Differences In Escape Responses Research Articles

Flight behavior of targeted fishes depends on variables other than fishing

Behavioral changes due to human predation can affect the functional role of targeted fishes and has implications for ecosystem and fisheries management. Wariness of targeted fishes towards divers, often measured as flight initiation distance (FID), has been shown to increase in areas where spear fishing pressure is higher. Additional research is required to understand how these patterns vary among different species and places. To support such studies, there is a need to explore the relationship of approach starting distance (SD) and other variables that influence measures of fish wariness. We used stereo video to record FID, a new direct measure of minimum approach distance (dMAD), and escape responses of targeted reef fishes in a marine reserve and heavily fished area in Hawai’i. We investigated the role of SD and 15 other variables in influencing FID and dMAD and tested differences between the reserve and fished area. SD explained a large portion of the variability in FID and somewhat less variability in dMAD. FID and dMAD were higher when fishes were travelling (vs feeding), increased with fish body length, and decreased with depth. When including these co-variates in models of FID and dMAD of targeted reef fishes, we found significant differences between study sites for dMAD, though not for FID. We also found differences in escape responses between sites. Based on these results, we recommend using stereo video to conduct measures of dMAD as a complement or alternative to FID, while simultaneously measuring SD and collecting additional data such as escape response. Relative effect sizes of SD and, to a lesser extent, other co-variates were large in comparison to site. Studies that use similar methods and do not control for or incorporate SD may produce biased results with regard to the effects of fishing pressure on flight behavior of targeted fishes.

Female cats, but not males, adjust responsiveness to arousal in the voice of kittens.

BackgroundThe infant cry is the most important communicative tool to elicit adaptive parental behaviour. Sex-specific adaptation, linked to parental investment, may have evolutionary shaped the responsiveness to changes in the voice of the infant cries. The emotional content of infant cries may trigger distinctive responsiveness either based on their general arousing properties, being part of a general affect encoding rule, or based on affective perception, linked to parental investment, differing between species. To address this question, we performed playback experiments using infant isolation calls in a species without paternal care, the domestic cat. We used kitten calls recorded in isolation contexts inducing either Low arousal (i.e., isolation only) or High arousal (i.e., additional handling), leading to respective differences in escape response of the kittens. We predicted that only females respond differently to playbacks of Low versus High arousal kitten isolation calls, based on sex-differences in parental investment.ResultsFindings showed sex-specific responsiveness of adult cats listening to kitten isolation calls of different arousal conditions, with only females responding faster towards calls of the High versus the Low arousal condition. Breeding experience of females did not affect the result. Furthermore, female responsiveness correlated with acoustic parameters related to spectral characteristics of the fundamental frequency (F0): Females responded faster to kitten calls with lower F0 at call onset, lower minimum F0 and a steeper slope of the F0.ConclusionsOur study revealed sex-specific differences in the responsiveness to kitten isolation calls of different arousal conditions independent of female breeding experience. The findings indicated that features of F0 are important to convey the arousal state of an infant. Taken together, the results suggest that differences in parental investment evolutionary shaped responsiveness (auditory sensitivity/ motivation) to infant calls in a sex-specific manner in the domestic cat.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0718-9) contains supplementary material, which is available to authorized users.

Flying high: limits to flight performance by sparrows on the Qinghai-Tibet Plateau.

Limits to flight performance at high altitude potentially reflect variable constraints deriving from the simultaneous challenges of hypobaric, hypodense and cold air. Differences in flight-related morphology and maximum lifting capacity have been well characterized for different hummingbird species across elevational gradients, but relevant within-species variation has not yet been identified in any bird species. Here we evaluate load-lifting capacity for Eurasian tree sparrow (Passer montanus) populations at three different elevations in China, and correlate maximum lifted loads with relevant anatomical features including wing shape, wing size, and heart and lung masses. Sparrows were heavier and possessed more rounded and longer wings at higher elevations; relative heart and lung masses were also greater with altitude, although relative flight muscle mass remained constant. By contrast, maximum lifting capacity relative to body weight declined over the same elevational range, while the effective wing loading in flight (i.e. the ratio of body weight and maximum lifted weight to total wing area) remained constant, suggesting aerodynamic constraints on performance in parallel with enhanced heart and lung masses to offset hypoxic challenge. Mechanical limits to take-off performance may thus be exacerbated at higher elevations, which may in turn result in behavioral differences in escape responses among populations.

Differences in the escape response of a grapsid crab in the field and in the laboratory.

Escape behaviours of prey animals are frequently used to study the neural control of behaviour. Escape responses are robust and fast, and can be reliably evoked under both field and laboratory conditions. Many escape responses are not as simple as previously suggested, however, and are often modulated by a range of contextual factors. To date it has been unclear to what extent behaviours studied in controlled laboratory experiments are actually representative of the behaviours that occur under more natural conditions. Here, we have used the model species Neohelice granulata, a grapsid crab, to show that there are significant differences between the crabs' escape responses in the field compared with those previously documented in laboratory experiments. These differences are consistent with contextual adjustments such as the availability of a refuge and have clear consequences for understanding the crabs' neural control of behaviour. Furthermore, the methodology used in this study mirrors the methodology previously used in fiddler crab research, allowing us to show that the previously documented differences in escape responses between these grapsid species are real and substantial. Neohelice granulata's responses are delayed and more controlled. Overall, the results highlight the adaptability and flexibility of escape behaviours and provide further evidence that the neural control of behaviour needs to be addressed in both the laboratory and field context.

