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15 pages, 3355 KiB

Open AccessArticle

Influence of Landscape Factors on Amphibian Roadkills at the National Level

by Neftalí Sillero, Katja Poboljšaj, Aleksandra Lešnik and Ali Šalamun

Diversity 2019, 11(1), 13; https://doi.org/10.3390/d11010013 - 17 Jan 2019

Cited by 20 | Viewed by 4967

Roads exert multiple effects on wildlife, from animal mortality, habitat and population fragmentation, to modification of animal reproductive behaviour. Amphibians are the most frequently road-killed animal group. Many studies have attempted to analyse the factors driving amphibian casualties on roads, but these factors [...] Read more.

Roads exert multiple effects on wildlife, from animal mortality, habitat and population fragmentation, to modification of animal reproductive behaviour. Amphibians are the most frequently road-killed animal group. Many studies have attempted to analyse the factors driving amphibian casualties on roads, but these factors are limited to the roads themselves (e.g., traffic, type of roads, roads crossing water bodies) or to structures along them (e.g., ditches, walls). Sometimes, roadkills are related to land use along the roads. We analysed the influence of landscape factors on roadkill hotspots at the national level (Slovenia). Specifically, we aimed at: (1) identifying hotspots of roadkills, (2) analysing whether records of amphibian presence on roads are related to the distribution of water bodies and (3) analysing which factors (proximity to water bodies or human factors) explain the distribution of hotspots. Hotspots were identified by Malo’s method. Roadkills were modelled with Maxent for the first time in Slovenia. The relationships between amphibian presence and hotspots with factors were analysed with GLM. A total of 237 road sections were identified as hotspots, corresponding to 8% of road sections and containing 90% of road-killed individuals. Proximity to forests, meadows and agricultural land were the most important variables in Maxent models. The number of roadkills depended on the proximity to agricultural land, forests, water bodies and wetland areas, while the number of hotspots additionally depended on the proximity to urban settlements. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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16 pages, 1456 KiB

Open AccessArticle

Reconnecting Amphibian Habitat through Small Pond Construction and Enhancement, South Okanagan River Valley, British Columbia, Canada

by Sara L. Ashpole, Christine A. Bishop and Stephen D. Murphy

Diversity 2018, 10(4), 108; https://doi.org/10.3390/d10040108 - 29 Sep 2018

Cited by 4 | Viewed by 4451

Abstract

The arid south Okanagan River Valley, British Columbia is a highly-modified landscape; where wetland and riparian habitat loss exceeds 85%, and 88% of remaining wetlands experience at least one harmful anthropogenic stressor. This multi-stressor landscape for amphibian species at risk led to a [...] Read more.

The arid south Okanagan River Valley, British Columbia is a highly-modified landscape; where wetland and riparian habitat loss exceeds 85%, and 88% of remaining wetlands experience at least one harmful anthropogenic stressor. This multi-stressor landscape for amphibian species at risk led to a collaborative stakeholder approach for habitat restoration and species recovery. The main project goal was to increase the quantity and quality of lowland wetland habitat by reconnecting known amphibian-breeding sites with constructed and/or enhanced small ponds. Long-term amphibian monitoring data were used to determine strategic locations for wetland construction and/or enhancement. Habitat enhancement outcomes (N_total = 21 sites) since 2006 include 10 newly constructed ponds, enhancement of eight re-contoured ponds after historic infilling, and invasive predatory species removal at three sites. Project ponds were monitored annually (2007 to 2014) for calling frogs, the presence of eggs, and metamorphic emergence. Early signs of colonization and metamorphic success for Great Basin Spadefoot (Spea intermontana) (N = 13 sites) and Pacific treefrog (Pseudacris regilla) (N = 7 sites) populations have been observed, however no records of Blotched tiger salamanders (Ambystoma mavortium) colonization has been detected. Wetland habitat construction and enhancement have doubled the number of available fishless ponds to support breeding within the study area and engaged landowners through voluntary stewardship. Whether constructed or enhanced ponds have aided species recovery is unclear, though the colonization and successful metamorphosis of some species provides early supporting evidence that it will. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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9 pages, 448 KiB

Open AccessArticle

Lack of Behavioral and Chemical Interference Competition for Refuges among Native Treefrogs and Invasive Cuban Treefrogs (Osteopilus septentrionalis)

by Kristine E. Hoffmann, Monica E. McGarrity and Steve A. Johnson

Diversity 2018, 10(3), 78; https://doi.org/10.3390/d10030078 - 01 Aug 2018

Cited by 2 | Viewed by 2968

Abstract

The introduction of a novel competitor can dramatically alter community dynamics, and competition-mediated impacts often result from biological invasions. Interference competition can be especially problematic as a source of methodological bias for studies seeking to evaluate population and community-level impacts of invasive species. [...] Read more.

