Distribution, Abundance, and Ecology of Terrapins in SW Louisiana
Female Diamondback Terrapin
Throughout the diamondback terrapin’s range, Louisiana likely holds the most available habitat of any other state for the species, with approximately 6500 km2 of brackish and saline marshes. Even though there is a vast amount of apparently suitable habitat, less is known in Louisiana about terrapins relative to other states in their range. Most historical terrapin records in Louisiana come from the southeastern coastal marshes, while few are known from southwestern Louisiana; for the latter, the most recent specimen or published records from the region date back to the 1970s.
We conducted distribution and abundance surveys from 2011 to 2014 across southwestern Louisiana. Terrapins were found at almost all historical localities and many previously unknown localities. Abundance varied considerably across sites, with terrapins considered "locally abundant." However, many sites had a small number of captures and the viability of these populations are unknown. This portion of the study was published in Chelonian Conservation and Biology. Along with distribution and abundance data, we also collected other life history data (i.e., morphological, reproductive, dietary), tissue samples for genetic analyses, and plastron photographs for pattern analysis. Annual sampling of three populations is ongoing to determine population structure and long-term population demographics of these populations.
Ecology and Conservation of Graptemys species
Yellow-blotched Sawbacks, Female (left) and male (right)
The genus Graptemys, commonly referred to as Map turtles or Sawbacks, contains the most turtle species of any North American turtle genus. Of the 14 species, eight are endemic to single river drainages of the southeastern United States. Even though the genus has a large number of species, researchers still know little about their basic life history and ecology. Their taxonomy has been equally challenging, with six Graptemys species described between 1950 and 2000. The last formally described species, G. pearlensis (Pearl River Map turtle, in 2010), further underscores the relatively little we know about the genus. It is possible that additional "cryptic species" may occur and be described in the future.
Unfortunately, many Graptemys species are considered species of concern or are considered state threatened/endangered. There are many threats to Graptemys species and most are associated with loss of riverine habitat and habitat alteration, which includes the desnagging of river systems (removal of fallen trees that provide basking platforms and substrate for food items), construction of reservoirs, river channelization, excessive water withdrawal, and water quality degradation. Additional threats include the intentional shooting of turtles as target practice, collisions with boats, collection for the pet trade, fisherman by-catch, and the destruction of nests on sandbars by recreational ATV riders.
While conducting dissertation research at The University of Southern Mississippi (lab of Carl Qualls), I focused on the conservation and ecology of G. flavimaculata (Yellow-blotched Sawback), which is a federally Threatened species found exclusively in the Pascagoula River system. From 2005-2009, research topics included (1) impacts of Hurricane Katrina on a coastal population, (2) distribution and abundance throughout the Pascagoula River system, (3) basking ecology, (4) conservation genetics, and (5) impacts of human recreation on behavior and physiology. Along with this species, I collected ecological data and genetic samples from other Graptemys species including G. pearlensis, G. oculifera (Ringed Sawback), and G. gibbonsi (Pascagoula Map turtle).
Following my dissertation work, I have continued to work with Graptemys species in southwestern Louisiana with professors Peter Lindeman (Edinboro University, PA), Eddie Lyons (McNeese State University, LA), and two graduate students at McNeese (Cybil Covic Huntzinger and Irvin Louque). This research focused on determining the distribution and population status of G. sabinensis (Sabine Map turtle) and Macrochelys temminckii (Alligator Snapping turtle), with both considered species of concern.
4 Yellow-blotch Sawbacks basking, lower Pascagoula River