Past Meeting, Jan 2022: Chris Bert – Map Turtles of the Susquehanna River


January 23, 2022 by lancasterherp

The Lancaster Herpetological Society (LHS) wants to thank everyone who was able to attend the first digital meeting of 2022. Furthermore, we want to thank Chris Bert for presenting his work surveying Map Turtles in the Susquehanna River.

If you were unable to attend the meeting, you can watch a recording of it HERE.

Chris has been a lover of turtles since he was a teenager. While not a biologist by profession, he has spent a substantial amount of time paddling the Susquehanna River in his kayak observing turtles, particularly after taking up residence by the river about a decade ago. The most abundant turtle that he encounters is the Northern Map Turtle (Graptemys geographica). As a habitat, they prefer large moving bodies of water. Northern Map Turtles are opportunistic omnivores, and tend to eat mollusks and crayfish, which are abundant in the Susquehanna River. Their name is derived from the pattern on the scutes of their shells, which resembles a topological map.

As with any water-based turtle, if you approach a Map Turtle while it is basking, it will quickly slide into the water to escape danger. Chris found that young hatchling Map Turtles usually do not do this, such that he could easily paddle up to them and pick them up. It is likely that they have not yet developed the instinct to slip away from potential harm. After casually observing the turtles on the Susquehanna River for a few years, Chris started to take detailed records at the encouragement of Walter Meshaka Jr from the State Museum of Pennsylvania.

Chris’ surveys are along the riverbank, looking for hatchling Map Turtles because they can be approached for taking measurements. His surveys are from April to October following a consistent route along the river starting from his house. The route takes him along both the east and west banks of the river. During each survey, he records the date and time, the temperature, and the presence of any cloud cover. When he finds a turtle, he notes which shore he found it on and what it was using as a basking surface. If he is able to catch it, he measures its carapace (top of the shell), and the plastron (the bottom, largely flat portion of the shell). He also indicates the life stage of the turtle, which he breaks up into hatchling, sub-adult, and adult.

Since 2018, Chris has completed a total of 26 surveys. In these surveys, he counted 471 Map Turtles, of which 265 were hatchlings. 150 were sub-adults, and 56 were adults. Since adult turtles are prone to slide away into the water after being approached, the number of recorded adults is unrepresentative of the actual number of adult turtles present. The hatchlings start to emerge from their nests in May and migrate to the river. Hatchlings are most abundant in June, and their numbers start to decrease through October, until they move to the bottom of the river to brumate over the winter.

Along with the survey data, Chris has made a plethora of additional observations while watching Map Turtles. Mother Map Turtles start nesting in June and July, and will often return to the same nesting sights each year. The baby Map Turtles will hatch in September, but do not emerge from their nests until June and July of the next year.

Along with Map Turtles, Chris has observed many other turtles including Eastern Musk Turtles, Snapping Turtles, and Wood Turtles. Wood Turtles are his favorite turtle species. If he is lucky enough to find one, he allows the turtle to come along with him in the kayak, before returning the turtle to where he found it.

As a next step for his surveying project, Chris is considering obtaining a permit to mark the turtles he captures. This would allow him to keep track of the turtles he finds, and get a sense of whether he is recapturing previous found turtles. Based on the number of turtles he has documented, the Map Turtle population in the Susquehanna River is healthy.

Once again, we want to thank Chris for his engaging talk and wonderful pictures. We wish him the best in his future surveys. Look out for future emails to describe upcoming events by the Lancaster Herpetological Society.

-Gregory Wier


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