Pyrethroid induced behavioral responses of Anopheles dirus, a vector of malaria in Thailand

Contact and noncontact behavioral actions of wild-caught Anopheles dirus in response to the operational field dose of three synthetic pyrethroids (bifenthrin, α-cypermethrin and λ-cyhalothrin) were evaluated using an exito-repellency test chamber. DEET was used as the repellency standard for comparison with the other three synthetic pyrethroids. Results showed that test specimens rapidly escaped from the test chamber when exposed to direct contact with a surface treated with each of the three synthetic pyrethroids and DEET. Alpha-cypermethrin demonstrated the strongest irritant action (84.9% escape), followed by DEET (77.0%), λ-cyhalothrin (68.6%) and bifenthrin (68.3%). In the noncontact configuration, fewer mosquitoes escaped from the test chambers as compared to contact trials, although a significant escape response was still observed as compared to the controls (P<0.05). We conclude that An. dirus exhibits both irritant and repellent actions in response the three pyrethroids testing in this study. The information obtained will allow us to better understand the behavioral responses of vectors to various chemicals and provide guidance when designing control strategies for targeting specific disease vectors.

Host feeding responses of Aedes aegypti (L.) exposed to deltamethrin

Escape responses of mated and unmated nulliparous Aedes aegypti mosquitoes were compared using three different concentrations of deltamethrin in the presence or absence of a live animal host using an excito-repellency (ER) test system. Both insecticide contact (excitation) and non-contact (repellency) test configurations were compared. For contact trials, mated mosquitoes showed similar escape movements among the three concentrations when host stimuli were absent. Significant differences in responses were seen between the lower concentrations of (LC(50) and LC(75) ) deltamethrin with and without hosts present (P<0.05). Presence or absence of host stimuli produced no significant differences in escape response for unmated females when exposed to the highest concentration (LC(90) ) of deltamethrin. Our findings indicate that as deltamethrin concentrations decrease to sublethal levels, mating status and host cues play a more significant role in escape behavior. Therefore, insemination can influence the outcome of feeding success and flight movement of nulliparous female Ae. aegypti in contact with deltamethrin and in the presence of live host stimuli. The ER assay system serves as a useful tool for observing excitation and repellency responses of Ae. aegypti to insecticides in the presence or absence of other environmental and biological cues that can affect mosquito behavior.

Risk recognition and variability in escape responses among intertidal molluskan grazers to the sun star Heliaster helianthus

Escape responses are a common form of inducible defense in the presence of a predator, which can be species-specific and adaptive. While conditions for their evolution have been amply investigated, little is known about variability in prey responses over the range of variation in predation risks typical of most systems. We characterized escape responses of 4 intertidal grazers (2 chitons, 2 fissurellid limpets) to the sunstar Heliaster helianthus. Comparisons were made among sites of apparently distinct predation risks: high risk, where the grazers constitute a significant portion of H. helianthus diet; moderate risk, where H. helianthus primarily consume preferred mussel prey; no risk of predation, where prey exist beyond the southern geographic limit of H. helianthus. Prey responses were highly specific to the H. helianthus stimulus. Escape responses differed among grazer species, but these differences did not correspond to taxonomic relatedness, nor to their intertidal vertical distribution. No differences in escape responses were observed between sites where H. helianthus exhibit different diets, suggesting that these grazer species cannot ‘perceive’ and/or respond to this apparent change in predation risk. In contrast, a greater proportion of individuals of all 4 species responded to the H. helianthus cue, predator recognition was significantly faster, and distance traveled after stimulation was greater at sites of predator-prey coexistence than at the site beyond the predator’s geographic range. Thus, longer contact history with the predator appears to favor greater capacity to display escape responses in all species examined. We highlight the importance of evaluating phenotypic responses to predators under natural conditions and across natural gradients of predation risks.

Age- and sex-related morphological and physiological differences influence escape capacity in House Sparrows (Passer domesticus)

Sexual dimorphism and age-related differences are sources that contribute to morphologic and physiologic variation within animal populations. Measurement of animal performance may indicate whether this variation is functionally relevant. Our study aimed to experimentally test this statement in a captive population of House Sparrows ( Passer domesticus (L., 1758)) by examining age- and sex-related differences in escape response and its relationship to several morphological (tarsus, wing, tail lengths, and body mass) and physiological traits (cell-mediated immunity, natural antibodies, complement activity, hematocrit, and stress response). Escape response from a predator is considered a good variable to measure animal performance, because natural selection clearly favours individuals that avoid predators successfully. Our experimental design also aimed to standardize possible confounding factors affecting escape behaviour under natural conditions. We exposed sparrows to short episodes of high predation risk by simulating the attack of a predator and assumed that the capture order of individuals was related to their escape capacity. The optimal strategy was the immediate escape response for all individuals. We found that first-year males were the best escapers. In support of the hypothesis, juvenile males gathered a better optimum of several morphological and physiological characters that related to capture order.

