Showing papers by "Aurélie Coulon published in 2007"

Testing Global Positioning System Performance for Wildlife Monitoring Using Mobile Collars and Known Reference Points

Abstract: To determine the spatial resolution of Global Positioning System (GPS) receiver data, rigorous testing is essential. We tested performance of the Lotek 3300 GPS collar for medium-sized mammals (Lotek Engineering, Inc., Newmarket, ON, Canada). To mimic real wildlife monitoring situations, we performed both static (stationary receiver) and mobile tests, placing the receiver collar on a dog. We compared fix locations of the mobile receiver with the actual trajectory described by a portable Trimble high-precision GPS. We determined performance in relation to habitat type and leaf cover. Location error was habitat-dependent, with the best results in open habitat and much poorer ones in forest, particularly coniferous-dominated forest. For both static and mobile tests, location accuracy was higher when the number of satellites contacted was high and when the residual positional dilution of precision (PDOP) value was low. However, location error was highly variable, even for a given PDOP value and a given number of satellites contacted. Finally, mobile collars performed less well than their static counterparts, presumably because of frequent changes of GPS position and orientation.

Using Radio-tracking and Direct Observation to Estimate Roe Deer Capreolus Capreolus Density in a Fragmented Landscape: A Pilot Study

Abstract: In this pilot study, we estimate roe deer Capreolus capreolus density in a fragmented landscape, using radio-tracking and direct observation in a Petersen-Lincoln framework with the joint hypergeometric maximum likelihood estimator. We used radio-tracking to obtain a direct count of the number of marked animals potentially observable in a given sample area, thus avoiding edge effects. We then carried out a coordinated observation survey, including drive beating, to ascertain the proportion of marked roe deer in the population sampled and thus generate a population estimate. Surveys were repeated three times in four sample blocks within the fragmented landscape, and estimates were compared to a sample block of a central forest in the same area. In general, roe deer are difficult to observe and census, but our experimental set-up in the fragmented landscape enabled us to observe on average 75% of marked animals present in a given survey (compared to 21.5% in the central forest). The variability in capture probability between individuals was low as three quarters of all marked individuals were observed in all, or all but one, of the surveys. Density estimates were largely similar across the sample blocks of the fragmented landscape (4.0-7.9 deer/100 ha), but lower than in the central forest (34.3 deer/100 ha). The variability of daily population estimates was quite low and similar in the fragmented landscape (CV of 25.9%) and the central forest (CV of 25.3%). Taking availability of woodland into account, the density in the fragmented landscape was as high, or higher, than in the central forest, reaching an exceptional 145.3 deer/100 ha of woodland in one survey area.