JOURNAL OF HERPETOLOGY

 

 

 

LRH:       Shorter Communications

RRH:       Shorter Communications

 

Seasonal movement in the Mississippi map turtle, Graptemys pseudogeographica kohnii, in the Coldwater River, Quitman County, Mississippi.

 

W.B. Cash1, 3 and S.R. Adams1, 2 Department of Biology

 

1 Department of Biology, University of Mississippi, University, Mississippi 38677, USA

2 Department of Zoology and Fisheries, and, Illinois Aquaculture Center, Southern Illinois University, Carbondale, Illinois 62901, USA

Key Words: turtles, Graptemys, movement, behavior

3 Present Address: Department of Biology, Maryville College, Maryville, Tennessee 37804

 

 

 

1corresponding author, cashben@maryvillecollege.edu

Freshwater turtles show seasonal variation in their movement and activity patterns (Carr, 1952; Ernst et al., 1994).  Such variation may be a part of the normal reproductive cycle of the turtle, preparation for hibernation, or a response to changing habitat quality (Sexton, 1959; Vogt, 1980; Pluto and Bellis, 1988).  Morreale et al. (1984), based on their study of the movement patterns of Trachemys scripta, predict that increases in movement and activity will be correlated with some aspect of reproduction, such as mate searching in males or nesting in females.  Thomas et al. (1999) also found seasonal variation in activity behavior, based on trapping data, for male and female T. scripta and attribute these seasonal differences to alternative reproductive strategies; males are increasing activity in the fall searching for mates and females increase their activity in the spring while nesting.  These increases in movements and activities may be hard to detect unless necessary baseline data have been collected (Gibbons, 1986; Gibbons et al., 1990). 

Data on the movement of Graptemys pseudogeographica are few (Ernst et al., 1994).  In Vogt’s (1980) study of Wisconsin G. p. pseudogeographica populations, seasonal movements were found to be associated with annual events such as reproduction and preparation for hibernation.  However, little is known about the abiotic variables (e.g. temperature, hydrology) associated with movements, and no data are available on the movement patterns of the southern U.S. subspecies, the Mississippi map turtle (G. p. kohnii).  Reproductive biology data are also limited for G. p. kohnii.  Egg laying begins in May or June (Dundee and Rossman, 1989), but the timing of other important annual cycle events, including the primary breeding season, remain unknown. 

In conjunction with a study of the swimming physiology of bigmouth (Ictiobus cyprinellus) and smallmouth (Ictiobus bubalus) buffalo (Adams, 1996), we set out to determine the activity/movement patterns of G. p. kohnii in the Coldwater River, Quitman County, Mississippi.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Non-baited hoop nets were used to sample a 3 km reach of the Coldwater River (approximately 10 km upstream of Marks, Quitman County, Mississippi; latitude 34.15.22, longitude 90.15.57) from 6 March 1995 to 5 May 1996.  Part of the integrated river system draining the Yazoo River Basin, the Coldwater River is a medium-sized floodplain river heavily influenced by anthropogenic factors, including a flood control reservoir (Arkabutla Lake) near the headwaters (Jackson, 1993).  The Coldwater River can be characterized as highly turbid with a moderate amount of coarse woody debris.  The river banks are very steep and the riparian zone is heavily impacted adjacent to the river.  Daily flow is highly variable due to hydraulic control structures at various points along the river.  Recorded annual mean water flow at Arkabutla Dam, Mississippi station 133-C, was 1022 cfs in 1995 and 1183 cfs in 1996 (US Army Corps of Engineers). 

Nets had seven hoops (no leads) and a mesh size of 2.5 cm.  Nets were positioned on the river bottom with the cod end upstream (i.e., turtles had to be moving upstream in order to be captured).  Hoop nets were placed 1-4 m from the water's edge, parallel with the river bank and in straight segments of the river (nets were not positioned directly within bendways).  Focal depth of nets was lowest in late summer/fall (typically 2-4 m) and highest in late winter/spring (6-8 m).  Nets were checked every 1-3 days, and water temperature and focal water velocity were measured 10 cm below the water surface.  Straight-line carapace length was measured to the nearest 0.1 cm.

