus infections of humans emanating from non-rodent (shrew) carrier hosts particularly in west Africa (Heinemann et al., 2016). The need to screen for possible prevalence of hantaviruses especially in suspect bats can contribute towards ascertaining the status of hantavirus prevalence in Namibia.