In the spring of 2005 I began a mark and recapture study on the three toed box turtle (terrapene carolina triunguis). The following pages are about my mark and recapture study.

Box turtles are camouflage experts. I never would have found this one without my dog.

Study area.

My study area consists of 160 acres on my family’s and my neighbor’s farms in Southeast Missouri. The study area consists of mostly forest, but there are also some fields and pastures. The terrain is rugged and steep in most places. The turtles seem to prefer the flat ground between the ravines and inhabit the gently sloping hills.

My study area is part of Crowley’s Ridge, a unique geological formation that was originally part of the Illinois land mass but was cut off from Illinois about 10,000 years ago by the Mississippi River. The Crowley’s Ridge turtles are too far away from the nearest box turtle population to allow gene flow. That means that the population is a genetic snapshot of what box turtles in Southeast Missouri and Southern Illinois were like thousands of years ago.

The study area. Yellow line = boundary

Procedure.

I trained my dog, Lady, to track box turtles. She catches most of the turtles because of her keen nose. Once I find a turtle I mark the location with a GPS, take weight and height measurements, note the type of habitat the turtle was in and what it was doing and then I mark it and let it go in the same spot where I found it.

Lady, the turtle finder.

The turtle population.

In the ‘05 field season I marked 42 box turtles. I plan to intensify my searches in the ’06 field season. I don’t have a good estimate yet as to how many turtles there are on the study area but I think it is in the 200 – 600 range. The sex ratio for my population is 37% female, 63% male. I am currently working on a model to predict population trends.

I believe that the population is declining. On the western part of the study area there are some railroad tracks. This year I found 12 turtles trapped between the tracks, 11 were dead. The sex ratio of turtles trapped between the tracks was 44% female, 56% male. As you can see the percentage of female turtles on the tracks verses the percentage of turtle in the forest indicates that the females are declining. Fewer females means fewer offspring which causes population decline. Because of the railroad and other factors I believe that the population has declined at least 50% over the past 150 years.

Other box turtles?

I believe that there are eastern box (T.c.carolina) turtle hybrids in the turtle population. Since Crowley’s Ridge was connected to Illinois and eastern box turtle live in Illinois then I should have eastern box turtles on my study area. That is not exactly the case. I have found some box turtle that look like eastern box turtles, but the majority of the turtles are three toed box turtles. Crowley’s Ridge must have come into contact with both the Tennessee Hills in Illinois and the Ozark Hills in Missouri at one point in time.

Three toed box turtle: right

Hybrid eastern and three toed box turtle: left

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