The impact of salinity exposure on survival and temperature tolerance of the Antarctic collembolan Cryptopygus antarcticus

The collembolan Cryptopygus antarcticus Willem is potentially exposed to habitat salinities equal to (or greater than) sea water, as a result of sea spray, drying of littoral habitats, dispersal or temporary entrapment on the surface of sea water, or exposure to localized salt deposits from dense vertebrate populations on terrestrial habitats. To test the impact of this exposure on C. antarcticus, the tolerance of the collembolan to being placed on the surface of sea water and solutions of higher salt concentrations is investigated. The effects of acclimation to exposure to liquids of different salinities [44, 100 and 200 parts per thousand (ppt) sea salt] on cold and heat tolerance, as well as thermal activity thresholds, are also explored. Cryptopygus antarcticus shows > 75% survival after 10 days of exposure to both sea water and 100‐ppt salt, whereas it exhibits significantly lower survival after 5 days (60% survival) and 10 days (40%) of exposure to a 200‐ppt solution. Body water content also decreases after exposure to all salinities, and particularly to the 200‐ppt solution, in which > 50% of body water is lost after 10 days. Acclimation results in greater cold tolerance, although heat tolerance at 33, 35 and 37 °C is either unaltered or reduced. The thermal activity thresholds of C. antarcticus at both high and low temperatures are also negatively affected by saline exposure. The data demonstrate the capacity of C. antarcticus to tolerate periods of exposure to saline conditions, and also show that this exposure can enhance cross‐tolerance to low temperatures. The present study also demonstrates that salinity‐associated stress at moderately low and high temperatures narrows the thermal range of activity, thus reducing the ability of collembolans to forage, develop and reproduce. © 2013 The Royal Entomological Society     

A COMPUTER-BASED TECHNIQUE FOR THE QUANTITATIVE ANALYSIS OF ANIMAL SOUNDS

ABSTRACT

The method usually used to identify different sounds or divisions of sounds is to compare sonagrams visually. There have been some attempts to reduce the subjectivity and increase the repeatability of this approach, for example by tracing the sonagrams onto paper and examining the areas of overlap and mismatch, the use of multi-variate statistics and digitising tablets. Digital recording of sounds has allowed sounds to be input directly into computers which can be used to display sounds and facilitate measurement. To date there has been little attempt at their use for analysis. We outline a series of programs which have been developed to compare statistically any unit of a sound with a pre-recorded library of similar units. The creation of such a library allows the rapid and objective categorisation of large numbers of sounds. These programs have been used to analyse songs recorded from wrens Troglodytes troglodytes and house crickets Acheta domesticus. Potential applications of this software to the field of bioacoustic investigation are discussed.     

A native dasyurid predator (common planigale,Planigale maculata) rapidly learns to avoid a toxic invader

Abstract Interactions between invasive species and native fauna afford a unique opportunity to examine interspecific encounters as they first occur, without the complications introduced by coevolution. In northern Australia, the continuing invasion of the highly toxic cane toad Bufo marinus poses a threat to many frog‐eating predators. Can predators learn to distinguish the novel toxic prey item from native prey (and thus, avoid being poisoned), or are longer‐term genetically based changes to attack behaviour needed before predators can coexist with toads? To predict the short‐term impact of cane toads on native predators, we need to know the proportion of individuals that will attack toads, the proportion surviving the encounter, and whether surviving predators learn to avoid toads. We quantified these traits in a dasyurid (common planigale, Planigale maculata) that inhabits tropical floodplains across northern Australia. Although 90% of naïve planigales attacked cane toads, 83% of these animals survived because they either rejected the toad unharmed, or killed and consumed the prey snout‐first (thereby avoiding the toxin‐laden parotoid glands). Most planigales showed one‐trial learning and subsequently refused to attack cane toads for long time periods (up to 28 days). Toad‐exposed planigales also avoided native frogs for up to 9 days, thereby providing an immediate benefit to native anurans. However, the predators gradually learnt to use chemical cues to discriminate between frogs and toads. Collectively, our results suggest that generalist predators can learn to distinguish and avoid novel toxic prey very rapidly – and hence, that small dasyurid predators can rapidly adapt to the cane toad invasion. Indeed, it may be feasible to teach especially vulnerable predators to avoid cane toads before the toads invade, by deploying low‐toxicity baits that stimulate taste‐aversion learning.     

Factors Affecting Detection of Burrowing Owl Nests During Standardized Surveys

Abstract: Identifying causes of declines and evaluating effects of management practices on persistence of local populations of burrowing owls (Athene cunicularia) requires accurate estimates of abundance and population trends. Moreover, regulatory agencies in the United States and Canada typically require surveys to detect nest burrows prior to approving developments or other activities in areas that are potentially suitable for nesting burrowing owls. In general, guidelines on timing of surveys have been lacking and surveys have been conducted at different times of day and in different stages of the nesting cycle. We used logistic regression to evaluate 7 factors that could potentially affect probability of a surveyor detecting a burrowing owl nest. We conducted 1,444 detection trials at 323 burrowing owl nests within 3 study areas in Washington and Wyoming, USA, between February and August 2000–2002. Detection probability was highest during the nestling period and increased with ambient temperature. The other 5 factors that we examined (i.e., study area, time of day, timing within the breeding season, wind speed, % cloud cover) interacted with another factor to influence detection probability. Use of call-broadcast surveys increased detection probability, even during daylight hours when we detected >95% of owls visually. Optimal timing of surveys will vary due to differences in breeding phenology and differences in nesting behavior across populations. Nevertheless, we recommend ≥3 surveys per year: one that coincides with the laying and incubation period, another that coincides with the early nestling period, and a third that coincides with the late nestling period. In northern latitudes, surveys can be conducted throughout the day. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):688–696; 2008)     

