Do house mice use UV cues when foraging?

Research on the behavioural ecology of ultraviolet (UV-A, wavelengths of 320–400 nm, hereafter: UV) sensitivity in terrestrial vertebrates has mainly focused on sexual signalling and foraging in birds and reptiles, whereas the fact that some rodents are also sensitive to UV light has been somewhat ignored. Here, we present the results of two behavioural experiments, which tested whether rodents use UV cues in foraging. In the first experiment we asked whether the colour contrast in the UV waveband is used as a foraging cue. House mice were offered UV-reflecting and UV-absorbing artificial food items in two different illuminations where UV light was either present or absent. The food items were offered to two groups of mice, one group on a UV-reflecting and the other on a UV-absorbing background. The second experiment investigated more specifically whether UV cues are especially important in dawn and dusk when short wavelengths are high in the proportion of available light. House mice showed no preference between the food items regardless of illumination or background. Therefore, our results indicate that house mice do not use UV cues in foraging.     

Do female black field crickets Teleogryllus commodus benefit from polyandry?

Female insects that mate multiply tend to have increased lifetime fitness, apparently because of greater access to male-derived resources (e.g. sperm, nuptial gifts) that elevate fertility/fecundity. Experiments that standardize the number of matings per female also show that polyandry can improve aspects of offspring performance, most notably early embryo survival (egg hatching success). This improvement is widely attributed to genetic benefits which would arise if polyandrous females skew paternity to produce fitter offspring. In two separate experiments with field crickets (Teleogryllus commodus) polyandrous females (two, three or four mates) did not have higher egg hatching success than monandrous females (effect sizes: r = 0.03 and 0.08 for the respective experiments), which is consistent with our finding of no sire effect on hatching success. Polyandry also had no effect on post-hatching offspring survival. Polyandrous females' offspring took significantly longer to mature but their sons were not heavier and their daughters were actually significantly smaller than those of monandrous females. Finally, after controlling for relative male size, monandrous females' sons were more successful when directly competing for a mate.     

Do gravid females become selfish? Female allocation of energy during gestation

Net energy availability depends on plasma corticosterone concentrations, food availability, and their interaction. Limited net energy availability requires energy trade-offs between self-maintenance and reproduction. This is important in matrotrophic viviparous animals because they provide large amounts of energy for embryos, as well as self-maintenance, for the extended period of time during gestation. In addition, gravid females may transmit environmental information to the embryos in order to adjust offspring phenotype. We investigated effects of variation in maternal plasma corticosterone concentration and maternal food availability (2 × 2 factorial design) during gestation on offspring phenotype in a matrotrophic viviparous lizard (Pseudemoia entrecasteauxii). Subsequently, we tested preadaptation of offspring phenotype to their postnatal environment by measuring risk-averse behavior and growth rate using reciprocal transplant experiments. We found that maternal net energy availability affected postpartum maternal body condition, offspring snout-vent length, offspring mass, offspring performance ability, and offspring fat reserves. Females treated with corticosterone allocated large amounts of energy to their own body condition, and their embryos allocated more energy to energy reserves than somatic growth. Further, offspring from females in high plasma corticosterone concentration showed compensatory growth. These findings suggest that while females may be selfish when gestation conditions are stressful, the embryos may adjust their phenotype to cope with the postnatal environment.     

Blue tail and striped body: why do lizards change their infant costume when growing up?

Ontogenetic changes in color and pattern that are not directlyrelated to reproduction are very common yet remain a poorlyunderstood phenomenon. One example is conspicuous colors inthe tails of fish, amphibians, and reptiles that fade out laterin life. We suggest a novel hypothesis: conspicuous tail colorsthat appear only in juveniles compensate for an increased activitylevel, deflecting imminent attacks to the tail. We observedblue-tailed, newly hatched lizards (Acanthodactylus beershebensis)in the field and compared 5 behavioral parameters with thoseof older individuals that had already lost their neonate coloration.In addition, we explored whether tail displays, often assumedto direct a predator's attention to the tail, disappear withthe color change. Striped blue-tailed hatchlings foraged moreactively than 3-week-old juveniles, spent a longer time in openmicrohabitats, and performed deflective tail displays. In comparison,2 other lacertids that do not undergo ontogenetic change didnot switch to safer foraging when growing up. The results suggestthat activity alteration may be a major factor affecting theontogenetic color and pattern change. Active lizards that foragein open habitats increase their probability of attack by ambushpredators. Conspicuous colors and deflection displays may shiftattacks to the expendable tail, increasing the prey's overallprobability of surviving attacks. The persistence of both stripedbody pattern and blue tail fits the active foraging period ofneonates and hence may be appropriate for other species thatdisplay a conspicuous tail accompanied by a striped pattern.     

