Influence Habitat Choice Research Articles

Physiological condition infers habitat choice in juvenile sockeye salmon.

The amount of time that juvenile salmon remain in an estuary varies among and within populations, with some individuals passing through their estuary in hours while others remain in the estuary for several months. Underlying differences in individual physiological condition, such as body size, stored energy and osmoregulatory function, could drive individual variation in the selection of estuary habitat. Here we investigated the role of variation in physiological condition on the selection of estuarine and ocean habitat by sockeye salmon (Oncorhynchus nerka) smolts intercepted at the initiation of their 650-km downstream migration from Chilko Lake, Fraser River, British Columbia (BC). Behavioural salinity preference experiments were conducted on unfed smolts held in fresh water at three time intervals during their downstream migration period, representing the stage of migration at lake-exit, and the expected timing for estuary-entry and ocean-entry (0, 1 and 3 weeks after lake-exit, respectively). In general, salinity preference behaviour varied across the three time periods consistent with expected transition from river to estuary to ocean. Further, individual physiological condition did influence habitat choice. Smolt condition factor (K) and energy density were positively correlated with salinity preference behaviour in the estuary and ocean outmigration stages, but not at lake-exit. Our results suggest that smolt physiological condition upon reaching the estuary could influence migratory behaviour and habitat selection. This provides evidence on the temporally dependent interplay of physiology, behaviour and migration in wild juvenile Pacific salmon, with juvenile rearing conditions influencing smolt energetic status, which in turn influences habitat choice during downstream migration. The implication for the conservation of migratory species is that the relative importance of stopover habitats may vary as a function of initial condition.

Behavioural tendencies associated with microhabitat use in a clonal gecko species living in the wild

Individual differences in behavioural traits influence habitat choice, and in turn, differences in used habitats shape different behavioural tendencies through plasticity. Here, I investigated the relationship between personality and microhabitat use in a free-living population of the clonal gecko Lepidodactylus lugubris. The study site is a small beachfront forest facing two environments with contrasting levels of human disturbance. I conducted a mark-recapture survey to assess the geckos’ spacing pattern and evaluated their boldness and exploration scores in the laboratory. The geckos exhibited a small range of movement and a high consistency in their perch height. Boldness was related to two microhabitat features, but exploration was not. Relatively shy geckos were found in trees near the roadside and on low branches, whereas relatively bold geckos were found on both the beachside and the roadside and on low to high branches. These patterns suggest that geckos in high-disturbance microhabitats may have frequently experienced artificial stimuli and become shy. However, the present results cannot exclude the possibility that individual differences are caused by other factors and that different personality types prefer and settle in different microhabitats. Although the actual mechanisms are unclear, my findings highlight that behaviour-related habitat use emerges even in clonal animals. Individuals within conspecifics show different spacing patterns and different behavioural tendencies. If clonal animals live in a spatially diverse environment, it is predicted that different microhabitats may gradually shape different personality types through developmental plasticity. Here, I investigated the association between the personality of clonal geckos and their microhabitat use in different levels of human disturbance. In contrast to the prediction, both juveniles and adults showed a similar pattern of boldness-related microhabitats; relatively shy individuals were found in putatively high-disturbance sites. This result suggests that the association between boldness and microhabitats is not gradually formed through a long-time scale but is likely generated within their early ontogenetic stage.

Habitat preferences by individual humpback whale mothers in the Hawaiian breeding grounds vary with the age and size of their calves

