ABSTRACT Abstract Lizards are appropriate organisms to investigate causes and correlates of commu... more ABSTRACT Abstract Lizards are appropriate organisms to investigate causes and correlates of communal egg laying because their general lack of parental care focuses attention on nest site choice. We field-tested hypotheses associated with nest site choice and communal egg laying in the delicate skink Lampropholis delicata, in south-eastern Australia. Specifically, we predicted that lizards would nest at sites with lower openness and solar radiation than random sites, but within crevices with higher humidity than random crevices. However, we predicted that these environmental factors would not differ between communal and solitary nest sites (based on previous research), but that egg mortality in communal nests would be higher than that in solitary nests due to conspecific interference. Despite being ground dwellers, skinks in this population nested above the ground level in narrow horizontal crevices within vertical faces of sandstone outcrops. At the broadest scale, skinks nested at sites with significantly lower canopy openness and incident (solar) radiation than random sites, while at the smallest scale, skinks nested in crevices with significantly higher relative humidity than potential nest crevices. Humidity averaged 94% in nest sites, and nesting females did not trade-off humidity for temperature, despite an inverse relationship between the two at potential nest sites. Of 60 nests, about half to two-thirds were communal. Communal nest sites did not differ from solitary nest sites with respect to temperature, humidity, rock size, aspect, height of crevice above ground, or crevice dimensions. Eggs from communal nests were three times more likely to desiccate and perish than eggs from solitary nests, a clear cost of communal nesting. Desiccation was caused by eggs being displaced from their original positions within the crevices, possibly by conspecific gravid females.
Woodland and forest degradation, driven predominately by agricultural and pastoral production, is... more Woodland and forest degradation, driven predominately by agricultural and pastoral production, is a crisis facing many species globally, in particular hollow‐dependent fauna. Large predatory species play important roles in both ecosystems and conservation strategies, but few studies have examined habitat selection of such species in intensively human‐modified landscapes. We quantified habitat selection and resource use by a large, top‐order and threatened snake (carpet python, Morelia spilota), between adjacent areas of high and low anthropogenic modification in inland Australia, a region that has undergone considerable alteration since European settlement. At the low‐impact site, snakes preferred tree hollows and a structurally complex understorey, whereas at the high‐impact site, snakes preferred homestead attics. Based on the decline of the species in this region, however, high‐impact landscapes may only support snakes when they are adjacent to low‐impact habitats. Invasive species comprised a large part of snake diets in both landscape types. Carpet pythons, with large home ranges and habitat requirements that overlap with many smaller threatened mammalian and avian fauna, are generally well liked and easily identifiable by rural landholders. Accordingly, they may play a key role in conservation strategies aimed at the protection of woodland and hollow‐dependent fauna in heavily modified landscapes of Australia's inland regions. However, invasive species, which tend to contribute to declines in native species inhabiting arid and semi‐arid Australia, are beneficial and important to pythons. Our study therefore highlights the diversity of effects that two major threats to biodiversity – habitat loss and invasive species – can have on different species within the same ecosystem.
The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (... more The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (ANS) was repurposed in mammals, via a "second vagal nerve", to suppress defensive strategies and support the expression of sociality. Three critical assumptions of this theory are that (1) the transition of the ANS was associated with the evolution of 'social' mammals from 'asocial' reptiles; (2) the transition enabled mammals, unlike their reptilian ancestors, to derive a biological benefit from social interactions; and (3) the transition forces a less parsimonious explanation (convergence) for the evolution of social behavior in birds and mammals, since birds evolved from a reptilian lineage. Two recently published reviews, however, provided compelling evidence that the social-asocial dichotomy is overly simplistic, neglects the diversity of vertebrate social systems, impedes our understanding of the evolution of social behavior, and perpetuates the erroneous belief that one group-non-avian reptiles-is incapable of complex social behavior. In the worst case, if PT depends upon a transition from 'asocial reptiles' to 'social mammals,' then the ability of PT to explain the evolution of the mammalian ANS is highly questionable. A great number of social behaviors occur in both reptiles and mammals. In the best case, PT has misused the terms 'social' and 'asocial'. Even here, however, the theory would still need to identify a particular suite of behaviors found in mammals and not reptiles that could be associated with, or explain, the transition of the ANS, and then replace the 'asocial' and 'social' labels with more specific descriptors.
