Impact of human disturbance on the thermoregulatory behaviour of the endangered ringed sawback turtle (Graptemys oculifera)

Abstract

1. Human recreational disturbance of riverine environments may be contributing to population declines of aquatic organisms worldwide. Aquatic turtles that are heavily dependent on basking in sunlight to maintain an optimal body temperature may abandon basking perches because they perceive humans as potential predators.2. The impact of boat traffic, the availability of basking structures, and various environmental factors on the basking behaviour of the ringed sawback turtle (Graptemys oculifera) was assessed at two sites on the Pearl River, Mississippi, USA. This information was used to model the likely effects of human disturbance on the body temperature of large female turtles.3. Both the duration of basking and the percentage of turtles in a basking group that abandoned their basking perch were influenced by the availability of alternative basking sites, frequency of boat traffic, boat speed enforcement zones ('wake' or 'no wake'), boat type, air temperature, weather conditions, and Julian day. A simulation model of anthropogenically disturbed and undisturbed adult female ringed sawbacks showed that disturbance probably decreases the mean daily body temperature, especially at higher disturbance probabilities and in May, when the air temperature is low. 4. Management recommendations are provided that minimize the adverse effects of unintentional human disturbance of the ringed sawback to enable more effective conservation of this endangered, endemic species. Such methods are likely to be useful elsewhere as recreational disturbance becomes a greater conservation issue worldwide.

Interactions between inland water‐based recreation and freshwater turtles: A review

“…Enge et al, 2014) or observing boat traffic and the effects boat presence had on turtles (e.g. Heppard & Buchholz, 2019). Recreation databases ( n = 5 articles) involved using previously collected data on recreation use, such as campsite usage (Laverty et al, 2016), recreation permits (Heppard & Buchholz, 2019), records of boat vessel crossing data (Turcotte et al, 2023) or boat registration data (Selman et al, 2013; Vecchioni et al, 2020).…”

“…For example, both turtle and human recreation visual surveys were used to study boat traffic impacts on turtle basking behaviour (e.g. Heppard & Buchholz, 2019; Pittfield & Burger, 2017; Selman et al, 2013). Also, when studying angler interactions with turtles, many articles focused on collecting turtle disturbance data (via capture survey, visual survey or X‐rays) and complemented it with human data collection (via opportunistic discussions with recreational fishers and riverine landowners on their observations and experiences interacting with turtles) (Browne et al, 2020; Galois & Ouellet, 2007; Leary et al, 2008; Steen et al, 2014; Steen & Robinson, 2017).…”

“…the bottom of shallow waters or the surface of the water) or perches such as driftwood and rocks. Recreational boating passing by turtle basking sites may cause basking turtles to retreat into the water, decreasing the length of time spent basking and thus thermoregulating (Heppard & Buchholz, 2019; Pittfield & Burger, 2017; Selman et al, 2013). For example, in the Pascagoula River, Mississippi, USA, 13% of yellow‐blotched map turtles ( G. flavimaculata ) did not return to bask following a boating disturbance, and those that did required 20 min to re‐initiate basking, which was more time needed than before the boating disturbance (Moore & Seigel, 2006).…”

“…Human disturbances may also affect the spatial ecology and basking perch preference of turtles. Boating presence has been speculated to decrease the occurrence of turtles basking gregariously on perches such as yellow‐blotched map turtles (Moore & Seigel, 2006), painted turtles (Pittfield & Burger, 2017) and ringed map turtles ( G. oculifera ) (Heppard & Buchholz, 2019). Gregarious basking increases turtle awareness of predators; if one individual retreats into the water, others basking nearby will soon follow (Shealy, 1976).…”

Determining home range, changes in habitat use with time, and the threats to an endangered freshwater turtle (Rafetus euphraticus) in Turkey

“…Urbanization is a serious threat for freshwater turtles; indeed, habitat loss by human activities affects survival, predation rates on turtle nests, and fitness through decreasing genetic connectivity between sub‐populations (Bodie, 2001; Marchand & Litvaitis, 2004; Aresco, 2005; Reid, Mladenoff & Peery, 2017; Santoro et al, 2020). In addition, recreational disturbance in river environments may be contributing to population declines of aquatic organisms worldwide (Heppard & Buchholz, 2019). With many historical sites, the Euphrates River is a centre of interest for national and international tourism.…”