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opencc-zeroMay 2024View details →

Data from: Boom and bust: The effects of masting on seed predator range dynamics and trophic cascades

Aim: Spatiotemporal variation in resource availability is a strong driver of animal distributions. In northern hardwood and boreal forests of the northeastern United States, tree mast events provide resource pulses that drive the population dynamics of small mammals, including the American red squirrel (Tamiasciurus hudsonicus), a primary songbird nest predator. This study sought to determine whether mast availability ameliorates their abiotic limits, enabling red squirrel elevational distributions to temporarily expand and negatively impact high elevation songbirds. Location: Northeastern United States Methods: We used two independent datasets to evaluate our hypotheses. First, we fit a dynamic occupancy model using data from camera trap surveys to evaluate red squirrel distributional responses to pulses in tree mast. We also assessed population responses using systematic auditory surveys analyzed with an open-population binomial mixture model. Further, we used modeled red squirrel abundance in nest-survival models to evaluate whether their abundance is correlated with daily nest survival of three songbird species. Results: Tree mast provided a critical resource pulse that resulted in a two-fold increase in the annual elevational distribution of red squirrels. The elevational distribution of red squirrels ranged from a minimum of ~450 m (range: 663 – 1145 m asl) following two consecutive years without a masting event to a maximum of over 1000 m (range: 443 – 1545 m asl) after a large mast event. Daily nest survival of three songbird species tended to decline with an increase in the abundance of red squirrels. Main Conclusions: Tree mast is a central biological phenomenon in many temperate and boreal forests. This study reveals how this resource pulse results in range changes in a small mammal that is both a seed and bird predator, as well as prey for many carnivores. Thus, understanding this phenomenon can inform the conservation and management of northern forests, including breeding songbirds.

opencc-zeroDec 2012View details →

Data from: Evolution mediates the effects of apex predation on aquatic food webs

Ecological and evolutionary mechanisms are increasingly thought to shape local community dynamics. Here, I evaluate if the local adaptation of a meso-predator to an apex predator alters local food webs. The marbled salamander (Ambystoma opacum) is an apex predator that consumes both the spotted salamander (Ambystoma maculatum) and shared zooplankton prey. Common garden experiments reveal that spotted salamander populations which co-occur with marbled salamanders forage more intensely than those that face other predator species. These foraging differences, in turn, alter the diversity, abundance and composition of zooplankton communities in common garden experiments and natural ponds. Locally adapted spotted salamanders exacerbate prey biomass declines associated with apex predation, but dampen the top-down effects of apex predation on prey diversity. Countergradient selection on foraging explains why locally adapted spotted salamanders exacerbate prey biomass declines. The two salamander species prefer different prey species, which explains why adapted spotted salamanders buffer changes in prey composition owing to apex predation. Results suggest that local adaptation can strongly mediate effects from apex predation on local food webs. Community ecologists might often need to consider the evolutionary history of populations to understand local diversity patterns, food web dynamics, resource gradients and their responses to disturbance.

opencc-zeroDec 2015View details →

Data from: Collateral damage or a shadow of safety? The effects of signaling heterospecific neighbors on the risks of parasitism and predation

Although males often display from mixed-species aggregations, the influence of nearby heterospecifics on risks associated with sexual signaling has not been previously examined. We tested whether predation and parasitism risks depend on proximity to heterospecific signalers. Using field playback experiments with calls of two species that often display from the same ponds, túngara frogs and hourglass treefrogs, we tested two hypotheses: (1) Calling near heterospecific signalers attractive to eavesdroppers results in increased attention from predatory bats and parasitic midges (Collateral Damage hypothesis); or (2) Calling near heterospecific signalers reduces an individual's predation and parasitism risks, as eavesdroppers are drawn to the heterospecifics (Shadow of Safety hypothesis). Bat visitation was not affected by calling neighbors. The number of frog-biting midges attracted to hourglass treefrog calls, however, rose threefold when played near túngara calls, supporting the collateral damage hypothesis. We thus show that proximity to heterospecific signalers can drastically alter both the absolute risks of signaling and the relative strengths of pressures from predation and parasitism. Through these mechanisms, interactions between heterospecific guild members are likely to influence the evolution of signaling strategies and the distribution of species at both local and larger scales.

