Predation avoidance and foraging efficiency contribute to mixed-species shoaling by tropical and temperate fishes

The formation of mixed-species social groups, whereby heterospecifics form and maintain either transient or stable groups with each other, can confer substantial fitness benefits to individuals. Such benefits may arise via multiple mechanisms associated with both predation avoidance and foraging efficiency. In fishes, mixed-species shoaling reportedly occurs where displaced tropical species (known as “vagrants”) interact with resident temperate species, although little is known about the nature and frequency of such interactions. To investigate this phenomenon, we used displaced tropical Indo-pacific Sergeant Abudefduf vaigiensis settling in temperate south-eastern Australia as a model system. Underwater visual surveys revealed shoal composition and size differed significantly between open-water and reef habitats, with shoals in open habitats being larger and more speciose. Shoals containing A. vaigiensis were mainly mixed-species, and larger and more speciose in open habitats than nearer to reef. Since both foraging efficiency (via access to plankton) and predation threat likely increase with increasing distance from reef habitat, we suggest that mixed-species shoaling mitigates predation risk whilst allowing increased foraging opportunities for A. vaigiensis in open areas. These findings provide support for the importance of mixed-species shoaling to the persistence of tropical reef fishes in temperate regions.     

Opportunistic Predation of Wild Turkey Nests by Wild Pigs

Wild pigs (Sus scrofa; i.e., feral hogs, feral swine) are considered an invasive species in the United States. Where they occur, they damage agricultural crops and wildlife habitat. Wild pigs also depredate native wildlife, particularly ground-nesting bird species during nesting season. In areas inhabited by wild turkeys (Meleagris gallopavo), nest destruction caused by wild pigs may affect recruitment. There is debate whether wild pigs actively seek ground-nesting bird nests or depredate them opportunistically. To address this debate, in 2016 we examined the movements of wild pigs relative to artificial wild turkey nests (i.e., control [no artificial nests], moderate density [12.5–25 nests/km²], and high density [25–50 nests/km²]) throughout the nesting season (i.e., early, peak, and late) in south-central Texas, USA. We found no evidence that wild pigs learned to seek and depredate wild turkey nests relative to nest density or nesting periods. Despite wild pigs being important nest predators, depredation was not a functional response to a pulsed food resource and can only be associated with overlapping densities of wild pigs and nests. Protecting reproductive success of wild turkeys will require reducing wild pig densities in nesting habitat prior to nesting season. © 2019 The Wildlife Society.     

Contrasting sensitivity of nestling and fledgling Barn Swallow Hirundo rustica body mass to local weather conditions

Local weather can influence the growth and development of young birds either indirectly, by modifying prey availability, or directly, by affecting energetic trade-offs. Such effects can have lasting implications for life history traits, but the nature of these effets may vary with the developmental stage of the birds, and over timescales from days to weeks. We examined the interactive effects of temperature, rainfall and wind speed on the mass of nestling and fledgling Barn Swallows Hirundo rustica both on the day of capture and averaging weather across the time since hatching. At the daily timescale, nestling mass was negatively correlated with temperature, but the strength of this association depended on the level of rainfall and wind speed; nestlings were typically heavier on dry or windy days, and the negative effect of temperature was strongest under calm or wet conditions. At the early lifetime timescale (i.e. from hatching to pre-fledging), nestling mass was negatively correlated with temperature at low wind speed. Fledgling body mass was less sensitive to weather; the only weather effect evident was a negative correlation with temperature at the daily scale under high rainfall that became slightly positive under low rainfall. These changes are consistent with weather effects on the availability and distribution of insects within the landscape (e.g. causing high concentrations of flying insects) and with the effects of weather variation on nest microclimate. These results together demonstrate the impacts of weather on chick growth, over immediate (daily) and longer term (nestling/fledgling lifetime) timescales. This shows that sensitivity to local weather conditions varies across the early lifetime of young birds (nestling–fledgling stages) and illustrates the mechanisms by which larger scale (climate) variations influence the body condition of individuals.     

