Nectar Bat Morphology: Adaptations for Specialization

Nectar bats are a highly specialized group of micro bats occupying the subfamilies Glossophaginae, Lonchophyllinae, Phyllonycterinae, and Bracyphillinae in the family Phyllostomidae (Kunz and Fenton 2003). They are found primarily in Central and South America and feed almost entirely on flower nectar, with some species occasionally exhibiting opportunistic feeding on pollen, fruit, and even insects. However, millions of years of natural selection since the Eocene epoch (approximately 55 Ma)  have resulted in the extreme specialization of some bats to obligate nectarivory, and they have the adaptations to show for it.

Bats in the subfamilies Lonchophyllinae and Glossophaginae show the most dramatic adaptations with regard to nectarivory. They possess an extremely long tongue, with hair-like papillae at the tip to facilitate nectar feeding through capillary action (Figure 1). For example, Glossophaga soricina is, on average, only 60mm in total body length, but can boast a tongue of up to 48mm (Tschapka and Dressler 2002). In addition to their long tongues, specialized nectar bats are characterized by a highly elongated skull and rostrum and noticeably diminished dentition. These adaptations allow the bat to easily reach inside flowers for nectar and withdraw from the flower quickly and efficiently (Figure 2; Tschapka and Dressler 2002).


 Figure 1. Cooper, M. 2006. A tube-lipped nectar bat (Anoura fistulata) sips nectar from a tube. Note extreme length of the tongue, which is more than half of the bat's total body length. This adaptation allows for quick and efficient nectar feeding. http://www.newscientist.com/article/dn10721-the-bat-with-the-incredibly-long-tongue.html; retrieved 29/3/2015.




 
Figure 2. Schneeberger, K. 2012. Elongated rostrum of an orange nectar bat (Lonchophylla robusta) adapted for easy access to nectar inside flowers. http://commons.wikimedia.org/wiki/File:Lonchophylla_robusta_head.jpg; retrieved 29/3/2015.


Whereas these specialized nectar bats clearly show some incredible morphological adaptations, many nectar bats also display physiological and behavioral adaptations to aid in nectar feeding. These evolutionary phenomena will be discussed in detail in future posts, along with the counter-adaptations shown by many of the plant species these bats visit.


References

KUNZ, T.H. and FENTON, M.B., 2003. Bat Ecology. Paperback edn. Chicago: University of Chicago Press.

TSCHAPKA, M. and DRESSLER, S., 2002. Chiropterophily: On Bat–Flowers and Flower Bats. Curtis's Botanical Magazine, 19(2), pp. 114.