A sub-set of turtles captured in October 1995 (14 male; 2 female) was transported to the laboratory for behavioral observation.  After a minimum of 3 d in the laboratory, groups including one female and 3-4 males were placed in 75 L (1 m x 0.8 m x 0.5 m) holding tanks (22° C room temperature).  Approximately 18 h of video were recorded from an overhead position in order to observe interactions between males and females.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fifty-five G. p. kohnii (51 male, 11.24 cm ± 0.117 SE carapace length; 4 female, 18.3 cm ± 0.689 SE) were captured during the study.  The highest catch per unit effort (CPUE; number of turtles per month/trap days per month) was in the months of October and November 1995 (Fig. 1).  Thirty-six turtles (33 male; 3 female) were captured over a 15 d period in October 1995 alone (65% of our sample) (Fig. 1).  The male to female sex ratio was 12.75:1 for our sample.

Peak turtle captures in October 1995 were correlated with declining water temperature and river stage.  Mean water temperature was highest in August 1995 (28.5° C), abruptly declined from September (26° C) through November (9° C), and was lowest in January 1996 (5° C) (Fig. 2).  Mean river stage varied from a high of 29.5 ft in March 1995 to a low of 19.5 ft in October 1995 (Marks, MS, Station 320).  During the period 15-30 October 1995, encompassing the 36 turtle captures, water temperature ranged from 20-15° C and river level was slowly dropping from 20.1-18.6 ft at the Marks, MS gauge.  Sub-surface water velocity at nets containing turtles averaged 12.5 cm/s (5-20 cm/s) during the 15-day period.   

Several characteristic behaviors were observed in the laboratory from 18-26 October 1995.  Male turtles swam vigorously around the female, typically first inspecting the cloacal region with their nostrils and then positioning themselves nose to nose with the female, bobbing their head up and down and titillating the female by rapidly vibrating their forelimbs.  Copulation attempts were made during our trials, however no successful copulations were observed.  Eleven of the 14 males (79%) exhibited courtship behavior.           

 

 

The timing and nature of the observed movement may have many implications.  In the more northern G. p. pseudogeographica populations, Vogt (1980) suggested that breeding takes place in the spring and in October and November in Wisconsin, primarily based on observed courtship and attempted copulation in outdoor holding enclosures.  Although our behavioral observations were limited, all of those behaviors that have been traditionally viewed as courtship-related (see Ernst et al., 1994) were observed.  We believe that our increased capture rate in October and November 1995 might be an indication of increased mate searching activity by males (Morreale et al., 1984; Thomas et al., 1999).  The poor capture rate in the spring suggests that fall may be the primary mating period for G. p. kohnii, however this can only be speculated because the basic reproductive biology of this species is unknown.  

Estimates of sex ratios for the G. p. kohnii have not been reported.  However, Vogt (1980) reported the sex ratio of Wisconsin G. p. pseudogeographica at 0.09:1 and 0.08:1 (male:female) when trapping near nesting beaches, 0.16:1 in shallow areas away from beaches and sloughs, and perhaps more realistic, 0.48:1 when trapping adjacent to over-wintering sites.  Timken (1968) likewise reported a female biased sex ratio (1:4 male to female) in map turtle populations from the upper Missouri River.  Our heavily male-biased sex ratio (12.75:1) indicates a possible male dominated movement, the extent of which cannot be determined from our data.

Many studies of Graptemys sp. have documented seasonal movements.  In Wisconsin, Vogt (1980) recorded October movement of false map turtles to wing dams along sloughs and channels and often observed congregation around hibernacula.  Jones (1996) found that in the yellow-blotched map turtle, G. flavimaculata, males increase activity in October in south Mississippi as water temperature decreased and water level increased and attribute this to mate searching activity, although the mating season of the turtle remains unknown.  Pluto and Bellis (1988) found that common map turtles, G. geographica, move seasonally from basking/feeding areas to deeper, slower pools in the fall, returning to basking areas in spring.  Both Pluto and Bellis (1988) and Jones (1996) found the fall movement corresponded with declining water temperatures.  No G. p. kohnii were captured during extensive sampling of the Coldwater River from 8 August to 10 September 1995 when water temperatures ranged from 29.5°-25° C.  The movement peaked in October when water temperature dropped to 20° C and declined when water temperatures dropped below 15° C in late November (Fig. 2).

