Hierarchical structure and feeding behaviours of free-range hens (Gallus gallus domesticus).

Chickens ( Gallus gallus domesticus ) are a social species and will form a hierarchy through agonistic dyadic encounters. This hierarchy will affect how different members of the flock access food, which may affect the specific feeding behaviours of the hens. The hierarchy of a 20-hen flock was determined by analysing videoed dyadic encounters between the hens and creating a dominance matrix. The feeding behaviours were assessed by simultaneously offering free food via a feeder and food distributed in the grass requiring foraging. Overall, all hens preferred to forage, however, significantly more dominant birds ate at the feeder than neutral or subordinate birds. Foraging is a natural behaviour that chickens will innately perform and is related to a positive welfare state. The methodology for determining the flock hierarchy and measuring feeding choices could be tested within the intensive farming environment to elucidate potential effects of dominance on feeding methods in commercial hens

Age of the Batoka basalts, norther Zimbabwe, and the duration of Karoo Large Igneous Province magmatism

Analysis of the Bakota basalts exposed in the Zambezi Gorge some 40 km east of Victoria Falls characterizes them as high Fe, moderately high Ti, and low K, P, and Zr tholeiites. The ⁴⁰Ar-³⁹Ar age determinations are tightly clustered at 180-179 Ma. All of the lavas that were samples have normal paleomagnetic polarity, and the corresponding pole position is 63.9°N, 260.6°E, A₉₅ = 14.9°. In South Africa, Lesotho, and Namibia the vast majority of Karoo basalts were extruded at 183 ± 1 Ma with some as young as 179 Ma [Duncan et al., 1997]. Paleomagnetic and geochemical correlation of the ~179 Ma rocks between Zimbabwe and Lebombo supports the conclusion that the age difference is real and hence confirms the estimates of ~ 5 Myr for the duration of emplacement of the Karoo Large Igneous Province.Keywords: Large igneous provinces, Karoo, Geochronology, Paleomagnetis