Do patients with diabetic neuropathy use a higher proportion of their maximum strength when walking?

Diabetic patients have an altered gait strategy during walking and are known to be at high risk of falling, especially when diabetic peripheral neuropathy is present. This study investigated alterations to lower limb joint torques during walking and related these torques to maximum strength in an attempt to elucidate why diabetic patients are more likely to fall. 20 diabetic patients with moderate/severe peripheral neuropathy (DPN), 33 diabetic patients without peripheral neuropathy (DM), and 27 non-diabetic controls (Ctrl) underwent gait analysis using a motion analysis system and force plates to measure kinetic parameters. Lower limb peak joint torques and joint work done (energy expenditure) were calculated during walking. The ratio of peak joint torques and individual maximum joint strengths (measured on a dynamometer) was then calculated for 59 of the 80 participants to yield the ‘operating strength’ for those participants. During walking DM and DPN patients showed significantly reduced peak torques at the ankle and knee. Maximum joint strengths at the knee were significantly less in both DM and DPN groups than Ctrls, and for the DPN group at the ankle. Operating strengths were significantly higher at the ankle in the DPN group compared to the Ctrls. These findings show that diabetic patients walk with reduced lower limb joint torques; however due to a decrement in their maximum ability at the ankle and knee, their operating strengths are higher. This allows less reserve strength if responding to a perturbation in balance, potentially increasing their risk of falling.     

Does capacity of DNA replication change during in vitro ageing?

We described elsewhere how a lack of change in the rate of DNA chain elongation occurred during in vitro ageing of human diploid fibroblasts. Here we further examined the rate of actual incorporation of tritiated thymidine, the center-to-center distance of replicons and the length of each phase of the cell cycle in order to extend our previous results to the other aspects of DNA replication. The results obtained showed that the rate of net DNA synthesis, the replicon size and the duration of S phase did not change during in vitro ageing. Our findings indicated that the reason why the greater part of the cell population at high population doubling levels becomes incapable of proliferating might not be the gradual decline in the ability of DNA replication. The regulation system(s) of DNA replication may alter during the period of culturing without any change in the capacities of the DNA replication machinery and, consequently, the non-cycling cells increase.     

Do trails affect relative abundance estimates of rainforest frogs and lizards?

The selection of a sampling protocol is critical to study amphibian and reptile communities and in many instances researchers have combined the use of visual encounter surveys (VES) conducted on trails and off trails. The effect of human‐made trails on relative abundance estimates of amphibians and reptiles has been assessed in a few temperate locations, but data are lacking for tropical sites. Our study was designed to address this issue by comparing abundance estimates of frogs and lizards on and off trails in a lowland rainforest in south‐eastern Perú. We used nocturnal VES to sample frogs and lizards along transects established on trails and off trails in two different forest types. We found that the observed relative abundance estimates of frogs and lizards were affected by the location of transects (on trail vs. off trail) and the type of forest (floodplain forest vs. terra firme forest). We also found an interaction between the two main effects, indicating that the effect of transect location with respect to trails varies as a function of habitat. Observed frog abundances were higher on trails than off trails, indicating that studies that include VES on trails will bias relative abundance estimates in contrast to studies that include only VES off trails. We suggest that transects should be established only off trails, especially for monitoring studies because trail use by humans can have a strong influence on observed animal abundance.     

Does land use change influence predation of bird nests?

