scholarly journals Rain reverses diel activity rhythms in an estuarine teleost

2013 ◽  
Vol 280 (1750) ◽  
pp. 20122363 ◽  
Author(s):  
Nicholas L. Payne ◽  
Dylan E. van der Meulen ◽  
Ruan Gannon ◽  
Jayson M. Semmens ◽  
Iain M. Suthers ◽  
...  
Keyword(s):  
Predation Risk ◽  
Environmental Variability ◽  
Activity Rhythm ◽  
Adaptive Significance ◽  
Diel Activity ◽  
Foraging Efficiency ◽  
Aquatic Animal ◽  
Diurnal Activity ◽  
Activity Rhythms ◽  
Trade Offs

Activity rhythms are ubiquitous in nature, and generally synchronized with the day–night cycle. Several taxa have been shown to switch between nocturnal and diurnal activity in response to environmental variability, and these relatively uncommon switches provide a basis for greater understanding of the mechanisms and adaptive significance of circadian (approx. 24 h) rhythms. Plasticity of activity rhythms has been identified in association with a variety of factors, from changes in predation pressure to an altered nutritional or social status. Here, we report a switch in activity rhythm that is associated with rainfall. Outside periods of rain, the estuarine-associated teleost Acanthopagrus australis was most active and in shallower depths during the day, but this activity and depth pattern was reversed in the days following rain, with diurnality restored as estuarine conductivity and turbidity levels returned to pre-rain levels. Although representing the first example of a rain-induced reversal of activity rhythm in an aquatic animal of which we are aware, our results are consistent with established models on the trade-offs between predation risk and foraging efficiency.

scholarly journals Diel patterns of foraging and microhabitat use by sympatric rainbow trout and bull trout: implications for adaptive differentiation and instream flow assessment

2021 ◽  
Author(s):  
Sean M. Naman ◽  
Jordan S Rosenfeld ◽  
Alecia S. Lannan
Keyword(s):  
Rainbow Trout ◽  
Habitat Use ◽  
Predation Risk ◽  
Habitat Suitability ◽  
Diel Activity ◽  
Foraging Efficiency ◽  
Bull Trout ◽  
Flow Management ◽  
Habitat Suitability Models ◽  
Trade Offs

Salmonids make flexible and adaptive trade-offs between foraging efficiency and predation risk that result in variable patterns of diel activity and habitat use. However, it remains unclear: (1) how patterns differ among salmonid species; and (2) how this affects the interpretation of habitat suitability models that inform instream flow management. We combined snorkel observations with experimental additions of cover to investigate how predation risk, cover, and bioenergetics affect diel activity and habitat use patterns by sympatric rainbow trout and bull trout in the Skagit River, BC, Canada. Both species foraged primarily at dusk, supporting the well-described trade-off between foraging efficiency and predation risk. However, only rainbow trout responded to cover additions, suggesting that risk tolerance and the nature of foraging-predation risk trade-offs differ between species. Diel shifts in activity and habitat use also substantially altered predictions of habitat suitability models, with potentially large consequences for flow management.

scholarly journals Winter activity patterns of American martens (Martes americana): rejection of the hypothesis of thermal-cost minimization

1997 ◽  
Vol 75 (5) ◽  
pp. 812-816 ◽  
Author(s):  
Gary S. Drew ◽  
John A. Bissonette
Keyword(s):  
Predation Risk ◽  
Cost Minimization ◽  
Activity Patterns ◽  
Martes Americana ◽  
Diel Activity ◽  
Foraging Efficiency ◽  
Behavioral Strategies ◽  
Vulnerability Hypothesis ◽  
Log Linear ◽  
American Martens

Despite their temperate to subarctic geographic range, American martens (Martes americana) possess a thermally inefficient morphology. The lack of morphological adaptations for reducing thermal costs suggests that marten may use behavioral strategies to optimize thermal budgets. During the winters of 1989–1990 and 1990–1991, we radio-collared and monitored the diel activity of 7 martens. A log-linear model suggested that the presence or absence of light was the only factor associated with marten activity patterns (p < 0.001). A regression of the percentage of active fixes on ambient temperature failed to detect an association (b = −4.45, p = 0.084, n = 12). Contents of marten scats suggested that their activity was consistent with the prey-vulnerability hypothesis. While martens must balance multiple life requisites, their activity patterns suggest that they accept increased thermal costs in order to increase foraging efficiency. However, the nocturnal activity of martens during winter was also consistent with the hypothesis that they may be able to limit their own exposure to predation risk. The nocturnal habits of Newfoundland martens in the winter were consistent with the hypothesis of avoidance of predation risk.

scholarly journals Nocturnal and diurnal activity of armored suckermouth catfish (Loricariidae: Pterygoplichthys) associated with wintering Florida manatees (Trichechus manatus latirostris)

2010 ◽  
Vol 8 (4) ◽  
pp. 893-898 ◽  
Author(s):  
Leo G. Nico
Keyword(s):  
River Basin ◽  
Activity Pattern ◽  
Diel Activity ◽  
Diurnal Activity ◽  
Trichechus Manatus ◽  
Trichechus Manatus Latirostris ◽  
Size Classes ◽  
Diel Activity Pattern ◽  
Spring System ◽  
Diel Period

