Endogenous activity rhythm in Talitrus saltator,Britorchestia brito (Crustacea,Amphipoda) and Tylos europaeus (Crustacea,Isopoda) from Barkoukech Beach (Tabarka,Tunisia)

The locomotor activity rhythm of three supralittoral crustacean species, Tylos europaeus (terrestrial isopod) and Britorchestia brito and Talitrus saltator (amphipod, Talitridea), was investigated in Barkoukech Beach. The rhythm was monitored in individual animals in spring under continuous darkness and constant temperature. Results revealed that whatever the species, actograms and mean activity curves showed that specimens of T. europaeus and T. saltator concentrated their activity during the subjective night; whereas, B. brito concentrated its activity during the subjective day. The three species exhibited a circadian locomotor rhythm with mean circadian period, respectively, equal to 24h41′ ± 0h44′, 24h46′ ± 0h55′ and 25h21′ ± 1h16′. The most stable locomotor rhythm was found in T. saltator (0.444 ± 0.246). Furthermore, individuals of T. europaeus were significantly more active (10h47′ ± 2h52′) than the two amphipods. Differences in the activity patterns of the three species will be discussed as an adaptative strategy to respond to interspecific competitive interactions.     

Winter browsing of brown hares: evidence for diet breadth expansion

Foraging theory predicts that diet breadth should expand as food availability decreases. We tested this by looking at the winter browsing behaviour of the brown hare Lepus europaeus. We predicted selective feeding on different woody plant species, diet generalisation under increasingly severe winter conditions and a rank preference between the different food items. Following a period of severe winter conditions, we censused browsing marks of brown hares on woody plants at six sites situated at different altitudes (340 – 600 m a. s. l.) in Upper Franconia, Germany. We assumed that access to ground vegetation, which is the general diet of brown hares, was more restricted at sites with higher snow cover. The results provided support for all of our predictions: Feeding intensity varied strongly between the different plant species indicating selectivity of feeding. The number and also the percentage of browsed woody plant species was positively correlated with the altitude of the study site indicating a wider diet breadth in situations where less food was available. On the basis of a rank model on the food choice of brown hares, which was evaluated by an independent data set, we conclude that brown hares show a rank preference with regard to different groups of woody plant species. Our findings support the assumption that food restricted hares increasingly include unfavourable, low quality items into the diet.     

Changes in Nightjar Caprimulgus europaeus populations in upland forests in Yorkshire

The Nightjar populations of Yorkshire's upland forests have grown significantly during recent years, probably as a result of a concurrent increase in the available area of suitable habitat due to forest management. In common with other populations it appears that the birds utilize younger, more open plantations. Comparison, based on discriminant analysis, of the habitat characteristics of forest plantations occupied and unoccupied by Nightjars suggests two things. First, that birds are more likely to occupy larger rather than smaller clearings and, second, that the study populations are close to their maxima. However, with continuing rotational felling, the area should continue to support a similar population.     

A potent, morph-specific parturition stimulant in the overwintering host plant of the black bean aphid, Aphis fabae

Abstract. The black bean aphid, Aphis fabae Scopoli, has a host‐alternating life cycle. Winged female autumn migrants (gynoparae) develop on numerous summer host plants but as adults will only colonize the winter host (spindle, Euonymus europaeus L.). When stylet activities of gynoparae were electrically recorded during access to a spindle leaf, the insects spent the majority (75%) of the 6‐h experimental period penetrating the plant surface and a large proportion of it (44%) ingesting from either phloem or xylem vessels. Most (95%) gynoparae initiated reproduction on spindle, producing 4.15 ± 0.59 offspring per adult by the end of the experiment (mean ± SEM). By contrast, gynoparae placed on a seedling of their natal, summer host (broad bean, Vicia faba L.) penetrated the plant for only 39% of the available time, rarely ingested plant sap and never reproduced. The number of nymphs deposited on spindle leaves was not correlated with the occurrence or duration of ingestion from vascular tissues, suggesting that parturition stimulants are detected before feeding, probably during penetration of nonvascular cells. Presentation of an aqueous spindle extract to the aphids in artificial feeding chambers showed that water‐soluble spindle factors evoke stimulation of parturition by gynoparae in 72‐h bioassays. The stimulant was extremely potent, remaining active until the total extracted material was diluted to less than 10 p.p.m. Stylet activities and reproductive responses were also evaluated for summer winged females (alate virginoparae), which have a broad host range, and will colonize both bean and spindle under laboratory conditions. On both of these plant species, virginoparae often ingested plant sap and deposited nymphs during the 6‐h electrical recording experiment (producing 4.60 ± 0.48 offspring on bean; 2.70 ± 0.35 on spindle: mean ± SEM), but no significant correlations were found between reproduction and the occurrence or duration of particular stylet activities. Aqueous host‐plant extracts had no effect on the numbers of offspring deposited by virginoparae in artificial feeding chambers, showing that this form of the aphid is not responsive to the spindle‐derived parturition stimulant. The results highlight the need for more information on the factors determining host acceptance and parturition by polyphagous aphid phenotypes.     

Multiple paternity in the European hedgehog

Previous observations have suggested that European hedgehogs Erinaceus europaeus are promiscuous, although there have been no direct studies of the mating system to confirm this. In this study, the genetic mating system of the European hedgehog was assessed by analysing mother–offspring groups using six polymorphic microsatellite loci. Evidence of multiple paternity was found in two of five litters analysed and therefore demonstrates the occurrence of polyandry in wild populations of hedgehogs.     

Does handling reduce the winter body mass of the European hare?

Winter body mass of the European hare Lepus europaeus Pallas 1778 was analyzed with a special focus on changes induced by handling. Data were obtained from large scale translocation (net catchments) during 1960–1980 in Poland. The influence of handling was compared using the mass of first-time captured and repeatedly-captured hares, and, in case of repeated capture, individuals’ mass changes were investigated. The average body mass ranged from 2.1 kg to 5.0 kg. Generally, fewer factors influenced the hare’s body mass than expected. Body mass was related to age and winter precipitation, while the date of catching, sex and temperature did not have an effect. Body mass of first-captured hares were significantly higher than the re-captured ones (3.99±0.42 vs. 3.88±0.48, mean ±SD). Body mass change between captures was related to the date of the first capture, and the duration between the first capture and re-capture. Following the initial capture, a slight (2.8±2.6), but significant decrease in body weight occurred. Thus, the handling of hares should be used with caution during studies or management of the species.