We investigated whether calf age and calf size influence habitat choice by humpback whale mother–calf pairs in their breeding grounds. During 1997–2008, we conducted focal follows of mother–calf pairs in Hawaiian waters. Tail-fluke identification photographs and calf lengths (measured through videogrammetry) were obtained. Water depth and sea-bed terrain type were derived from GPS data. Identification photographs were matched so that the habitat choices could be established within breeding seasons. Across 72 mother–calf pairs resighted over various intervals within a breeding season, magnitude of depth change between initial and final sightings increased significantly with resighting interval. There was a significant increase from initial depth to final depth for relatively long resighting intervals (27–51 days), but no significant difference for relatively short resighting intervals (2–26 days). Although there was no preference for sea-bed terrain type by mother–calf pairs at their initial sighting, there was a preference for rugged terrain at their final resighting. A resource selection model indicated that the relative probability of a location being used by a mother–calf pair increased (as a function of water depth and rugged sea-bed terrain type) from initial to final sighting; a finding supported by subsequent tests of habitat preference versus availability. For 96 measured calves, calf length and water depth were positively correlated, even when ordinal day of measurement was controlled for statistically; a finding confirmed by a general linear model that simultaneously investigated the relationship between water depth, sea-bed terrain type, number of escorts, ordinal day and calf size. Thus, both calf age and size influence habitat choice by mother–calf pairs in their breeding grounds. The movement of mothers and their maturing calves into deeper waters where they favour rugged sea-bed terrain appears to be part of a suite of behavioural changes during the pre-migratory phase of residency in the breeding grounds.

Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) response to relative humidity with and without host cues

ABSTRACTTrichogramma ostriniae is a parasitoid wasp species that is used as a biological control for several lepidopteran agricultural pests. Our study examined the effects of relative humidity (RH) on the behaviour of female T. ostriniae. In Y-tube RH choice assays, wasps generally chose higher RH over lower RH but the latency time taken to make a choice displayed no clear patterns that could be ascribed to the magnitude of the RH difference between arms of the Y-tube. In trials conducted in glass arenas with fixed humidities, the conditional probabilities of transition from searching to interacting with the leaf disk, and from interacting with leaf disks to antennal egg drumming and oviposition, were not significantly different among the RH levels, nor were there differences in latency times. These findings suggest that the level of RH may influence habitat choice but have little effect on search efficacy.

Movement of amphibians through agricultural landscapes: The role of habitat on edge permeability

Long-term population persistence depends on successful dispersal and colonization. Within agricultural landscapes, dispersing individuals encounter a variety of edge types. How individuals respond to edges can dictate whether they are permeable to dispersal or act as barriers, with consequences for population connectivity. Using two amphibian species, bullfrogs (Lithobates catesbeianus) and Blanchard’s cricket frogs (Acris blanchardi), we conducted two studies to address (1) how abiotic factors influence habitat choice and (2) how habitat choice and movement behavior change based on edge type (edges were between grass–corn, grass–forest, and forest–corn habitats). In the first experiment we found that both species preferred high soil moisture environments during both the day and night; and at night neither species showed a preference for ground or canopy cover. However, during the day bullfrogs had a preference for both ground and canopy cover, while cricket frogs showed no preference. In the second experiment, we found that bullfrogs had no overall preference for one habitat type over another; they were observed traveling along the edge of two habitats. Cricket frogs, on the other hand, showed a strong aversion to forest habitat. We concluded that behavioral responses to different habitats may explain current population trends; movement along edge habitat may allow bullfrogs to readily disperse through altered landscapes whereas cricket frog declines may occur in areas experiencing reforestation due to increased isolation. Conservation practices in agricultural land will likely improve landscape connectivity for these species, especially for declining cricket frog populations.

Phenotypic Integration in Response to Incubation Environment Adaptively Influences Habitat Choice in a Tropical Lizard

Phenotypic integration, in which a suite of traits change in a correlated or covarying response to shifts in environmental conditions, may enhance an organism's fitness. In skinks, rocky environments select for longer limbs and rapid running and climbing. We examined whether differences in nest temperature coincident with specific habitats caused phenotypically integrated effects on morphology, locomotor performance, and behavior in the skink Carlia longipes. Specifically, we determined whether microhabitat choices were integrated with adaptive morphology for each habitat. Using a split-clutch design, we incubated eggs at thermal regimes that mimicked the thermal environments of nests from two habitat types (forest = warm; rocky = cool). Hatchlings from cool incubation environments had longer limbs and greater running and climbing speeds, which are likely to be beneficial for rocky habitats. In addition, individuals from cool incubation environments selected rocky microhabitats more frequently than did hatchlings from warm incubation environments. We demonstrate phenotypic integration in response to nest temperature that affected morphology, performance, and ultimately habitat selection in a way that should increase hatchling fitness.