Worldwide, many areas of agricultural land which were once covered with native vegetation have been converted to tree plantations. Such landscape transformation can influence the dynamics of wildlife populations through, for example, altering rates of predation (e.g. predation of nests of birds). Nest predation can influence reproductive success and, in turn, may alter populations by affecting juvenile recruitment. We quantified predation of bird nests in woodland remnants surrounded by two types of land use, grazing farmland and exotic Radiata pine (Pinus radiata) plantation. We also examined differences in predation rates between artificial and natural nests. We found both artificial and natural nests were more susceptible to nest predation in woodland remnants surrounded by a pine plantation than in woodland remnants located within farmland. Our study suggests that higher levels of nest predation may reduce occupancy of woodland remnants by small‐bodied birds over time, including species of conservation concern. This may have been occurred as a result of the conversion of semi‐cleared grazing land to exotic pine plantation.     

Do different speed types of action potentials exist in higher plants?

The problem of paradoxically different values of speeds of the propagation of action potentials in conduction pathways of higher plants is considered. Possible causes of this phenomenon are discussed.     

Do female tamarins use visual cues to detect fruit rewards more successfully than do males?

Primates are unique among eutherian mammals for possessing trichromatic colour vision. It is generally proposed that trichromacy evolved to aid detection of ripe fruits against mature foliage. However, while trichromacy is routine in all Old World monkeys and apes (the catarrhines), a cone opsin polymorphism in New World monkeys (the platyrrhines) results in foraging groups with mixed capacities for chromatic distinction. Although 50-66% of female platyrrhines are trichromatic, all males are dichromatic. Here, we test the hypothesis that trichromatic platyrrhines use visual cues to detect fruit rewards more successfully than do males. Specifically, we ask whether female emperor tamarins, Saguinus imperator imperator, and saddleback tamarins, S. fuscicollis weddelli, are the first members of their foraging group to locate food patches; and, furthermore, whether they are more successful than males in using colour, shape and size cues to discriminate between sham and reward feeding sites. Our results show that females and males do not differ in their ability to locate or discriminate between feeding sites. We conclude that trichromatic vision in female tamarins does not confer an advantage for detecting yellow fruit rewards against mature foliage. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Trichomes as dangerous lollipops: Do lizards also use caterpillar body and frass odor to optimize their foraging?

When attacked by herbivores, plants produce toxic secondary metabolites that function as direct defenses, as well as indirect defenses that attract and reward predators of the offending herbivores. These indirect defenses include both nutritive rewards such as extra floral nectar, as well as informational rewards, such as the production and release of volatile compounds that betray the location of feeding herbivores to predators. Herbivory of Nicotiana attenuata by the tobacco hornworm (Manduca larvae) alters the volatile profiles of both the plant and larval headspace. Herbivory-elicited specific changes in the volatile profiles are detected by arthropod predators of Manduca larvae. The known predators that perceive volatile cues induced by Manduca herbivory of N. attenuata are insects that target Manduca at early developmental stages, when the larvae are still small; large, late-instar larvae may have outgrown these predation risks. However, here we offer evidence that branched chain aliphatic acids derived from the digestion of plant O-acyl sugars from trichomes may betray Manduca larvae to lizard predators during late developmental stages as well.     

Persistence of community structure: what happens when you change taxonomic scale?

It is common in community ecology to use the species as the taxonomic category of interest, yet in rich tropical assemblages containing guilds of very similar species this may not be appropriate. Such assemblages may be organized at the level of guilds rather than at the finer species level. In a ten-year study of assemblages of fish at One Tree Reef, Great Barrier Reef, we found species composition and the number of fish on a given lagoonal patch reef vary greatly across time (Sale and Douglas 1984; Sale et al. in preparation). The mean average proportional similarity of a reef's assemblage to itself at different times (censuses) is usually low at a value of around 0.5. This apparent variability may be ecologically irrelevant noise if organization is at the higher guild level. We have recast our database at the guild level to test this possibility. Thirteen guilds were defined by the diets, foraging habitats and times of the individual species comprising them. Similarity of an assemblage to itself at successive censuses was re-calculated using the number of individuals in each guild instead of the numbers in each species. This analysis yielded significantly higher levels of similarity (P<0.01) among censuses. To test whether this increase in similarity was due solely to the smaller number of categories used to calculate the similarity indices, 5 sets of randomly generated guilds were constructed using a Monte Carlo approach. No significant difference (P>0.05) was found between the average similarity among censuses when assemblages were classified into these null guilds and when they were classified according to the real guilds. These results indicate that shifting to the larger taxonomic scale of guilds does not reveal a significantly more persistent assemblage structure than that revealed when analysis is at the smaller scale of species. There is no evidence of an underlying organization of these assemblages at the guild level.     

