Tropical Bat Houses

– By Meredith Van Acker

During my time interning at Finca Bona Fide I was involved with constructing and erecting bat houses.

The Role of Bats:

There are many benefits from the presence of bats in the natural world, especially on a permaculture farm. Insectivorous bats play an active role in determining how many (potentially damaging) pests are in the air and on the ground. Consequently, bats can help farmers with plant growth and health through this natural pest management. Nectar-feeding bats are critical pollinators for many plants, such as agave and giant cacti, and also improve genetic diversity through cross- pollination of plants. Also, fruit-eating bats can aid in reforestation through seed dispersal. In addition, a useful product that can result from bat house construction is bat guano. Bat guano provides a high concentration of nutrients to plants and the surrounding soil due to its high levels of nitrogen and phosphorus. The guano can be used or sold as fertilizer to surrounding farms and community members.

The Role of the Bat Houses

The bat houses serve multiple purposes for the farm and the bats including:

– Safe roosting sites for the bats.

– Integrated pest management practices for the farm systems.

– Guano harvesting for the fertilization of farm soil.

All of these factors had to be considered in determining the best placement for the houses. To meet roosting preferences for the bats we ensured the houses received 6-8 hours of sunlight daily in an open space with a large swoop zone and as far away from potential predator perches (other trees and structures) as possible. We also placed the houses close to areas of high existing bat activity and food sources.

Integrated pest management is an environmentally sensitive approach to managing insects that works towards the least possible impact on people, the property and the surrounding environment. It uses information on the life cycle of pests and their relationship with their environment for the appropriate management of insects. Therefore, in order for the bats to interrupt the life cycle of pests the houses were placed near water sources on the farm that become sites for hatching insects.

The Construction of the Bat Houses:

We used local cedar which is naturally resistant to insects and decay and treated it with linseed oil for natural weather resistance. The first house had three chambers with grooved chamber partitions for the bats to hang inside the house.

For the last two houses, we ripped the wood in order to create thinner and lighter boards. This was a labor intensive and time-consuming process, as it had to be done almost entirely with a handsaw. Needless to say we improved our upper body strength significantly:) Moreover, the new design resulted in less wasted material.  With the lighter houses we were able to securely mount the houses to withstand against the strong winds and rain. The roofs have a three-inch overhang to protect the house during the rainy season as well. The roof shingles were made from collected aluminum cans from the volunteers and a local restaurant.

The picture below show the inside of the chambers.

The next big challenge was choosing a site on the farm to mount the houses. We decided to place two houses on one pole to increase the efficiency for guano harvesting in the future and save on the number of poles needed. The houses were mounted on logs that were at least 12 feet in height. We placed two houses back to back on one pole and the third (and heaviest) house on its own pole.

Two houses were placed in an open space near the Casa del Sol, a three bed volunteer housing structure. This structure was experiencing issues with bats flying above the beds at night and leaving droppings in the structure. For both bat houses to receive balanced sunlight, one house was placed facing south and the other faced north. A new channel was recently dug out in front of Casa del Sol to catch water during the rainy season and feed into the farm’s watering system. This was expected to bring an increase in insects in that area and is not preferred for the volunteer experience as well as for the health of the plants. Therefore, the increase of bats in the area would be highly beneficial.

The last house was placed across the pond from another volunteer housing structure, the Hilton. The house was placed with the entrance facing southwest over the open pond to catch optimal sunlight. The pond was dry when we put the house up because it was in the midst of the dry season. However, it fills up with water during the rainy season and becomes a problem area for insects. Therefore, this placement satisfies the main goals for the houses, ideal roosting conditions, meets integrated pest management concerns and offers a viable site for guano collection.

The project serves as an example of the ideals of permaculture, stacking functions within time and space. When we look at the design of a landscape the functions of each part should work within the whole system. And in permaculture it involves the human and ecological system in a way that meets the needs of the localized area as well as allows for the cycles to continue being productive and self-sustaining. Once the houses become occupied they will be an integral part to the ecological systems that are in place at Finca Bona Fide. They can serve as a link between the human constructed environment of the farm and the existing wildlife that creates the regions’ biodiversity.

 

If you have any questions, feel free to email me at mvanack@gmail.com!