These data clearly indicate increased fall activity or a male-biased population movement similar to those observed in other studies.  It is difficult to determine whether our observed male-biased capture of G. p. kohnii was associated with increased reproductive activity, a response to changing habitat conditions (food availability), or a seasonal migration to winter areas without more intensive study.

 

 

 

 

 

 

 

 

Acknowledgements

We thank S. S. Knight and R. Brent Thomas for critically reviewing this manuscript.  Thanks also to L. Banks and D. S. Haworth III (US Army Corps of Engineers, Vicksburg District) for the hydrologic data.  Turtles were captured under a scientific collecting permit issued to WBC by Mississippi Department of Wildlife, Fisheries and Parks and handled under the UM IACUC protocol #96-012. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Literature Cited

Adams, S. R. 1996. Swimming performance of bigmouth, Ictiobus cyprinellus (Valenciennes), and smallmouth buffalo, Ictiobus bubalus (Rafinesque). MS Thesis, Department of Biology, University of Mississippi, Oxford. 114 pp.

Carr, A. F. 1952. Handbook of Turtles: The Turtles of the United States, Canada, and Baja California, Cornell University Press Ithaca, New York.

Dundee, H. A. and D. A.Rossman. 1989. The Amphibians and Reptiles of Louisiana. Louisiana State University Press, Baton Rouge.

Ernst, C. H., R. W. Barbour and J. E. Lovich. 1994. Turtles of the United States and Canada. Smithsonian Institution Press, Washington.

Gibbons, J. W. 1986. Movement patterns among turtle populations: Applicability to management of the desert tortoise. Herpetologica 42:104-113.

Gibbons, J. W., J. L. Greene and J. D. Congdon. 1990. Temporal and spatial movement patterns of sliders and other turtles. In Life History and Ecology of the Slider Turtle. (ed. J. W. Gibbons), pp. 201-215. Smithsonian Institution Press, Washington DC.

Jackson, D. C. 1993. Floodplain river fish stock responses to elevated hydrological regimes in unimpacted stream reaches and stream reaches impacted by clearing, dredging, and snagging. Polish Archives of Hydrobiology 40:77-85.

Jones, R. L. 1996. Home range and seasonal movements of the turtle Graptemys flavimaculata. J. Herpetol. 30:376-385.

Morreale, S. J., J. W. Gibbons and J. D. Congdon. 1984. Significance of activity and movement in the yellow-bellied slider turtle (Pseudemys scripta). Can. J. Zool. 62:1038-1042.

Pluto, T. G. and E. D. Bellis. 1988. Seasonal and annual movements of riverine map turtles, Graptemys geographica. J. Herpetol. 22:152-158.

Sexton, O. J. 1959. Spatial and temporal movements of a population of the painted turtle, Chrysemys picta marginata (Agassiz). Ecol. Monog. 29:113-140.

Timken, R. L. 1968. Graptemys pseudogeographica in the upper Missouri River of the northcentral United States. J. Herpetol. 1:76-82.

Thomas, R. B., N. Vogrin and R. Altig. 1999. Sexual and seasonal differences in behavior of Trachemys scripta (Testudines: Emydidae). Journal of Herpetol. 33:511-515.

Vogt, R. C. 1980. Natural history of the map turtles Graptemys pseudogeographica and G. ouachitensis in Wisconsin. Tulane Studies in Zoology and Botany 22:17-48.

 

 

 

 

 

 

 

 

 

 

 

Figure 1.  Monthly catch per unit effort (CPUE, number of turtles/trap days) for Mississippi map turtles in the Coldwater River, Quitman County, Mississippi for the sampling period beginning March 1995 and ending May 1996.  Number of turtles captured in each month is indicated over each bar.

 

Figure 2.  Monthly mean river stage (ft) and water temperature (°C) for the Coldwater River, Quitman County, Mississippi.