The foraging of New Zealand honeyeaters

Abstract

New Zealand has three species of honeyeaters, all of which feed on nectar, fruit, and ‘insects’. There is disagreement between published data and those becoming available from long-term studies on the relative proportion of these items in the diet. The effect of factors such as body size, dominance status, degree of movement, and time of year on diet and foraging behaviour are outlined, and predictions of differences between species and between sexes are made. A brief comparison of foraging in relation to the flora is made between New Zealand and Australian species.     

Some aspects of the biology of the hedgehog (Erinaceus europaeus L.) in the Manawatu,New Zealand

In a study area of 16.3 ha of dairy pasture and pine plantations in the Manawatu region of the southern North Island, 150 hedgehogs were marked and 356 recaptures recorded between 1 January 1970 and 24 June 1971. Population density was estimated at between 1.1/ha in winter and 2.5/ha in summer and autumn. Only 11 females and 5 males were considered to be residents, and these used overlapping feeding ranges of similar extent. Concentrations of food organisms became foci of hedgehog activity. During winter, when an estimated 20% of the population died, movement was restricted to the vicinity of the nest site; the hedgehogs hibernated fitfully during July‐October. The breeding season as such extended at least from November to March; some breeding activity was observed in most months, however. The average life span of adults was 1.97 years. The causes of 6 natural deaths and the incidence of abscesses and external parasites were noted.     

Sequential foraging of dusky dolphins with an inspection of their prey distribution

The aim of this work was to analyze the sequential foraging behavior of dusky dolphins (Lagenorhynchus obscurus). Foraging sequences were defined when more than two feeding bouts occur with a traveling bout between them. We hypothesized that traveling costs of searching for prey patches were related to the time spent feeding on a patch. In addition, the distribution and seasonal variation of anchovy schools were studied in the area to better understand dolphins' behavior. We observed dolphins from a research vessel from 2001 to 2007, and recorded their location and behavior. Anchovy data were collected during two hydro‐acoustic surveys. Dusky dolphin behaviors varied seasonally; they spent a greater proportion of time traveling and feeding in the warm season (Kruskal‐Wallis: H = 172.07, P < 0.01). During the cold season dolphin groups were more likely to exhibit diving behavior and less surface feeding. We found a positive correlation between searching and foraging time (r = 0.88, P = 0.019), suggesting that the costs associated with searching were compensated by an increase in the energy intake during the foraging bout. There was an association between dusky dolphin and anchovy distribution, in that they co‐varied spatially and seasonally.     

Same Temporal Niche,Opposite Rhythmicity: Two Closely Related Bioluminescent Insects With Opposite Bioluminesce Propensity Rhythms

Arachnocampa species, commonly called glowworms, are flies whose larvae use light to attract prey. Here we compare rhythmicity in two of the nine described species: the Tasmanian species, Arachnocampa tasmaniensis, which inhabits caves and wet forest, and the eastern Australian mainland species, A. flava, primarily found in subtropical rainforest. Both species show the same nocturnal glowing pattern in external (epigean) environments and the same inhibition of bioluminescence by light and both species show circadian regulation of bioluminescence. We find that the underlying circadian bioluminescence propensity rhythm (BPR) of the two species peaks at opposite phases of the day:night cycle. Larvae of A. flava, placed in constant darkness in the laboratory, bioluminesce during the subjective scotophase, typical of nocturnal animals, whereas A. tasmaniensis shows the opposite tendency, bioluminescing most intensely during the subjective photophase. In A. tasmaniensis, which are exposed to natural day:night cycles, light exposure during the day overrides the high bioluminescence propensity through negative masking and leads to a release of bioluminescence after dusk when the BPR is on the wane. A consequence is that A. tasmaniensis is able to start glowing at any phase of the light:dark cycle as soon as masking by light is released, whereas A. flava is locked into nocturnal bioluminescence. We suggest that the paradoxical BPR of A. tasmaniensis is an adaptation for living in the cave environment. Observations of bioluminescence in colonies of A. tasmaniensis located in the transition from a cave mouth to the dark zone show that glowing is inhibited by light exposure but a peak bioluminescence follows immediately after “dusk” at their location. The substantial difference in the circadian regulation of bioluminescence between the two species probably reflects adaptation to the cave (hypogean) habitat in A. tasmaniensis and the forest (epigean) habitat in A. flava. (Author correspondence: d.merritt@uq.edu.au)     

