Selection of diurnal refuges by the nocturnal squirrelfish, <Emphasis Type="Italic">Holocentrus rufus</Emphasis>

We examined the diurnal refuges occupied by the nocturnal squirrelfish, Holocentrus rufus, to describe refuges and the behavior associated with their use and to determine which, if any, refuge characteristics were selected. We tagged 21 H. rufus on two sites on a fringing reef in Barbados, West Indies, identified the refuges they used (n = 57), measured ten characteristics of each refuge and the surrounding microhabitat, and monitored their refuge use for 4 weeks. To evaluate refuge selection, we measured the same characteristics on a comparable number of unused potential refuges (n = 67) on the same reefs and used classification tree models to determine which characteristics separated used from unused refuges. Each fish used 1–9 refuges, which did not overlap among individuals and were defended against intrusion by conspecifics and some heterospecifics. Fish with more than one refuge frequently moved among them. There was strong site fidelity with no immigration of untagged fish or emigration of tagged fish on either reef during the study period and no additional refuges being occupied over the 4-week period. Refuges were primarily holes, open at one or two ends, which varied in size, distance from the reef edge, entrance orientation, and vertical relief at the entrance. Holes used as refuges differed significantly from unused holes mainly in characteristics related to the vertical position of their entrance, but the classification tree models differed for the two sites. This study provides the first detailed information on characteristics of daytime refuges used by a nocturnally active reef fish and the first evidence of selectivity of refuges. It suggests that the abundance and characteristics of holes on reefs could influence the density of H. rufus on natural reefs.     

Effects of Food Availability on Space and Refuge Use by a Neotropical Scatterhoarding Rodent

Animals that rely on refuges for safety can theoretically increase their foraging area without simultaneously increasing predation risk and travel costs by using more refuges. The key prediction of this theory, a negative correlation between food abundance, home range size and the number of refuges used, has never been empirically tested. We determined how home range size and refuge use by the Central American agouti (Dasyprocta punctata) varied across a gradient of abundance of the agoutis' principal food source: seeds and fruits of the palm Astrocaryum standleyanum. We used both manual and automated radio telemetry to measure space use of 11 agoutis during 2 mo of the Astrocaryum fruiting season, and of another set of 10 agoutis during 6 mo in which the animals largely relied on cached Astrocaryum seeds. We found that agoutis living in areas of lower food density had larger home ranges, and that all individuals used multiple refuges. The number of refuges, however, was not correlated with home range size. Consequently, agoutis that had larger home ranges roamed farther from their refuges. These results suggest that agoutis increase their home range size in response to food scarcity at the cost of their safety.     

The role of refuges in the persistence of Australian dryland mammals

Irruptive population dynamics are characteristic of a wide range of fauna in the world's arid (dryland) regions. Recent evidence indicates that regional persistence of irruptive species, particularly small mammals, during the extensive dry periods of unpredictable length that occur between resource pulses in drylands occurs as a result of the presence of refuge habitats or refuge patches into which populations contract during dry (bust) periods. These small dry‐period populations act as a source of animals when recolonisation of the surrounding habitat occurs during and after subsequent resource pulses (booms). The refuges used by irruptive dryland fauna differ in temporal and spatial scale from the refugia to which species contract in response to changing climate. Refuges of dryland fauna operate over timescales of months and years, whereas refugia operate on timescales of millennia over which evolutionary divergence may occur. Protection and management of refuge patches and refuge habitats should be a priority for the conservation of dryland‐dwelling fauna. This urgency is driven by recognition that disturbance to refuges can lead to the extinction of local populations and, if disturbance is widespread, entire species. Despite the apparent significance of dryland refuges for conservation management, these sites remain poorly understood ecologically. Here, we synthesise available information on the refuges of dryland‐dwelling fauna, using Australian mammals as a case study to provide focus, and document a research agenda for increasing this knowledge base. We develop a typology of refuges that recognises two main types of refuge: fixed and shifting. We outline a suite of models of fixed refuges on the basis of stability in occupancy between and within successive bust phases of population cycles. To illustrate the breadth of refuge types we provide case studies of refuge use in three species of dryland mammal: plains mouse (Pseudomys australis), central rock‐rat (Zyzomys pedunculatus), and spinifex hopping‐mouse (Notomys alexis). We suggest that future research should focus on understanding the species‐specific nature of refuge use and the spatial ecology of refuges with a focus on connectivity and potential metapopulation dynamics. Assessing refuge quality and understanding the threats to high‐quality refuge patches and habitat should also be a priority. To facilitate this understanding we develop a three‐step methodology for determining species‐specific refuge location and habitat attributes. This review is necessarily focussed on dryland mammals in continental Australia where most refuge‐based research has been undertaken. The applicability of the refuge concept and the importance of refuges for dryland fauna conservation elsewhere in the world should be investigated. We predict that refuge‐using mammals will be widespread particularly among dryland areas with unpredictable rainfall patterns.     

