HISTORICAL RESEARCH ON REPTILES AND AMPHIBIANS OF THE MISSISSIPPI RIVER:  THE 
NECESSITY OF FUTURE LONG-TERM STUDIES

James T. Lamer1, John K.Tucker2, and Michael A. Romano1

Reptiles and amphibians represent a significant component of the Mississippi 
River and associated habitats.  Based on sampling at Great Rivers Field 
Station, turtle biomass makes up a substantial amount of the fauna present 
within backwater lakes along the lower Illinois River.  For instance, in 
Lower and Middle Swan Lake alone, 88,000 to 300,000 red-eared sliders, 
Trachemys scripta elegans,  are estimated to occupy the lake at any one time 
based on long-term mark and recapture data.  Nevertheless, amphibian and 
reptile fauna have largely been overlooked in studies along the Mississippi 
River.  For example, in the 40-year history of the Mississippi River Research 
Consortium, no herpetology studies appeared until the 20th meeting in 1988 
when Michael Pappas and Bruce Brecke presented a paper entitled, “A field 
study of Blanding’s turtle, Emydoidea blandingii, at Weaver Dunes, Wabasha 
County, Minnesota”.  It was another 7 years before a frog survey at the Mark 
Twain National Wildlife Refuge was presented (Bernstein et al.  1995). Since 
that time, herpetological studies have gradually increased and become a 
staple at the consortium.  However, the recent declines in both amphibians 
and reptiles coupled with global climate change demand that increased efforts 
to monitor these animals be made.  For example turtles may be particularly 
sensitive to changing climates because they have temperature dependent sex 
determination (TS).  Studies conducted at the Great Rivers Field Station 
examined hatchlings, reproductive ecology, and population demography of the 
red-eared slider (Trachemys scripta elegans) in aquatic habitats of the lower 
Illinois River in Jersey and Calhoun Counties, Illinois between 1994 and 
2007.  In initial studies, the sex ratio was balanced but became 
progressively more male biased with the passage of time.  Large cohorts of 
newly recruited males seem to underlie the increasing male bias.  Recruitment 
more than doubled between 2001 and 2006 and these turtles were strongly male 
biased.  In part, this change reflects the increased male bias among 
hatchlings and a pattern of increasing reproductive output.  Climatic warming 
may have driven the demographic changes observed.  A period of warming at the 
site (0.12 ºC per year between 1992 and 2006) has allowed females to lay more 
eggs by lengthening the nesting season by about three weeks.  Increasing the 
length of the nesting season allows females to lay an extra clutch, which may 
account for the increased recruitment.  This clutch is laid when soil 
temperatures are relatively low explaining the male bias in newly recruited 
turtles.  The impact of the increased number of male turtles on the 
population is uncertain.  However, female condition has declined about 7% 
between 1994 and 2006 suggesting that an effect may be occurring.  Dramatic 
changes in range have also been observed in some species.  The green 
treefrog, Hyla cinerea, was limitedto  southern Illinois.  Recently we  
documented large choruses of green tree frogs in Jersey County, Illinois some 
110 km north of the previous northernmost record for this species in 
Illinois.  Moreover,  12 other reptile and amphibian species have extended 
their ranges northward based on recently reported records.  Additional 
examples and suggestions for reptile and amphibian monitoring will be 
presented.