Bat diversity

While bats never reached as great a level of diversity as pterosaurs and birds, they are nevertheless quite diverse. Today bats are the second largest group of mammals, with more than 1100 known living species. The largest group, rodents, have more than twice as many species, but they are less biologically diverse than the bats (Altringham, 2011).

Bats are divided into two groups- the microbats and the megabats. The microbats are the more original bats, while megabats are a younger group with the oldest known megabat, Archaeopteropus, living around 35 million years ago. The names "microbat" and "megabat" are somewhat misleading as there do exist big microbats and small megabats. The real differences in the groups are features such as the more elongated, dog-like, faces of the megabats and the fact that most megabats have lost their echolocation abilities (Altringham, 2011).

Figure 1: A blossom bat pollinates a flower. Despite its small size, this is actually a megabat, showing that size is not the defining feature of the two bat groups.  Photographer: Mike Trenerry.

While most bats have retained the insectivore lifestyle of their ancestors, there are many who have exploited other niches. The megabats and some microbats have become frugivores and nectarivores. There are also bats who have evolved a fishing lifestyle, such as Latin America's bulldog bats, who use echolocation to detect the ripples caused by fish near the surface of rivers and ponds. There are also a number of predatory bats, such as the false vampire bats and the frog eating bats (Levy, 1999).

Figure 2: A bulldog bat catches a tasty fish.  Photographer: J. Scott Altenbach.

There are even a few bats who evolved to feed on blood. Namely Latin America's vampire bats. As well as the standard echolocation ability, vampire bats also possess two heat sensing pits in their face, to help seek out warm blood vessels near their prey's skin surface. Their razor-sharp triangular teeth shave away overlying tissue and nick the blood vessel and special anticoagulants in their saliva keeps the blood flowing (Levy, 1999).

Figure 3: A vampire bat shows off the tools of the trade- razor-sharp triangular teeth for nicking blood vessels.  Photographers: Michael Fogden & Particia Corbis.

While no bat ever became flightless, New Zealand's lesser short-tailed bat spends much of its time down on the ground, foraging for insects, berries and nectar on the forest floor. Unlike other bats its wings are not attached to the hindlimbs, so it can move about on the ground more easily than other bats can (Fitter, 2009).

Figure 4: A lesser short-tail bat foraging around in a New Zealand forest.  Photographer: Rod Morris.

Next shall be this blog's conclusion.

References
Altringham, J. D. (2011). Bats: From Evolution to Conservation. Oxford University Press: Oxford.
Fitter, J. (2009). New Zealand Wildlife. Bradt Travel Guides Ltd: England.
Levy, C. K. (1999). Evolutionary Wars: A Three-Billion-Year Arms Race. W. H. Freeman and Company: New York.

Image sources
Figure 1: Accessed May 19, 2015, from: http://www.wettropics.gov.au/site/resized/80-08082012022826-0-119-990-389-990x389-cropped-mtlittleblossombat2.jpg
Figure 2: Accessed May 19, 2015, from: http://www.vnews.com/csp/mediapool/sites/dt.common.streams.StreamServer.cls?STREAMOID=H_kR6yEGutZtjodlwCi2aM$daE2N3K4ZzOUsqbU5sYv$HB5zCCfOaoycRvYQB8Y5WCsjLu883Ygn4B49Lvm9bPe2QeMKQdVeZmXF$9l$4uCZ8QDXhaHEp3rvzXRJFdy0KqPHLoMevcTLo3h8xh70Y6N_U_CryOsw6FTOdKL_jpQ-&CONTENTTYPE=image/jpeg
Figure 3: Accessed May 19, 2015, from: http://images.nationalgeographic.com/wpf/media-live/photos/000/005/cache/common-vampire-bat_505_600x450.jpg
Figure 4: Accessed May 19, 2015, from: http://blogs.scientificamerican.com/media/inline/blog/Image/CrawlingBat.jpg