Biologist love islands. It’s true, we really do. Animals isolated on oceanic islands inspired both Charles Darwin and Alfred Wallace to independently come up with the theory of evolution by natural selection, and continue to be a focus of research today. Thus, it is surprising that so little is known about the fauna of Central America’s largest island, Coiba Island. The lack of research is even more surprising when you consider that the island has a unique form of what may be North America’s most studied wild mammal, the White-tailed Deer, living on it.
Approximately 27 miles off of Panama’s Pacific coast, Coiba was formed over 20,000 years ago, providing enough time for substantial genetic isolation to occur on any species able to colonize it. To date, 17 terrestrial mammal species, excluding 25 bat species, have been identified on the island. Nine of these were likely to have been introduced within the last century, leaving only nine native terrestrial mammals, five of which are endemic. The only proper survey of the mammals of Coiba Island was conducted by J.H. Batty in 1902, and for good reason (Olson 2008). Research on Coiba has certainly been limited by the penal colony established on the island from 1919-2004, where Panama sent some of its most notorious criminals and gang members such as those of “Los Hijos de Dios” (The Children of God), and “Los Chuckys” (named after the possessed doll of the 80’s horror flick “Child’s Play”). Vivid tales of violence, torture, and political murder during the dictatorship of Torrijos and Noriega filtered back to the mainland instilling a general fear of the island. While rough on the people living on Coiba, this penal period provided protection to the island’s forest and approximately 80% of Coiba’s forest still remains today (ANAM 2009). With the prison now closed, Coiba is gaining a reputation as a popular tourist destination and is protected as a World Heritage Site and National Park.
But what animals patrol underneath the forest canopy? Are the rumors of big cats existing on the island true? Is it possible that, somewhere within the 50,000 hectare island, mammals remain that have yet to be documented? These mysteries were the motivation behind our new camera trap pilot survey of the island’s mammals
In May of 2011, I deployed ten cameras along a trail on the Northeast corner of Coiba Island to capture a snapshot of the diversity, abundance, and activity patterns of its terrestrial mammals. In total, only four mammal species were documented: the Coiban Agouti, Panamanian White-throated Capuchin, Coiba Island White-tailed Deer, and Black-eared Opossum. Compared with our similar surveys on mainland Panama, the agoutis and capuchins of Coiba Island were very common; the agoutis were photographed 2-7 times more often than typical mainland sites and the monkeys 10-100 times more. This information alone is extremely interesting and may suggest two things: 1. There is a general lack of native predators on the island, causing an expected spike in smaller mammal populations. 2. Coiba’s capuchins may come to the ground more frequently than those of the mainland.
One of the shiest animals I photographed was the Coiba Island White-tail Deer (Odocoileus virginianus rothschildi). Our camera trap photos show that they walked in front of our cameras twenty-eight times, or about once every 10 days, and that they are active throughout the day with an apparent peak around dusk (17:00 – 19:00). These photos generated the most attention from Coiba’s park rangers back at the ANAM dining hall, the only place at the station with both a table and electricity during the day. Their interest came as a bit of a surprise since I saw deer so frequently in the mornings while hiking on Coiba, but reminds me why they are the most popular mammal on the continent. And these are special deer – they look like no other white-tailed deer in the world.
Oldfield Thomas first described the Coiba Island White-tail Deer in 1902 while documenting the private collection of Walter Rothschild, the very same specimens that J.H. Batty collected during his trip to Coiba earlier that year (Olson 2008, Thomas 1902, Allen 1904). The most distinguishing characteristic, aside from their isolated range, is their size; much smaller than Panama’s mainland white-tail species O.v. costaricensis. Additionally, adult O. rothschildi have much darker coats and the white spots of fawns tend to be more inconspicuous. Are their coats more cryptic in response to hunting, was there once a significant non-human predator on the island that influenced this potential adaptation, or is this simply the result of a founder effect?
Average dimensions of the animal are unknown although both Allen and Thomas included measurements in their descriptions. I say this because Thomas’ measurement of the head and body (1120mm) differ from Allen’s (avg. 2287mm) by over 1000mm. In addition, the measurements described by Allen were supplied by Batty, whose information often prompted complaints from Allen, and at times was unreliable or completely fictitious (Olson 2008). Both Allen and Thomas collected measurements from the skulls of six individuals (avg. length 205mm; avg. breadth 86mm). Even then both Thomas and Allen agree that this is the smallest in its genus, humorously describing it as a, “tiny little deer…”
There is obviously much to learn about this little guy as well as the rest of the mammals of Coiba. Plans to continue and expand the camera trap operation are underway. Proper measurements, as well as blood, tissue, and fecal samples also need to be collected. These can help, as they say, set the record straight, and provide valuable behavioral, genetic, and physiological data for future research.
Despite its horrific past, Coiba’s future is has huge potential. The number of scientific research projects on and around Coiba is steadily increasing, such as the recent submarine expedition of Hannibal Bank. Tourism is also increasing with visitors attracted to the unparalleled experience of scuba diving in one of the world’s richest marine biodiversity hotspots. Be sure to visit Coiba if you have the chance. Spend some time diving. Get a tour of the historical prison. Maybe even catch a glimpse of the tiny Coiba Island White-tail Deer. I know you’ll have a great time. After all, biologists are not the only ones who love islands…
By Zach Welty
Allen, J.A. 1904. “Mammals from Southern Mexico and Central and South America.” Published by order of the Trustees, American Museum of Natural History. v20.
ANAM. 2009. “Plan de Manejo del Parque Nacional Coiba.” Compiladores JL Maté, D Tovar, E Arcia,Y Hidalgo, STRI.
Olson, Storrs L. 2008. “Falsified Data Associated with Specimens of Birds, Mammals, and Insects from the Veragua Archipelago, Panama, Collected by J. H. Batty.” American Museum Novitates 3620(1):1. Retrieved (http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1206%2F592.1).
Thomas, O. 1902. “On Some Mammals of Coiba Island, Off The West Coast of Panama.” Novitates Zoologicae 9:135-137.