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Michael Jenkin, James Zacher, Richard Dyde, Laurence Harris and Heather Jenkin

Abstract

The perceived direction of up depends on both gravity and visual cues to orientation. Static visual cues to orientation have been shown to be less effective in influencing the perception of upright (PU) under microgravity conditions than they are on earth (Dyde et al., 2009). Here we introduce dynamic orientation cues into the visual background to ascertain whether they might increase the effectiveness of visual cues in defining the PU under different gravity conditions. Brief periods of microgravity and hypergravity were created using parabolic flight. Observers viewed a polarized, natural scene presented at various orientations on a laptop viewed through a hood which occluded all other visual cues. The visual background was either an animated video clip in which actors moved along the visual ground plane or an individual static frame taken from the same clip. We measured the perceptual upright using the oriented character recognition test (OCHART). Dynamic visual cues significantly enhance the effectiveness of vision in determining the perceptual upright under normal gravity conditions. Strong trends were found for dynamic visual cues to produce an increase in the visual effect under both microgravity and hypergravity conditions.

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Mathilde Soazandry, Bertrand Razafimahatratra, Christian Randrianantoandro, Richard Jenkins and Jonah Ratsimbazafy

Abstract

Information on the distribution and abundance of chameleons in Madagascar is required to develop conservation plans that integrate protected area management and sustainable use. We surveyed chameleons in eight sites in deciduous forest in Menabe, western Madagascar. Brookesia brygooi was the most frequently detected species, with a population density of 35 ha–1. Furcifer species were less common, with calculated densities of 7.2 ha–1 (F. labordi), 3.0 ha–1 (Furcifer sp.) and 1.3 ha–1 (F. oustaleti). Chameleon abundance varied according to altitude (B. brygooi) and no clear effect from logging was detected (all species). A lack of information on chameleon diurnal habitat requirements impedes a fuller assessment of the extent to which these species are tolerant to forest degradation. There were interspecific differences in the height of nocturnal perches and additional studies are needed to determine whether these are related to diurnal resource partitioning. Furcifer labordi and Furcifer sp. are of conservation concern because they are restricted to native forests in western Madagascar.

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Hantalalaina Elisoa Fideline, Raphali Rodlis Andriantsimanarilafy, Daniel Rakotondravony, Joseph Christian Randrianantoandro, Roma Randrianavelona and Richard Jenkins

Abstract

Madagascar's Brookesia dwarf chameleons are believed to require relatively intact forest for survival. Although they have featured in herpetological surveys, taxonomic reviews and trade assessments, very little is known about their microhabitat requirements or ecology. Over a 5 night period in a deciduous forest in western Madagascar we recorded the night roosting sites for three sympatric Brookesia species. We calculated the area and distance between successive night roost locations and described the characteristics of each roost. Distance between roosts and the area used were larger for B. brygooi and B. perarmata than B. exarmata. The distance between roosts was significantly greater for male than female B. brygooi and B. perarmata. Roost sites were generally in low vegetation (<0.75 m) with the animals located on stems or leaves. Roost height differed significantly between the species, with B. brygooi using the highest perches and B. exarmata the lowest.