South American Cane Toads (Rhinella marina) have been introduced into several regions outside of ... more South American Cane Toads (Rhinella marina) have been introduced into several regions outside of their native distribution. Outside of their native range, few predators have been documented preying upon R.marina due to their potent toxins secreted in defense. However, prevalence of a toxin resistance gene makes it possible for some snakes of the sub-family Natricinae to consume native toads. We documented successful consumption of the invasive cane toad by the Southern Watersnake (Nerodia fasciata) in southwest Florida, both in the wild and in the laboratory. Southern Watersnakes from populations that existed both with and without cane toads successfully consumed toad prey without obvious ill-effect. Southern Watersnakes in southwest Florida are thus resistant to, and readily consume cane toads, an otherwise relatively predator-free invasive species in Florida. More dietary field data and controlled experiments that measure resistance to multiple prey items, sizes, and frequency wil...
The marine toad Bufo marinus is native to northern South America, parts of Central America and So... more The marine toad Bufo marinus is native to northern South America, parts of Central America and Southern Texas. It was deliberately introduced into Australia's tropical north‐east in 1935 in an unsuccessful attempt to control the cane beetle, a damaging insect pest of sugarcane crops. The toads quickly established in the new environment and began to spread. Today, they inhabit most of the Australian tropics and sub‐tropics and have reached Western Australia. Models predict that global warming will enable the toads to extend their range further south. They cause severe environmental impacts, as all life stages of B. marinus contain bufadienolides, alkaloid substances toxic to vertebrates, resulting in death of the predators ingesting it. The continental scale of this biological invasion in combination with the remoteness of the areas affected, poses a specific set of challenges to potential control approaches for cane toads. This review covers different biocontrol strategies pursu...
Underwater video is increasingly being used to record and research aquatic fauna in their natural... more Underwater video is increasingly being used to record and research aquatic fauna in their natural environment, and is emerging alongside Dual Frequency Identification Sonar (DIDSON) as a powerful tool in Australian freshwater ecology. We review current progress with field-based applications of underwater video in studying Australian freshwater fish and crustacean ecology. Drawing upon searches of online literature databases and our expert knowledge, we located 11 relevant publications: five set in the Murray-Darling Basin, three in the Eastern Province, two in the Northern Province and a single study in the Pilbara Province. In total, 10 studies reported using video for fish ecology, while three studies included crustaceans. Across the 11 publications, eight examined threatened species, while the remaining studies developed video techniques for surveying species richness in remote or difficult to access habitats. Habitat-use was also a dominant theme (seven studies). Seven of the eight studies that centred on threatened species focused on at least one percichthyid species in either the Murray-Darling Basin or the Eastern Province. Miniaturisation in equipment and increases in compact battery capacity seem to have driven a shift from above-water battery supplies and data storage to small, inexpensive and mobile underwater cameras. We foresee wider use of video in freshwater ecology primarily in the study of animal behaviour and also to improve species detection in field surveys. There is scope for testing novel techniques such as animal-borne video and unmanned underwater vehicles and making use of video in citizen science initiatives.
Climate warming is forecasted to cause extinctions, but populations could theoretically avoid ext... more Climate warming is forecasted to cause extinctions, but populations could theoretically avoid extinction in a rapidly changing environment via adaptive evolution (i.e., evolutionary rescue), precluding the need for intervention. Although strong links between a changing climate and the physiology of an organism are expected, climate effects can be buffered by behavior. Nest site choice behavior, for example, can reduce environmental variation that would be experienced by embryos placed randomly with respect to environmental temperatures. We tested four provisions of this prediction by quantifying nest sites and "potential" nest sites in the Florida softshell turtle (Apalone ferox). First, turtles chose nest sites with mean canopy openness values (32-47%) that were intermediate between the shadiest (14-17%) and the sunniest potential nest sites (36-57%) available. Second, canopy openness, incident radiation intensity, and nest temperatures were generally, positively related to one another, indicating definitive thermal consequences of nest site choice. Third, our study revealed ample, cooler nest sites available to turtle mothers within close proximity to nest sites utilized; by nesting in the most shaded sites, softshell turtle mothers could depress mean nest temperatures by ∼2 • C. Fourth, the growth of vegetative cover throughout incubation had negligible effects on canopy openness, incident radiation intensity, and nest temperatures, supporting the potential for mothers to "predict" developmental temperatures using temperature cues during nest site choice. Finally, our data revealed considerable variation in canopy openness chosen by nesting mothers; such behavior could thus, be subject to natural selection via embryonic mortality under future warming. Collectively, our study suggests that Florida softshell turtles, and probably other turtle species nesting in relatively open areas, may be able to counter climate change effects on developing embryos by nesting in more shaded microhabitats, assuming nest site choice behavior is heritable and can evolve at a sufficient rate to keep pace with climate warming.