Efficacy evaluation of anthelmintics: which methods to use in the field?

Efficacy evaluation of anthelmintics is very important even in veterinary practice due to the existence of acquired resistance, poor quality of anthelmintics in several region of the world, and nedds for quarantine strategy prior introduction of new animals. Clearly, flock evaluation can be opposed to individually based evaluations. I propose that individually based evaluations should be preferred in field condition controls: although they are more sophisticated on a statistical basis, the availability of a software for calculations renders the proposal realistic.     

Do immigrant female bonobos prefer older resident females as important partners when integrating into a new group?

Primates - Intergroup transfer is a critical part of the life history of group-living species, with considerable variation in its timings and patterns among species. Immigrant female bonobos are...     

Know when to run,know when to hide: can behavioral differences explain the divergent invasion success of two sympatric lizards?

Invasive species represent a select subset of organisms that have successfully transitioned through each stage of the introduction process (transportation, establishment, and spread). Although there is a growing realization that behavior plays a critical role in invasion success, few studies have focused on the initial stages of introduction. We examined whether differences in the grouping tendencies and exploratory behavior of two sympatric lizard species could contribute to their divergent invasion success. While the nondirected activity of the two species did not differ, the invasive delicate skink (Lampropholis delicata) was found to be more exploratory than the congeneric noninvasive garden skink (L. guichenoti), which enabled it to more effectively locate novel environments and basking site resources. The delicate skink also exhibited a greater tendency to hide, which may act to enhance its probability of ensnarement in freight and cargo and decrease its likelihood of detection during transit. The grouping tendencies of the two species did not differ. Together, our results suggest that while the two species have an equivalent "opportunity" for unintentional human-assisted transportation, several pre-existing behavioral traits may enhance the success of the delicate skink in negotiating the initial stages of the introduction process, and subsequent post-establishment spread.     

Do hormonal changes that appear at the onset of puberty determine the strategies used by female rats when solving a navigation task?

The present set of experiments evaluated the possibility that the hormonal changes that appear at the onset of puberty might influence the strategies used by female rats to solve a spatial navigation task. In each experiment, rats were trained in a triangular shaped pool to find a hidden platform which maintained a constant relationship with two sources of information, one individual landmark and one corner of the pool with a distinctive geometry. Then, three test trials were conducted without the platform in counterbalanced order. In one, both the geometry and the landmark were simultaneously presented, although in different spatial positions, in order to measure the rats' preferences. In the remaining test trials what the rats had learned about the two sources of information was measured by presenting them individually. Experiment 1, with 60-day old rats, revealed a clear sex difference, thus replicating a previous finding (Rodríguez et al., 2010): females spent more time in an area of the pool that corresponded to the landmark, whereas males spent more time in the distinctive corner of the pool even though the remaining tests revealed that both sexes had learned about the two sources of information. In Experiment 2, 30-day old female rats, unlike adults, preferred to solve the task using the geometry information rather than the landmark (although juvenile males behaved in exactly the same way as adults). Experiment 3 directly compared the performance of 90- and 30-day old females and found that while the adult females preferred to solve the task using the landmark, the reverse was true in juvenile females. Experiment 4 compared ovariectomized and sham operated females and found that while sham operated females preferred to solve the task using the landmark, the reverse was true in ovariectomized females. Finally, Experiment 5 directly compared adult males and females, juvenile males and females, and ovariectomized females and found that adult males, juvenile males and females, and ovariectomized females did not differ among them in their preferred cue, but they all differed from adult females.     

Predicting future distributions of mountain plants under climate change: does dispersal capacity matter?