Can protective attributes of artificial refuges offset predation risk in lizards?

Artificial refuges are often used to supplement habitat in areas where natural shelters have been degraded or removed. Although artificial refuges are intended to support particular species, they may be equally attractive and accessible to others, including predators. We explored the influence of snake predation risk and shelter attributes on the overnight use of different artificial refuges (timber, tiles, and iron) using the predator‐prey relationship between Boulenger's skink, Morethia boulengeri and the curl snake, Suta suta. We collected adult M. boulengeri from two bioregions in south‐eastern Australia: the Riverina, where the two species co‐occur, and the South Western Slopes, where S. suta does not occur. Two adult S. suta were collected for use as chemical donors. We conducted four experiments on overnight refuge choice to determine: (i) predator‐scent avoidance, (ii) artificial refuge preferences, (iii) a trade‐off between a preferred refuge and predator‐avoidance, and (iv) the effect of gap height on refuge preference. We found that skinks avoided predator‐scented refuges in favour of identical, but unscented refuges. Skinks preferred timber refuges, and most skinks maintained this preference when predator‐scent was added. However, when gap height was manipulated, skinks shifted to the refuge with the smallest gap. Skinks displayed complex regional variation in behaviour; skinks from both bioregions avoided predator‐scent, but in the trade‐off experiment, skinks from the South Western Slopes were less likely to avoid predator‐scented timber refuges than those from the Riverina. Our findings suggest that protective refuge attributes, such as small gap height, can offset the risk implied by predator‐scent within a refuge. This study highlights the need to consider predator‐prey interactions when designing and using artificial refuges for habitat restoration or biological monitoring.     

Avoiding the flow: refuges expand the swimming potential of coral reef fishes

While many coral reef fishes utilise substratum refuges, the direct influence of water flow and swimming ability on such refuging patterns is yet to be established. This study examined the swimming ability and refuging behaviour of a labrid (Halichoeres margaritaceus) and a pomacentrid (Pomacentrus chrysurus) that inhabit high flow, wave-swept coral reef flats. Field observations of refuging patterns were combined with experimental evaluations in a flow tank using a replica of a substratum hole frequently used by these species. Under a range of flow speeds commonly found on the reef flat (0–60 cm s⁻¹), flow within the substratum refuge was reduced to speeds of 0–12 cm s⁻¹, representing a 75–100% flow reduction. Swimming ability of each species was then tested at 60 cm s⁻¹ with and without access to this flow refuge. Both species were able to maintain activity within the 60 cm s⁻¹ flow for considerably longer when provided with a refuge, with increases from approximately 39 min to 36 h for H. margaritaceus and 8 min to 88 h for P. chrysurus. Despite H. margaritaceus having the strongest swimming ability without access to a refuge, P. chrysurus was able to maintain swimming activity more than twice as long as H. margaritaceus when provided with a refuge. These increases in activity are probably due to energetic savings, with this type of refuge providing an estimated 95% energy saving over swimming directly into a unidirectional flow of 60 cm s⁻¹. These results highlight the major advantages provided by refuging behaviour and emphasise the importance of habitat refuges in shaping patterns of habitat use in reef fishes.     

