Sex, size and isotopes: cryptic trophic ecology of an apex predator, the white shark Carcharodon carcharias

Demographic differences in resource use are key components of population and species ecology across the animal kingdom. White sharks (Carcharodon carcharias) are migratory, apex predators, which have undergone significant population declines across their range. Understanding their ecology is key to ensuring that management strategies are effective. Here, we carry out the first stable isotope analyses of free-swimming white sharks in South Africa. Biopsies were collected in Gansbaai (34.5805°S, 19.3518°E) between February and July 2015. We used Stable Isotope Bayesian Ellipsis in R and traditional statistical analyses to quantify and compare isotopic niches of male and female sharks of two size classes, and analyse relationships between isotopic values and shark length. Our results reveal cryptic trophic differences between the sexes and life stages. Males, but not females, were inferred to feed in more offshore or westerly habitats as they grow larger, and only males exhibited evidence of an ontogenetic niche shift. Lack of relationship between δ13C, δ15N and female shark length may be caused by females exhibiting multiple migration and foraging strategies, and a greater propensity to travel further north. Sharks  3 m, drivers of which may include individual dietary specialisation and temporal factors. The differences in migratory and foraging behaviour between sexes, life stages, and individuals will affect their exposure to anthropogenic threats, and should be considered in management strategies

The alarm behaviour of grass-cutting ants and the pheromone enhancement of bait for their control

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN031612 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Polyethism and the importance of context in the alarm reaction of the grass-cutting ant, Atta capiguara

Leaf-cutting ants exhibit an aggressive alarm response. Yet in most alarm reactions, not all of the ants encountering a disturbance will respond. This variability in behaviour was investigated using field colonies of Atta capiguara, a grass-cutting species. Crushed ant heads were applied near foraging trails to stimulate alarm reactions. We found that minor workers were disproportionately likely to respond. Only 34.7+/-2.8% of ants travelling along foraging trails were minor workers, but 82.1+/-6.1% of ants that responded were miners. Workers transporting grass did not respond at all. The alarm response was strongest at the position and time where miners were most abundant. Ants were more likely to respond when they were travelling along trails with low rather than high traffic. Minor workers followed a meandering route along the trail, compared with the direct route taken by foragers. We argue that an important function of minor workers on foraging trails is to patrol the trail area for threats, and that they then play the key role in the alarm reaction

Fly populations associated with landfill and composting sites used for household refuse disposal

Calyptrate fly populations were monitored with sticky traps at the following sites in Hampshire, UK during August to November 1998: a landfill and composting site (Paulsgrove), a site adjacent to this landfill (Port Solent), a site with no landfill nearby (Gosport), and a composting site with no landfill nearby. Overall, house flies Musca domestica (Linnaeus) and lesser house flies Fannia spp. were not important constituents of the dipteran catch, while bluebottles (Calliphora spp.) and greenbottles (Lucilia spp.) comprised approximately 12% of the total. Very large fly populations were found at the two composting sites, and it seems likely that these provide ideal breeding grounds for a range of fly species since they offer an abundance of warm decaying organic matter. Large fly populations were also evident at the landfill site. The suitability of household waste for the development of calyptrate Diptera was confirmed in a controlled trial: a mean of 0.43 adults emerged per kilo of one-week-old waste. Since many hundreds of tonnes of waste are delivered to the landfill daily, it is clear that the landfill is likely to substantially increase the local population of calyptrate flies. However, the data suggest that there was little movement of Diptera from the landfill to Port Solent situated approximately 500 m away. The most important calyptrate flies at this site were the cluster flies Pollenia rudis (Fabricius) and P. amentaria (Scopoli); the landfill site is unlikely to provide a suitable breeding site for these flies, as the larvae develop as parasites of earthworms. Significantly more flies emerged from one-week-old than from two-week-old household waste. A comparison of different barriers to the emergence of adult house flies from waste demonstrated that sacking provided an effective barrier to fly emergence, but that soil did not differ significantly from control treatments. If managed appropriately, it seems that the use of sacking over landfill waste could substantially reduce associated fly populations

Susceptibility of Italian agile frog populations to an emerging strain of Ranavirus parallels population genetic diversity.

Western populations of the Italian agile frog (Rana latastei) experience widespread genetic depletion. Based on population genetic theory, molecular models of immunity and previous empirical studies, population genetic depletion predicts increased susceptibility of populations to emergent pathogens. We experimentally compared susceptibility of R. latastei populations upon exposure to an emerging strain of Ranavirus, frog virus 3 (FV3), using six populations spanning the geographical range and range of population genetic diversity found in nature. Our findings confirm this prediction, suggesting that the loss of genetic diversity accompanying range expansion and population isolation is coincident with increased mortality risk from an emergent pathogen. Loss of heterozygosity and escape from selection imposed by immunologically cross-reactive pathogens may potentially generate range-wide variation in disease resistance