Settlement decisions by the two-spotted spider mite Tetranychus urticae

In silk-spinning arthropods, silk can be used for web building, protection, and communication. Silk is an informative material about the presence of conspecifics. It can therefore inform on habitat suitability and hence assist in habitat choice. In this context, we investigated the influence of silk on microhabitat choice by the two-spotted spider mite, Tetranychus urticae. Three factors that could potentially influence habitat choice were manipulated: the strain, number, and the stage of mites. Our study showed that these factors all influence the choice of microhabitat. The tendency of whether to settle on a silk-covered area was influenced by the origin of mites (strain effect). Adult females showed a higher tendency to settle on an area covered with the silk laid by numerous congeners (number effect). Moreover, larvae seemed to be more responsive to the presence of silk than adults (stage effect). This suggests that individuals use silk as a social cue in selecting their microhabitat and that the spatial organization and group behaviour seem to be shaped by the individuals’ response to social cues, such as the amount of silk already present.

Personality and habitat segregation in giant sea anemones (Condylactis gigantea)

Animal personality is described as consistent differences in individual behavior across time or context, and may vary spatially. Bolder animals are more likely to migrate, grow slowly, or explore than shyer animals. Personality types within a population can also differ between discrete habitats or continuously across an environmental gradient. We examined the distribution of giant sea anemone (Condylactis gigantea) responses to disturbance across a continuous habitat gradient to determine whether anemones' habitat selection is explained by individual variation. On four different occasions we induced individual anemones to retract their tentacles by touching them with a model blue crab (Callinectes sapidus) and recorded the time for their tentacles to relax into their original state. We also recorded several environmental variables associated with each anemone. We found that individual anemones behaved in consistently different ways and that a combination of seagrass measurements and the number of close conspecifics, as well as their tentacle color, significantly explained this variation. This indicates that personality may either influence habitat choice, or that habitats favor certain personalities. Ultimately, personality types are segregated by habitat type, which suggests that such variation could lead to reproductive isolation.

The importance of a good neighborhood: dispersal decisions in juvenile common lizards are based on social environment

Within a population, dispersers are likely to differ in their motivation and adaptations to disperse; yet individual heterogeneity in dispersal decisions is still poorly documented. In the common lizard, females can be classified into 3 types of ventral color (yellow, orange, and mixed) that signal alternative strategies in reproduction and behavior. The reproductive success of these alternative strategies depends on the frequency of each color type in their local environment. Therefore, we predicted that adaptive emigration and settlement decisions should differ between color types and respond to the social composition of the environment. To test this prediction, we analyzed juvenile local dispersal decisions in response to an experimental manipulation of the local color type frequencies. Offspring from orange or mixed females showed decreased dispersal rate in populations where the frequency of yellow females was increased, and those who dispersed chose to settle in environments with lower female density but higher frequency of yellow females. Our results demonstrate that the composition of the social environment is used as a direct cue for dispersal decisions that provides information on resource competition and environment quality. The frequency of female color types is thus a key parameter of the social environment that influences habitat choice decisions. However, the pattern of spatial autocorrelation of adult females was not consistent with these color-related dispersal patterns, which suggest that other processes also participate in shaping the distribution of individuals at the population scale.