Time-restricted foraging under natural light/dark condition shifts the molecular clock in the honey bee,Apis mellifera

ABSTRACT

Honey bees have a remarkable sense of time and individual honey bee foragers are capable of adjusting their foraging activity with respect to the time of food availability. Although, there is compelling experimental evidence that foraging behavior is guided by the circadian clock, nothing is known about the underlying molecular mechanisms. Here we present for the first time a study that explores whether time-restricted foraging under natural light-dark (LD) condition affects the molecular clock in honey bees. Food was presented in an enclosed flight chamber (12 m × 4 m × 4 m) either for 2 hours in the morning or 2 hours in the afternoon for several consecutive days and daily cycling of the two major clock genes, cryptochrome2 (cry2) and period (per), were analyzed for three different parts of the nervous system involved in feeding-related behaviors: brain, subesophageal ganglion (SEG), and the antennae with olfactory sensory neurons. We found that morning and afternoon trained foragers showed significant phase differences in the cycling of both clock genes in all three tissues. In addition, the phase differences were more pronounced when the feeder was scented with the common plant odor, linalool. Together our findings suggest that foraging time may function as a Zeitgeber that might have the capability to modulate the light entrained molecular clock.     

Wild plants eaten in childhood: a retrospective of Estonia in the 1970s–1990s

In this ethnobotanical study, the authors provide the first quantitative analysis of the use of wild edible plants in Estonia, describing the domains and assessing the food importance of different species. The information was collected using free‐listing written questionnaires and concerned plants used by the respondents in their childhood. As part of a major study, this article covers the responses of professionals with some botanical education at vocational or university level, to ensure the greatest possible reliability without using voucher specimens. Fifty‐eight respondents provided information on the use of 137 plant taxa, corresponding to approximately 6% of the native and naturalized vascular plants of Estonia. According to use frequency, the most typical wild food plant of Estonia is a fruit, eaten raw as a snack. The results clearly signal that the majority of famine and food shortage plants had already been forgotten by the end of the 20^th century, but new plants have been introduced as green vegetables for making salads. Despite changes in the nomenclature of the plants, the use of wild food plants in Estonia was still thriving at the turn of the 20^th century, covering many domains already forgotten in urbanized modern Europe. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172 , 239–253.     

Phenylacetaldehyde attracts male and female apple clearwing moths,Synanthedon myopaeformis,to inflorescences of showy milkweed,Asclepias speciosa

Synanthedon myopaeformis Borkhausen (Lepidoptera: Sesiidae) is a diurnal clearwing moth native to Eurasia that was recently introduced into British Columbia (BC) and Ontario, Canada, where it has become a serious pest in apple orchards. In BC, these moths commonly feed on nectar of inflorescences, particularly that of showy milkweed, Asclepias speciosa Torrey (Apocynaceae). We investigated the relative importance of visual and olfactory cues, and the key floral semiochemical(s) mediating attraction of S. myopaeformis to A. speciosa. In field experiments, inflorescences left exposed or enclosed in cheesecloth bags dyed green induced similar visitation rates by moths, indicating that olfactory cues are attractive. Among the >10 floral odourants that elicited responses from moth antennae in coupled gas chromatographic‐electroantennographic detection analyses, phenylacetaldehyde induced the most frequent proboscis extension reflexes of male and female moths. Among eight floral odourants that were field‐tested singly, phenylacetaldehyde attracted 35 times more male and female moths than any other candidate semiochemical. Attractiveness of phenylacetaldehyde could not be enhanced by admixture with other floral odourants at the ratios or concentrations tested indicating that it alone may mediate attraction of S. myopaeformis to the inflorescences of A. speciosa. The potential use of phenylacetaldehyde as bait to monitor or mass‐trap populations of male and female S. myopaeformis should be investigated.