Sex-determining mechanisms are broadly categorised as being based on either genetic or environmen... more Sex-determining mechanisms are broadly categorised as being based on either genetic or environmental factors. Vertebrate sex determination exhibits remarkable diversity but displays distinct phylogenetic patterns. While all eutherian mammals possess XY male heterogamety and female heterogamety (ZW) is ubiquitous in birds, poikilothermic vertebrates (fish, amphibians and reptiles) exhibit multiple genetic sex-determination (GSD) systems as well as environmental sex determination (ESD). Temperature is the factor controlling ESD in reptiles and temperature-dependent sex determination (TSD) in reptiles has become a focal point in the study of this phenomenon. Current patterns of climate change may cause detrimental skews in the population sex ratios of reptiles exhibiting TSD. Understanding the patterns of variation, both within and among populations and linking such patterns with the selection processes they are associated with, is the central challenge of research aimed at predicting the capacity of populations to adapt to novel conditions. Here we present a conceptual model that innovates by defining an individual reaction norm for sex determination as a range of incubation temperatures. By deconstructing individual reaction norms for TSD and revealing their underlying interacting elements, we offer a conceptual solution that explains how variation among individual reaction norms can be inferred from the pattern of population reaction norms. The model also links environmental variation with the different patterns of TSD and describes the processes from which they may arise. Specific climate scenarios are singled out as eco-evolutionary traps that may lead to demographic extinction or a transition to either male or female heterogametic GSD. We describe how the conceptual principles can be applied to interpret TSD data and to explain the adaptive capacity of TSD to climate change as well as its limits and the potential applications for conservation and management programs.
The precise manner in which vertebrate species utilize urban environments remains to be explored ... more The precise manner in which vertebrate species utilize urban environments remains to be explored in a variety of taxa, with snakes in particular being poorly studied. Watersnakes (Genus: Nerodia) are semiaquatic snakes found throughout the eastern United States and are known to occur in urban systems. Four species of watersnake are commonly found in freshwater environments in southeastern Louisiana: Mississippi Green Watersnake, Plain-bellied Watersnake, Southern Watersnake, and Diamondbacked Watersnake. Plain-bellied Watersnake and Southern Watersnake preferentially feed on anurans, while Mississippi Green Watersnake and Diamond-backed Watersnake tend to be more piscivorous in their feeding habits. Water depth is important in structuring anuran and sh community structure, with shallower water bodies typically supporting higher anuran abundance and richness, and deeper waters supporting more shes. We examined watersnakes in canal transects of varying depth in Kenner, Louisiana to test the hypotheses that species that feed on anurans would be more abundant in shallower canals, while species that preferentially feed on shes would be more abundant in deeper canals. We found signi cant correlation between watersnake assemblage and anuran/ sh community structure, with the Plain-bellied Watersnake most abundant in the shallowest canal transects, Mississippi Green Watersnake most abundant in transects of intermediate depth, and Diamond-backed Watersnake most abundant in the shallow transects. The former two species largely followed the hypothesized trends, while the Diamond-backed Watersnake did not.
Abstract. Recreational activities can be detrimental to biodiversity; for example, off-road vehic... more Abstract. Recreational activities can be detrimental to biodiversity; for example, off-road vehicle traffic (e.g., ATV riding), which has become increasingly popular in recent decades, can threaten wildlife. Although ATV riding around wetlands may threaten the shallow nests of turtles, there are no data on the effect of ATVs on turtle nests. We studied nest site choice and nest survival in two species of softshell turtles (Apalone mutica and A. spinifera) along a river in Louisiana before (1993–1994) and after (2015–2016) ATV riding became popular at the site to determine whether ATVs were an important source of nest mortality, and whether there was an effect of nest site choice on nest survival. ATVs were the most common source of nest mortality (one-third of nests destroyed); nest mortality was significantly positively related to increased ATV traffic but was not influenced by species or nest site choice. Experiments with surrogate eggs and an ATV revealed that the most vulnerable nests to ATV mortality were those that were shallower, were driven over more slowly, and were turned upon. We recommend restricting the access of riding clubs to the river; enforcement of regulations on isolated riders from adjacent residential areas will be logistically and financially challenging.