Evaluation of Electric Fencing to Inhibit Feral Pig Movements

Abstract: Natural resource managers and agricultural producers are seeking innovative tools to minimize damages caused by rapidly expanding feral pig (Sus scrofa) populations. One tool that has received little scientific inquiry is the use of exclusion fences to protect economically and ecologically sensitive areas. Our objectives were to evaluate the ability of electric fencing to minimize feral pig movements in a captive setting as well as in rangeland and agriculture land. In captivity, we tested a 1-, 2-, and 3-strand electric fence. In our captive trial, we found 65% fewer intrusions (F_2,18 = 20.46, P < 0.001) for electric fences (x̄ = 12.4, SE = 2.8) compared with nonelectric fences (x̄ = 35.6, SE = 6.9). We found no difference (F_2,9 = 1.85, P = 0.212) for 1-strand (x̄ = 28.1, SE = 7.8), 2-strand (x̄ = 14.2, SE = 3.2), and 3-strand (x̄ = 16.9, SE = 4.3) electric fences. However, we found 50% and 40% fewer crossings for the 2- and 3-strand fences, respectively, compared with the 1-strand fence. In our rangeland trial, we found 49% fewer intrusions (F_2,18 =4.39, P = 0.028) into bait stations with a 2-strand electric fence (x̄ =4.1, SE = 1.8) compared with no fence (x̄ =8.1, SE = 2.4). Finally, in our agriculture trial, we found 64% less damage (X²₂ = 5.77, P = 0.016) to sorghum crops with a 2-strand electric fence (x̄ = 4.48, SE = 0.01%) compared with no electric fence (x̄ = 12.46, SE = 0.03%). Furthermore we found no (X¹₁ = 3.72, P = 0.054) wildlife pathways in areas with an electric fence (x̄ = 0.0, SE =0.0) compared with no fence (x̄ = 2.4, SE= 1.3). No electric fence design we tested was 100% pig-proof However, we found electric fencing restricted feral pig movements. Combining electric fencing with other damage control methods in an integrated management program may be the best method for alleviating feral pig damages.     

Y chromosome microsatellite markers identified from the tammar wallaby (Macropus eugenii) and their amplification in three other macropod species

Microsatellites were identified from three fully sequenced Y chromosome‐specific bacterial artificial chromosome clones from the tammar wallaby, Macropus eugenii. Ten microsatellites were genotyped in male tammar wallabies. Four loci were polymorphic with between two and six alleles per locus. Eleven different haplotypes were identified from 22 male tammar wallabies. No amplifications were obtained from female samples. Each microsatellite was also shown to amplify reliably in at least one other macropod species. These markers may therefore prove useful as some of the first male‐specific genetic markers for marsupials, with potential application to studies of male‐biased dispersal and mating systems.     

The usefulness of sensitivity analysis for predicting the effects of cat predation on the population dynamics of their avian prey

Sensitivity analyses of population projection matrix (PPM) models are often used to identify life-history perturbations that will most influence a population's future dynamics. Sensitivities are linear extrapolations of the relationship between a population's growth rate and perturbations to its demographic parameters. Their effectiveness depends on the validity of the assumption of linearity. Here we assess whether sensitivity analysis is an appropriate tool to investigate the effect of predation by cats on the population growth rates of their avian prey. We assess whether predation by cats leads to non-linear effects on population growth and compare population growth rates predicted by sensitivity analysis with those predicted by a non-linear simulation. For a two-stage, age-classified House Sparrow Passer domesticus PPM slight non-linearity arose when PPM elements were perturbed, but perturbation to the vital rates underlying the matrix elements had a linear impact on population growth rate. We found a similar effect with a slightly larger three-stage, age-classified PPM for a Winter Wren Troglodytes troglodytes population perturbed by cat predation. For some avian species, predation by cats may cause linear or only slightly nonlinear impacts on population growth rates. For these species, sensitivity analysis appears to be a useful conservation tool. However, further work on multiple perturbations to avian prey species with more complicated life histories and higher-dimension PPM models is required.     

Functional significance of the dark central floret of Daucus carota (Apiaceae) L.; is it an insect mimic?

In Daucus carota L. (Apiaceae) the florets comprising the central umbellet of inflorescences are usually pink or dark purple, presenting a marked contrast to the surrounding umbellets, which are generally white. The number of dark florets varies, and some inflorescences have no dark florets. It has been proposed that the dark florets function as an insect mimic, and in so doing serve to attract insects to the flower. In contrast, other authors, Darwin included, suggest that they are functionally redundant. The present study examined whether the dark florets attract insects, and also whether this effect can be replicated by replacing these florets with an insect. At the study site in Portugal the predominant insect visitor was the beetle Anthrenus verbasci L. (Dermestidae), which is similar in size and shape to the dark florets. Large inflorescences and those with more dark florets attracted more beetles than small inflorescences and those with fewer or no dark florets. Inflorescences with the dark florets removed attracted fewer beetles visitors compared with intact inflorescences. Inflorescences in which the dark florets were replaced with one or a cluster of five dead, freeze-killed A. verbasci attracted more beetles than inflorescences from which the dark florets had been removed. Replacement of the dark florets with a relatively large Meloid beetle resulted in the attraction of markedly fewer A. verbasci . We conclude that the dark florets can act as an insect attractant for some insect groups by acting as an insect mimic, and that they are adaptive, in contrast to the speculations of Darwin.