opencc-zeroDec 2016View details →

Data from: Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics

Global forage-fish landings are increasing, with potentially grave consequences for marine ecosystems. Predators of forage fish may be influenced by this harvest, but the nature of these effects is contentious. Experimental fishery manipulations offer the best solution to quantify population-level impacts, but are rare. We used Bayesian inference to examine changes in chick survival, body condition and population growth rate of endangered African penguins Spheniscus demersus in response to eight years of alternating time-area closures around two pairs of colonies. Our results demonstrate that fishing closures improved chick survival and condition, after controlling for changing prey availability. However, this effect was inconsistent across sites and years, highlighting the difficultly of assessing management interventions in marine ecosystems. Nevertheless, modelled increases in population growth rates exceeded 1% at one colony; i.e. the threshold considered biologically meaningful by fisheries management in South Africa. Fishing closures evidently can improve the population trend of a forage-fish dependent predator – we therefore recommend they continue in South Africa and support their application elsewhere. However, detecting demographic gains for mobile marine predators from small no-take zones requires experimental time-frames and scales that will often exceed those desired by decision-makers.

opencc-zeroJun 2021View details →

Complex multi-predator effects on demographic habitat selection and community assembly in colonizing insects

Running the gauntlet of predators consumes critical time and energy resources, as all species are vulnerable to one or, typically, more predators at some life stage. Prey employ a vast array of mechanisms to avoid predation, and predators, likewise, come in a bewildering variety. Thus, defensive adaptations are rarely one size fits all. Considerable work has addressed multi-predator consumptive effects, but we now know that non-consumptive effects of predators can dramatically impact individuals, (meta)populations, and (meta)communities. However, little is known regarding the community-wide dynamics of non-consumptive effects generated by multiple predators. Predator avoidance by choosing a patch that is free of a particular predator or predators can be the most effective strategy if conditions at colonization are a reliable predictor of absence, which is often true for fish in freshwater systems. We experimentally manipulated composition of the predator assemblage in aquatic mesocosms in a substitutive design, with zero, one, two, or three caged predatory fish species (one benthic, one pelagic, and one surface fish) at constant density and biomass, and assayed responses of naturally colonizing aquatic insects. We addressed three related questions; first, how do members of a diverse assemblage of colonizing aquatic insects respond to this variation in species and species combinations, second, do individual species (and higher taxa), respond differently to single vs multiple predator species (species richness), and third how do any responses to fish species and species combinations, and effects on species richness, translate into community-wide changes in the composition of colonists. Prey had varied responses to specific predators or combinations of predators, resulting in distinct community composition across treatments and higher β-diversity with predators. Prey showed emergent multi-predator effects, where certain species only responded to predator species combinations, but not to any individual predator, and stronger effects of multiple predator vs single predator treatments, despite strong responses to individual predators in many taxa. Habitat selection effects can range from the individual to the metacommunity, and the dynamics of habitat selection in response to predators is a complex function of predator identity, density, richness, species composition, and patch spatial context.

opennotspecifiedFeb 2016View details →

Figure 3 in Nest-site microhabitat association of red-billed leiothrix in subtropical fragmented forest in central China: evidence for a reverse edge effect on nest predation risk?

Figure 3. Nonmetric multidimensional scaling (NMS) ordination of 237 sample units of microhabitat characteristics in the forest, and the joint plot of NMS scores with important microhabitat variables (r2> 0.2). The first and third axes represent 30% and 46% of the total variation, respectively.

opennotspecifiedFeb 2016View details →

Figure 4 in Nest-site microhabitat association of red-billed leiothrix in subtropical fragmented forest in central China: evidence for a reverse edge effect on nest predation risk?