Prey refuges as predator hotspots: ocelot (Leopardus pardalis) attraction to agouti (Dasyprocta punctata) dens

We tested the hypothesis that prey refuges attract predators, leading to elevated predator activity in the vicinity of refuges. We used camera traps to determine whether the spatial activity of a predator, the ocelot (Leopardus pardalis), was biased toward refuge locations of its principal prey, the agouti (Dasyprocta punctata). We radio-tracked agoutis at night to locate active refuges and compared the activity of ocelots between these refuges and surrounding control grid locations. We found that ocelots visited the area near agouti refuges significantly more often and for longer periods of time than control locations, and that they actively investigated the refuge entrances. Both occupied and unoccupied refuges were visited, but the duration of inspection was longer at occupied refuges. As the ocelots could probably not see the agoutis within the refuges, olfaction likely cued foraging ocelots. Two refuges were repeatedly visited by the same ocelots on different days, suggesting spatial memory. Overall, our results suggest that predators can be attracted to prey refuges or refuging prey. The benefits to prey of staying nearby a refuge would thus be counterbalanced by higher likelihoods of predator encounter. This should stimulate prey to use multiple refuges alternatingly and to not enter or exit refuges at times of high predator activity.     

The role of refuges in biological invasions: A systematic review

Aim

Ecological refuges buffer organisms against stressors and mediate a range of species interactions. However, their role in the context of biological invasions has yet to be synthesized, despite the increasing prevalence and impact of non-native species. To address this, we conducted a systematic review aiming to determine the extent to which refuges are considered explicitly in the invasion literature and to synthesize their function.

Location

Global.

Time period

Present day.

Major taxa studied

All.

Methods

Our search of the literature was conducted using the SCOPUS and Web of Science databases and followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) protocol. We obtained 315 records of refuge use in biological invasions from 300 studies. From each record, we extracted information relating to the experimental design, species characteristics and refuge type, where available.

Results

Refuges and refuge-mediated processes are widely reported in the invasion literature. Native species commonly use refuges to avoid non-native predation and competition, with spatial complexity and habitat heterogeneity key factors in facilitating their coexistence. Records show that artificial structures safeguard non-natives in their introduced range. However, there were key differences in the use of such structures in marine and terrestrial environments. Moreover, the enhanced structural complexity created by non-native plants and bivalves is often reported to act as a predation refuge for other species.

Main conclusions

The ubiquity of refuge-based processes suggests that refuges can play an important role in affecting the persistence, spread and impacts of non-native species, either through previously described mechanisms (i.e. refuge-mediated apparent competition and the persistent pressure scenario) or through a mechanism we describe (i.e. when non-native species use existing refuges), or both.     

Intraspecific variation in home range exclusivity by female green razorfish, Xyrichtys splendens (family Labridae), in different habitats

Female green razorfish, Xyrichtys splendens, were studied in the field in three shallow tropical marine habitats: sandbed, Thalassia grassbed, and coral rubble bottom. Individuals showed varying degrees of home range overlap (one measure of territoriality) in each habitat, due to differences in predator pressure, the availability of refuges, and water turbidity. In a large scale field manipulation, a 68 m² bed of artificial seagrass (300 'grass' blades per m²) was planted at one site with low turbidity, thereby increasing the availability of refuges. The females' home ranges overlapped more, whereas control fish did not change their home range use, indicating that home range exclusivity in this species is a function of refuge distribution. Female X. splendens apparently have the phenotypic plasticity to adapt their social behavior to local conditions; in this case, the availability of economically inexpensive refuges, and the risk of predation as a function of the turbidity of the water.     

