I have a true passion for amphibians, those creatures with moist skin and sticky toes that many people fear or dislike. They are jumpy and at times hard to find, yet that’s nothing more than a challenging proposition to a frog fan like me. This time the trip took me for the second time in less than 6 months to the Bocas del Toro district in Panama. There’s something magical happening in this area composed of the mainland and few surrounding islands to the point that scientist called them the Galapagos of the Caribbean. By now you should know the importance of the Galapagos Islands and if you don’t here’s a tip. The Galapagos are a living evolution laboratory, where we can observe the effects of adaptive radiation, a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms. In the case of Bocas del Toro, a tiny frog has evolved many different phenotypes – a description of observable physical, physiological or behavioral characteristics that separate a group of individuals from the rest of the species. Different from genotypes which are the actual genetic identity, phenotypes are affected by both the genotype and the unique environmental conditions surrounding the individual. My subject is a tiny frog — Oophaga pumulio — a.k.a. the Strawberry Poison Dart Frog. In it’s most common form it looks like the one below.
The challenging part was finding these tiny frogs no more than one inch in length while dodging the weather. For starters, these guys don’t like bad weather. In order to find them I needed to hear them first. Too much rain and they go mute, making them nearly impossible to find on the leaf litter of the forest floor. Even when the conditions were optimal, they will choose impossible places from where to call, making them inaccessible or difficult to photograph. Walking through muddied trails, slipping down the hill sides or landing on large puddles of water made the adventure more exciting at times. Once found then I had to battle the elements and the gear. Constant drizzle and high humidity sabotaged the gear more than once. The copious sweat getting in the eyes and all over the cameras added to the miserable ground conditions. To visit some of the sites where these frogs can be found we had to take boats. One of the interesting things about these frogs is the fact that several phenotypes can be found in one same island. In the case of Isla Bastimentos there are at least three different forms of the frog. Isla Colon also have their share. Every large island in the Bocas del Toro archipelago offers at least two phenotypes. But the mainland offer a unique set of conditions that produced even more phenotypes. Geographical isolation by either rivers or mountains provided enough separation for the establishment of various morphs, occasionally only separated by a river and in places where two distinct population exist, you can even find some individuals sharing characteristics of both populations. Insane to think that such a small area produced so much color evolution, but considering these frogs have a tiny range and small number of offspring. Below are some of the phenotypes I found during a three day expedition.
But there’s more to these tiny frogs. Their aposematic
coloration announcing their toxicity is just one of the traits that allow them
to survive in the wild. Their reproduction is extremely complicated for a frog
and I even show a high degree of parental care. The males attract the females
by means of their calls. Once they find each other, they mate by means of a
“cloacal kiss”. Soon after the female lays up to five eggs on a small puddle of
water, usually collected on leaves on the forest floor. During this period the
male urinates on the eggs to keep them moist if the water evaporates, and
rotates the eggs before they turn into tadpoles. Ten to fourteen days later the
tadpoles emerge from the eggs. At this point the female takes full care of the
tadpoles. As the water dries out, she will carefully move the tadpoles to water
filled vegetation usually bromeliads. To
prevent cannibalism among the tadpoles, the female deposits a single tadpole
per section of the plant. The collected water is low in nutrient, so the female
deposit unfertilized eggs to feed the tadpoles until they are ready to leave
the water phase fifty days later.
Nothing more exciting than being able to document this
species and its many phenotypes. But the work is not complete. There are many more
phenotypes still to be documented. The adventure continues on a follow up expedition
in 2022.