03 December 2017

Frogs, conservation, and the agricultural matrix

March 2017

By Anat M. Belasen

Conservation can sometimes seem like an amorphous, nebulous, unattainable goal. One school of thought believes the goal of conservationists is to restore abused land to primary forest. They argue this is the best and fastest way to see results. This may be fast on a per site basis, but land conversion can be slow and--especially if you're just a few people-- it’s hard to get it to catch on around the world. Another school of thought (spearheaded by Ivette Perfecto, John Vandermeer, and colleagues) believes that we need a grander paradigm shift if conservation is going to happen on a global scale. Instead of presenting human land use as essentially at odds with conservation (viewing conservation success as nature at its most pristine), these conservationists argue that humans can be part of nature if we change the way we use land. Specifically, we need to change agricultural practices on a large scale, and especially in the tropics, if we wish to conserve biodiversity. This latter school of thought is based on both theory and empirical research that show that rustic forms of agriculture, such as shade coffee and cabruca cacao, can actually maintain nearly equal levels of [animal] biodiversity compared with pristine forest.

My first three dissertation chapters are focused on the intersection of landscape modification (habitat fragmentation) with disease susceptibility. The underlying hypothesis that I am attempting to test is that as populations become fragmented, they become more susceptible to disease. After attending meetings of the New World Agriculture and Ecology Group (NWAEG) as well as a few joint lab meetings of the Perfecto and Vandermeer ("Perfectomeer") research groups at U. Michigan, I started to wonder about the true usability of this research in conservation. I became interested in not just looking at fragmentation as a binary variable (fragmented versus not), but in examining the effects on wildlife of different types of habitat modification (rustic landuse vs. intensive agriculture vs. pristine forest).  So I decided to go to the epicenter of rustic farming and cacao capital of Brazil: Bahia.

A cacao tree in Igrapiuna, Bahia, Brazil. Cacao flowers and fruits are borne on the trunk of the tree.

On my first research trip to Brazil with the James Lab (January 2014), the first field site we visited was the Serra Bonita (“beautiful mountain”) reserve in Camacan, Bahia (“Bah-EE-yuh”). Serra Bonita was such a magical place - it is an incredibly biodiverse patch of high elevation forest, located on the top of a mountain in the middle of cacao country (Costa de Cacau). There were so many exotic hummingbirds, monkeys, insects, and of course frogs. Just outside of our doorstep at the high elevation field station was a misty tropical wonderland, waiting to be explored. This was the kind of tropical paradise I had always dreamed of visiting, and I always hoped to go back since that first year.

The view of Camacan from the top of Serra Bonita.

That hope became a reality when I returned to Bahia in January 2017 to collect samples from a variety of habitats to determine how landuse affects amphibian health and disease susceptibility. My first stop (after meeting new collaborators including Mirco Solé and Victor Dill at the State University of Santa Cruz in Ilhéus, Bahia) was Serra Bonita, but this time I and my field assistants stayed in the new low elevation research station, at the base of the mountain. The station was built between a patch of forest and a patch of cabruca cacao. Cabruca is a style of cacao farming in which the native canopy of tall, old trees is left intact, while the subcanopy is removed and replaced with cacao trees. Because cacao evolved as an understory tree, cabruca farming is a way of producing cacao commercially but in a more natural setting. Our team alternated between visiting patches of forest and patches of cabruca each night, capturing as many frogs as we could and swabbing all of them in the same night before releasing them.

Three of the focal species that we sampled at Serra Bonita. Top: Pithecopus rohdei (Rohde’s leaf frog). Middle: Rhinella crucifer (striped toad). Bottom: Dendropsophus elegans (elegant forest treefrog).

Next, we traveled to a different forest reserve, the Michelin Reserve. The Michelin Reserve is located about two hours north of our homebase of Ilhéus, Bahia. At first I thought the resemblance between the name of the reserve and the tires on my car was a coincidence, but soon I learned that the French rubber company did in fact own the reserve. On the Michelin reserve are a number of cerigueras, or rubber tree plantations. Rubber trees are very tall and skinny, and in many of the rubber groves there is cacao planted beneath (presumably to maximize commercial output from the land). Between these rubber groves are patches of pristine forests, with some being obviously very old (huge trees!). To offset the use of Brazilian land for rubber production, Michelin maintains and protects a number of large patches of high quality forest, which is inhabited by a surprisingly high diversity of animals. We captured the most frogs out of all of the sites at the Michelin Reserve, as well as the highest diversity of frogs.

Cabruca-style cacao planted among tall skinny (white-trunked) rubber trees in the Michelin Reserve.  

This rubber/cacao grove was covered with tiny bromeliads and was beautiful in the pinkish purple light of dusk.

The “teenage” Aparasphenodon brunoi

Finding a juvenile Aparasphenodon brunoi (Bruno’s cask-headed frog) in a forest patch at Michelin was a real treat. This was only the second individual of this species on record for the Michelin Reserve. Adults generally exhibit muted dark gray-brown coloration with dark brown eyes but have impressively large, bone-plated heads (which is where the common name of “cask-headed frog” derives). Very young individuals, on the other hand, exhibit striking silver patterns on the back and have bright red eyes, but they lack the characteristic bony head plates. This individual was a “teenager” and possessed the best attributes of both life stages. To make the discovery of this frog even more exciting, this is one of the only venomous frogs known to science, and can produce venom that is 25x more potent than that of pitvipers.

One iteration of my Bahia research team taking a break from the drive back to Ilhéus to enjoy a beautiful view of the ocean. From left to right: Joice Ruggeri, me (Anat Belasen), Rafael “Hobbit” Benetti, and Renato Martins.

After our first stay in Michelin, we returned to Camacan to sample fragmented areas surrounding the Serra Bonita Reserve. We talked with a number of farmers to be sure it was alright to sample on their land, and then returned at night to follow the sounds of calling frogs until we hit the jackpot. Some of these fragmented sites host huge densities of frogs, but mainly species that are able to exploit lower quality habitat. It could be that fragmentation filters out species that can be strong competitors in a mixed community, but are more sensitive to abiotic factors that change with fragmentation. Therefore the species that remain would experience competitive release and attain "unnaturally" high densities.

A large Phyllomedusa bahiana (the Bahian leaf frog) found in a patch of cabruca in Camacan, just outside of the Serra Bonita reserve. I’m fairly certain this is the largest tree frog I have ever captured - its SVL (length of the body, including the head, not including the legs) had to be close to 4 inches.

Finally, we returned to the Michelin Reserve to complete our sampling within reserve as well as sample the fragments surrounding the reserve. The forest fragments in Igrapiuna were bigger compared with Camacan. This is probably why we were able to find more sensitive, leaf-litter dwelling species like Physalaemus signifer and Haddadus binotatus.

A big (~½”) female
Physalaemus signifer (Girard’s dwarf frog) found in a forest fragment in Igrapiuna, just outside of the Michelin Reserve.

With over 800 swabs collected and genetic samples from over half of the frogs we swabbed, it was time to go back to Michigan and hunker down in the lab (with lots of help from my two wonderful research assistants, of course!). It’s now up to me to get as much information out of these samples as possible. The hope is that these data will give us some idea of the effects of different farming practices on frogs and their disease susceptibility, to inform conservation efforts of these sensitive and diverse animals.