Survival Through Bottlenecks of Vole Cycles: Refuge or Chance Events?

In small rodent populations with wide-amplitude fluctuations and low-density bottlenecks, the individuals that survive through the bottlenecks may gain major fitness advantages as they will be the founders of the following population expansion. Most hypotheses assume that there exists a physical or behavioural refuge from increased predation risk, and that the survivors are most likely individuals adapted to use such refuges. A recent hypothesis suggests that survival probability is habitat-dependent so that some otherwise sub-optimal habitats provide a spatial refuge from predation risk by the main predator(s). We used spatially replicated long-term (1981–2004) trapping and tracking data of voles (field vole Microtus agrestis and sibling vole M. rossiaemeridionalis) and their main predators (weasel Mustela nivalis and stoat M. erminea) to test predictions based on this hypothesis. We did not find support for the hypothesis. We did not find marked phase-dependent differences in the habitat-level distribution of Microtus voles. Habitat types with low Microtus vole abundance had, on average, comparable predator activity than the main Microtus vole habitats, indicating that there were no habitat-level refuges from predators. There appeared to be no permanent site-level refuges: the spatial distribution of voles varied from one bottleneck to another. This suggests that survival through bottlenecks is at least partly determined by chance events. We propose that in this kind of systems, where relatively short-lived prey are hunted by nomadic or widely ranging predators, short-term anti-predator responses may increase survival prospects as efficiently as more costly anti-predator adaptations, and there is no apparent need to maintain special adaptations to bottleneck situations that occur at infrequent intervals.Co-ordinating editor: J. Tuomi     

Spatio‐temporal analysis of the role of faecal depositions in aggregation behaviour of the triatomine Rhodnius prolixus

Several triatomine species aggregate over conspecific faeces. In some domestic species, this behaviour might help individuals to find their refuges because faeces are usually deposited around such places. In the present study, the defaecation behaviour of the triatomine bug Rhodnius prolixus Stål (Heteroptera: Reduviidae) is described in detail, including the temporal pattern of aggregation of nymphs with different nutritional status to faeces of different post‐deposition times. First, using an experimental arena, the spatial distribution of faecal deposition spots released by nymphs, in relation to the position of a refuge, is recorded. The results show that a high density of faeces is deposited inside the refuge, and few and distant spots, in relation to the position of the refuge, are dropped outside. Second, whether the aggregation behaviour of nymphs is altered by the time elapsed from deposition of the faeces, and by the nutritional status of the insects, is determined. The post‐deposition time of the faeces strongly modulates the aggregation response of the insects. Differences in aggregation between fed and unfed insects are only marginally significant; however, different temporal windows of aggregation according to the post‐deposition times of the faeces are demonstrated between bugs of different nutritional status. The results are discussed with respect to the relevance of the aggregation signal in relation to the characteristics of the natural refuges used by R. prolixus.     

Consequences of refuge for the functional response of Dermestes ater (Coleoptera: Dermestidae) to Musca domestica (Diptera: Muscidae)

It is well known that a predator has the potential to regulate a prey population only if the predator responds to increases in prey density and inflicts greater mortality rates. Predators may cause such density-dependent mortality depending on the nature of the functional and numerical responses. Yet, few studies have examined the relationship between the addition of refuges and the characteristic of functional response fits. We investigated whether addition of a refuge changed the type of functional response exhibited by Dermestes ater on Musca domestica, comparing the inherent ability of D. ater to kill houseflies in the absence and in the presence of refuge. An additional laboratory experiment was also carried out to assess handling and searching times exhibited by D. ater. Logistic regression analyses revealed a type III functional response for predator–prey interaction without refuge, and results were described by the random predator equation. The mean number of prey killed did not differ between experimental habitats, indicating that the addition of refuge did not inhibit predation. However, predators that interacted with prey without refuge spent less time searching for prey at higher densities, increasing predatory interaction. We concluded that this interaction may be weak, because data from experiments with refuge fitted poorly to models. However, the high variability and the nonsignificance of the data from the experiment with refuge show the importance of refuge for promoting spatial heterogeneity, which may prevent prey extinction.     

