Karen Lips, an amphibian ecologist and tropical biologist, is an associate professor at the University of Maryland in College Park. She contributed this article to LiveScience's
It was a dark and steamy night and clouds of insects were biting our faces and hands as we carefully examined a tiny emerald glass frog. I was with my team of researchers in the middle of the jungle in the mountains of Panama. We were standing on slippery rocks in the middle of a stream doing our annual census of amphibians and reptiles in Parque Nacional Omar Torrijos. Every year since 1998, we've been following individually marked frogs to see how long they live, where they live, and how many frogs are in this population.
We used to spend hours every night capturing and marking dozens of these glass frogs, but in 2004, a pathogenic fungus called Batrachochytrium dendrobatidis (Bd) invaded this site and wiped out hundreds and hundreds of amphibians.
The emerald glass frog survived, but it is much less abundant today and it takes us only an hour to run the same transect. Because we marked animals before the epidemic and after the epidemic, we can compare how many infected frogs live as long as uninfected frogs. This can tell us why some populations persist, but are not recovering; it tells us why some populations continue to decline; and it can tell us how fast or slow those populations are changing. It might help us figure out whether the problem is the death of adults, or lack of survival in young stages, and it can help identify habitats where populations are improving and places where they are doing worse. [ In Photos: 40 Freaky Frogs ]
A really good example of the importance of population studies is a recent paper featuring research from the Australian tropics. Those scientists showed that after two decades of coexisting with Bd, populations of the common mist frog continue to decline, even though the scientists never found any dead frogs. They were able to link the decline in population abundance to intensity of infection by Bd. This is really important, because Bd is now found across the globe, and in hundreds of species of amphibians, but dead frogs are detected only occasionally. This paper shows us that just because we do not see die-offs does not mean amphibians are not dying and that population declines are not happening. [ Frog Fungus Causes Grisly Death by Dehydration ]
A few weeks ago, a group of scientists from the U.S. Geological Survey published a paper that described slow, but steady, population declines in 48 species from 34 sites across the United States. What was most concerning was that even widespread species we thought were relatively stable were declining. This matches with the many stories I hear from concerned citizens who say that they don't see or hear as many frogs in their backyards as they used to. Because those scientists spent the time to count amphibians, they were they able to detect the slow loss in those populations.
We need more studies like these that can go beyond the distribution of threats and can show us how amphibian populations respond to disease so that we can design appropriate conservation and management actions to protect those species.
For example, if population declines are slow and steady, we might have time to experiment with different management practices; but if populations are declining quickly, we might need to establish captive assurance colonies or take tissues for cryopreservation to protect evolutionary lineages.
Likewise, we need to know which age class, sex or subpopulation might be the limiting step in population recovery. If the problem is in the tadpole stage and none survive to become adults, then we might want to design a reintroduction program that adds more adults to the system. If adults are very rare, we might do better to add hundreds of eggs, tadpoles or juveniles to jumpstart recovery.
Numbers are also important because they are the currency of conservation. The IUCN Redlist makes decisions on the level of species endangerment based on the number of individuals and the number of populations, and how quickly those numbers are going up or down. The official listing of species is the first step in prioritizing research and conservation efforts to address those threats, and is used to dedicate funding and other resources.
Today, anybody can contribute data to online databases of plants and animals (e.g., http://www.inaturalist.org), or participate in research projects through citizen scientist programs. Whether the frogs are increasing or decreasing, we need to know: Just how many frogs are there?
So count with me: one frog, two frog, red frog, blue frog.
Follow Lips on Twitter @ kwren88.
The views expressed are those of the author and do not necessarily reflect the views of the publisher. This article was originally published on LiveScience.com .