“…Moreover, nesting of E. macquarii is spread over about 2 months in the south of its distribution and 4 months further north, with females producing up to three clutches of eggs annually (Chessman 1978;Georges 1983;Booth 2010). Its nesting is triggered by rainfall (McCosker 2002;Booth 2010), as in many other freshwater turtle species (Czaja et al 2018), and is therefore concentrated during rain events. However, there is no evidence that E. macquarii migrates to nest communally in the manner of some sea turtles.…”
Section: Discussionmentioning
confidence: 99%
“…However, there is no evidence that E. macquarii migrates to nest communally in the manner of some sea turtles. Nesting during rain is probably adaptive regardless of the species of nest predator, because heavy rain softens soil to facilitate nest excavation, and can disguise nests from predators (Legler 1954;Czaja et al 2018).…”
It has been asserted that introduced red foxes (Vulpes vulpes) destroy ~95% of nests of freshwater turtles in south-eastern Australia, are more efficient predators of freshwater turtle nests than Australian native predators, and are driving Australian freshwater turtle species to extinction. Available information was reviewed and analysed to test these assertions. Nest predation rates for all predators including foxes averaged 70% across Australia and 76% for south-eastern Australia compared to 72% for North America where freshwater turtles co-exist with many native predators, including foxes. Predation rates on Australian freshwater turtle nests did not differ significantly where foxes were included in the identified nest predators and where they were not, but sample sizes were very small. Evidence was lacking of foxes being the primary driver of population declines of Australian freshwater turtles, and some turtle populations are stable or increasing despite exposure to fox predation. Australian native species can be effective nest predators, and their role has probably been usurped by foxes to some degree. Where research shows that increased recruitment is necessary to conserve Australian freshwater turtle populations, strategies such as electric fencing of nesting beaches, nest protection cages and ex situ incubation of turtle eggs will probably be more cost-effective than efforts to reduce fox numbers. Further research is also needed to better understand the biological and environmental factors that regulate nest predation rates.
“…Moreover, nesting of E. macquarii is spread over about 2 months in the south of its distribution and 4 months further north, with females producing up to three clutches of eggs annually (Chessman 1978;Georges 1983;Booth 2010). Its nesting is triggered by rainfall (McCosker 2002;Booth 2010), as in many other freshwater turtle species (Czaja et al 2018), and is therefore concentrated during rain events. However, there is no evidence that E. macquarii migrates to nest communally in the manner of some sea turtles.…”
Section: Discussionmentioning
confidence: 99%
“…However, there is no evidence that E. macquarii migrates to nest communally in the manner of some sea turtles. Nesting during rain is probably adaptive regardless of the species of nest predator, because heavy rain softens soil to facilitate nest excavation, and can disguise nests from predators (Legler 1954;Czaja et al 2018).…”
It has been asserted that introduced red foxes (Vulpes vulpes) destroy ~95% of nests of freshwater turtles in south-eastern Australia, are more efficient predators of freshwater turtle nests than Australian native predators, and are driving Australian freshwater turtle species to extinction. Available information was reviewed and analysed to test these assertions. Nest predation rates for all predators including foxes averaged 70% across Australia and 76% for south-eastern Australia compared to 72% for North America where freshwater turtles co-exist with many native predators, including foxes. Predation rates on Australian freshwater turtle nests did not differ significantly where foxes were included in the identified nest predators and where they were not, but sample sizes were very small. Evidence was lacking of foxes being the primary driver of population declines of Australian freshwater turtles, and some turtle populations are stable or increasing despite exposure to fox predation. Australian native species can be effective nest predators, and their role has probably been usurped by foxes to some degree. Where research shows that increased recruitment is necessary to conserve Australian freshwater turtle populations, strategies such as electric fencing of nesting beaches, nest protection cages and ex situ incubation of turtle eggs will probably be more cost-effective than efforts to reduce fox numbers. Further research is also needed to better understand the biological and environmental factors that regulate nest predation rates.
