Living in my new house in Manuel Antonio I get primate visitors almost daily. It's a true joy being able to watch them pass through on either their morning or afternoon routes, swinging and jumping through the surrounding forest. Having no walls on my house, only open space with screens in between me and the trees outside it feels as if I were out there with them, and the inclined slope the house was built on actually puts me at the level of the canopy outside me.  

The White Faced monkeys, the most common visitors are noticeably curious and precocious. The trees nearby are close enough to me inside for the White Face to come straight up to the house, look in the through the screens at me and jump on and across my roof. They seem to have no problem at all transitioning from the natural to human environment to get from one place to another.

This whole scene repeated several times over the course of a few days got me thinking about how the human environment affects connectivity and habitat use for wild animals. In my case, my house serves as a connecter for White Face monkeys, whose traditional means of transportation is achieved by and through trees, which of course were what was found on this spot before the house was built. We can say that by some virtue of the design of this house and the site it sits on this particular species of primate posseses the ability to cross from the trees on one side to those on the other. On one occasion I also witnessed several Squirrel Monkeys run across the roof as they passed through the area. For them as well, the roof seemed a perfectly adecuate piece of the natural environment for their use.

Connectivity is a very important characteristic where human development coexists with natural areas, and especially so in an area with such high species diversity, Manuel Antonio. Connectivity can be thought of as a measure of a particular species' ability to move around within its natural environment. This concept must be approached on an individual species level, each one examined for its own particular ability to move from place A to place B while it carries out its unique life functions. Every species moves in a different way, and has a different level of tolerance for disturbances in its environment. Different leves of connectivityTo look at both extremes as a means of understanding this concept, we can study two animals with vastly different means of achieving transportation. Scarlet McCaws (Ara macao) ) work well to illustrate a high level of tolerance to disturbance and the ability to travel accross large distances of variable habitat. On the other extreme we can picture a poison dart frog (Dendrobates auratus) , whose natural habitat is the forest floor, with abundant leaf cover and shade. Poison dart frogs, as well as most small amphibians only occupy a small range of possibly several square meters, travelling relatively short distances each day. Scarlet McCaws can occupy a comparatively enourmous range and travel large distances on a daily basis.

Connectivity and its sibling concept, habitat fragmentation, are both concepts that can be used to explain a species' ability to move through its environment in a certain geographical location. Certain species have higher tolerances for disturbance than others. In the case of Scarlet McCaws, they are able to cross highly disturbed areas, such as agricultural fields and cattle pasture,  to get from one forest patch to another. With a series of smaller fragments allowing these birds the chance to periodically rest along the way, very large expanses of highly modified habitat can be crossed to reach other patchs of natural habitat containing neccesary resources. Poison dart frogs may in turn have trouble crossing a 2 meter wide trail through a completely closed forest if there are not sufficeint levels of ground cover to provide a safe passage across. As in these two examples, the unique lifestyle and physical capabalities of each type of wild animal defines in a significant way its ability to travel through different environments. Even plants exhibit similar charecteristics depending on their modes of seed dispersal.Stepping stones across modified habitat

Consecuently, these measures, conenctivity and habitat fragmentation, play an important role in the longetivity and health of wildlife populations. In an area like Manuel Antonio, with high levels of development pressure they can take on particularly critical roles in ensuring the long-term health of many species, including White Face Monkeys and the other two species of primate found here.

When looking for means of achieving a sustainable growth of human environments, especially those in biodiversity hotspots, measuring and setting goals for connectivity become crucial. Envision an environment in which buildings and other human constructed elements can serve the dual roles of providing resources and utility to humans at the same time as providing the same for wildlife. Instead of dull and lifeless concrete walls, imagine walls covered in vegatation that can provide both food and shelter for wildlife. Roofs that allow arboreal species to easily cross from one side to the other of a building, instead of preventing passage. Habitat corridors can also be integrated into the space not left in a fully natural state around a building, but also not part of the structure itself, such as parking lots and gardens. If there are abundant terrestrial species such as ground dwelling mammals and lizards habitat corridors can lead them from one fragment safely and easily to another through the modified portion of the property, or even better, small buildings can possibly be built slightly raised from the ground to allow connectivity below.

Many qualities of these systems will have to be well examined and studied to find out which methods and designs work best. Physical connectivity can be measured, such as the distance from one tree crown to the next, and the ability of any human constructed elements in between to allow connectivity can be studied with already exisiting structures. Species diversity and abundance at exisiting structures can be measured, and the characteristics of those sites with the highest values analyzed to look for influences allowing these high levels of wildlife. This type of evaluation can be used to rate already existing buildings and inform future designs.

Have any of you thought of similar ideas near you? Or seen examples of connectivity created by human elements? Let me know, I'd love to hear about it.

Some images borrowed with permission from: Bentrup, G. 2008. Conservation buffers: design guidelines for buffers, corridors, and greenways. Gen. Tech. Rep. SRS-109. Asheville, NC: USDA, Forest Service, Southern Research Station.