Lemming winter habitat choice: a snow-fencing experiment

The insulative value of early and deep winter snow is thought to enhance winter reproduction and survival by arctic lemmings (Lemmus and Dicrostonyx spp). This leads to the general hypothesis that landscapes with persistently low lemming population densities, or low amplitude population fluctuations, have a low proportion of the land base with deep snow. We experimentally tested a component of this hypothesis, that snow depth influences habitat choice, at three Canadian Arctic sites: Bylot Island, Nunavut; Herschel Island, Yukon; Komakuk Beach, Yukon. We used snow fencing to enhance snow depth on 9-ha tundra habitats, and measured the intensity of winter use of these and control areas by counting rodent winter nests in spring. At all three sites, the density of winter nests increased in treated areas compared to control areas after the treatment, and remained higher on treated areas during the treatment. The treatment was relaxed at one site, and winter nest density returned to pre-treatment levels. The rodents' proportional use of treated areas compared to adjacent control areas increased and remained higher during the treatment. At two of three sites, lemmings and voles showed significant attraction to the areas of deepest snow accumulation closest to the fences. The strength of the treatment effect appeared to depend on how quickly the ground level temperature regime became stable in autumn, coincident with snow depths near the hiemal threshold. Our results provide strong support for the hypothesis that snow depth is a primary determinant of winter habitat choice by tundra lemmings and voles.

A two-level problem: habitat selection in relation to prey abundance in an ambush predator, the speckled rattlesnake (Crotalus mitchellii)

Summary Understanding how food distribution influences habitat choice is a central goal of behavioural ecology. Because animals select habitats at different scales, and because the selection criteria used may be scale-dependent, studies examining the significance of food in relation to habitat selection should ideally incorporate more than one spatial scale. We relied on spatial ecology data and prey abundance estimates to examine whether prey (rodent) abundance is a consistent predictor of habitat selection at two different spatial scales in an ambush predator, the speckled rattlesnake (Crotalus mitchellii), during the mating and post-mating seasons. At the macrohabitat level, selection and avoidance of particular macrohabitats by C. mitchellii positively correlated with rodent abundance during the post-mating season. Because most snake foraging activity occurs during the post-mating season, this finding suggests that C. mitchellii selects macrohabitats that increase prey encounter rates. In contrast, rodent abundance was relatively low at the microhabitats selected by the snakes. Therefore, the higher prey abundance in C. mitchellii’s preferred macrohabitat did not translate into increased access to prey at the snake microhabitats, indicating that prey distribution may not be a constant predictor of predator habitat choice across spatial scales. Indirect evidence suggests that lower prey abundance at the snake microhabitats was the result of changes in rodent behaviour (e.g., avoiding or reducing activity at snake locations) to decrease predation risk. Our study underscores the dynamics of predator‐prey interactions in nature, and emphasizes the challenges that ambush predators may face when foraging for risk-sensitive prey.

Patterns of Variation in the Influence of Natal Experience on Habitat Choice

The experience of animals in their natal or larval habitats has long been considered a potential source of variation in the habitat choices made later during dispersal. This idea has been of particular interest to evolutionary biologists because of the role such variation plays in the formation of host races and species. However, experiments that have tested for the effect of natal experience on habitat choice have produced widely variable results, leading to disagreement about the ecological importance of these effects. Here, I review the results of experiments within a broad range of animal taxa to assess the potential sources of variation in observed effects of natal experience on habitat choice. I provide a comprehensive summary of previous studies and demonstrate that when natal experience influences habitat choice, it nearly always increases the acceptance of the natal habitat type. Furthermore, I discuss mechanisms that allow natal experience to affect later habitat choice and describe how these mechanisms are influenced by various experimental design elements, such as the life stage at which early experience is provided to subjects. I conclude by reviewing the adaptive hypotheses for why animals might or might not respond to natal experience, and also how these hypotheses might explain interspecific differences in the importance of natal experience during habitat selection decisions. By understanding in what species, and in which contexts, experience influences habitat selection, we will be able to predict the ecological and evolutionary consequences of these effects more accurately.