Several Pterygoplichthys species, members of the Neotropical catfish family Loricariidae, have been widely introduced outside their native ranges. In this paper, I present observations on the diel activity pattern of non-native Pterygoplichthys, tentatively identified as P. disjunctivus, with respect to their attachment and grazing on endangered Florida manatees, Trichechus manatus latirostris. The study was conducted in December 2009 at Volusia Blue Spring, an artesianal spring system in the St. Johns River basin, Florida (USA). Supplemented by information gathered during previous visits to the spring site, this study revealed that adult Pterygoplichthys are active throughout the diel period (day, twilight and night). However, juvenile Pterygoplichthys were largely nocturnal and only at night did they consistently join adults in attaching to manatees. The juveniles generally remain hidden during the day, probably responding to presence of diurnal predators, mainly birds. Differences in diel behaviors among different Pterygoplichthys size classes in Florida are consistent with published observations on loricariids inhabiting clearwater streams within their native ranges.

scholarly journals Breaking through evolutionary constraint by environmental fluctuations

2015 ◽  
Author(s):  
Marjon GJ de Vos ◽  
Alexandre Dawid ◽  
Vanda Sunderlikova ◽  
Sander J Tans
Keyword(s):  
Escherichia Coli ◽  
Environmental Variability ◽  
Model System ◽  
Evolutionary Constraint ◽  
Apparent Paradox ◽  
Epistatic Interactions ◽  
Genetic Constraints ◽  
Trade Offs ◽  
Fluctuating Environments ◽  
Genetic Constraint

Epistatic interactions can frustrate and shape evolutionary change. Indeed, phenotypes may fail to evolve because essential mutations can only be selected positively if fixed simultaneously. How environmental variability affects such constraints is poorly understood. Here we studied genetic constraints in fixed and fluctuating environments, using theEscherichia coli lacoperon as a model system for genotype-environment interactions. The data indicated an apparent paradox: in different fixed environments, mutational trajectories became trapped at sub-optima where no further improvements were possible, while repeated switching between these same environments allowed unconstrained adaptation by continuous improvements. Pervasive cross-environmental trade-offs transformed peaks into valleys upon environmental change, thus enabling escape from entrapment. This study shows that environmental variability can lift genetic constraint, and that trade-offs not only impede but can also facilitate adaptive evolution.

scholarly journals Living in mixed species groups promotes predator learning in degraded habitats

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Douglas P. Chivers ◽  
Mark I. McCormick ◽  
Eric P. Fakan ◽  
Randall P. Barry ◽  
Maud C. O. Ferrari
Keyword(s):  
Predation Risk ◽  
Abiotic Factors ◽  
Alarm Cues ◽  
Learning Mechanisms ◽  
Trade Offs ◽  
Chemical Alarm Cues ◽  
Pomacentrus Amboinensis ◽  
Predator Foraging ◽  
Predator Learning ◽  
Predator Odour

AbstractLiving in mix-species aggregations provides animals with substantive anti-predator, foraging and locomotory advantages while simultaneously exposing them to costs, including increased competition and pathogen exposure. Given each species possess unique morphology, competitive ability, parasite vulnerability and predator defences, we can surmise that each species in mixed groups will experience a unique set of trade-offs. In addition to this unique balance, each species must also contend with anthropogenic changes, a relatively new, and rapidly increasing phenomenon, that adds further complexity to any system. This complex balance of biotic and abiotic factors is on full display in the exceptionally diverse, yet anthropogenically degraded, Great Barrier Reef of Australia. One such example within this intricate ecosystem is the inability of some damselfish to utilize their own chemical alarm cues within degraded habitats, leaving them exposed to increased predation risk. These cues, which are released when the skin is damaged, warn nearby individuals of increased predation risk and act as a crucial associative learning tool. Normally, a single exposure of alarm cues paired with an unknown predator odour facilitates learning of that new odour as dangerous. Here, we show that Ambon damselfish, Pomacentrus amboinensis, a species with impaired alarm responses in degraded habitats, failed to learn a novel predator odour as risky when associated with chemical alarm cues. However, in the same degraded habitats, the same species learned to recognize a novel predator as risky when the predator odour was paired with alarm cues of the closely related, and co-occurring, whitetail damselfish, Pomacentrus chrysurus. The importance of this learning opportunity was underscored in a survival experiment which demonstrated that fish in degraded habitats trained with heterospecific alarm cues, had higher survival than those we tried to train with conspecific alarm cues. From these data, we conclude that redundancy in learning mechanisms among prey guild members may lead to increased stability in rapidly changing environments.

scholarly journals Combined effect of risk type and activity rhythm on anti-predator response of the shore crab Gaetice depressus (Crustacea: Grapsidae)

2006 ◽  
Vol 86 (6) ◽  
pp. 1401-1405 ◽  
Author(s):  
Ryo Sakamoto ◽  
Atsushi Ito ◽  
Satoshi Wada
Keyword(s):  
Predation Risk ◽  
Laboratory Experiments ◽  
Activity Rhythm ◽  
Combined Effect ◽  
Shore Crab ◽  
Octopus Vulgaris ◽  
Active Period ◽  
Inactive Period ◽  
Predator Response ◽  
Chemical Stimuli

The response of the shore crab Gaetice depressus to predation risk stimuli of either the octopus Octopus vulgaris or crushed conspecifics was examined at two different time phases in the activity rhythm (active and inactive period) by laboratory experiments. When octopus chemical stimuli were introduced to the experimental aquarium, the crab activity decreased in the active period (night) but not in the inactive period (daytime). When the chemical stimuli of crushed G. depressus were introduced, the activity of the crabs increased in the inactive period although the stimuli decreased the activity in the active period. This indicates that G. depressus adjust their anti-predator response according to a combination of the type of predation risk and also the activity rhythm.

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