Notes from the Field: Fruit Bat Ecology and Forest Conservation in Tanzania

This guest post is from Roosevelt University senior Sustainability Studies major and Environmental Science minor Nicole Burns, who went to Tanzania this May as a part of RU biology professor Norbert Cordeiro’s Conservation Biology Africa 369 class. Here Nicole reports on the field work on fruit bats and forest ecology she and other students did in Tanzania’s East Usambara Mountains.

Walking through waist-high tea plants on an incline (N. Burns)

Walking through waist-high tea plants on an incline (N. Burns)

Seed dispersal and pollination by frugivorous bats is vital in tropical ecosystems to facilitate forest regeneration yet is rarely studied, especially in East Africa and, more specifically, within the East Usambara mountain range in northern Tanzania. In order to better understand how dispersal behavior by bats is affected by environmental degradation (i.e., land developed for agriculture) and to gather quantitative data on what species are primarily dispersed and how far the seeds are traveling, fellow SUST senior Josh Campbell, biology major Carmen Alvarez, and I performed two relevant experiments within the Amani Nature Reserve in May of 2013.

These bats’ feeding behavior entails carrying fruits and seeds to a feeding roost, where they eat the fruits and drop, spit, or defecate a pile of waste directly underneath the roost. These piles of waste are termed “wadges,” and can be identified by observing germinated seedlings of bat-dispersed plants near a tree’s base.

A bat wadge dominated by M. eminii seedlings (N. Burns)

A bat wadge dominated by M. eminii seedlings (N. Burns)

Our experiment had two parts: in the first (unrelated to this post), we wanted to track how far bats were carrying fruits from source to feeding roost by utilizing seed traps and radio tracking equipment. In the other part, we wanted to compare the density of feeding roosts in fragmented forests and agricultural land; so we took two roost censuses, one in an area of fragmented forest and the other in a tea plantation.

One of our seed traps, baited with bananas and the fruits of Anthrocleista grandiflora. We discovered that the bats much preferred the bananas to A. grandiflora, and on the third trial we were very excited to find all our fruits and transmitters had been scooped up. However, due to issues with our tracking equipment, we were unable to recover the transmitters. (N. Burns)

One of our seed traps, baited with bananas and the fruits of Anthrocleista grandiflora. We discovered that the bats much preferred the bananas to A. grandiflora, and on the third trial we were very excited to find all our fruits and transmitters had been scooped up. However, due to issues with our tracking equipment, we were unable to recover the transmitters. (N. Burns)

For the forest portion, we randomly selected four 20-meter square plots within a section of forest, identified the wadges within them, and recorded the plant species and quantities within the wadges. Over the four study areas, the most abundant species turned out to be Maesopsis eminii (we recorded 854 seedlings!), which is interesting for several reasons.

M. eminii is both native and endemic to the area, and its fast-growing properties make it the perfect species to combat the degradation of forests; however, it is also known to be invasive in some areas, meaning that it will multiply so quickly and abundantly that it can choke out other important native tree species. Thus, I would like to someday do further research of whether or not the dispersal of M. eminii by fruit bats is harming or helping this specific area.

Collecting data underneath an isolated tree, with tea plants surrounding the wadge (N. Burns)

Collecting data underneath an isolated tree, with tea plants surrounding the wadge (N. Burns)

In the tea plantation, we would survey the area in search of an isolated tree with sufficient canopy cover (which bats prefer for protection, especially in open areas) and then take our census under the tree. This was a tad difficult, since the entire area was covered in very dense tea plants and was very hilly (The photos included here give you an idea of the setting).

This research connects to my current summer class, PLS 391 Seminar in Natural Science, in which we have analyzed current science news articles and their depiction of the scientific method in action. An article I located for class discussion, “New Tools to Hunt New Viruses,” addresses how people are at risk for contracting bat-carried diseases. This got me wondering if those consuming tea from this plantation are also at risk, since the bats are essentially spitting and defecating directly onto the plants.

Obviously, one would need to do more research to answer many other questions, such as: Are the bats in the area known for carrying and spreading disease? Is there any history of people in the area catching diseases carried by bats? What processes do the plants go through from plantation to plate, and do these processes lower the risk of humans contracting bat-carried diseases?

Nicole BurnsNicole Burns is a senior SUST major at Roosevelt University and an occasional contributor to this blog. She is a co-founder of the RU student environmental organization, RU Reforesting.

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