Intraspecific competition drives multiple species resource polymorphism in fish communities

It has been hypothesized that inter‐specific competition will reduce species niche utilization and drive morphological evolution in character displacement. In the absence of a competitor, intra‐specific competition may favor an expansion of the species niche and drive morphological evolution in character release. Despite of this theoretical framework, we sometimes find potential competitor species using the same niche range without any partitioning in niche. We used a database on test fishing in Sweden to evaluate the factors (inter‐ and intraspecific competition, predation, and abiotic factors) that could influence habitat choice of two competitor species. The pattern from the database shows that the occurrence of perch and roach occupying both littoral and pelagic habitats of lakes in Sweden is a general phenomenon. Furthermore, the results from the database suggest that this pattern is due to intra‐specific competition rather than inter‐specific competition or predation. In a field study, we estimated the morphological variation in perch and roach and found that, individuals of both species caught in the littoral zone were more deeper bodied compared to individuals caught in the pelagic zone. Pelagic perch fed more on zooplankton compared to littoral perch, independent of size, whereas the littoral perch had more macroinvertebrates and fish in their diet. Pelagic roach fed more on zooplankton compared to littoral roach, whereas littoral individuals fed more on plant material. Furthermore, we sampled littoral and pelagic fish from another lake to evaluate the generality of our first results and found the same habitat associated morphology in both perch and roach. The results show a consistent multi‐species morphological separation in the littoral and pelagic habitats. This study suggests that intra‐specific competition is possibly more important than inter‐specific competition for the morphological pattern in the perch‐roach system.

The role of different types of detached macrophytes in the food and habitat choice of a surf-zone inhabiting amphipod

Allorchestescompressa is the dominant macroinvertebrate species in wrack accumulations on surf zones of south-western Australia. These amphipods were provided with a choice of macrophyte material representing brown and red algae and seagrass in a series of preference experiments in the laboratory and field. Feeding experiments showed that A. compressa exhibited a strong preference for particular types of macrophytes (P < 0.01). Amphipods primarily consumed brown algae, with 69–98% of the biomass of Ecklonia radiata and 64% of the biomass of Sargassum sp. lost over the experiments. This study has shown that the amphipod A. compressa exhibits a clear preference for brown algae over red algae and seagrass as food. In terms of habitat preference, tank experiments using a series of pair-wise comparisons showed that, in the absence of fish predators, A. compressa selected seagrass as its preferred habitat over the other types of wrack (P < 0.001). When satiated or starved, between 68 and 83 and 79 and 98% of amphipods were found in Amphibolis and Posidonia, respectively. In contrast, field-cage experiments revealed that A. compressa preferred either mixed wrack, brown algae or red algae over seagrass as a habitat (P < 0.01). The contrasts between results from the laboratory and field suggest that other factors such as the presence of predators, water flow and light could influence habitat choice in the surf zone. This study shows that allochthonous material transported to surf zones from other habitats therefore play different roles in driving secondary production in this shoreline habitat.

Habitat disturbance, not predation, is all that is required to influence habitat choice in juvenile snakes: A rejoinder to Lill

Austral EcologyVolume 31, Issue 7 p. 905-906 Habitat disturbance, not predation, is all that is required to influence habitat choice in juvenile snakes: A rejoinder to Lill JONATHAN K. WEBB, JONATHAN K. WEBB School of Biological Sciences, The University of Sydney, NSW 2006, Australia (Email: [email protected]); and Search for more papers by this authorMARTIN J. WHITING, MARTIN J. WHITING School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South AfricaSearch for more papers by this author JONATHAN K. WEBB, JONATHAN K. WEBB School of Biological Sciences, The University of Sydney, NSW 2006, Australia (Email: [email protected]); and Search for more papers by this authorMARTIN J. WHITING, MARTIN J. WHITING School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South AfricaSearch for more papers by this author First published: 12 October 2006 https://doi.org/10.1111/j.1442-9993.2006.01702.xRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume31, Issue7November 2006Pages 905-906 RelatedInformation

Do changes in risk-taking affect habitat shifts of sticklebacks?

