Nesting sites in agricultural landscapes may reduce the reproductive success of populations of Blanding’s Turtles (Emydoidea blandingii)

Abstract

Almost all turtle species nest in terrestrial environments and maternal site selection represents a critical component of nest success. Females use cues in the current environment to predict the future conditions for embryo development. However, in disturbed landscapes, current and future conditions may not be correlated. We compared selection of nest sites by Blanding’s Turtles (Emydoidea blandingii (Holbrook, 1838)) in a (relatively undisturbed) park and a (heavily disturbed) agricultural landscape in Ontario, Canada, using field measurements and satellite imagery. Environmental variables were compared using logistic regression and Akaike’s information criterion (AIC) based on data measured at nest (presence) and random (pseudoabsence) locations. Specific environmental variables associated with site selection differed between study areas. Most notably, NDVI (normalized difference vegetation index, a proxy for vegetation cover) increased significantly during the year at the agricultural locale, corresponding with the growth of planted fields. No parallel change was observed at the park locale where canopy cover remained more consistent. An increase in vegetation cover may alter nest temperatures and soil moisture. Combined with the unpredictability in timing of crop sowing and harvesting, findings suggest that nests in agricultural fields may act as ecological sinks and that other species nesting in similarly altered habitats may be subjected to the same threats.

Multi-scale Assessment of Rock Barrens Turtle Nesting Habitat: Effects of Moisture and Temperature on Hatch Success

“…Some species traverse long distances (.6 km) to reach suitable nesting sites (e.g., Edge et al, 2010;Millar and Blouin-Demers, 2011). If natural nesting habitat is limited, turtles may nest in anthropogenic sites such as road shoulders or agricultural fields which can negatively affect hatch success (e.g., Kolbe and Janzen, 2002;Mui et al, 2015;Thompson et al, 2018). Protecting nest habitat and understanding the factors contributing to hatch success is an important component of managing populations of at-risk turtles because nest success can be as low as 0% in some Ontario populations (Environment and Climate Change Canada [ECCC], 2018a) and population recruitment rates are low due to delayed sexual maturity (Congdon et al, 1993), high nest predation rates (Marchand and Litvaitis, 2004), and dependence on nest incubation conditions (e.g., Kolbe and Janzen, 2002).…”

“…Freshwater turtles nest in beaches (Bowen and Janzen, 2008;Hughes et al, 2009), agricultural fields (Mui et al, 2015;Thompson et al, 2017), soil deposits in rocky landscapes (Petokas and Alexander, 1980;Brooks, 1998, 2000;Beaudry et al, 2010;Markle and Chow-Fraser, 2014;Francis et al, 2019), small clearings (Thompson et al, 2017;Piczak and Chow-Fraser, 2019), and even beaver lodges (Obbard and Brooks, 1980;Francis et al, 2019). Female nestsite selection is critical because it influences hatch success through site-specific characteristics that affect nest moisture and temperature including canopy cover, slope, substrate type, and nest depth (e.g., Kolbe and Janzen, 2002;Morjan, 2003;Hughes and Brooks, 2006;Mitchell and Janzen, 2019).…”

Agricultural land use creates evolutionary traps for nesting turtles and is exacerbated by mercury pollution

“…Current evidence suggests that many reptile populations worldwide are in rapid decline (Brown, Bennett, & Potts, , Gibbons et al., , Smith et al., , Whitfield et al., ), and land use and pollution are suspected contributors to many declines (Brown et al., , Díaz, Carbonell, Virgós, Santos, & Tellería, , Dorrough & Ash, , Sarre, ). Our work adds to a small body of literature on adverse effects of agricultural land use on turtle embryos and hatchlings (Freedberg et al., , Pappas et al., , Saumure & Bider, ), and raises concern that the selection of agricultural fields for nesting by turtles (Beaudry, DeMaynadier, & Hunter, , Freedberg et al., , Mui et al., ), particularly in mercury polluted areas, is a maladaptive behavior that may create evolutionary traps that are ultimately damaging to turtle populations (Battin, , Schlaepfer, Runge, & Sherman, ). Importantly, we provide some of the first experimental evidence linking agricultural thermal conditions to developmental outcomes, providing mechanistic insight into prior field observations.…”

“…For example, in numerous species of aquatic turtles, females select natural nest sites that have a high degree of solar exposure (such as sandy or rocky patches adjacent to rivers and streams) because of the importance of incubation temperature on embryonic survival and offspring phenotype. However, they also exploit recently tilled agricultural fields for nesting, presumably because of increased solar exposure and/or easier nest excavation (Freedberg, Lee, & Pappas, 2011, Mui et al, 2015. Although the developmental consequences arising from animals being attracted to nest in agricultural fields are not well studied (but see Freedberg et al, 2011), turtles incubated at low temperatures generally have smaller body sizes and lower posthatch growth rates than those incubated at intermediate or higher temperatures (Bobyn & Brooks, 1994, Brooks, Bobyn, Galbraith, Layfield, & Nancekivell, 1991, McKnight & Gutzke, 1993, Rhen & Lang, 1995.…”

Nest site selection and nesting behavior of the mud turtle Kinosternon scorpiodes (Testudines, Kinosternidae) in Palo Verde National Park, Costa Rica: implications for management

“…For turtles and many other animals, nest predation is a major cause of reproductive failure (Oddie et al 2015;Voves et al 2016), making nest site selection an important component of fitness. As a result, maternal site selection represents a critical component of nest success (Mui et al 2016).…”