“…We were surprised to find that increased precipitation in July was correlated with a delay in nesting in Chelydra, over ten months later. Although previous studies have examined the impact of precipitation on nest timing during the nesting season (see review in Czaja et al., 2018), no study has examined the effects on nest timing of precipitation outside the nesting season. Increased precipitation in July at our site was correlated with colder mean daily July maximum temperatures ( R = .38; p = .007; N = 48 years), but average July temperatures were not related to nest timing in Chelydra .…”
A frequent response of organisms to climate change is altering the timing of reproduction, and advancement of reproductive timing has been a common reaction to warming temperatures in temperate regions. We tested whether this pattern applied to two common North American turtle species over the past three decades in Nebraska, USA. The timing of nesting (either first date or average date) of the Common Snapping Turtle (Chelydra serpentina) was negatively correlated with mean December maximum temperatures of the preceding year and mean May minimum and maximum temperatures in the nesting year and positively correlated with precipitation in July of the previous year. Increased temperatures during the late winter and spring likely permit earlier emergence from hibernation, increased metabolic rates and feeding opportunities, and accelerated vitellogenesis, ovulation, and egg shelling, all of which could drive earlier nesting. However, for the Painted Turtle (Chrysemys picta), the timing of nesting was positively correlated with mean minimum temperatures in September, October, December of the previous year, February of the nesting year, and April precipitation. These results suggest warmer fall, and winter temperature may impose an increased metabolic cost to painted turtles that impedes fall vitellogenesis, and April rains may slow the completion of vitellogenesis through decreased basking opportunities. For both species, nest deposition was highly correlated with body size, and larger females nested earlier in the season. Although average annual ambient temperatures have increased over the last four decades of our overall fieldwork at our study site, spring temperatures have not yet increased, and hence, nesting phenology has not advanced at our site for Chelydra. While Chrysemys exhibited a weak trend toward later nesting, this response was likely due to increased recruitment of smaller females into the population due to nest protection and predator control (Procyon lotor) in the early 2000s. Should climate change result in an increase in spring temperatures, nesting phenology would presumably respond accordingly, conditional on body size variation within these populations.
“…Rain potentially renders digging more efficient by softening substrate (Seabrook, 1989), thereby speeding up nesting events and decreasing predation risk for the mother. Rainfall may also erase predatory cues on nests, although this varies depending on the amount of rainfall Czaja et al, 2018). The most obvious downside to nesting in rain is the possibility of heavy rain drowning nests.…”
Section: Discussionmentioning
confidence: 99%
“…High-intensity rainfall events stimulate nesting initiation in some bird species and in Collared Iguanas (Grant and Grant, 1989;Lloyd, 1999;Randriamahazo and Mori, 2001). Nesting during or after rainfall offers benefits for terrestrially nesting aquatic reptiles in particular, as it minimizes evaporative water loss (Wilson et al, 1999), potentially optimizes locomotion over softened substrate (Pike, 2008), and may reduce predation risk (Czaja et al, 2018). However, excessive rainfall can inhibit embryonic development of offspring during the incubation period (Bodensteiner et al, 2015), or even drown nests (Kraemer and Bell, 1980;Campos, 1993).…”
Nesting is an essential, yet variable, reproductive behavior in most oviparous organisms. Although many factors conceivably influence nesting behaviors, it is unclear which factors strongly influence terrestrial nest timing in aquatic nonavian reptiles. As climate is changing rapidly, understanding the relative influences of biotic and abiotic factors on nesting behaviors may yield important information on future changes in daily and seasonal nesting activity. We collected hourly data to examine the significance of local weather conditions to the timing of within-season nesting activity in a large population of Painted Turtles (Chrysemys picta). We quantified nesting activity as the ratio of females who nested to all females who could nest in each hour, adjusting the size of the denominator to include the time required to shell a subsequent egg clutch. We then used zero-inflated models to identify potential weather predictors of presence/absence of nesting activity and strength of nesting responses (i.e., the fraction of turtles nesting that could nest). Higher temperatures and rainfall predicted stronger nesting responses, whereas lower temperatures and no rainfall predicted the absence of nesting activity, indicating that both temperature and rainfall are important cues in within-season nesting phenology. Our study enhances our understanding of abiotic influences on the terrestrial nesting behavior of aquatic organisms.
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