Differences in escape response of fish in protected and fished Mediterranean rocky reefs

In both protected and fished rocky reefs in the southern Adriatic Sea, the behaviour of the sea breams Diplodus sargus and D. vulgaris (both targeted by spear-fishing) in the presence of divers was found to be mostly negative (i.e. escape response). However, at protected reefs sea breams frequently swam into the closest shelters, whereas in fished reefs they mostly escaped in open water. This study suggests that spear-fishing may alter the escape response of fish from natural predators and that marine reserves may re-establish natural behaviour patterns.

Effects of Physiological Conditioning on Behavioral Avoidance by Using a Single Age Group of &lt;I&gt;Aedes aegypti&lt;/I&gt; Exposed to Deltamethrin and DDT

The behavioral and physiological responses of 6-d-old Aedes aegypti (L.) adult females exposed to deltamethrin and DDT were characterized using a free-choice excito-repellency test system. Excluding varying pretest age and carbohydrate availability as possible confounders, insecticide contact (measuring irritancy) and noncontact (measuring repellency) behavioral assays were conducted on two nonbloodfed groups, either unmated or mated (nulliparous), and two blood-fed groups, either parous or newly full-engorged mosquitoes. The degree of escape response to deltamethrin and DDT varied according to the physiological conditioning. Escape rates from contact and noncontact chambers with deltamethrin were more conspicuous in nonbloodfed groups compared with mosquitoes previously bloodfed. There were no significant differences in escape responses between unmated and nulliparous test populations. With DDT, a more pronounced escape response was observed in unmated compared with other physiological conditions. More moderate escape response was seen in nulliparous mosquitoes, and the least was observed in full bloodfed test individuals, regardless of test compound. Ae. aegypti, regardless of pretest conditioning, was completely susceptible to deltamethrin, whereas showing high resistance to DDT. Despite profound differences in resistance, there was no significant difference in avoidance response between chemicals and mosquito conditioning. Moreover, pre- and postbloodmeals were found to influence assay outcome and thus to have relevance on the interpretation of susceptibility and excito-repellency assays.

Dietary segregation of krill‐eating South Georgia seabirds

The diets of six of the main seabird species (two petrels, two albatrosses, two penguins) breeding at Bird Island, South Georgia were studied simultaneously during the chick‐rearing period in 1986. For five species, Antarctic krill Euphausia superba was the main food (39–98% by mass); grey‐headed albatrosses took mainly the ommastrephid squid Martialia hyadesi (71%) and only 16% krill. The size of the krill taken was similar between seabird species, although there were small but significant differences between penguins and the other species. Sex and reproductive status of krill, however, was different between all seabird species, reflecting some combination of differences in foraging ranges, selectivity by predators, or differences in escape responses of krill. For the krill‐eating species, the rest of the diet varied substantially between species, comprising Martialia and nototheniid fish (blackbrowed albatross and, along with lanternfish, white‐chinned petrel), lanternfish and amphipods (Antarctic prion and macaroni penguin), and icefish (gentoo penguin). Long‐term data on breeding success and information on diet in 5–10 other years suggest that in 1986 seabird diet and reproductive performance was indicative of a year of good availability of krill around South Georgia. In such circumstances, ecological segregation between krill‐eating species appears to be maintained chiefly by differences in foraging range and feeding methods, which are reviewed. This situation is rather different from the few studies of seabird communities elsewhere, where prey type and size are believed to be the main mechanisms of dietary segregation.

Predation by an introduced clam as the likely cause of substantial declines in zooplankton of San Francisco Bay

The clam Potamocorbula amurensis was introduced into the San Francisco Bay estuary (California, USA) in 1986 and became abundant in late 1987. Within a year, chlorophyll concentration and the abundance of adults of 3 common estuarine copepod species had declined by 53 to 91 %, providing an opportunity to examine mechanisms by which benthic grazing might control the abundance of pelagic populations. Declines in chlorophyll and abundance of the 3 species of copepod coincided approximately with the geographic range of the clam population. The decline in abundance of the copepod Eurytemora affinis was accompanied by a decrease in the ratio of nauplii to adults, but not in the ratio of eggs to females. Therefore, the decline in abundance may be due to elevated mortality of nauplii rather than food limitation of reproductive rate. We argue that direct predation by P. amurensis is the cause of the reduced sunrival of nauplii, and therefore of the depressed abundance of adults. Experimentally determined clearance rates of P. amurensis on E. affins nauplii averaged 0.11 1 clam-' d-'. If that clearance rate applied in the field, the clams could remove 8.2% of the nauplii d-I. This removal rate is sufficient to explain the observed rate of population decline. P. amurensis appears to have become well established, and copepod populations of the bay so far have failed to rebound. Thus this invasion may have permanent effects. In a broader sense, predation on zooplankton by soft-bottom benthos may be an important, and heretofore overlooked, source of mortality in shallow waters. Selectivity occurring through differences in escape response and vertical position could make bivalve predation an important influence on biomass and species composition of inshore zooplankton.