Selection of food patches by sympatric herbivores in response to concealment and distance from a refuge

Small herbivores face risks of predation while foraging and are often forced to trade off food quality for safety. Life history, behaviour, and habitat of predator and prey can influence these trade‐offs. We compared how two sympatric rabbits (pygmy rabbit, Brachylagus idahoensis; mountain cottontail, Sylvilagus nuttallii) that differ in size, use of burrows, and habitat specialization in the sagebrush‐steppe of western North America respond to amount and orientation of concealment cover and proximity to burrow refuges when selecting food patches. We predicted that both rabbit species would prefer food patches that offered greater concealment and food patches that were closer to burrow refuges. However, because pygmy rabbits are small, obligate burrowers that are restricted to sagebrush habitats, we predicted that they would show stronger preferences for greater cover, orientation of concealment, and patches closer to burrow refuges. We offered two food patches to individuals of each species during three experiments that either varied in the amount of concealment cover, orientation of concealment cover, or distance from a burrow refuge. Both species preferred food patches that offered greater concealment, but pygmy rabbits generally preferred terrestrial and mountain cottontails preferred aerial concealment. Only pygmy rabbits preferred food patches closer to their burrow refuge. Different responses to concealment and proximity to burrow refuges by the two species likely reflect differences in perceived predation risks. Because terrestrial predators are able to dig for prey in burrows, animals like pygmy rabbits that rely on burrow refuges might select food patches based more on terrestrial concealment. In contrast, larger habitat generalists that do not rely on burrow refuges, like mountain cottontails, might trade off terrestrial concealment for visibility to detect approaching terrestrial predators. This study suggests that body size and evolutionary adaptations for using habitat, even in closely related species, might influence anti‐predator behaviors in prey species.     

Performance as a fish predator of largemouth bass [<Emphasis Type="Italic">Micropterus salmoides</Emphasis> (Lacepède)] invading Japanese freshwaters: a review

This review focuses on how predator performance of the invasive largemouth bass [Micropterus salmoides (Lacepède)] has been, or will be, formed in Japanese freshwaters. Predation impacts of largemouth bass on fish communities appear pervasive in both Japanese as well as North American freshwaters. Factors affecting performance as a piscivorous predator are (1) light intensity and water clarity, (2) oxygen depletion, (3) prey size and gape size, (4) behavioral refuge of prey, (5) weed beds as refuge for prey fish, (6) interaction with bluegill. Size and behavioral refuges requirements are so rigorous that they may have evolved only in some North American prey fish species like bluegill; therefore, most Japanese native fish species are unlikely to be equipped with such refuges. However, refuge habitats like aquatic weed beds could develop in Japanese freshwaters, allowing prey fish species to survive under predation pressure. The density, architecture, and species composition of aquatic plants may affect their suitability as refuges. Studies in Japanese waters have suggested that the presence of rich aquatic vegetation or invasive bluegill in bass-introduced waters have suppressed the predation impact of largemouth bass on fish communities. In addition to these environmental factors, original genotypic and phenotypic traits of the introduced largemouth bass, and hybridization between different lineages of largemouth bass or with Florida bass [Micropterus floridanus (Lesueur)] may be involved in further adaptation of invasive largemouth bass to Japanese freshwaters.     

