Derek Madden

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We explore here the occurrence of aggressive ants in an apparently symbiotic relationship with the savanna tree Acacia drepanolobium and their effects on giraffe herbivory on the Athi-Kapiti Plains, Kenya. Trees taller than 1.3 m were more likely to be occupied by aggressive ants in the genus Crematogaster than were shorter trees. Ants wereconcentrated on(More)
We report evidence from controlled experiments that long straight thorns deter herbivory by browsers. Cut branches of three woody species that had their thorns removed suffered significantly greater herbivory by a tethered goat than did paired intact branches. Branches on living Acacia seyal plants that had their thorns removed suffered significantly(More)
A new set of flux intensity maps for energetic protons in the South Atlantic Anomaly (SAA) region is presented for the epoch 2000-2006 based on data from the compact environment anomaly sensor (CEASE) flown onboard the tri-service experiment-5 (TSX-5) satellite in a 410 km x 1710 km, 69 degree inclination orbit. Maps for > 23 Mev, > 38 MeV, > 66(More)
Dosimeter data taken on the APEX (1994-1996), CRRES (1990-1991) and DMSP (1984-1987) satellites have been used to study the low altitude (down to 350 km) radiation environment. Of special concern has been the inner edge of the inner radiation belt due to its steep gradient. We have constructed dose models of the inner edge of the belt from all three(More)
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