Size affects intraspecific aggression and response to predation threat in juvenile American lobsters

2021 ◽  
Vol 168 (4) ◽  
Author(s):  
Joshua P. Lord
Keyword(s):  
Intraspecific Aggression ◽  
Predation Threat

Mechanisms responsible for the niche shift of brook charr, Salvelinus fontinalis Mitchill, when living sympatrically with creek chub, Semotilus atromaculatus Mitchill

1984 ◽  
Vol 62 (8) ◽  
pp. 1548-1555 ◽  
Author(s):  
Pierre Magnan ◽  
Gérard J. FitzGerald
Keyword(s):  
Laboratory Experiments ◽  
Salvelinus Fontinalis ◽  
Niche Shift ◽  
Intraspecific Aggression ◽  
Brook Charr ◽  
Semotilus Atromaculatus ◽  
High Level ◽  
Gill Raker ◽  
Creek Chub ◽  
Study Laboratory

When brook charr, Salvelinus fontinalis Mitchill, are in allopatry in oligotrophic Québec lakes, they feed largely on macrobenthic invertebrates. However, when brook charr cooccur with creek chub, Semotilus atromaculatus Mitchill, they feed largely on zooplankton. In the present study, laboratory experiments showed that creek chub were more effective than brook charr in searching for hidden, patchily distributed prey. The searching efficiency of an individual chub feeding in a group was improved through social facilitation. In contrast, the high level of intraspecific aggression observed in brook charr prevents the formation of such feeding groups. In the laboratory, brook charr were able to displace creek chub from the food source because of interspecific aggression. Data are presented showing that chub are morphologically better adapted than charr to feed on benthos (subterminal orientation of the mouth and protrusible premaxillae), while the charr are better adapted than chub to feed on zooplankton (gill raker structure). Differences in feeding behaviour, morphology, and relative abundance between these species appear to be important in the observed niche shift of brook charr in nature.

Gregariousness and intraspecific aggression in Iberian bullfinches (Pyrrhula pyrrhula iberiae) throughout the year

Behaviour ◽  
2021 ◽  
pp. 1-28
Author(s):  
Ángel Hernández
Keyword(s):  
Breeding Season ◽  
Foraging Strategy ◽  
Intraspecific Aggression ◽  
Northwestern Spain ◽  
Pyrrhula Pyrrhula

Abstract This study provides novel information about gregariousness and intraspecific aggression in Iberian bullfinches (Pyrrhula pyrrhula iberiae) in northwestern Spain. Small monospecific parties never exceeding 10 individuals were seen throughout the year, larger in winter on average. Males considerably outnumbered females within the groups. Adult flocks were frequent only in winter. In spring, many of the adult groups were mixed-sex assemblages composed of pairs plus supernumerary males. Sightings of juvenile groups, up to seven individuals, were common in summer–autumn. The vigilance role in mixed-sex assemblages, including pairs, appeared to be the responsibility of males based on sex-specific vigilance rates. The highest frequency of aggressive encounters, mainly male against male, occurred during the breeding season, associated with mate defence. Females attacked males, not the contrary, which supports reversed sexual dominance in bullfinches. Gregariousness probably acted as an anti-predatory and foraging strategy.

Aggressive Behaviour of Black Skimmers (Rynchops Niger)

Behaviour ◽  
1981 ◽  
Vol 76 (3-4) ◽  
pp. 207-222 ◽  
Author(s):  
Joanna Burger
Keyword(s):  
New York ◽  
Reproductive Cycle ◽  
Aggressive Behaviour ◽  
Sandy Beach ◽  
Time Of Day ◽  
Intraspecific Aggression ◽  
Mixed Species ◽  
The Real ◽  
Common Terns ◽  
Rynchops Niger

AbstractThe aggressive behaviour of skimmers was studied in a mixed species colony of black skimmers and common terns located on a sandy beach in New York. The levels and intensity of intraspecific aggression varied according to sex, season, and time of day. Males engaged in more intraspecific aggression, whereas females engaged in more interspecific defense. These differences suggest that interspecific defense is an appropriate response to the real threat of chick loss due to other birds (of both species). In general, females were defending space and their chicks, whereas males seemed to defend space, their chicks, and females. The aggression observed at any point in the reproductive cycle correlates with the magnitude of the threat.

scholarly journals Size-selective mortality fosters ontogenetic changes in collective risk-taking behaviour in zebrafish, Danio rerio

2021 ◽  
Author(s):  
Tamal Roy ◽  
Robert Arlinghaus
Keyword(s):  
Danio Rerio ◽  
Risk Taking ◽  
Direct Selection ◽  
Small Fish ◽  
Control Line ◽  
Selective Mortality ◽  
Predation Threat ◽  
Size Selection ◽  
Risk Of Predation ◽  
The Impact