Figure 4. Nonmetric multidimensional scaling (NMS) ordination of 134 sample units of microhabitat characteristics in the scrub-grassland, and the joint plot of NMS scores with important microhabitat variables (r2> 0.2). The first and second axes represent 78% and 15% of the total variation, respectively.

opennotspecifiedFeb 2016View details →

Figure 1 in Nest-site microhabitat association of red-billed leiothrix in subtropical fragmented forest in central China: evidence for a reverse edge effect on nest predation risk?

Figure 1. Study areas and vegetation types for nest-site selection of the red-billed leiothrix in Daweishan Nature Reserve (DSNR; 28°20′54″–28°28′47″N, 114°01′51″–114°12′52″E), Hunan Province, China.

opencc-zeroSep 2021View details →

The effects of novel leaf litter deposition on competitive, predator–prey and host–parasite interactions of American toad larvae

Wetland plant communities are changing rapidly due to a wide range of human activities. The deposition of leaf litter from novel plant communities can alter both the chemical and physical habitat of aquatic ecosystems. Lesser understood are the ecological consequences of novel leaf litter inputs in aquatic communities. Towards this goal, we used two plant invasion scenarios (comparing native black huckleberry to exotic autumn olive and native swamp loosestrife to exotic purple loosestrife) to simulate a shift in wetland plant communities. In this study, we investigated the effects of novel leaf litter leachates on three aquatic ecological interactions: intraspecific competition, predation, and parasitism. We examined how leaf litter leachates influence the interactions of American toad larvae (Anaxyrus americanus) with their conspecifics, a dragonfly predator (Anax spp.) and a trematode parasite (Echinostomatidae). We found that leaf litter type influenced competitive interactions only for the huckleberry versus autumn olive comparison. We did not detect any effects of leaf litter type on predator-prey interactions. Finally, litter type strongly influenced host-parasite interactions for both leaf litter comparisons, altering host susceptibility, parasite survival and net infection rates. These results highlight the breadth of potential ecological repercussions of shifting wetland plant communities for native ecosystems.

opencc-zeroJan 2023View details →

Predation cues amplify the effects of parasites on the personality of a keystone grazer

1. Parasites can alter species interactions either by modifying infected host behavior or by influencing behavioral responses in uninfected individuals. Salt marsh ecosystems are characterized by a predator-prey interaction between the keystone grazer, Littoraria irrorata, and its main predator, Callinectes sapidus, both integral players in mediating the productivity of these habitats. 2. Littoraria also acts as the first intermediate host for at least four species of digenetic trematode. Parasite infection has been shown to decrease grazing and climbing in populations of Littoraria, though effects on infected host response to predators has not been investigated. Moreover, how infection might increase or decrease among-individual variation in behavior (i.e., animal personality) is still unknown. Here we ask how trematode infection affects the expression of boldness in the antipredator responses of L. irrorata in both the absence and presence of a predator cue. 3. We find that individual boldness varies substantially, and repeatability tends to increase as the number of stressors increases, with infected individuals exposed to a predator cue showing the strongest expression of behavioral types. 4. Parasitism amplifies this effect, though the parasite itself does not appear to directly induce behavioral changes: infected snails show no evidence of decreased climbing or differences in refuge use as compared to their uninfected counterparts. Infection might therefore drive the expression of condition-dependent personality differences evident only under high-risk conditions. 5. Group infection status strongly influenced behavioral reaction norms: uninfected individuals grouped with an infected snail were more responsive to predation risk, exhibiting increased climbing behavior and spending less time in the water. Here parasites are influencing personality indirectly by inducing avoidance behaviors in healthy individuals, though only in high-risk environments. 6. The potential for exposure to parasites and predators fluctuates greatly across marsh ecosystems. Given the ecological importance of this predator-prey relationship, trematode infection can act as an important, though indirect, determinant of overall salt marsh community structure, health, and function.

opencc-zeroApr 2023View details →

Data for: Effects of domestication and captive breeding on reaction to moving objects: Implications for avoidance behaviors of obstacles and predators by masu salmon Oncorhynchus masou

