In the Mountains
August 24, 2006

This beautiful little Cardioglossa oreas is found on a few of the Cameroonian
mountains. During our work, the team found them in forests but also along
a grassy stream. The pattern on the back of this frog can vary alot between
individuals, sometimes there are many small spots and other times
the back is nearly completely black.

During a two-week trip through the West and Northwest Provinces, our team visited montane grasslands and forests, as well as a few crater lakes. It was a great trip because we found many exciting things and were shown great hospitality in many villages. Studying the organisms that live at the tops of mountains is interesting because it can help scientists to learn about the history of those mountains. But how can animals living today teach us about the past—about the millions of years over which these mountains have been shaped? We start by learning that some species of plants and animals live only at the tops of mountains.

Our team targeted forests in the mountains because some species of frogs are only found there, not in the surrounding lowland areas (areas of lower elevation). In addition, certain species are found only at the top of one specific mountain, and other species are found at the tops of many different mountains. This raises the question, “How did these species get to all of these different mountain-tops if they are not also found at lower elevations?” The answers lie in the history of the forests found on the mountains.

In the Bamboutos Mountains, there are a handful of peaks.
This particular bunch is located about in the middle of the
Bamboutos and is often referred to as Les Dents de Bamboutos
("The teeth of the Bamboutos".)

Over millions of years, the Earth has alternately switched between being relatively warm and relatively cool. In the past, there were many time periods in which the planet was much cooler than it is today. In the places where we find montane forest today, it is often cool and very wet—the same condition that would have been more widespread during the cooler parts of Earth’s history. The reason that the same species are found today in the forests on different mountains is because in those cooler pasts, the forests extended much farther down the mountains. So, the forests which are now isolated at the tops of different mountains were either connected or very close to each other. This means that organisms would have been able to move freely between the mountains.

This small species of toad, Wolterstorffina mirei, is found only
in the mountains of Cameroon. We usually find them hiding
under rocks or logs in grasslands. For a toad, it looks rather odd
with its skinny body and long, thin arms. There are three species
of Wolterstorffina and this one is known from the Bamboutos Mountains
and possibly also around Mount Oku. Genetic analysis shows that these
species may be closely related to two very small toad species that
live in the trees of forests of southern Cameroon.

Today, the earth is warm, and the forests of different mountains are not connected to one another. The land at lower elevations is too warm and dry for many montane frogs to live. Many species of amphibians can not move between forests easily. All of this means that we are able to learn about the history of the forests by studying the animals living in them. Amphibians are great animals to use for this purpose because many species can only live at very specific altitudes and are restricted to a particular type of habitat. So if you study the history of the frogs, you can begin to get at the history of the forests as well. For example, if we realize that a certain frog species is found on two mountains that are close to each other, we might guess that at one point the forests on those mountains were touching, probably because the planet was cooler, allowing the forest plants to spread downhill and join together.

Studying just one species or even a group of similar species can give us some insight into the forests’ history, but that picture may not be complete. In order to get a more complete picture, we need to study the history of many unrelated species found on different mountains. A main goal of our fieldwork is to collect frogs from the grasslands and forests of many different mountains. By analyzing genetic data from species found there, we can begin to put together a picture of the history of the frogs and also the special habitats in which we find them.

This small toad, Werneria bambutensis, is found on a few mountains
in Cameroon including Mount Bamboutos, for which it is named,
and Mount Oku. The relationship of the different Werneria species
in Cameroon is still poorly understood.

During our work, we have collected many species that are found only in the mountains. In the past two weeks, we’ve worked in both the Bamboutos Mountains and around Mount Oku, one of the highest mountains in West Africa at just over 3000 meters. Earlier in the trip we also collected many frogs from Mount Manengouba and Mount Mbam. There are species of Cardioglossa, Astylosternus, Werneria, and Wolterstorffina that are found on many of these mountains but not in the lowlands between them. For example, Cardioglossa melanogaster is known only from a few mountains, including Mt. Manengouba, whereas another closely related species, Cardioglossa schioetzi, was previously known just from highlands of eastern Nigeria and a small part of far western Cameroon. During our fieldwork, our team also found Cardioglossa schioetzi at two new places, Mt. Mbam and Mt. Oku. This is exciting because we can now begin to ask interesting questions about the distribution and evolution of these species: “The two species look slightly different, but how different is their DNA?” “How have the montane forests where these different species live been connected in the past?” “Did these two montane species evolve from a widespread, lowland species like Cardioglossa leucomystax?” Not only will these questions lead us to know more about these particular frogs, but they will also form a starting point for understanding other groups of animals that live in the same forests and mountains.

The team taking a break for lunch near the summit of the Bamboutos
Mountains. For lunch in the field, the team usually takes along bread
with either honey, chocolate, or cheese. We try to eat a big breakfast
so that we don't need to carry much with us during the day.

There is still a lot of research to be done on the amphibians of Cameroon. In order to do a thorough study of the diversity of Cameroon’s frogs, it will be necessary to return to Cameroon many times in the future. There are certainly many more discoveries to be made!