Evolution of resistance to Bt crops: directional selection in structured environments

Abstract Widespread use of transgenic crops that express an insecticidal endotoxin from Bacillus thuringiensis increases the risk of evolution of resistance by the European corn borer and other insect pests. To delay resistance evolution, the high‐dose/refuge strategy is being implemented for Bt maize and Bt cotton. We develop a general modelling framework to understand the invasion and spread of alleles conferring resistance. We show that at least three processes are involved in explaining the effectiveness of the high‐dose/refuge strategy: the intensity of selection, assortative (non‐random) mating due to spatial subdivision, and variation in male mating success also due to spatial subdivision. Understanding these processes leads to a greater range of possible resistance management tactics. For example, efforts to encourage adults to leave their natal fields may have the unwanted effect of speeding rather than slowing resistance evolution. Furthermore, when Bt maize causes high mortality to susceptible target pests, spraying insecticides in refuges to reduce pest populations may not greatly disrupt resistance management.     

Parasitoid and moth movement from refuge to crop

Refuges may provide habitat and resources which enhance population size of natural enemies of herbivorous pests and add to their colonisation into target crops, potentially increasing effectiveness of biological control. They may also allow for an increase in numbers of herbivorous pests. In addition, these refuges may be attractive so that natural enemies aggregate there, neglecting predation and parasitism of pests in the crop. We investigate the movements of marked Diadegma semiclausum (Hellén) a key larval parasitoid, and the adult stage of the host it attacks, diamondback moth, Plutella xylostella (L.), from an on-farm flowering refuge of Brassica vegetables to the Brassica crop. Our results showed that parasitoids and moths visit the flowering refuge, and that they move from the refuge into the crop before and after disturbing the refuge by ploughing. For D. semiclausum, the pattern of movement from the refuge into the crop was similar for males and females, but more males than females were captured. Ploughing the refuge resulted in increased dispersal by males but not females into the crop. Neither moths nor parasitoids preferentially aggregated around the flowering refuge, instead most often their spatial pattern was random throughout the field indicating that they are quite vagile, quickly moving to distances >100 m. This basic understanding of the movements of these insects has implications beyond this system and is relevant to any agricultural system implementing a refuge to enhance natural enemy effectiveness.     

Recruitment of marine invertebrates: the role of active larval choices and early mortality

Summary Spatial variation in the recruitment of sessile marine invertebrates with planktonic larvae may be derived from a number of sources: events within the plankton, choices made by larvae at the time of settlement, and mortality of juvenile organisms after settlement, but before a census by an observer. These sources usually are not distinguished.A study of the recruitment of four species of sessile invertebrates living on rock walls beneath a kelp canopy showed that both selection of microhabitats by settling larvae and predation by fish may be important. Two microhabitats were of interest; open, flat rock surfaces, and small pits and crevices that act as refuges from fish predators.The polychaete Spirorbis eximus and the cyclostome bryozoan Tubulipora spp. showed no preference for refuges, but settled apparently at random on the available substrata. Tubulipora was preyed upon heavily by fish, while Spirorbis was relatively unaffected. The bryozoans Celleporaria brunnea and Scrupocellaria bertholetti both recruited preferentially into refuges. Scrupocellaria were preyed upon, while Celleporaria juveniles seemed unaffected. Predation by fish modified the spatial distribution (Tubulipora), abundance (Tubulipora), or size distribution (Scrupocellaria) of the juvenile population, or had relatively little effect (Celleporaria, Spirorbis).All of the above events occur within three weeks of settlement. Since inferences about the effect of larval events on the population dynamics of adult organisms are often based on observations of the patterns of recruitment after one or two months, they are therefore likely to be misleading.     