The distribution of individuals is often the outcome of conflicting demands, such as between predator avoidance and reproduction. A factor that has seldom been considered in studies on habitat choice is time-dependent changes in risk-taking. We investigated the distribution of threespine sticklebacks, Gasterosteus aculeatus, over two breeding seasons and found it to change with time towards shallower areas with a more open habitat structure. Shallow and structurally less complex habitats were probably favorable due to a higher reproductive rate, but costly due to an increased risk of predation. Contrary to expectation, changing predation pressure was not a predictor of the shift in habitat use and, thus, not the proximate cue. Instead date was the main predictor. This suggests that increased risk-taking in relation to predation contributed to the habitat shift. The possibility was supported by a laboratory experiment that showed sticklebacks to take larger risks and prefer more predator-exposed areas at the end of the season than at the start of the season. These results demonstrate that temporal changes in risk-taking occur and can influence habitat choice, which points to the importance of considering risk-taking, in addition to predation pressure, when studying the effect of predators on distribution.

Habitat choice in shoals of roach as a function of water temperature and feeding rate

Temperature and food availability are two important factors which affect fish growth and therefore are expected to influence habitat choice in fish. In this study, shoals of 16 juvenile roach, Rutilus rutilus, were given a choice between two chambers that differed in temperature by 1·5°C or 3°C whereas food availability was the same in both chambers (ratio 1 : 1) or higher in the colder one (ratio 4 : 1). The number of fish in each chamber was recorded for 10 min each during a pre‐feeding, feeding and post‐feeding period. Roach generally preferred the warmer over the colder chamber during the pre‐feeding periods. Temperature had a significant effect on the distribution of fish during all three time periods whereas food availability was a significant factor only during the feeding period. The important role of temperature was emphasized further by the fact that a relatively small difference in the temperature gradient of 1·5°C had a stronger effect on fish distribution than a four times higher feeding rate during the feeding period. The implications for growth rates of such short‐term decision‐making of roach are discussed.

Larval behavior, settlement preference, and induction of metamorphosis in the temperate solitary ascidian Molgula citrina Alder & Hancock

Tadpole larvae of the solitary ascidian Molgula citrina Alder & Hancock were examined in behavioral and settlement bioassays to test their reactions to several physical and biotic cues known to influence habitat choice in larvae of other ascidian species. These assays revealed that M. citrina larvae, though previously reported to lack photoreception, are nonetheless strongly influenced by lighting cues when sampling potential substrata. Larval responses to other settling larvae, adult conspecifics, a congener, and an heterospecific superior competitor were also tested. Larvae settled randomly with respect to each other both in the dark and under ambient light conditions, suggesting that the gregarious settlement exhibited by larvae of many benthic invertebrates does not occur in this species. In bioassays testing the metamorphosis-inducing potential of homogenized tunic from adult ascidians, M. citrina larvae responded differentially to the three ascidian species examined. Percent metamorphosis in a population of M. citrina larvae decreased when exposed to conspecific tunic material, but increased in the presence of tunic homogenate from the heterospecific competitor. Settlement responses of M. citrina larvae to light cues and to water-borne chemicals may influence adult distributions in this ascidian species.

Competitive ability influences habitat choice in marine invertebrates

Patterns of distribution and abundance of sessile marine epi-benthic invertebrates are controlled by three factors: (1) the presence and abundance of larvae which are competent to settle, (2) the choice of settling sites by recruiting larvae, and (3) the biotic and physical events occurring during and after settlement. Although there is much information on the distribution of larvae and seasons of recruitment 1–3, substratum selection 4–6 and post-settlement events 7–15, very little is known of the ecological and evolutionary relationships between these factors5,16–18. Natural selection acts on entire life cycles, thus information about these relationships is essential for understanding patterns of recruitment and survival. For example, sessile organisms can modify the course of post-recruitment events by selective settlement and directional growth19. Here, I present evidence that the larvae of several taxa of marine invertebrates avoid substrata where there is a high probability of death caused by a superior spatial competitor.