Expedición Melanocephala! (Or How I Learned to Avoid the Acacia Tree)


Recently I returned from a week-long trip into the rainforests of Costa Rica to search for the Black-headed Bushmaster (Lachesis melanocephala), one of the most secretive and difficult-to-observe vipers in the world. We suspect that this species is vulnerable to declines, but currently lack data, and our efforts are geared to allow us to assess the status of this species to be able to conserve them. Our survey location was Parque Nacional Piedras Blancas in the vicinity of Golfito, Costa Rica. Piedras Blancas is an important biological corridor between the Osa Peninsula and the rest of Costa Rica, but it has had very little scientific study. With that in mind, the Área de Conservación Osa (ACOSA; think of it as the equivalent of the National Park Service for the national parks around the Osa) was excited by our bushmaster expedition as a way to generate herpetological observations for the park, as a general inventory of reptiles and amphibians has not been done. Our partner on the bushmaster project, Guido Saborío, works for ACOSA and he helped coordinate our survey so that we would go to some of the best places for reptiles and amphibians in the park, including bushmasters. We were guided by an ACOSA park ranger named Oscar; Oscar had lived in the area before the park was formed and had seen several bushmasters through the years.

Our plan was to backpack into a more remote area of the park for 3 days, and spend the rest of the time based out of an ACOSA station exploring other ridges in the area. In addition to Oscar, I was joined by five other adventurers. Although Guido was unable to come with us due to another work assignment, two Tico friends, Manuel Sanchez and Marcelo Carvajal, were able to come along. I had met Manuel and Marcelo for the first time on my December 2012 visit to the region, and I was very glad to have them along again, both for their extensive knowledge of Costa Rican herpetofauna, but also because they are a lot of fun to have around (and they cook up some good pinto). Making their first trips to Costa Rica were Brett Baldwin from the San Diego Zoo representing the Bushmaster Species Survival Plan (SSP) group for our surveys, and two volunteers I had worked with at the University of Idaho, Brannon Durant and Isaiah Hoyer. All assembled on Sunday morning, we signed our name to a piece of paper labeled “Expedición Melanocephala”, hopped in a Range Rover (scattering basilisks sprinting on water as we drove through rivers) and were dropped off to hike into the rain forest.

So how do you look for Black-headed Bushmasters? You hike up and down steep ridges, spreading out to increase your chances of discovering animals, but trying not to get lost in the thick forest. You look in the nook of every tree buttress you see, and look under fallen trees, all the while avoiding coming face-first with a terciopelo (Bothrops asper) or inadvertently lightly brushing against an acacia tree and consequently being swarmed by a horde of protective, stinging ants. (The San Diego Zoo had better watch out for its acacia tree it uses in an exhibit, as Brett was threatening its future existence at multiple times!) I had brought an additional tool to attempt to open up the world of the bushmaster: a camera designed to search pipes and toilets, but also very suitable for searching burrows and hollow trees, where we expect bushmasters take refuge and lay their eggs. And finally you spend some time walking (and slipping) along river courses because February is the dry season and snakes might congregate at this resource. You repeat this each day, going out both during the day and night. And you sweat a lot (well, at least if you are me!).

Despite all of these efforts, we did not observe a bushmaster. Of course, that was our major objective, but we were also realistic – for such a rare snake, it’s simply going to take a lot of cumulative time and effort. This doesn’t mean there weren’t successes – our camera system proved to be quite rugged and gave us clear views into the subterranean systems. I look forward to continuing to use this equipment to understand what species might be hiding in the forest. And we got a great start in putting together a herpetological inventory for the park. We observed 49 species of reptiles and amphibians, representing 21 different taxonomic families. We observed species that are rarely seen such as Leptophis riveti (Despax’s Parrot Snake), Enuliophis sclateri (the Panda Bear Snake), and Porthidium porrasi (White-tailed Hognose Viper) and lots of treefrogs, glass frogs, anoles, toads, cat-eyed snakes, and terciopelos. At the end of the trip, Oscar expressed to us his pleasure with how the trip went and invited us to join him again later in the year in the rainy season, where in his experience, the bushmasters are more active. I’m already looking forward to planning another expedition!

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