The introduction of a novel competitor can dramatically alter community dynamics, and competition-mediated impacts often result from biological invasions. Interference competition can be especially problematic as a source of methodological bias for studies seeking to evaluate population and community-level impacts of invasive species. We used polyvinyl chloride (PVC) refugia to conduct laboratory trials to determine whether behavioral or chemical cues of invasive Cuban treefrogs (Osteopilusseptentrionalis) interfere with artificial refuge use by conspecifics or treefrogs native to Florida (USA). We found no evidence of behavioral or chemical competition for refuges by Cuban treefrogs or native treefrogs. The inability of native treefrogs to avoid chemical cues from Cuban treefrogs, despite living sympatrically with the invasive treefrogs for 10–20 years, has important implications for predation risk. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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16 pages, 1704 KiB

Open AccessArticle

Cross-Life Stage Effects of Aquatic Larval Density and Terrestrial Moisture on Growth and Corticosterone in the Spotted Salamander

by Julie F. Charbonnier, Jacquelyn Pearlmutter, James R. Vonesh, Caitlin R. Gabor, Zachery R. Forsburg and Kristine L. Grayson

Diversity 2018, 10(3), 68; https://doi.org/10.3390/d10030068 - 19 Jul 2018

Cited by 14 | Viewed by 4392

Abstract

For organisms with complex life cycles, conditions experienced during early life stages may constrain later growth and survival. Conversely, compensatory mechanisms may attenuate negative effects from early life stages. We used the spotted salamander, Ambystoma maculatum, to test how aquatic larval density [...] Read more.

For organisms with complex life cycles, conditions experienced during early life stages may constrain later growth and survival. Conversely, compensatory mechanisms may attenuate negative effects from early life stages. We used the spotted salamander, Ambystoma maculatum, to test how aquatic larval density and terrestrial moisture influence juvenile growth, food intake, evaporative water loss and water reuptake rates, and corticosterone levels. We conducted an outdoor mesocosm experiment to manipulate larval density and transferred metamorphosed salamanders into low and high terrestrial moisture treatments in laboratory terrariums. After the larval stage, high-density salamanders were significantly smaller and had higher corticosterone release rates than those from low-density treatments. Salamanders in the low terrestrial moisture treatment consumed fewer roaches, had lower mass-specific growth rates, higher water reuptake, and higher corticosterone release rates than salamanders in high terrestrial moisture treatments. Across moisture treatments, smaller salamanders had higher mass-specific growth rates than larger salamanders. Our results suggest that salamanders can partially compensate for competition in the larval aquatic habitat with increased growth as juveniles, but this response is dependent on terrestrial habitat quality. Thus, the persistence of early life stage effects can be an important, yet context-dependent, component of amphibian life cycles. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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12 pages, 3414 KiB

Open AccessArticle

Assessing the Use of Artificial Hibernacula by the Great Crested Newt (Triturus cristatus) and Smooth Newt (Lissotriton vulgaris) in Cold Climate in Southeast Norway

by Børre K. Dervo, Jon Museth and Jostein Skurdal

Diversity 2018, 10(3), 56; https://doi.org/10.3390/d10030056 - 05 Jul 2018

Cited by 5 | Viewed by 6203

Abstract

Construction of artificial overwintering habitats, hibernacula, or newt hotels, is an important mitigation measure for newt populations in urban and agricultural areas. We have monitored the use of four artificial hotels built in September 2011 close to a 6000 m² breeding pond [...] Read more.

Construction of artificial overwintering habitats, hibernacula, or newt hotels, is an important mitigation measure for newt populations in urban and agricultural areas. We have monitored the use of four artificial hotels built in September 2011 close to a 6000 m² breeding pond in Norway. The four hotels ranged from 1.6 to 12.4 m³ and were located from 5 to 40 m from the breeding pond. In 2013–2015, 57 Great Crested Newts (Triturus cristatus) and 413 Smooth Newts (Lissotriton vulgaris) spent the winter in the hotels. The proportions of juveniles were 75% and 62%, respectively, and the hotels may be important to secure recruitment. Knowledge on emigration routes and habitat quality for summer use and winter hibernation is important to find good locations for newt hotels. The study documented that newts may survive a minimum temperature of −6.7 °C. We recommend that newt hotels in areas with harsh climate are dug into the ground in slopes to reduce low-temperature exposure during winter. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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15 pages, 1362 KiB

Open AccessArticle

Training for Translocation: Predator Conditioning Induces Behavioral Plasticity and Physiological Changes in Captive Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis) (Cryptobranchidae, Amphibia)

by Erin K. Kenison and Rod N. Williams

Diversity 2018, 10(1), 13; https://doi.org/10.3390/d10010013 - 09 Mar 2018

Cited by 9 | Viewed by 4602

Abstract

Translocations are stressful, especially when captive animals are naïve to natural stimuli. Captive eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) identify predatory fish as threats, but may be more vulnerable to predation and stress because of inexperience with them. We investigated the use [...] Read more.

