-We documented a significant mortality event affecting a southwestern pond turtle (Actinemys pallida) population living in a lake in southern California, USA. The area around the lake was impacted by a large wildland fire in 2013 that occurred during a protracted drought. As the mortality event was still unfolding, we collected data in 2014 on water quality, demographic structure, and short-term survivorship of the population. Water quality was poor with low levels of dissolved oxygen and high salinity of up to 45.90 ppt. Many turtles were severely emaciated and coated with a pale mineralized layer on their shells and skin. Estimated survival rate was low leading to a projected 90% decline in 134 days and a high probability of extirpation within a year. The lake was dry in September 2015 with no evidence of live turtles. Necropsies and low volumetric body condition indices suggested death by starvation. Although this semi-aquatic species has the ability to aestivate in upland habitats during periods of low water or move to other nearby water bodies, it is unlikely that many were able to do so because of their extremely poor condition and the severity of the drought conditions throughout the area.Keywords: climate / evaporite / starvation / survivorship / water quality Résumé -Les effets de la sécheresse et du feu dans l'anéantissement d'un abondant vertébré semiaquatique dans un milieu lacustre du sud-ouest des États-Unis. Nous avons relevé un événement de forte mortalité affectant une population de tortues du sud-ouest (Actinemys pallida) vivant dans un lac au sud de la Californie, États-Unis. Les environs du lac ont été touchés par un grand incendie forestier en 2013 qui s'était produit au cours d'une sécheresse prolongée. Comme l'événement de mortalité continuait à se dérouler, nous avions recueilli des données en 2014 sur la qualité de l'eau et sur la structure démographique et la survie à court terme de la population. La qualité de l'eau était faible avec de bas niveaux d'oxygène dissous et une salinité élevée allant jusqu'à 45,90 ppm. De nombreuses tortues étaient gravement émaciées et revêtues d'une couche minéralisée pâle sur leurs carapaces et leurs peaux. Le taux de survie estimé était faible, ce qui a entraîné un déclin attendu de 90 % en 134 jours et une probabilité de disparition élevée dans un délai d'un an. Le lac était à sec en septembre 2015 sans aucune preuve de tortues vivantes. Des nécropsies et de faibles indices de condition corporelle volumétrique suggéraient la mort par inanition. Bien que cette espèce semi-aquatique ait la capacité d'estiver dans les habitats des hautes-terres pendant les périodes de basses eaux ou de se déplacer vers d'autres plans d'eau avoisinants, il est peu probable que beaucoup de tortues aient pu le faire en raison de leur très mauvais état et de la sévérité des conditions de sécheresse dans toute la région.
Prolonged drought due to climate change has negatively impacted amphibians in southern California, U.S.A. Due to the severity and length of the current drought, agencies and researchers had growing concern for the persistence of the arroyo toad (Anaxyrus californicus), an endangered endemic amphibian in this region. Range-wide
Climate change and prolonged drought have negatively impacted amphibians in southern California, U.S.A. Due to the severe drought from 2012–2016, agencies and researchers had growing concern for the persistence of the arroyo toad (Anaxyrus californicus), an endangered endemic amphibian in this region. Range-wide surveys for this species had not been conducted for at least 20 years. In 2017–2020 we conducted collaborative surveys for arroyo toads at historical locations. We surveyed 87 of the 115 total sites having historical records and confirmed that the arroyo toad is currently extant in 60 of 87 sites and 19 of 25 historically occupied watersheds. Only detection/non-detection and not population size was recorded, therefore potential declines at the population level could not be assessed. In other amphibian species, body condition has been documented to decrease with a decrease in water availability. To further investigate the drought’s impact on this species, we calculated an average body condition index annually for arroyo toads using allometric measurements recorded from 1996–present. This index was plotted against precipitation records over time. Our data show that body condition did not significantly change during drought years, but hydro-regulation may be masking an effect. Our study suggests that this species shows some resiliency to climate change and drought, and that mitigating invasive species, hydro-modification, and other anthropogenic drivers may currently be the most beneficial strategy for toad conservation. Arroyo toad conservation actions may also provide simultaneous benefits to several other native species that share the same habitat.
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