Domestication and captive breeding can compromise obstacle- and predator-avoidance of animals in the wild. Whereas previous studies only examined these effects in combination, here we examine them individually by comparing the abilities of wild, F1 (offspring of wild parents), and captive-bred (approx. F15) masu salmon (Oncorhynchus masou) to avoid a falling object under experimental conditions. Rates of avoidance failure were low (wild, 12.5%; F1, 10.7%; captive-bred, 8%) under light conditions but increased under dark conditions (wild, 11.1%; F1, 32.1%; captive-bred, 60.0%). We attribute the elevated avoidance-failure rate among F1 fish to the lack of learning opportunities in hatchery environments, and the further elevation of avoidance-failure rate among captive-bred fish to the degradation of sensory organ function. These results imply reduced survival rates for F1 and captive-bred fish in the wild and are consistent with the low stocking efficiencies reported for captive-bred masu salmon.

FIG. 7 in Differential Survival and the Effects of Predation on a Color Polymorphic Species, the Red-Backed Salamander (Plethodon cinereus)

FIG. 7. Kaplan-Meier survival plots of (a) avian attacks and (b) mammalian attacks on striped and unstriped clay models (n = 40 each) that were checked weekly over 3 wk. (a) Unstriped models of P. cinereus were significantly more likely to not be attacked by birds (solid line, n = 38) than striped models (dashed line, n = 31) (Z = 5.04, P = 0.0248). (b) There was no difference in models' ''survival'' from mammalian attacks based on color (striped: n = 31; unstriped: n = 30; Z = 0.07, P = 0.787).

FIG. 6 in Differential Survival and the Effects of Predation on a Color Polymorphic Species, the Red-Backed Salamander (Plethodon cinereus)

FIG. 6. The cumulative model weights for encounter probability (p) in Spring 2013, 2014, 2015 showed equivocal support for both age and color morph (a X c) affecting encounter probability in the spring seasons; the null model (.) had similar weights. In Fall 2013 and 2014, the model including both age and color morph (a X c) was more heavily weighted than the other models in each year.

FIG. 4 in Differential Survival and the Effects of Predation on a Color Polymorphic Species, the Red-Backed Salamander (Plethodon cinereus)

FIG. 4. Color morph frequencies varied based on age but not adult sex. Juveniles of P. cinereus (SVL <28 mm) had a significantly higher frequency (mean ± SE) of striped individuals than adults (SVL> 35 mm; X2 = 3.177, P = 0.049, n = 356). Adult males and females of Plethodon cinereus (SVL> 1 35 mm) did not differ in frequencies of striped and unstriped color morphs (X2 = 0.90, P = 0.210, n = 286).

FIG. 3 in Differential Survival and the Effects of Predation on a Color Polymorphic Species, the Red-Backed Salamander (Plethodon cinereus)

FIG. 3. Examples of clay model replicates of adult striped (top) and unstriped (bottom) Plethodon cinereus.

FIG. 2 in Differential Survival and the Effects of Predation on a Color Polymorphic Species, the Red-Backed Salamander (Plethodon cinereus)

FIG. 2. Map of the location of the study site (Nanticoke River Wildlife Management Area, Wicomico County, Maryland, USA) in Eastern North America.

FIG. 1 in Differential Survival and the Effects of Predation on a Color Polymorphic Species, the Red-Backed Salamander (Plethodon cinereus)

FIG. 1. Examples of striped (left) and unstriped (right) Plethodon cinereus. The striped individual pictured here has a previously autotomized tail, which, while originally striped (see Moore and Ouellet, 2014; Fig. 1), grew back without a red stripe (Petranka, 1998).

FIG. 5 in Differential Survival and the Effects of Predation on a Color Polymorphic Species, the Red-Backed Salamander (Plethodon cinereus)

FIG. 5. The cumulative model weights for survival (ψ) in Spring 2013, 2014, 2015 showed that both age and color morph (a X c) affected survival probability in the spring seasons. In Fall 2013 and 2014, the null model (.) was more heavily weighted than models including age or color.

publicFeb 2021View details →

The effects of predation-risk on prey stoichiometry: A meta-analysis

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