Turbulence disturbs vertical refuge use by Chaoborus flavicans larvae and increases their horizontal dispersion

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DNA-Based Population Demographics of Black Bears in Coastal North Carolina and Virginia

ABSTRACT Noninvasive genetic sampling has become a popular method for obtaining population parameter estimates for black (Ursus americanus) and brown (U. arctos) bears. These estimates allow wildlife managers to develop appropriate management strategies for populations of concern. Black bear populations at Great Dismal Swamp (GDSNWR), Pocosin Lakes (PLNWR), and Alligator River (ARNWR) National Wildlife Refuges in coastal Virginia and North Carolina, USA, were perceived by refuge biologists to be at or above cultural and perhaps biological carrying capacity, but managers had no reliable abundance estimates upon which to base population management. We derived density estimates from 3,150 hair samples collected noninvasively at each of the 3 refuges, using 6–7 microsatellite markers to obtain multilocus genotypes for individual bears. We used Program MARK to calculate population estimates from capture histories at each refuge. We estimated densities using both traditional buffer strip methods and Program DENSITY. Estimated densities were some of the highest reported in the literature and ranged from 0.46 bears/km² at GDSNWR to 1.30 bears/km² at PLNWR. Sex ratios were male-biased at all refuges. Our estimates can be directly utilized by biologists to develop effective strategies for managing and maintaining bears at these refuges, and noninvasive methods may also be effective for monitoring bear populations over the long term.     

Quantifying rates of random mating in western corn rootworm emerging from Cry3Bb1‐expressing and refuge maize in field cages

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is the most significant pest of field maize, Zea mays L. (Poaceae), in the USA. Maize plants expressing Bt toxins targeting the corn rootworm complex have been widely adopted and are the primary insecticidal control measure for this pest in North America. Insect resistance management tactics using various refuge structures have been adopted to ensure Bt products will retain durability. An assumption of the refuge strategy is that males and females emerging from Bt and refuge plantings mate randomly; this has not been tested in the field. We conducted cage studies using field populations of WCR in Indiana, USA, to generate empirical field data on mating rates between beetles emerging from Cry3Bb1‐expressing Bt and refuge maize plants. Two refuge configurations were tested; all refuge plants were labeled using the stable isotope ¹⁵N. This mark persists in adult beetles after eclosion, allowing for collection and analysis of isotopic ratios of all beetles. Additional data collected included adult emergence rates, timing and sex ratios for each of the treatments, and head capsule size and dry weights of beetles collected. Treatment had a significant effect on dry weight; mean dry weight decreased in Bt‐only treatments. Fisher's exact test of proportions of mating pairs of refuge and Bt insects indicated that mating was not random in 20% strip refuges and 5% seed blend treatments. We found high percentages of beetles that fed on Bt‐expressing plants as larvae, suggesting that mating between resistant beetles may not be rare even if random mating did occur.     

Experimental manipulation reveals the importance of refuge habitat temperature selected by lizards

Refuges provide shelter from predators, and protection from exposure to the elements, as well as other fitness benefits to animals that use them. In ectotherms, thermal benefits may be a critical aspect of refuges. We investigated microhabitat characteristics of refuges selected by a heliothermic scincid lizard, Carlia rubrigularis, which uses rainforest edges as habitat. We approached lizards in the field, simulating a predator attack, and quantified the refuge type used, and effect of environmental temperatures (air temperature, substrate temperature and refuge substrate temperature) on the amount of time skinks remained in refuges after hiding (emergence time). In respone to our approach, lizards were most likely to flee into leaf litter, rather than into rocks or woody debris, and emergence time was dependent on refuge substrate temperature, and on refuge substrate temperature relative to substrate temperature outside the refuge. Lizards remained for longer periods in warmer refuges, and in refuges that were similar in temperature to outside. We examined lizard refuge choice in response to temperature and substrate type in large, semi‐natural outdoor enclosures. We experimentally manipulated refuge habitat temperature available to lizards, and offered them equal areas of leaf litter, woody debris and rocks. When refuge habitat temperature was unmanipulated, lizards (85%) preferred leaf litter, as they did in the field. However, when we experimentally manipulated the temperature of the leaf litter by shading, most skinks (75%) changed their preferred refuge habitat from leaf litter to woody debris or rocks. These results suggest that temperature is a critical determinant of refuge habitat choice for these diurnal ectotherms, both when fleeing from predators and when selecting daytime retreats.