ABSTRACT Abstract Lizards are appropriate organisms to investigate causes and correlates of commu... more ABSTRACT Abstract Lizards are appropriate organisms to investigate causes and correlates of communal egg laying because their general lack of parental care focuses attention on nest site choice. We field-tested hypotheses associated with nest site choice and communal egg laying in the delicate skink Lampropholis delicata, in south-eastern Australia. Specifically, we predicted that lizards would nest at sites with lower openness and solar radiation than random sites, but within crevices with higher humidity than random crevices. However, we predicted that these environmental factors would not differ between communal and solitary nest sites (based on previous research), but that egg mortality in communal nests would be higher than that in solitary nests due to conspecific interference. Despite being ground dwellers, skinks in this population nested above the ground level in narrow horizontal crevices within vertical faces of sandstone outcrops. At the broadest scale, skinks nested at sites with significantly lower canopy openness and incident (solar) radiation than random sites, while at the smallest scale, skinks nested in crevices with significantly higher relative humidity than potential nest crevices. Humidity averaged 94% in nest sites, and nesting females did not trade-off humidity for temperature, despite an inverse relationship between the two at potential nest sites. Of 60 nests, about half to two-thirds were communal. Communal nest sites did not differ from solitary nest sites with respect to temperature, humidity, rock size, aspect, height of crevice above ground, or crevice dimensions. Eggs from communal nests were three times more likely to desiccate and perish than eggs from solitary nests, a clear cost of communal nesting. Desiccation was caused by eggs being displaced from their original positions within the crevices, possibly by conspecific gravid females.
Woodland and forest degradation, driven predominately by agricultural and pastoral production, is... more Woodland and forest degradation, driven predominately by agricultural and pastoral production, is a crisis facing many species globally, in particular hollow‐dependent fauna. Large predatory species play important roles in both ecosystems and conservation strategies, but few studies have examined habitat selection of such species in intensively human‐modified landscapes. We quantified habitat selection and resource use by a large, top‐order and threatened snake (carpet python, Morelia spilota), between adjacent areas of high and low anthropogenic modification in inland Australia, a region that has undergone considerable alteration since European settlement. At the low‐impact site, snakes preferred tree hollows and a structurally complex understorey, whereas at the high‐impact site, snakes preferred homestead attics. Based on the decline of the species in this region, however, high‐impact landscapes may only support snakes when they are adjacent to low‐impact habitats. Invasive species comprised a large part of snake diets in both landscape types. Carpet pythons, with large home ranges and habitat requirements that overlap with many smaller threatened mammalian and avian fauna, are generally well liked and easily identifiable by rural landholders. Accordingly, they may play a key role in conservation strategies aimed at the protection of woodland and hollow‐dependent fauna in heavily modified landscapes of Australia's inland regions. However, invasive species, which tend to contribute to declines in native species inhabiting arid and semi‐arid Australia, are beneficial and important to pythons. Our study therefore highlights the diversity of effects that two major threats to biodiversity – habitat loss and invasive species – can have on different species within the same ecosystem.
The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (... more The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (ANS) was repurposed in mammals, via a "second vagal nerve", to suppress defensive strategies and support the expression of sociality. Three critical assumptions of this theory are that (1) the transition of the ANS was associated with the evolution of 'social' mammals from 'asocial' reptiles; (2) the transition enabled mammals, unlike their reptilian ancestors, to derive a biological benefit from social interactions; and (3) the transition forces a less parsimonious explanation (convergence) for the evolution of social behavior in birds and mammals, since birds evolved from a reptilian lineage. Two recently published reviews, however, provided compelling evidence that the social-asocial dichotomy is overly simplistic, neglects the diversity of vertebrate social systems, impedes our understanding of the evolution of social behavior, and perpetuates the erroneous belief that one group-non-avian reptiles-is incapable of complex social behavior. In the worst case, if PT depends upon a transition from 'asocial reptiles' to 'social mammals,' then the ability of PT to explain the evolution of the mammalian ANS is highly questionable. A great number of social behaviors occur in both reptiles and mammals. In the best case, PT has misused the terms 'social' and 'asocial'. Even here, however, the theory would still need to identify a particular suite of behaviors found in mammals and not reptiles that could be associated with, or explain, the transition of the ANS, and then replace the 'asocial' and 'social' labels with more specific descriptors.
