Bog Turtle Ecology Study
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The following account illustrates how a narrowly focused ecological study helped to understand some of the interrelationships of one species, thereby better learning what might affect its abundance and distribution.
The bog turtle, Glyptemys muhlenbergi, (formerly Clemmys muhlenbergii) is classified as an endangered species. It is a small, highly secretive turtle that prefers to live in shallow wetlands with open vegetation (trees and shrubs are not too abundant). While doing a 5-year ecological study of one population in a 7.1 hectare (17.6 acre) wetland, I discovered that slugs (similar to snails but without a shell) were their preferred food item. Through extensive trapping and hand capturing, I determined the population size to be over 65 turtles, but they only occupied half of the swamp. Why were they so abundant but so unequally distributed? It took me almost four years to figure out a possible answer which I discovered in part by good luck.
The bog turtle, Glyptemys muhlenbergi, (formerly Clemmys muhlenbergii) is classified as an endangered species. It is a small, highly secretive turtle that prefers to live in shallow wetlands with open vegetation (trees and shrubs are not too abundant). While doing a 5-year ecological study of one population in a 7.1 hectare (17.6 acre) wetland, I discovered that slugs (similar to snails but without a shell) were their preferred food item. Through extensive trapping and hand capturing, I determined the population size to be over 65 turtles, but they only occupied half of the swamp. Why were they so abundant but so unequally distributed? It took me almost four years to figure out a possible answer which I discovered in part by good luck.
One morning I arrived before sunrise at the swamp to start my daily research work. For safety reasons, I never entered when it was still dark but this time for some unknown reason I decided to do so. So I put on my waders and grabbed my flashlight. As I meandered slowly and carefully through the wetland, I saw something truly amazing - one species of plant called boneset was covered with enormous numbers of slugs. They were foraging on their leaves. Obviously, boneset's leaves had some special appeal since other nearby species of plants were not under attack. However, when the sun appeared over the swamp, the slugs quickly crawled down the plants and disappeared into the wet debris that surrounded the boneset. This is why I never saw them, since I always did my research during the daylight hours! As a consequence of this observation, I quickly mapped out the location of boneset. The part of the swamp where bog turtles were rarely found had no boneset. Additional research work showed that slugs had a minimal presence in these locations. However, wherever boneset was located, bog turtles were nearby. By using radio transmitters, that were placed on the back shell of numerous bog turtles, I could follow their movements and activity cycles. Thus, I discovered that the bog turtles would come to slug abundant locations and forage on this slow, protein-rich prey as they left the plants in the early morning. The turtles would then return to their home site and remain inactive (burrowing into the mud) for several days, digesting their prey. So with little energy expenditure on their part, they were acquiring a high energy and nutrient rich meal. This energy could then be channeled into growth and reproduction. The unevenly distributed boneset supported a large slug population that was the primary food item of the bog turtles. These interrelationships helped to account for the abundance and distribution of the bog turtles at this swamp.
Reference:
Gemmell, D.J. 1998. Feeding ecology of the bog turtle, Clemmy muhlenbergii. Bull. N.J. Acad. Sci. 43:1-4.
Reference:
Gemmell, D.J. 1998. Feeding ecology of the bog turtle, Clemmy muhlenbergii. Bull. N.J. Acad. Sci. 43:1-4.
Slug herbivory on boneset
Credits: Bog Turtle, Bog Turtle Habitat, Boneset, Slug (Dennis J. Gemmell)