Effects of human disturbance on the behavior and physiology of an imperiled freshwater turtle

Abstract

The effect of human disturbance on wildlife is of increasing interest because of the growing use of wildlands by humans for recreation. Few studies have documented the effect of human disturbance on behavior and physiology simultaneously, with no studies existing for any turtle species. Turtles are one of the most endangered taxonomic groups and many are of conservation concern, including the yellow‐blotched sawback (Graptemys flavimaculata), a freshwater turtle of the Pascagoula River system, Mississippi, USA. We studied G. flavimaculata individual‐ and population‐level basking behavior, while also documenting the effects of human disturbance on basking behavior at recreationally disturbed and control sites. We also assessed the physiological response of turtles to human disturbance by measuring heterophil/lymphocyte levels (H:L; higher levels indicate increased stress) and shell condition of captured turtles at the 2 sites. At the individual level, disturbed turtles at the recreationally disturbed site basked for significantly shorter durations than undisturbed turtles at the same site and undisturbed turtles at the control site; disturbed turtles at the control site basked longer than all groups possibly because the few instances of disturbances all occurred during a time of year when basking durations were longest. At the population level, we detected significantly lesser basking percentages at the recreationally disturbed site relative to the control site, possibly because of natural differences among the sites (i.e., a more stable thermal environment) or because of the higher level of human disturbance. At the recreationally disturbed site, more disturbances occurred on weekend and weekend bordering days relative to weekdays, and larger and slower boats disturbed significantly greater percentages of basking turtles compared to smaller and faster watercraft. Further, turtles from the disturbed site had significantly higher H:L levels relative to the undisturbed site, and an index of shell condition was significantly poorer at the disturbed site. Boating records indicate that the impact of recreational boating at the disturbed site likely has grown over the last 22 years because of an increase in the number and size of boats using the river; this trend will likely continue unless restrictions are enacted by managers and/or state entities to limit the number and size of boats that access the river. © 2013 The Wildlife Society.

Long-term effects of land use on perinatal mortality in the Endangered Saimaa ringed seal population

“…In such cases, a disturbance may have severe immediate effects at the individual level (such as increases in heart rate or stress hormone levels), which may ultimately affect the viability of the population (e.g. Regel & Pütz 1997, Weimerskirch et al 2002, Ellenberg et al 2006, Selman et al 2013. Also, these immediate responses may be transformed into long-term changes and hence adversely influence demographic parameters such as survival and reproductive success (Fowler 1999, Frid & Dill 2002, Weimerskirch et al 2002, Müllner et al 2004, Ellenberg et al 2006.…”

High Connectivity Observed in Populations of Ringed Sawbacks,Graptemys oculifera, in the Pearl and Bogue Chitto Rivers Using Six Microsatellite Loci

“…However, we faced the same logistical constraints Selman et al (2013a) pointed out in their study in that many areas of these upstream reaches of the Pearl River are difficult to sample for a variety of reasons including a lack of available boat launches, poor navigability (i.e., high deadwood density and shallow water), and lower densities of G. oculifera. Furthermore, many of these upstream populations that are not exposed to regular boating traffic are more wary of canoes or boats in the river (Selman et al, 2013b).…”

Behavior and temperature modulate a thermoregulation–predation risk trade‐off in juvenile gopher tortoises

“…Reemergence times were shorter when burrows were cooler, presumably because physiological costs were greater. We suspect that this phenomenon is more widespread in turtles, including aquatic species that terminate aerial basking in response to disturbance (Moore & Seigel, ; Polich & Barazowski, ; Selman, Qualls, & Owen, ). Adjusting hiding time in response to refuge temperature also suggests a precise thermoregulatory strategy.…”