South American Cane Toads (Rhinella marina) have been introduced into several regions outside of ... more South American Cane Toads (Rhinella marina) have been introduced into several regions outside of their native distribution. Outside of their native range, few predators have been documented preying upon R.marina due to their potent toxins secreted in defense. However, prevalence of a toxin resistance gene makes it possible for some snakes of the sub-family Natricinae to consume native toads. We documented successful consumption of the invasive cane toad by the Southern Watersnake (Nerodia fasciata) in southwest Florida, both in the wild and in the laboratory. Southern Watersnakes from populations that existed both with and without cane toads successfully consumed toad prey without obvious ill-effect. Southern Watersnakes in southwest Florida are thus resistant to, and readily consume cane toads, an otherwise relatively predator-free invasive species in Florida. More dietary field data and controlled experiments that measure resistance to multiple prey items, sizes, and frequency wil...
The marine toad Bufo marinus is native to northern South America, parts of Central America and So... more The marine toad Bufo marinus is native to northern South America, parts of Central America and Southern Texas. It was deliberately introduced into Australia's tropical north‐east in 1935 in an unsuccessful attempt to control the cane beetle, a damaging insect pest of sugarcane crops. The toads quickly established in the new environment and began to spread. Today, they inhabit most of the Australian tropics and sub‐tropics and have reached Western Australia. Models predict that global warming will enable the toads to extend their range further south. They cause severe environmental impacts, as all life stages of B. marinus contain bufadienolides, alkaloid substances toxic to vertebrates, resulting in death of the predators ingesting it. The continental scale of this biological invasion in combination with the remoteness of the areas affected, poses a specific set of challenges to potential control approaches for cane toads. This review covers different biocontrol strategies pursu...
Underwater video is increasingly being used to record and research aquatic fauna in their natural... more Underwater video is increasingly being used to record and research aquatic fauna in their natural environment, and is emerging alongside Dual Frequency Identification Sonar (DIDSON) as a powerful tool in Australian freshwater ecology. We review current progress with field-based applications of underwater video in studying Australian freshwater fish and crustacean ecology. Drawing upon searches of online literature databases and our expert knowledge, we located 11 relevant publications: five set in the Murray-Darling Basin, three in the Eastern Province, two in the Northern Province and a single study in the Pilbara Province. In total, 10 studies reported using video for fish ecology, while three studies included crustaceans. Across the 11 publications, eight examined threatened species, while the remaining studies developed video techniques for surveying species richness in remote or difficult to access habitats. Habitat-use was also a dominant theme (seven studies). Seven of the eight studies that centred on threatened species focused on at least one percichthyid species in either the Murray-Darling Basin or the Eastern Province. Miniaturisation in equipment and increases in compact battery capacity seem to have driven a shift from above-water battery supplies and data storage to small, inexpensive and mobile underwater cameras. We foresee wider use of video in freshwater ecology primarily in the study of animal behaviour and also to improve species detection in field surveys. There is scope for testing novel techniques such as animal-borne video and unmanned underwater vehicles and making use of video in citizen science initiatives.
Climate warming is forecasted to cause extinctions, but populations could theoretically avoid ext... more Climate warming is forecasted to cause extinctions, but populations could theoretically avoid extinction in a rapidly changing environment via adaptive evolution (i.e., evolutionary rescue), precluding the need for intervention. Although strong links between a changing climate and the physiology of an organism are expected, climate effects can be buffered by behavior. Nest site choice behavior, for example, can reduce environmental variation that would be experienced by embryos placed randomly with respect to environmental temperatures. We tested four provisions of this prediction by quantifying nest sites and "potential" nest sites in the Florida softshell turtle (Apalone ferox). First, turtles chose nest sites with mean canopy openness values (32-47%) that were intermediate between the shadiest (14-17%) and the sunniest potential nest sites (36-57%) available. Second, canopy openness, incident radiation intensity, and nest temperatures were generally, positively related to one another, indicating definitive thermal consequences of nest site choice. Third, our study revealed ample, cooler nest sites available to turtle mothers within close proximity to nest sites utilized; by nesting in the most shaded sites, softshell turtle mothers could depress mean nest temperatures by ∼2 • C. Fourth, the growth of vegetative cover throughout incubation had negligible effects on canopy openness, incident radiation intensity, and nest temperatures, supporting the potential for mothers to "predict" developmental temperatures using temperature cues during nest site choice. Finally, our data revealed considerable variation in canopy openness chosen by nesting mothers; such behavior could thus, be subject to natural selection via embryonic mortality under future warming. Collectively, our study suggests that Florida softshell turtles, and probably other turtle species nesting in relatively open areas, may be able to counter climate change effects on developing embryos by nesting in more shaded microhabitats, assuming nest site choice behavior is heritable and can evolve at a sufficient rate to keep pace with climate warming.
