Body size of ectotherms constrains thermal requirements for reproductive activity in seasonal environments

Abstract

Body size may influence ectotherm behaviour by influencing heating and cooling rates, thereby constraining the time of day that some individuals can be active. The time of day at which turtles nest, for instance, is hypothesized to vary with body size at both inter- and intra-specific levels because large individuals have greater thermal inertia, retaining preferred body temperatures for a longer period of time. We use decades of data on thousands of individual nests from Algonquin Park, Canada, to explore how body size is associated with nesting behaviour in painted turtles (Chrysemys picta (Schneider, 1783), small bodied) and snapping turtles (Chelydra serpentina (Linnaeus, 1758), large bodied). We found that (1) between species, painted turtles nest earlier in the evening and at higher mean temperatures than snapping turtles, (2) within species, relatively large individuals of both species nest at cooler temperatures, and relatively larger painted turtles nest later in the evening compared to smaller painted turtles. Our data support the thermal inertia hypothesis, and may help explain why turtles in general exhibit geographic clines in body size: northern environments experience more daily variation in temperature, and larger size may evolve, in part, for retention of preferred body temperature during terrestrial forays.

Thermal physiology of queens reveals insights into climate vulnerability in two co-occurring native bumble bees (Bombus)

“…Instead, the breadth of thermal tolerance did not differ across species, in line with other findings that body size in Bombus does not impact thermal tolerance estimates within a caste (Maebe et al, 2021). While research on other ectotherms has uncovered support for the process of thermal inertia operating to allow larger individuals to gain and lose heat more slowly than smaller individuals (e.g., Labra et al, 2009;Zamora-Comacho et al, 2014;Azócar et al, 2016;Connoy et al, 2020), bumble bee queens may be too small for meaningful differences in thermal inertia to manifest. B. auricomus queens were significantly larger than B. impatiens queens by only slightly more than 0.1 g, which may not be large enough for thermal inertia to produce meaningful differences in thermal tolerances.…”

Nesting Behavior and Ecology in a Captive Population of Alligator Snapping Turtles (Macrochelys temminckii)

“…Common Snapping Turtles display a bimodal temporal nesting strategy with nesting primarily occurring in the morning between the hours of 0600 and 1200 or in the evening from 1800 to 2400 h (Congdon and Gatten 1989; Congdon et al 1987, 2008). Some freshwater turtle species exhibit either crepuscular or diurnal temporal nesting patterns (e.g., Congdon and Gatten 1989, Connoy et al 2020, Jackson and Walker 1997, Webb 1962), whereas other freshwater turtles and most sea turtles nest nocturnally (Alho and Pádua 1982, Congdon et al 1983, Doody et al 2009, Ehrenfeld 1979, Miller et al 2003, Tucker et al 2014). Diurnal nesting has been hypothesized to be a predator-avoidance strategy (Congdon and Gatten 1989, Congdon et al 1983).…”

“…Congdon and Gatten (1989) found body temperatures of diurnally nesting turtles to be significantly higher than ambient temperature in the shade, presumably due to increased heat load from solar radiation. Large turtles lose heat more slowly than small turtles (Weathers and White 1971), which may afford them the ability to nest at night or constrain nesting to cooler hours (Connoy et al 2020). Nesting, as it relates to time of day, could also be influenced by natural variation in the diel activity of the turtles (Doody et al 2009)—adult M. temminckii have been observed to be active at night (Ewert et al 2006)—or by variation in activity levels of other organisms (such as humans).…”

The nature of science: The fundamental role of natural history in ecology, evolution, conservation, and education

“…Studies that rely on natural history observations, by contrast, can span much longer periods and therefore provide data uniquely suited to understanding natural biotic patterns, as well as their perturbations, at relevant timescales. Poignant examples include the multi‐year coral reef community structure dataset collected from the Buck Island Reef National Monument (Bythell et al., 2000 ); several multi‐decade‐spanning datasets being collected at the Algonquin Wildlife Research Station, including body size, nesting behavior, and nest temperature of turtles (Connoy et al., 2020 ), reproductive performance and survival of Canada jays ( Perisoreus canadensis ; Derbyshire et al., 2015 ), auditory monitoring of white‐throated sparrows ( Zonotrichia albicollis ; Falls, 1981 ), and population monitoring of small mammals (Fryxell et al., 1998 ); and, in an extreme and famous example, the 30‐year (at time of publishing) Darwin's finches dataset developed by Peter and Rosemary Grant (Grant & Grant, 2002 ). Data collected over such timespans are not only crucial for understanding how natural ecosystems function but are also the only way to test whether predictive models based on experimentation or simulation accurately reflect natural processes (Azaele et al., 2006 ).…”