Many studies have investigated the potential impacts of climate change on the distribution of plant species, but few have attempted to constrain projections through plant dispersal limitations. Instead, most studies published so far have simplified dispersal as either unlimited or null. However, depending on the dispersal capacity of a species, landscape fragmentation, and the rate of climatic change, these assumptions can lead to serious over- or underestimation of the future distribution of plant species.
To quantify the discrepancies between simulations accounting for dispersal or not, we carried out projections of future distribution over the 21st century for 287 mountain plant species in a study area of the western Swiss Alps. For each species, simulations were run for four dispersal scenarios (unlimited dispersal, no dispersal, realistic dispersal, and realistic dispersal with long-distance dispersal events) and under four climate change scenarios.
Although simulations accounting for realistic dispersal limitations did significantly differ from those considering dispersal as unlimited or null in terms of projected future distribution, the unlimited dispersal simplification did nevertheless provide good approximations for species extinctions under more moderate climate change scenarios. Overall, simulations accounting for dispersal limitations produced, for our mountainous study area, results that were significantly closer to unlimited dispersal than to no dispersal. Finally, analysis of the temporal pattern of species extinctions over the entire 21st century revealed that important species extinctions for our study area might not occur before the 2080–2100 period, due to the possibility of a large number of species shifting their distribution to higher elevation.     

Do metal-rich plants deter herbivores? A field test of the defence hypothesis

Some plant species growing on metalliferous soils are able to accumulate heavy metals in their shoots up to very high concentrations, but the selective advantage of this behaviour is still unknown. The most popular hypothesis, that metals protect plants against herbivores, has been tested several times in laboratory conditions, with contradictory results. We carried out the first large-scale test of the defence hypothesis in eight natural populations of the model Zn hyperaccumulator Thlaspi caerulescens J. and C. Presl (Brassicaceae). In two climatic regions (temperate, Belgium–Luxembourg, and Mediterranean, southern France), we worked in metalliferous and in normal, uncontaminated environments, with plants spanning a wide range of Zn concentrations. We also examined the importance of glucosinolates (main secondary metabolites of Brassicaceae) as antiherbivore defences. When exposed to natural herbivore populations, T. caerulescens suffered lower herbivory pressures in metal-enriched soils than in normal soils, both in Belgium–Luxembourg and in southern France. The trapping of gastropods shows an overall lower population density in metalliferous compared to normal environments, which suggests that herbivory pressure from gastropods is lower on metalliferous soils. In addition, foliar concentration of glucosinolates was constitutively lower in all populations from metal-enriched soils, suggesting that these have evolved towards lower investment in organic defences in response to lower herbivory pressure. The Zn concentration of plants had a protective role only for Belgian metallicolous plants when transplanted in normal soils of Luxembourg. These results do not support the hypothesis that Zn plays a key role in the protection of T. caerulescens against enemies. In contrast, glucosinolates appear to be directly involved in the defence of this hyperaccumulator against herbivores.     

Matrix dimensionality in demographic analyses of plants: when to use smaller matrices?

Large data requirements may restrict the use of matrix population models for analysis of population dynamics. Less data are required for a small population matrix than for a large matrix because the smaller matrix contains fewer vital rates that need to be estimated. Smaller matrices, however, tend to have a lower precision. Based on 37 plant species, we studied the effects of matrix dimensionality on the long-term population growth rate (λ) and the elasticity of λ in herbaceous and woody species. We found that when matrix dimensionality was reduced, changes in λ were significantly larger for herbaceous than for woody species. In many cases, λ of woody species remained virtually the same after a substantial decrease in matrix dimensionality, suggesting that woody species are less susceptible to matrix dimensionality. We demonstrated that when adjacent stages of a transition matrix are combined, the magnitude of a change in λ depends on the distance of the population structure from a stable stage distribution, and the difference in the combined vital rates weighted by their reproductive values. Elasticity of λ to survival and fecundity usually increased, whereas elasticity to growth decreased both in herbaceous and in woody species with reduced matrix dimensionality. Changes in elasticity values tended to be larger for herbaceous than for woody species. Our results show that by reducing matrix dimensionality, the amount of demographic data can be decreased to save time, money, and field effort. We recommend the use of a small matrix dimensionality especially when a limited amount of data is available, and for slow-growing species having a simple matrix structure that mainly consists of stasis and growth to the next stage.