Sex-determining mechanisms are broadly categorised as being based on either genetic or environmen... more Sex-determining mechanisms are broadly categorised as being based on either genetic or environmental factors. Vertebrate sex determination exhibits remarkable diversity but displays distinct phylogenetic patterns. While all eutherian mammals possess XY male heterogamety and female heterogamety (ZW) is ubiquitous in birds, poikilothermic vertebrates (fish, amphibians and reptiles) exhibit multiple genetic sex-determination (GSD) systems as well as environmental sex determination (ESD). Temperature is the factor controlling ESD in reptiles and temperature-dependent sex determination (TSD) in reptiles has become a focal point in the study of this phenomenon. Current patterns of climate change may cause detrimental skews in the population sex ratios of reptiles exhibiting TSD. Understanding the patterns of variation, both within and among populations and linking such patterns with the selection processes they are associated with, is the central challenge of research aimed at predicting the capacity of populations to adapt to novel conditions. Here we present a conceptual model that innovates by defining an individual reaction norm for sex determination as a range of incubation temperatures. By deconstructing individual reaction norms for TSD and revealing their underlying interacting elements, we offer a conceptual solution that explains how variation among individual reaction norms can be inferred from the pattern of population reaction norms. The model also links environmental variation with the different patterns of TSD and describes the processes from which they may arise. Specific climate scenarios are singled out as eco-evolutionary traps that may lead to demographic extinction or a transition to either male or female heterogametic GSD. We describe how the conceptual principles can be applied to interpret TSD data and to explain the adaptive capacity of TSD to climate change as well as its limits and the potential applications for conservation and management programs.
The precise manner in which vertebrate species utilize urban environments remains to be explored ... more The precise manner in which vertebrate species utilize urban environments remains to be explored in a variety of taxa, with snakes in particular being poorly studied. Watersnakes (Genus: Nerodia) are semiaquatic snakes found throughout the eastern United States and are known to occur in urban systems. Four species of watersnake are commonly found in freshwater environments in southeastern Louisiana: Mississippi Green Watersnake, Plain-bellied Watersnake, Southern Watersnake, and Diamondbacked Watersnake. Plain-bellied Watersnake and Southern Watersnake preferentially feed on anurans, while Mississippi Green Watersnake and Diamond-backed Watersnake tend to be more piscivorous in their feeding habits. Water depth is important in structuring anuran and sh community structure, with shallower water bodies typically supporting higher anuran abundance and richness, and deeper waters supporting more shes. We examined watersnakes in canal transects of varying depth in Kenner, Louisiana to test the hypotheses that species that feed on anurans would be more abundant in shallower canals, while species that preferentially feed on shes would be more abundant in deeper canals. We found signi cant correlation between watersnake assemblage and anuran/ sh community structure, with the Plain-bellied Watersnake most abundant in the shallowest canal transects, Mississippi Green Watersnake most abundant in transects of intermediate depth, and Diamond-backed Watersnake most abundant in the shallow transects. The former two species largely followed the hypothesized trends, while the Diamond-backed Watersnake did not.
Abstract. Recreational activities can be detrimental to biodiversity; for example, off-road vehic... more Abstract. Recreational activities can be detrimental to biodiversity; for example, off-road vehicle traffic (e.g., ATV riding), which has become increasingly popular in recent decades, can threaten wildlife. Although ATV riding around wetlands may threaten the shallow nests of turtles, there are no data on the effect of ATVs on turtle nests. We studied nest site choice and nest survival in two species of softshell turtles (Apalone mutica and A. spinifera) along a river in Louisiana before (1993–1994) and after (2015–2016) ATV riding became popular at the site to determine whether ATVs were an important source of nest mortality, and whether there was an effect of nest site choice on nest survival. ATVs were the most common source of nest mortality (one-third of nests destroyed); nest mortality was significantly positively related to increased ATV traffic but was not influenced by species or nest site choice. Experiments with surrogate eggs and an ATV revealed that the most vulnerable nests to ATV mortality were those that were shallower, were driven over more slowly, and were turned upon. We recommend restricting the access of riding clubs to the river; enforcement of regulations on isolated riders from adjacent residential areas will be logistically and financially challenging.
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Papers by Jeremiah Doody