Challenges of dehydration result in a behavioral shift in invasive toads

Madelaire, Carla Bonetti; Barsotti, A; Wagener, Carla; Sugano, Yuri Y. Vieira; Baxter‐Gilbert, James; Gomes, Fernando Ribeiro; Measey, John

doi:10.1007/s00265-020-02866-5

Cited by 10 publications

(11 citation statements)

References 89 publications

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“…Moreover, glucocorticoids potentiate the effects of angiotensin II (ANG II) mediating drinking behavior in mammals (Ganesan and Sumners, 1989;Sumners et al, 1991;Takei, 2000), and can similarly stimulate water seeking-behavior in anurans. Interestingly, hydrated individuals of S. gutturalis who had their CORT artificially increased, through transdermal application, showed an increase in water-seeking behavior (Madelaire et al, 2020). Considering that invasive toads tended to show lower hydration levels than native toads under field conditions, this higher efficiency in finding water due to increased CORT when dehydrated might favor the dispersal of the invasive Cape Town population.…”

Section: Discussionmentioning

confidence: 98%

Challenges of a novel range: Water balance, stress, and immunity in an invasive toad

Barsotti

Madelaire

Wagener

et al. 2021

Comparative Biochemistry and Physiology Part A: Molecular &

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Species introduced by human activities can alter the normal functioning of ecosystems promoting negative impacts on native biodiversity, as they can rapidly expand their population size, demonstrating phenotypic plasticity and possible adaptive capacity to novel environments. Twenty years ago, the guttural toad, Sclerophrys gutturalis, was introduced to a peri-urban area of Cape Town, with cooler and drier climatic characteristics than its native source population, Durban, South Africa. Our goal was to understand the phenotypic changes, in terms of physiology and immunity, of populations in native and novel environments. We evaluated body index (BI), field hydration level, plasma corticosterone levels (CORT), proportion of neutrophils: lymphocytes (N: L), plasma bacterial killing ability (BKA), and hematocrit (HTC) in the field, and after standardized stressors (dehydration and movement restriction) in males from the native and invasive populations. Toads from the invasive population presented lower BI and tended to show a lower field hydration state, which is consistent with living in the drier environmental conditions of Cape Town. Additionally, invasive toads also showed higher BKA and N:L ratio under field conditions. After exposure to stressors, invasive animals presented higher BKA than the natives. Individuals from both populations showed increased CORT after dehydration, an intense stressor for these animals. The highest BKA and N:L ratio in the field and after submission to stressors in the laboratory shows that the invasive population has a phenotype that might increase their fitness, leading to adaptive responses in the novel environment and, thus, favoring successful dispersion and population increase.

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Section: Discussionmentioning

confidence: 98%

Challenges of a novel range: Water balance, stress, and immunity in an invasive toad

Barsotti

Madelaire

Wagener

et al. 2021

Comparative Biochemistry and Physiology Part A: Molecular &

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“…In the case of the invasive population near Cape Town, eggs and tadpoles are presumed to have been unintentionally introduced via a consignment of aquatic ornamental plants in 1998 (De Villiers 2006 ; Measey et al 2017 ). This urban-invasive Cape Town population has since shown rapid adaptation to the drier climate in the Cape region in the adult stage, altering their behavior, physiology, and reproductive strategy (Vimercati et al 2018 , 2019 ; Madelaire et al 2020 ; Barsotti et al 2021 ).…”

Section: Methodsmentioning

confidence: 99%

No evidence for innate differences in tadpole behavior between natural, urbanized, and invasive populations