Translocations are stressful, especially when captive animals are naïve to natural stimuli. Captive eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) identify predatory fish as threats, but may be more vulnerable to predation and stress because of inexperience with them. We investigated the use of predator conditioning to prepare hellbenders, behaviorally and physiologically, for the presence of a common predator, largemouth bass (Micropterus salmoides). We reared hellbenders for 30 d with and without continuous exposure to largemouth bass kairomones and heterospecific alarm cues and found conditioned hellbenders became less active compared to unconditioned individuals (p = 0.017). After conditioning, we exposed hellbenders to water, a low concentration of kairomones, or a high concentration of kairomones in a closed respirometer system. We measured activity within respirometer chambers and routine metabolic rate. We found unconditioned hellbenders exposed to low and high concentrations of kairomones were 41% and 119% more active than conditioned animals (p = 0.002 and p < 0.001). Moreover, conditioned individuals had on average 6.5% lower metabolic rates across all three kairomone concentrations compared to unconditioned individuals (p = 0.017). Our data suggest that predator conditioning induces behavioral avoidance tactics and physiological changes that could improve future translocation efforts for hellbenders and other imperiled species. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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12 pages, 490 KiB

Open AccessArticle

Evaluation of Conspecific Attraction as a Management Tool across Several Species of Anurans

by Valerie L. Buxton, Michael P. Ward and Jinelle H. Sperry

Diversity 2018, 10(1), 6; https://doi.org/10.3390/d10010006 - 22 Jan 2018

Cited by 6 | Viewed by 4021

Abstract

Amphibian populations are declining worldwide, with habitat loss and alteration being a primary driver of many declines. Management strategies to mitigate these declines include translocation and creation or restoration of breeding habitats, yet these techniques are not always effective. We examined whether conspecific [...] Read more.

Amphibian populations are declining worldwide, with habitat loss and alteration being a primary driver of many declines. Management strategies to mitigate these declines include translocation and creation or restoration of breeding habitats, yet these techniques are not always effective. We examined whether conspecific attraction—a management tool frequently used in avian conservation—would be similarly valuable in management and conservation of anuran amphibians (i.e., frogs and toads). We broadcast conspecific chorus sounds at unoccupied, artificial breeding ponds for six anuran species across three field sites. We documented when frogs arrived at each pool and when eggs were laid. We compared differences in number of pools found with adults and egg masses between playback and control pools and examined latency to first colonization. We found that Mexican spadefoots colonized playback ponds faster and more often than control ponds, while Cope’s gray treefrogs, Arizona treefrogs, green frogs, spring peepers, and wood frogs exhibited weak or non-existent responses. We discuss why breeding ecology may influence tendency to exhibit conspecific attraction and how this behavior could be used in amphibian management and conservation. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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Review

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14 pages, 250 KiB

Open AccessReview

Ecophysiology of Amphibians: Information for Best Mechanistic Models

by Rafael P. Bovo, Carlos A. Navas, Miguel Tejedo, Saulo E. S. Valença and Sidney F. Gouveia

Diversity 2018, 10(4), 118; https://doi.org/10.3390/d10040118 - 26 Oct 2018

Cited by 25 | Viewed by 5406

Abstract

Several amphibian lineages epitomize the faunal biodiversity crises, with numerous reports of population declines and extinctions worldwide. Predicting how such lineages will cope with environmental changes is an urgent challenge for biologists. A promising framework for this involves mechanistic modeling, which integrates organismal [...] Read more.

Several amphibian lineages epitomize the faunal biodiversity crises, with numerous reports of population declines and extinctions worldwide. Predicting how such lineages will cope with environmental changes is an urgent challenge for biologists. A promising framework for this involves mechanistic modeling, which integrates organismal ecophysiological features and ecological models as a means to establish causal and consequential relationships of species with their physical environment. Solid frameworks built for other tetrapods (e.g., lizards) have proved successful in this context, but its extension to amphibians requires care. First, the natural history of amphibians is distinct within tetrapods, for it includes a biphasic life cycle that undergoes major habitat transitions and changes in sensitivity to environmental factors. Second, the accumulated data on amphibian ecophysiology is not nearly as expressive, is heavily biased towards adult lifeforms of few non-tropical lineages, and overlook the importance of hydrothermal relationships. Thus, we argue that critical usage and improvement in the available data is essential for enhancing the power of mechanistic modeling from the physiological ecology of amphibians. We highlight the complexity of ecophysiological variables and the need for understanding the natural history of the group under study and indicate directions deemed crucial to attaining steady progress in this field. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

49 pages, 4846 KiB

Open AccessReview

Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies

by Andrew R. Blaustein, Jenny Urbina, Paul W. Snyder, Emily Reynolds, Trang Dang, Jason T. Hoverman, Barbara Han, Deanna H. Olson, Catherine Searle and Natalie M. Hambalek

Diversity 2018, 10(3), 81; https://doi.org/10.3390/d10030081 - 04 Aug 2018

Cited by 47 | Viewed by 12502

Abstract

Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are [...] Read more.

Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease. Full article

(This article belongs to the Special Issue Conservation and Ecology of Amphibians)

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