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See detailMonitoring Lions (Panthera leo) using Digital 3D Models of their Tracks
Marchal, Antoine ULiege

Doctoral thesis (2017)

As the Earth may be entering a new human-influenced geological time, the Anthropocene, the pressure on biodiversity due to increasing human populations and activities is unprecedented. Monitoring animal ... [more ▼]

As the Earth may be entering a new human-influenced geological time, the Anthropocene, the pressure on biodiversity due to increasing human populations and activities is unprecedented. Monitoring animal populations is essential to gain demographic data and assess their viability. Because of the difficulties linked to invasive methods that involve direct observation or handling, many researchers have explored alternative approaches such as using tracks. Tracks are the material by-product of the interaction between terrestrial animals and their physical environment due to gravity. The interpretation of tracks exists since the dawn of mankind and is a crucial factor for human evolution. As an integral part of hunting, the art of tracking involves cognitive thinking that may well be part of the origin of science. However, monitoring species through their tracks is controversial due to several reasons: unreliable recording techniques limited to two-dimensions, manipulator bias, substrate variation, misidentification of the foot from which each track originates, and subjective identification of the age, sex and/or individual. The aim of this thesis was to evaluate the possibility of monitoring lions Panthera leo through digital three-dimensional (3D) models of their tracks. The first step was to assess close-range digital photogrammetry as a low-cost, rapid, practical and reliable field technique for the digital 3D modelling of lion paws, tracks and trails. A trail, that is a continuous sequence of tracks made by the same individual, reflects the morphology and kinematics of that individual. The use of traditional morphometrics enabled the extraction of variables such as distances, angles and areas from the digital 3D trails originating from individuals of known age, sex and/or identity. When comparing adult lions walking at the same gait (i.e. same kinematics), the trail variables provided sufficient information to identify the sex and individual. The digital solution permitted the extraction of more variables than the usual pace, stride and straddle. These additional variables enabled a better discrimination between the sexes and individuals. As for the paw and track morphology, traditional morphometrics conveys limited information about the geometric structure, and fails to quantify the shape variations along curves and surfaces. To overcome these drawbacks, geometric morphometrics allowed the extraction of the form (i.e. size and shape) by means of superimposed fixed landmarks, and curve- and surface-slider semi-landmarks. Using fixed landmarks, the paws and tracks presented enough shape variation to identify their position along the anteroposterior (front or hind) and mediolateral (right or left) axes. We used fixed landmarks, with and without curve- and surface-sliders, on paws and tracks from lions of known age, sex and/or identity. The identification of the age and sex from the paws, and the age, sex and individual from the tracks achieved higher accuracies when using size and shape variables together rather than independently. The information from curves and surfaces offered an advantage for the identification from the tracks but not from the paws. Due to the variation in anatomy, paw morphology and individuality in walking, tracks and trails contain information about the individual lion that created them. Recent advances in digital close-range photogrammetry and geometric morphometrics allow the recording and extraction of that information, which can then provide data to help monitor lion populations using a non-invasive approach. [less ▲]

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See detailBack on Track... in 3D
Marchal, Antoine ULiege; Lejeune, Philippe ULiege; De Bruyn, Nico

Poster (2016, September 04)

Ecological monitoring provides basic information on population status and distribution that is crucial for conservation, research and management strategies. Studies using tracks are controversial due to ... [more ▼]

Ecological monitoring provides basic information on population status and distribution that is crucial for conservation, research and management strategies. Studies using tracks are controversial due to past misuses tainted with subjectivity. Advances in photogrammetry literally add another dimension to the recording techniques, and geometric morphometrics provides an appropriate approach for the study of track shape variation. Tracks are back on track in conservation! [less ▲]

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See detailFoot identification from digital 3D models of lion tracks and paws
Marchal, Antoine ULiege; Lejeune, Philippe ULiege; De Bruyn, Nico

Conference (2016, March 15)

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See detailConserving wildlife amongst the cotton fields. A third of a century of experience at the Nazinga Game Ranch, Burkina Faso
Bouché, Philippe; Lejeune, Philippe ULiege; Bailly, Vincent et al

in Environmental Monitoring & Assessment (2016), 188

Established in the early 1970 as a participatory wildlife production area, the Nazinga Game Ranch turned into an island of conservation surrounded by cultivation.We asked ourselves how long-term ungulate ... [more ▼]

Established in the early 1970 as a participatory wildlife production area, the Nazinga Game Ranch turned into an island of conservation surrounded by cultivation.We asked ourselves how long-term ungulate trends are affected in a context of continuous human pressure. To find out, we compiled and analysed the data of yearly line-transect counts of mammals carried out since 1985. Results showed that large species such as the elephant (Loxodonta africana) and large antelopes increased or showed stable populations. In contrast, medium and small ungulates showed continuously decreasing trends. During the same period, rainfall, water availability from artificial water points and the crop encroaching outside Nazinga Game Ranch increased. After an initial significant reduction, illegal human signs increased. However, we showed that human signs were positively correlated with the abundance of large ungulates but negatively correlated with the abundance of medium and small ones. In conclusion, this study showed that some isolated mammal populations could be restored and maintained in the long term, in spite of being surrounded by highly cultivated areas. [less ▲]

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See detailVirtual plaster cast: digital 3D modelling of paws and tracks via photogrammetry
Marchal, Antoine ULiege; De Bruyn, Nico; Lejeune, Philippe ULiege

Conference (2015, July 17)

Detailed reference viewed: 32 (3 ULiège)