Mühlenhaupt

Baxter‐Gilbert

Makhubo

et al. 2022

Behav Ecol Sociobiol

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Animals are increasingly challenged to respond to novel or rapidly changing habitats due to urbanization and/or displacement outside their native range by humans. Behavioral differences, such as increased boldness (i.e., propensity for risk-taking), are often observed in animals persisting in novel environments; however, in many cases, it is unclear how these differences arise (e.g., through developmental plasticity or evolution) or when they arise (i.e., at what age or developmental stage). In the Guttural Toad ( Sclerophrys gutturalis ), adult urban toads from both native and invasive ranges are bolder than conspecifics in natural habitats. Here, we reared Guttural Toad tadpoles in a common garden experiment, and tested for innate differences in boldness across their development and between individuals whose parents and lineage came from rural-native, urban-native, and urban-invasive localities (i.e., origin populations). Tadpoles did not differ in their boldness or in how their boldness changed over ontogeny based on their origin populations. In general, tadpoles typically became less bold as they aged, irrespective of origin population. Our findings indicate that differences in boldness in free-living adult Guttural Toads are not innate in the tadpole stage and we discuss three possible mechanisms driving phenotypic divergence in adult boldness for the focus of future research: habitat-dependent developmental effects on tadpole behavior, decoupled evolution between the tadpole and adult stage, and/or behavioral flexibility, learning, or acclimatization during the adult stage. Significance statement To determine if animals can persist in urban areas or become invasive outside their native ranges, it is important to understand how they adapt to life in the city. Our study investigates if differences in boldness that have been found in adult Guttural Toads ( Sclerophrys gutturalis ) represent heritable differences that can also be found in early life stages by rearing tadpoles from eggs in a common garden experiment. We did not find any differences in boldness among tadpoles from rural-native, urban-native, and urban-invasive origin populations. Our findings suggest that differences in boldness are not innate and/or that boldness is a behavioral trait that is decoupled between the tadpole and the adult stage.

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“…In this paper, we assess efficacy and efficiency of alternative management strategies for an invasive population of the guttural toad, Sclerophrys gutturalis (Power, 1927), in a peri-urban residential area of Cape Town (Measey et al 2017). Invasive guttural toads, which were first detected in Cape Town in 2000 ( de Villiers 2006), use garden ponds for breeding (Vimercati et al 2017a, b) and have adaptively responded to the unfamiliar environmental settings of the invasive range (Vimercati et al 2018(Vimercati et al , 2019Madelaire et al 2020;Barsotti et al 2021;Mühlenhaupt et al 2021). In 2010, the City of Cape Town contracted a private company to decrease the population size and limit expansion of the invasive population (Davies et al 2020a, b) by removing toads from their breeding sites.…”

Section: Introductionmentioning

confidence: 99%

Cost-benefit evaluation of management strategies for an invasive amphibian with a stage-structured model

Vimercati¹,

Davies²,

Hui³

et al. 2021

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Management strategies for invasive populations should be designed to maximise efficacy and efficiency, i.e. to accomplish their goals while operating with the least resource consumption. This optimisation is often difficult to achieve in stage-structured populations, because costs, benefits and feasibility of removing individuals may vary with stage. We use a spatially-explicit stage-structured model to assess efficacy of past, present and alternative control strategies for invasive guttural toads, Sclerophrys gutturalis, in Cape Town. The strategies involve removal of variable proportions of individuals at different life-history stages and spatial scales. We also quantify the time necessary to implement each strategy as a proxy of financial resources and we correct strategy outcomes by implementation of time to estimate efficiency. We found that the strategy initially pursued in Cape Town, which did not target any specific stage, was less efficient than the present strategy, which prioritises adult removal. The initial strategy was particularly inefficient because it did not reduce the population size despite allocating consistent resources to remove eggs and tadpoles. We also found that such removal might be detrimental when applied at high levels. This counter-intuitive outcome is due to the ‘hydra effect’: an undesired increase in population size caused by removing individuals before overcompensatory density dependence. Strategies that exclusively remove adults ensure much greater management efficiency than those that also remove eggs and tadpoles. Available management resources should rather be allocated to increase the proportion of adult guttural toads that are removed or the spatial extent at which this removal is pursued.

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Challenges of dehydration result in a behavioral shift in invasive toads

Cited by 10 publications

References 89 publications

Challenges of a novel range: Water balance, stress, and immunity in an invasive toad

Challenges of a novel range: Water balance, stress, and immunity in an invasive toad

No evidence for innate differences in tadpole behavior between natural, urbanized, and invasive populations

Cost-benefit evaluation of management strategies for an invasive amphibian with a stage-structured model

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Challenges of dehydration result in a behavioral shift in invasive toads

Cited by 10 publications

References 89 publications

Challenges of a novel range: Water balance, stress, and immunity in an invasive toad

Challenges of a novel range: Water balance, stress, and immunity in an invasive toad

No evidence for innate differences in tadpole behavior between natural, urbanized, and invasive populations

﻿Cost-benefit evaluation of management strategies for an invasive amphibian with a stage-structured model

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Cost-benefit evaluation of management strategies for an invasive amphibian with a stage-structured model