AbstractSize-selective mortality is common in fish populations and can operate either in a positive size-selective fashion or be negatively size-selective. Through various mechanisms (like genetic correlations among behaviour and life-history traits or direct selection on behaviour co-varying with growth rate or size-at-maturation), both positive- and negative size-selection can result in evolutionary changes in behavioural traits. Theory suggests that size-selection alone favours boldness, but little experimental evidence exists about whether and to what extent size-selection can trigger its evolution. Here we investigated the impact of size-selective mortality on boldness across ontogeny using three experimental lines of zebrafish (Danio rerio) generated through positive (large-harvested), negative (small-harvested) and random (control line) size-selective mortality for five generations. We measured risk-taking during feeding (boldness) under simulated aerial predation threat and in presence of a live cichlid. We found that boldness decreased with ontogenetic age under aerial predation threat, and the small-harvested line was consistently bolder than controls. Collective personality emerged post larval stages among the selection lines. In presence of a cichlid, the large-harvested line was bolder at the highest risk of predation. The large-harvested line showed higher variability and plasticity in boldness across life stages and predation risks. Collectively, our results demonstrate that size-selective harvesting may evolutionarily alter risk-taking tendency. Size-selection alone favours boldness when selection acts on small fish. Selection typical of fisheries operating on large fish favours boldness at the highest risk of predation and increases behavioural variability and plasticity. There was no evidence for positive size-selection favouring evolution of shyness.

scholarly journals Acoustic and visual adaptations to predation risk: A predator affects communication in vocal female fish

2021 ◽  
Author(s):  
Isabelle Pia Maiditsch ◽  
Friedrich Ladich
Keyword(s):  
Sound Pressure ◽  
Dominant Frequency ◽  
Pressure Level ◽  
Female Fish ◽  
Predation Threat ◽  
Calling Behaviour ◽  
Sound Levels ◽  
Astronotus Ocellatus ◽  
Visual Signalling ◽  
Ecological Constraint

Abstract Predation is an important ecological constraint that influences communication in animals. Fish respond to predators by adjusting their visual signalling behaviour, but the responses in calling behaviour in the presence of a visually detected predator are largely unknown. We hypothesize that fish will reduce visual and acoustic signalling including sound levels and avoid escalating fights in the presence of a predator. To test this we investigated dyadic contests in female croaking gouramis (Trichopsis vittata, Osphronemidae) in the presence and absence of a predator (Astronotus ocellatus, Cichlidae) in an adjoining tank. Agonistic behaviour in T. vittata consists of lateral (visual) displays, antiparallel circling and production of croaking sounds and may escalate to frontal displays. We analysed the number and duration of lateral display bouts, the number, duration, sound pressure level and dominant frequency of croaking sounds as well as contest outcomes. The number and duration of lateral displays decreased significantly in predator as compared to no-predator trials. Total number of sounds per contest dropped in parallel but no significant changes were observed in sound characteristics. In the presence of a predator dyadic contests were decided or terminated during lateral displays and never escalated to frontal displays. The gouramis showed approaching behaviour towards the predator between lateral displays. This is the first study supporting the hypothesis that predators reduce visual and acoustic signalling in a vocal fish. Sound properties, in contrast, did not change. Decreased signalling and the lack of escalating contests reduce the fish’s conspicuousness and thus predation threat.

scholarly journals Background choice as an anti-predator strategy: the roles of background matching and visual complexity in the habitat choice of the least killifish

2012 ◽  
Vol 279 (1745) ◽  
pp. 4192-4198 ◽  
Author(s):  
Karin Kjernsmo ◽  
Sami Merilaita
Keyword(s):  
Alternative Hypothesis ◽  
Visual Complexity ◽  
Empirical Support ◽  
Fish Predation ◽  
Habitat Choice ◽  
Black Stripe ◽  
Predation Threat ◽  
Visual Appearance ◽  
Background Matching ◽  
Least Killifish

Because background matching improves concealment, prey animals have traditionally been expected to prefer parts of the habitat that match their visual appearance. However, empirical support for this is scarce. Moreover, this idea has recently been challenged by an alternative hypothesis: visual complexity of the background impedes prey detection, and hence prey could instead prefer complex parts of the habitat. We used the least killifish to test, with and without predation threat, for the importance of the visual similarity between the fish and the background, and the level of visual complexity of the background. We observed their choice between backgrounds patterned with elements based on the longitudinal black stripe of the fish. Predation risk was important under some circumstances, and induced a preference for a background of matching horizontal stripes compared with mismatching vertical stripes. Interestingly, females under predation threat showed a preference for a complex background of randomly oriented and overlapping stripes compared with matching stripes, whereas males did not discriminate between these two. Additionally, males showed a preference for matching stripes compared with complex shapes, whereas females did not discriminate between these backgrounds. We conclude that matching is important in the choice for safe habitat, but some aspects of visual complexity may override or act together with background matching.

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